Bridgestone Motorcycle Parts Discussion Board

Bridgestone Tech Talk => Engine => Topic started by: robinkwmack on September 21, 2019, 12:33:26 PM

Title: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: robinkwmack on September 21, 2019, 12:33:26 PM
Alright, reaching out to the knowledgeable folks here on the forum to try and figure out a reoccurring issue with my 1969 RS200 MkII.

First off some info on how I am running it.
87 oct fuel
40:1 yamalube premix in tank
cleaned points but haven't checked timing. Seems to be either fine or close to what it should be.

I got the bike from the grandson of the original owner who parked it in 1971 at just under 3k miles. I tore the cylinders apart and was able to figure out exactly why he had parked it. (Broken engine stud that then caused a head gasket leak.) I fixed the stud, put in a new gasket and the bike fired right up. I road it for maybe 300-500 miles with a gas leak on the left side. So I brought it to the local vintage motorcycle mechanic just to have them go through the carbs since I couldn't find why the leak was happening, had them make sure everything was set to "stock" so I could then tune it myself. They found the left float had a hole in it causing the leak and replaced it fixing that problem. with some carb cleaner I was able to find out there was a slight base gasket leak as well on the right cylinder. But about 50-100 miles after getting it back from them I lost compression on the right cylinder and found out that I had melted a hole in the center of the piston. Thinking that it was the base gasket issue I put a new piston on, new gaskets and it fired right up and ran like a top, but like an idiot, I did not check the carb seeing as it just came back from the shop, but then 50-100 miles later, same problem. Hole in the piston on the exact same road as when it happened before. I had noticed that the right fuel line was not filling up all the way and almost seemed "empty" only allowing a trickle at throttle, so I think the issue with the right cylinder is the right carb needs to be gone through again and readjusted and cleaned. But while I was in there I noticed some transmission oil was getting onto the crank when I turned it by hand (brown oil), very slight, but enough for me to realize I should do the crank seals as well.

So here are my questions:

Could my ignition coil be causing the spark plug to fire "hot" resulting in the melted piston?

Could it be an ignition timing issue?

Could the crank shaft seal leak be causing it to run lean as well?

What part number is that seal anyways? and what other parts will I need to do, or should do, while I have it open? I have had a hard time tracking it down in the parts catalogue and don't want to waste time and money trying to track it down seeing as I am 26 and basically broke and have already basically thrown away a few hundred bucks in a few hundred miles.

This time I will be sure to go through both carbs, all the cylinder gaskets again as well as that new right piston. I just can't afford to keep replacing that expensive piece.

Any insight would be a huge help and much appreciated.

Thank you.
-Robin
Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: OldSwartout on September 22, 2019, 05:26:04 PM
The right side crankshaft seal you need is 09090-109, 28 oil seal.  The seal could cause a lean condition that would melt the piston, but a leak big enough to cause  melted piston would let a lot of transmission oil past and cause a lot of smoke while riding.  My best guess is it is the ignition timing advanced  too much on the right side. I don't think the coil itself will cause an early spark.  Of course, some of the other items you've considered are still possibilities. The carburetor might still be suspect - if you're certain there isn't a blocked jet, check the main jet size. It should be a 90 or 95. Compare to what the left side has. Check is to see if fuel will flow through the float valve freely. With the carburetor still connected to the fuel line, just leave the bowl off, hold over a container and turn on the gas. It should flow a steady stream. If that's good, check the float height per the service manual. I had a Suzuki that had the float set too low in the bowl, it would starve at high rpm, yet everything looked good otherwise.

Maybe others on here have more suggestions or experiences that will help.
Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: OldSwartout on September 22, 2019, 05:31:19 PM
An outside chance is that the fuel cap isn't vented properly. Usually, an unvented cap will just cause the bike to slowly die of fuel starvation on both cylinders as fuel flow slows; however, I know from experience that the right cylinder on these bikes will start to miss first when running out of gas.
Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: BRT-GTR on September 23, 2019, 05:04:32 PM
          If the fuel cap vent is ok (just blow through it), take the fuel tap off and clean it thoroughly, tubes, filters etc.
Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: Old BS Guy on September 26, 2019, 03:37:33 AM
Yes, of course, start from the top down and validate the tank cap, but it should affect both sides equally, not selectively. Still, good cause for checking. The only thing not mentioned here, unless I missed it, is the bowl vent for the carb, and under the circumstances seems most likely given the other carb is doing fine. I do agree, however, that validating each part from the cap down is required. Slim chance it's ignition, but ignition must always be vetted before carburetion in any diagnostic to prevent mistakes with fuel.
Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: BRT-GTR on September 26, 2019, 03:48:51 PM
    Going back to basics, melting pistons are due to a cylinder running way too hot. Primary causes are weak petrol/air mixture IE, lack of fuel, too much air due to leak  and /or ignition timing advanced too far. Plug firing too early.
Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: rwgibbon on September 26, 2019, 04:57:48 PM
Regarding what would melt a piston, I agree with Brian.

Randy
Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: robinkwmack on September 26, 2019, 09:32:09 PM
Thank you all for all of the great responses.

There was never any white smoke, I only noticed brown oil on the crank when I had the cylinders off and when I turned the engine over by hand. But I know that that right seal likes to go, so would rather do it now then later.

Are there any other gaskets or seals I will be encountering and might replace at the same time as the crank seal? Obviously know about the base and head gaskets, I already have another set of those ready to roll.

Petcock is new and fuel flows freely out of both nipples when nothing is attached. Fuel cap used to not vent, so I drilled a new hole, definitely is venting.

Also any help with how to get to and replace that crank seal would be much appreciated. Haven't opened this motor up that much yet but I do have the repair book to go by.

I am thinking that side keeps melting due to the carb, I will double check the timing and set it appropriately and also make sure the carb is adjusted and cleaned as it should. before firing it back up. Definitely seems like it has something to do with the right carb. Fuel will fill when you first turn on the gas, but after running it the fuel turns to an incredibly slow trickle, barely able to see it coming through and flicking the line/filter to move air bubbles doesn't help either.

Thanks again for all of the help and any future help. Once I know exactly what I need to order I will start getting this thing back on the road.
Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: BRT-GTR on September 27, 2019, 09:03:01 AM
        Fuel will flow at good rate when tap first switched on (bowls empty due to evaporation) but will reduce when the bowls are full. However, the lines should fill with petrol,  air running back up to the tank. Have a look at that new tap, could be an issue there.
     Check right carb for correct jets, needle jet, the needle itself and position of needle clip (all shown in manual). Also check float height, that's a likely source of weak mixture. Correct spark plugs ?, you can't just use any type, heat range has to be correct.                        Brian.
Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: robinkwmack on September 28, 2019, 08:10:08 PM
Everything on the bike is incredibly stock, except for the home made air filter, the turn signals that I added, tires and chain. Spark plug is in range, I am going to check ignition timing after I get it back together so I am thinking something in the carb got blocked some how, or the float was not adjusted correctly. Going to order up parts soon and tear into it again. Petcock flows as it should and gas cap is venting properly. (It was not venting so now I know it is)


Are there any guides on this forum for getting to and replacing that oil seal? I like to have an idea of the direction I am going before just taking it all apart completely.

Thanks again for the help folks.
Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: OldSwartout on September 30, 2019, 09:14:06 AM
The service manual is available under the Downloads section of this forum. There is a 50-175 Service Manual and a 175 Technical Manual, both have similar info.

The general steps are:  Drain transmission oil, remove carburetor cover, remove carburetor (let it hang by it's cables out of the way), remove kickstarter, remove right engine side cover, remove nut on end of crankshaft (left hand thread), remove clutch thrust plate, springs and retaining nut and remove clutch assembly, remove rotary valve cover, replace seal.  This can be done with the engine in the frame of course, but you will have to move the footpeg.  When reassembling, be sure to align the punch marks on the pinion, clutch gear and alternator gear.

Plan to buy or make a new side cover gasket.
Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: robinkwmack on October 30, 2019, 04:56:28 PM
So after a month and a half of trying to get in touch with Richard, I finally was able to get parts ordered. Put in the new piston and bike runs great. BUT, I have a new dilemma. Fixing the underlying fuel issue that is causing the roasted pistons.

So, thank you OldSwartout for that info in regards to the oil seal. I think mine might actually be fine, but might replace it early spring before the next riding season.

So now onto the underlying issue in regards to fuel to the right cylinder. I can get fuel if the float bowl is completely empty. No overflowing and fuel stops, but when the bike is running, especially under throttle the fuel line is running out of fuel and filling with air. This happens with the gas cap on and off, the petcock is clean and clear and flows freely when disconnected, when the float needle is not in the closed position fuel flows freely through the fill valve. So it seems that fuel is not flowing from the tank to the right carb when everything is sealed up and "tight". I cleaned the jets and needle again. My question is if there is some sort of air vent on the carb that I might be missing that is causing this vacuum to occur.


This is starting to get really frustrating and makes it so I can only ride for 1-3 miles before the fuel in the line between the petcock and carb is drained.

Any thoughts or suggestions would be greatly appreciated. Thanks!

Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: Bridgestone Man on October 30, 2019, 05:58:30 PM
I have an idea, try trashing the guy where you got your parts.  I am sure this will help. 

Sam Keys
Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: robinkwmack on October 30, 2019, 07:43:45 PM
Can't tell if this is sarcasm or not. I was just stating the reason why I wasn't back to this post any time sooner and it was due to not having the piston to put back in. Not trashing on anyone.



I would like to keep the discussion in these comments relevant to the issues at hand. Thank you.

Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: Jeff Bar on October 30, 2019, 08:00:35 PM
 popcorn
Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: dcr on October 31, 2019, 11:08:29 AM
I have an idea, try trashing the guy where you got your parts.  I am sure this will help. 

Sam Keys

^^ Wow - that came out of nowhere ^^
Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: Jeff McBrayer on October 31, 2019, 11:33:52 AM
I understand what Sam was saying.  Jeff
Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: OldSwartout on October 31, 2019, 06:00:02 PM
The carbs vent two ways. The main bowl vent is on the left side, the overflow tube can also serve as a vent. The main vent is large enough that it would be difficult to plug accidentally, but would be worth checking.

Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: BRT-GTR on November 01, 2019, 04:54:38 PM
         Think you've baffled everyone with your problem, so will have go. Re-read the whole post and comment as follows :-
        Use 95oct fuel or above.
        40:1 yamalube is a low ratio, these engines were never designed for such low ratios,(these oils didn't exist in the 60s) increase to at least 32:1 or higher, will give the engine more protection.
        '' timing close to what it should be'' is not good enough for a high performance 2stroke. Points opening exactly as timing pin drops into crank slot, that's good enough !!

    The fuel flow issues you describe defy logic. Not doubting you, you can only state what you see. I don't understand why the line will not stay full of fuel. Do other RS200 owner find the same ?, does the fuel tap construction prevent air venting back into the tank ? IE, an airlock.

   You either have a carb with a fundamental fault or there is more than one fault. Right float leaking when engine running would allow fuel to drain into carb and engine but would give poor running due to rich mixture. Float valve sticking would reduce fuel flow, viton rubber tipped valves can stick in the seat and have a wire clip that attaches to the float tang to drag the valve open. Worn float pin pivot holes are common and will prevent accurate float height setting. I would try a different carb or swap the carbs over and see if the problem transfers to the left side.

 Alternatively, you may have an air leak on the carb spigot, disc valve cover or the crankcase joint, all of which would result in a weak mixture. A crankcase pressure test would prove the case joints. That's the best I can offer at this time, maybe others can chip in with any new suggestions.
                                                                                                                            Brian.


   

Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: dcr on November 04, 2019, 05:06:35 PM
Any chance the fuel line you are using is to narrow to carry enough volume when running?

Just a thought.

Dan
Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: robinkwmack on November 10, 2019, 11:43:24 AM
Hey there, sorry for the delay! I did not get any notifications about responses to this thread and I am still stuck with this issue and as one of you said, it really does defy logic. I have gone through the carb multiple times with carb cleaner and I am still having the same issue. I even adjusted the float to allow a little more fuel to see if that was the issue but nope, and ran like it was getting too much fuel.

I will start using 91 octane and change the ratio as you recommended. I have been using only yamalube as my mix oil. Going to tear into it all one more time and see if one of the vents is clogged, but I am PRETTY dang sure I have sprayed out every last crevice in that damn carb. I doubt it is the float valve sticking since when I remove the float bowl fuel will gush from the tank as normal (through the fuel line into the carb). So it seems to be refusing to let more fuel in once the float bowl is filled for the first time, when running or not. It is a true anomaly. Last thing I need to iron out before I can truly ride it more than 3 miles. Runs great except for this issue and maybe needing some new clutch plates, but that's for a later date.

Thank you all again for chipping in, hopefully I can get at least one solid ride in before it's far too cold here in Western Massachusetts.

I'll be checking back here more frequently than I have before now that I know responses don't always send notification emails.
Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: rwgibbon on November 10, 2019, 02:53:20 PM
I just finished getting a 350 GTR running and no matter how many times
I cleaned and adjusted the right carb I could not get it to run properly.

The right carb did not appear to be letting fuel get through to the right
cylinder. Even though it always had fuel in its bowl.

I finally put a different carb on it and it now is running like it should. It idols and
responds to the throttle.

No matter how good you think you have cleaned the carb sometimes there is
something in one of the galleys you just can't clean.

Have you tried swapping the carb's?

That could help identify if it is a carb problem.

Good luck and don't give up.

Regards

Randy


Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: robinkwmack on January 12, 2020, 02:24:54 PM
Alright, since global warming has decided to show its nasty head with a 65 degree day in January here in Massachusetts, I finally had some motivation to try and dive into this fuel issue again and STILL NO LUCK!!!.

So! I put on yet another aftermarket petcock, this is the second one because the stock petcok was long gone and if I remember correctly leaking. I think I just tossed it?

These are the petcocks that I Have used, has anyone used these without issue? I am starting to think this might be what is wrong.

https://www.ebay.com/itm/BRIDGESTONE-200-SS-FUEL-TANK-SWITCH-VALVE-PETCOCK-ASSEMBLY-22mm/142089114440?epid=2239374381&hash=item21152bd348:g:p14AAOSwK89ZwuER

So, I am still getting the same issue, no fuel to the right carburetor AFTER the float has been filled. The line and float will fill as they should, then I will ride the bike for 1-3 miles and an air pocket will form in the line up at the carb as if a vacuum has been formed.....But only on that one fuel line. Left carb is fine. Today I put the new petcock on, removed and VERY DEEPLY cleaned the right carburetor, thought the issue was fixed, got to a coffee shop, and walla! Air pocket is back.

Again, left carb is fine, both carbs are adjusted as they should be, bike runs like a top, just will eventually run out of fuel on the right side. (I have already replaced to pistons thank you very much, heh)

Also, tank is very much venting, I can hear it, I even drilled extra holes to be safe, this issue occurs with the cap on or off, does not matter. I am able to fill the fuel line by leaving the petcok on and pulling the fuel line letting fuel spill into the line and then plug it back in. (how I got home)

So here are my only thoughts, I bumped into a buddy of mine and he mentioned could be ignition timing is slightly off and that's causing back pressure to build up just slightly. I would think if this was the case it would not run like it does (well).

My other thought is that these aftermarket petcocks are just not meant to work with these bikes. Sadly mine is long gone so I will have to source one from Richard, or find an old crusty one and rebuild it.


If I can't get this figured out I will just be selling this bike and moving on. Heck, my dream bike is for sale  only about an hour or so away so my motivation to keep figuring out this dang issue is dwindling.

Hope to hear from some, or all of you shortly and again, thank you for all of the help thus far.
Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: BRT-GTR on January 13, 2020, 12:46:08 PM
        These two strokes can be fustrating !, I've spent months trying to cure a light load running issue without success. Can appreciate how teed off you are.

         I have one of those fuel taps and in theory the outlets/filter chamber could airlock. Try swapping the two outlet fuel tubes over on back of tap to see if the fuel issue changes to the opposite carb.

        If OK, I can only suggest checking the float on the right side to see if it is catching on the side of the float bowl. I have found the floats can vary in where they are soldered to the cross arm.  Beyond that I'm stumped.
                        Brian.
Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: robinkwmack on January 13, 2020, 01:01:02 PM
Hey, I appreciate the reply and thanks for appreciating my frustrations, ha. I will try flipping the fuel lines and see if if it switches sides, but leave the same fuel line to the carbs, just switch it at the tap.

I did have an issue with the left float where it had a hole in it but that was fixed, is there a way of making it so this float fits better if it is in fact catching or do I need a new float? It's just odd because if the float was catching I should have running issues, either too little or too much fuel to that side. The thing runs like a top though, just will run when cold and then won't get fueled once warmed up and ran.

Another thought I had is maybe the fuel line is collapsing somewhere? It is new and pretty heavy duty so I highly doubt it, but did notice the line gets pretty flexible once the bike is warmed up. I might remove the line and open up the carb boot hole for it a tiny bit and see if that does anything.

Any more thoughts are greatly appreciated seeing as I am kinda hitting a dead end and considering just moving back to the trusted 4 stroke thumper world.

Thanks again.
Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: OldSwartout on January 13, 2020, 04:29:52 PM
If a float is catching or dragging inside the float bowl, just bend the bracket a little. I've done that a time or two.
Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: BRT-GTR on January 14, 2020, 07:33:09 AM
            Another thought based on your response above. What is the internal diameter of the fuel tube you are using. needs to be at least 4mm to provide adequate fuel flow.
           We are limited in the choice of fuel tube we can use due to the diameter of the hole in the carb boot. A thick wall tube might be closing up sufficiently to restrict the fuel flow, so that's worth examining.
Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: robinkwmack on January 14, 2020, 09:41:47 AM
I can't remember the exact measurements on the fuel line but it is larger than stock due to the larger outlets on the aftermarket petcock. I did drill the carb boot holes slightly bigger but I think I might need to make them slightly larger. My thought is, everything seemed fine for while on my ride, at least, longer than usual, but once I stopped and checked after everything had warmed up, that's when the fuel stopped flowing. So I am thinking once the bike gets warm and the fuel line gets warm and pliable, that's when it might be collapsing. Now it is back to normal cold temps outside so I will try and get it warmed up to temp without freezing my ass off and see if a larger fuel line hole in the carb boot helps at all.


Problem is, I did already talk to my bank about a loan for this new (1979) bike.......Which is my dream bike, but regardless I would like to get this thing to have no issues so I can either enjoy it fully, instead of only 30 minute rides, or sell it for top dollar.

Thanks again for the help all, I will report back.
Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: OldSwartout on January 14, 2020, 10:01:08 AM
Another WAG, but If you are using larger fuel line than normal, do you have it tightly clamped to the spigots on the petcock? BRT-GTR asked if it was possible that an air lock wouldn't vent the air back into the tank. I think that is the case on any bike with a sediment bowl on the petcock. The fuel doesn't come straight from the tank, but goes into the bowl first. Air would have to travel up the line, then downward into the sediment bowl, below the fuel level in it, to get back up to the tank, keeping it trapped in the line.

I have also seen plastic/rubber lines with a hairline split or slit that would allow air in, in case of any vacuum at all, but won't leak liquid out. You might try replacing that line and making certain it is clamped tightly to the petcock.
Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: robinkwmack on January 14, 2020, 10:39:27 AM
Thanks for the recommendation, the fuel line is new and is VERY tightly press fitted onto the outlets, no clamps needed. The fuel line is either 1/4" ID or 3/8" ID, I do not recall exactly. I do know that it is a very tight seal. The issue seems to arise once the bike is warm, thus why I am leaning towards a collapse down at the boot. Going to let the bike idle until it's hot so I don't have to freeze my ass off and enlarge the boot fuel line hole slightly and see if that changes anything. Should have an update by tonight.
Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: robinkwmack on January 14, 2020, 04:17:20 PM
Okay, so.....I just got back from a ride, the same distance as the other day, and I am still having the issue. This is with the fuel line hole into the carb opened up a little bit more and a brand new fuel line.


BUT!!!! I have an idea........The banjo bolt on the carb is still using the original fiber crush washers........wish do weep a little bit.......I am wondering if this is my issue, if it is pulling enough air in through it to cause this problem. It would make sense because it seems to show up when everything is hot.
Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: robinkwmack on January 14, 2020, 06:26:49 PM
Well frig.......I tracked down 4 aluminum washers and they were the absolute last the motorcycle shop had in a random mix box of washers, lucky me.....unlucky mean, turns out the threads for the banjo bolt were beginning to strip (inside the carb) and I ended up driving it home all the way. The leak got worse and worse the more times I tried to install the bolt........I think the shop I brought it to caused this issue, just as they had stripped a bolt on my oil pump.....So, it's either time to helacoil the inlet threads, or get a whole new carb............The saga continues and Richard hasn't gotten back to me in regards to other parts yet. Hoping to hear back soon.
Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: robinkwmack on February 01, 2020, 05:42:21 PM
Well folks.....I think this may be the end for me and this ole Bridgestone. I picked up a used carburetor because I thought the issue might have been the stripped threads on the fuel inlet letting air sneak in......Well cleaned the carb up good, installed it and the bike ran like a top still......but then the air pocket returned. Again, only on the right side and not the left. It only occurs when you are giving it throttle, doesn't seem to occur during idle and only comes about ones the bike has warmed up. I am perplexed

BRT-GTR you had mentioned checking crank case pressure. How would I go about doing that? Could this be causing a fuel issue? I am just convinced it is an issue in the carbm, fuel line or petcock seeing as air wouldn't be coming from the engine backwards into the fuel line. It may even be the aftermarket petcock, but it only happens when the bike is warm, which wouldn't effect the petcock, unless it is an airlock occuring and it takes that much time to really build up the vaccuum? But that doesn't make sense to me


BUT
Lucky for me, I found my dream motorcycle that happens to be a 4 stroke and a motor I already know inside and out so this was my last attempt at ironing out this issue before selling the bike and figuring out what I would be listing it at. It's sad because it runs so damn good, I am the second owner, first owner parked it dead in 1971 and I got it running in 2019 even adding turn signals! It's been really fun to work on, it is really fun to ride and I would keep it around if this issue was not present.


I will be listing it locally on craigslist (now at the lower price because this issue is still present) and will also list it on here. Feel free to DM me about it as well.

Thank you all for your help, I will keep tinkering on it until it is sold, but my main focus will now be on this new bike.

Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: BRT-GTR on February 03, 2020, 03:32:52 PM
    Sorry to hear you're giving up on the Bridgestone but I might do the same in your position.
    We are all perplexed by this one !!
       I'm pretty sure it's that aftermarket fuel tap air locking. The outlet drillings are right at the top of the filter chamber, there's nowhere to accomodate any air that comes back up the outlet tube. This air is unable to vent. My GTR taps are drilled slightly down the chamber and can still pass fuel with a small air build up at the top of the chamber.
       Alternatively, long shots, have you tried swapping the right coil or condensers. Both can fail when warm and don't assume that new old stock parts are ok. That's caught a few people out.
        Good luck, Brian.
Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: AlanJohn on February 04, 2020, 09:16:44 AM
l've got a few Bridgestones and all of them get an air bubble in the fuel tubes but it's never stopped one running and l ride them all on a around trip of 28 miles with no issues l personally don't think that your problems are with the fuel lines and air bubbles
Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: BS Mechanic on February 04, 2020, 01:31:04 PM
I'll second AlanJohn's experience.  I've noted the air bubbles in my 350 ever since I replaced the original black tubes with clear ones back in about 1970.  As he says, it's never caused any problems in about 50,000 miles of riding. 

My suspicion is that air gets into the line due to engine vibration, but only enough to allow a few bubbles to come up from the carb bowls.  The fuel flows around the bubbles just fine, you just don't see it.  It really doesn't take much fuel flow to run the engine.

I suspect that either you have other problems causing overheating or piston damage, or you're just chasing ghosts.

Unfortunately I don't have any suggestions to help figure out if the problem you are seeing is actually stopping the fuel flow or just visible bubbles.

 

Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: robinkwmack on February 05, 2020, 11:47:49 AM
Well seeing as I have melted holes in and replaced two pistons already due to the fuel line running dry, this is not just a normal air pocket. I'm thinking about drilling the holes inside the petcock larger and seeing if that helps at all. I am starting to lean towards the aftermarket petcock, but the problem is, this is the second one, same design though, but the same issue. It is clear that zero fuel is coming from the tank once this issue starts up, thus why I am leaning towards air lock in the petcock.

But out of curiosity, how does one know if they are over heating? Also, how would this cause the fuel line issue? I am following the fuel/oil ratio that Richard recommends, fuel is plenty, lubrication is plenty and the bike runs like a top, pistons and rings are in wonderful shape too.

It's extra odd because I rode around for 200 miles with the aftermarket petcock, fuel issue happened after local shop touched it. He deleted the oil pump (one of the bolts was leaking) it is still attached but he removed the drive gear so air wasn't pumped in through the oil tank.

I'm going to try and drill out the petcock holes larger/maybe even just make it so it always flows (no on off, which will be a pain and require draining any time I need to work on it.)
Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: Jeff Bar on February 05, 2020, 12:54:13 PM
robin i do not mean to be a smart #%@# but if the problem developed after shop took off oil pump, perhaps that is where the problem is. just trying to help.  see  you Jeff
Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: OldSwartout on February 05, 2020, 01:06:48 PM
I don't think deleting the oil pump could possibly affect the fuel line; however, the line from the oil pump to the right side rotary valve intake could leak air into the intake stream if not properly capped. The line runs from the oil pump, then across outside the crankcase behind the cylinders to a fitting on the right side of the crankcase, where it matches up with the rotary valve cover inside, which routes the oil to the intake throat. If that line is open anywhere along that route and sucking air, it very well could cause your issue with overheating and destroying pistons.

Also, if the oil pump is still in place, as it sounds like in your post, depending on the position of the drive shaft in the oil pump, and if the oil inlet line to the oil pump is disconnected or the oil tank empty, it may be possible to suck air through the oil pump into the line to the right (or left) side. If you are not going to use the oil pump, the fitting where the line attaches to the right side crankcase should be securely capped. Likewise, the fitting where oil enters the left side rotary valve cover should be capped.
Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: BS Mechanic on February 05, 2020, 07:41:11 PM
Is it possible that something is limiting the fuel flow, but not completely stopping it?  I can recall such a case, where the fuel flow was obstructed enough to limit fuel flow to just slightly less than the engine required.  It didn't become evident while driving till the fuel bowl got nearly empty.  The engine slowly got leaner and leaner, and finally just slowed down.

I found it by disconnecting the fuel line from the carb, and watching the fuel flow rate into a separate container over several minutes.  Initially the flow seemed good, but it slowed to a much lower rate, not enough to supply the engine at anything but idle.  The root cause was some sort of "fuzz" in the fuel inlet tube in the tank.  It was slowing but not stopping the fuel flow.
Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: AlanJohn on February 06, 2020, 03:44:17 AM
l'd take it back to the place that obviously caused the problem sort the pump out put on a new one or whatever it needs and from what you've said that should be an end to it
Also the oil pump is a very simple part to replace and in my opinion should be on the bike and working why would you not have it there?
Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: BRT-GTR on February 06, 2020, 02:57:49 PM
    Robin,
           This is the first time you've mentioned removal of the oil pump by local shop. As you say the bike ran fine for a few hundred miles before their work. I have to agree with Jeff and Alan, something they have done (but I can't say what) is likely to be the root cause of this issue. OldSwartout has suggested some possible causes. Take it back and give them a good talking to !!   Maybe, print this topic and show them.
    Question - did it previously run fine all the time with the after market fuel tap, not just when it was cold..                                                                         Brian.
Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: moonpup on February 06, 2020, 03:24:56 PM


IF it's the aftermarket petcock....

Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: AlanJohn on February 06, 2020, 04:09:41 PM
l like that Mike
Title: Re: Need Help: 1969 RS200 MkII, Melting Hole In Piston & Crank Seal Leak
Post by: BRT-GTR on February 09, 2020, 02:45:48 PM
       Depends on your budget, how much you are prepared to pay, what parts are worth to you, parts availablity and your judgement of quality.
     Higher cost should equal better quality but not always the case these days. There are a lot of greedy sellers / service providers out there.
        Or, am I just getting cynical in my old age ??
                                                                                  Grumpy old git.  Haha.