Author Topic: Racer Resurrection  (Read 70588 times)

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Offline bsracer

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Re: Racer Resurrection
« Reply #260 on: September 11, 2019, 12:04:13 PM »
I looked at my carb settings. I guess I tried some different things and didn't record them. I have the following:

4f15 needle
25 pilot
190 main
24/1 fuel mixture.

I had the clip in the bottom position and the mixture screw was farther out than I can remember. It was running rich last time out but I had also just reamed out a set of needle jets. My carbs are different than yours with a mix of jets from a few different carbs. I run 2.0 fuel valves as a replacement to the 1.5 stock ones that come in the carbs. I also swapped the float bowls with the external main jet type to some from a more modern 65cc mx bike with the large bottom hex screw access. I use the needle jets from these as well because they have the plastic shield around the main to keep down frothing. These carbs also have the neoprene black floats instead of the brass ones in the SR carbs. I've rattled more than a few of those apart.

paul

p.s. we'll see how it goes at Barber

Offline al_pritchard

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Re: Racer Resurrection
« Reply #261 on: October 05, 2019, 09:52:54 AM »
I think you called it Brian. Unfortunately.

Tore down the top end to double check, and sure enough it's not to spec. Not even close. When I sent the cylinders off to Millennium for Nickel plating, we settled on a 0.002" clearance between piston and cylinder. I included the Wiseco pistons with the cylinders so they could be used for measuring the proper bore size. And everything came back in exceptional condition. Except as it turns out the cylinder bore size - are cylinders like people, expanding slightly over time?  ;D

Looks like what I actually have is 0.015" piston to cylinder clearance.
Bore: 1.9685"
Piston: 1.9535"

Rookie mistake, I ASSuMEd that the parts would be within speck. And it looks like they are not. I think my assumption was reinforced by what I thought was the correct ring gap. Such a learning curve...

Wiseco ring gap recommendations look like: Bore Size in inches x 0.005".

My ring gap with a feeler gage measures at 0.016". Looks like it should be closer to 0.009"

Time to jump on a call with Millennium.
Al Pritchard
Highlands, NJ

BS175 Racer

Offline al_pritchard

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Re: Racer Resurrection
« Reply #262 on: October 14, 2019, 12:52:15 PM »
So I had a good chat with Millennium yesterday. I really recommend them! They were amazingly supportive in trying to help me track down where the issue might be. And unbelievably patient in dealing with someone with out an engineering, or two stroke development background.

From Millenniums notes
1.9697" - Cylinder
1.9695" - Piston

I don't have the best calipers - simple digital ones. But if I set it to 1.9695", I can ever so gently slide it down the bore.

The problem comes with the piston size. They have 1.9695 in their notes, but I get  1.9550" on my caliper. Giving us a piston to cylinder clearance of 0.0147 (about the 0.015" above)

I'll get them back on the phone later this afternoon. Hopefully they have a note with the serial, or part number for the piston I sent in. Otherwise, this is going to be a costly mistake.


By the way the measurement I get for the RM cylinder is 1.9550"
« Last Edit: October 15, 2019, 07:41:09 PM by al_pritchard »
Al Pritchard
Highlands, NJ

BS175 Racer

Offline BRT-GTR

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Re: Racer Resurrection
« Reply #263 on: October 14, 2019, 03:49:28 PM »
    Al,
         As you sent them the cylinders and pistons, I don't see how the fault can be anyone's but theirs. I assume you have fitted the same pistons to your engine.  I use digital calipers all the time and find them pretty accurate.
        Surprising but sometimes they just get it wrong. Have now tried to fit two sets of Renntec engine bars to my Kawasaki W800. First set, rear mount bolt hole was 10mm out of position, they admitted the jig was damaged. Second set, would have had to  force front mounts in by 10mm to get them to fit so back they went. They have gone quiet on me and are having to sourcing a similar bike to check if bars are correct. I await their findings !! Had to contact Managing Director before receiving any explanation from them, lesson :- complain to the top man.
                             Brian.
« Last Edit: October 15, 2019, 05:15:23 AM by BRT-GTR »
Unspoiled by progress.
I'm so glad I grew up in the 60s & 70s. I did so much stupid stuff and there's no record of it.............Anywhere !!

Offline vinny g

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Re: Racer Resurrection
« Reply #264 on: October 15, 2019, 04:19:56 PM »
Hi Al.
 This is a carb setting issue, it's as simple as that. Any issues with primary compression would cause the opposite problem to the one you have....it wouldn't want to start but once running woud improve. I've had my race engines show 90psi with single ring pistons on the only time I've ever checked it. This was at a meeting where a fellow competitor with a 200 Yamaha had a test gauge and asked if he could compare the two bikes. From memory the Yam was around 135psi. At the time I said I wasn't that bothered by any reading as I knew the engine was perfect. Four wins over the Yamaha over the weekend just confirmed that.
 
  Paul called it: Go to extremes with carb settings until you see improvements and take that as a pointer. You'll be amazed at the difference changes can make, quite literally from unrideable to race winner. I think you're rich on the needle/needle jet. I'd be looking at 4D3/4 needle and an N series jet holder. Mess around all you want with main jet etc...you won't go anywhere until that combination, on a small discvalve engine, is near perfect.

Remember: over standard you now have bigger carbs, inlet ports,disc valve timing and an exhaust system calling for fuel.

Lastly, don't give up. I started exactly where you are now and after a season of pushing and cursing sorted it in an hour. Experience is hard earned.

 All the best, Vince

Offline al_pritchard

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Re: Racer Resurrection
« Reply #265 on: October 15, 2019, 07:42:22 PM »
UPDATED THE POST ABOVE TO CORSS OUT SOME BAD MEASUREMENTS

Imperial measurements now have Paul, and Vince in the lead for what is going on. Sorry Brian.

Thanks for the encouragement Vince, I'm not giving up yet. Loving the learning curve.

The measurements from Millennium are 100%. It's the nut holding the caliper that's off. Im my case it was HOW I was measuring the piston. So a little lesson for those playing along at home. When measuring a piston you do it from about 2/3 down from the top. I learned this, and a lot about thermal expansion today. :-)





Smallest needle I have is a #4D8. And it doesn't look like JetsAreUs has anything smaller. So I'll try that as a start - just because I love to hear her run. And go on the hunt for a #4D3.
Al Pritchard
Highlands, NJ

BS175 Racer

Offline SR-175

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Re: Racer Resurrection
« Reply #266 on: October 16, 2019, 05:03:01 AM »
Hi Al,

I have one #4D3 needle. Maybe someone else here has another ?

I doubt I have another but will have a rummage one more time to be sure.

ray

Offline vinny g

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Re: Racer Resurrection
« Reply #267 on: October 16, 2019, 12:55:52 PM »
 I'll look through what parts I have as I no longer run 22mm carbs. I know I have a pair of 4D8 needles that, I'd guess, you would want to run in a N4 ish needle jet holder. I think you're too rich on the main jet also but until needle/needle jet is correct it won't matter too much. I'd think 190/195 is about right as a starter. If the needle jets you have, or can obtain, take the round slot head jet then I'm going for a 110.

Interestingly, I still run the same sort of combination in 28mm carbs but from the 5 series.

Offline al_pritchard

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Re: Racer Resurrection
« Reply #268 on: October 16, 2019, 07:07:50 PM »
What is the series of the VM22 Needle Jet?

It’s stamped 132 then the Mikuni square and O-0 under it. But JersAreUs doesn't have a 132 series.

I can't find a reference to a 132 series any ware. It looks close to a 175 or 176. But that is the case, it looks like an N-0 is not available.



« Last Edit: October 17, 2019, 09:34:00 AM by al_pritchard »
Al Pritchard
Highlands, NJ

BS175 Racer

Offline bsracer

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Re: Racer Resurrection
« Reply #269 on: October 17, 2019, 12:53:33 PM »
I just took those needle jets out of my jet box because I'm not using that type. I'd look for them and see what I have. I thought I had O-0 had maybe O-6. Similar problems at Barber this year. Hot and humid. Went from a  190 main down to a 160 and was still too rich.


paul

Offline bsracer

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Re: Racer Resurrection
« Reply #270 on: November 09, 2019, 11:04:45 AM »
I finally found those jets and they are 132 O-6's


paul

Offline al_pritchard

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Re: Racer Resurrection
« Reply #271 on: November 12, 2019, 06:02:07 PM »
Before the temperatures plunged, I drug the bike out yesterday. Wanted to test the 170 Jet, and have one more tries before it was on to fix all the little things I'm not happy with over the winter.

As part of documenting, and double checking everything before trying to start again. I found a problem... Seems when I set the timing last, I must have bumped something as I was frighteningly off. It was way out - and by way out like in the single digit degree BTDC. It was a scant 0.007 BTDC.

So it's no wonder it has no power delivery, and was so exceedingly rich. It never had the opportunity to burn the fuel before it flung it out the exhaust. Was basically acting like a big self propelled fuel pump.

Needless to say I'm a bit embarrassed. But for future builders, and amateur engine tuners. Triple check the timing!

Put the 20 pilot, and 200 main back in. Opened the air screw up 3/4 turn. And pushed as fast as I could. BANG, GROWLE! (Not quite that fast, it actually took a couple tries. But it was cool so...)

So with that we go into the winter with the big problem solved. It runs, and makes power.
Al Pritchard
Highlands, NJ

BS175 Racer

Offline bsracer

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Re: Racer Resurrection
« Reply #272 on: November 14, 2019, 10:12:40 AM »
Glad to see you got it figures out! I've got a mountain of work to get done for next season. Still can't believe AHRMA got Laguna Seca in February!!

paul

Offline SR-175

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Re: Racer Resurrection
« Reply #273 on: November 15, 2019, 03:26:58 AM »
Congrats Al !!!

Online craig641

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Re: Racer Resurrection
« Reply #274 on: November 26, 2019, 10:36:38 PM »
Paul, 

Are the series 132 needle jets you're using the bleed type?  And do you remember where you found them?

Craig

Offline bsracer

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Re: Racer Resurrection
« Reply #275 on: November 27, 2019, 11:26:21 AM »
Hey Craig.

I run different carbs at the moment so I'm not using those. They are the bleed type. The 132's come in the stock SR175 racer 22mm carbs and the Kawasaki A1 22mm carbs. I just found a similar 155 O-4 but I only have one and have no idea where I got it from.

paul

p.s. Did you get to run the bike with the new pipes yet? Laguna Seca in Feb!

 


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