Author Topic: Racer Resurrection  (Read 69527 times)

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Offline OldSwartout

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Re: Racer Resurrection
« Reply #220 on: January 12, 2019, 08:35:06 PM »
175 Crankshaft Degrees vs. piston stroke from TDC.
« Last Edit: January 12, 2019, 08:48:58 PM by OldSwartout »
Karl Swartout
Mooresville, IN
BS175 Roadracer
BS350 GTR

Offline al_pritchard

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Re: Racer Resurrection
« Reply #221 on: February 13, 2019, 04:16:33 PM »
When we last tuned into our program...

WARNING - If you have a crease, or a crack in your tube. Don't do this. Go get a new tube.

Im my continued failed attempt to align my rear wheel with the front wheel. I came to the realization that the fork tubes were a little bent. Making it exceedingly difficult to get the front spaced equally between the forks. Not out a lot, but just enough that by the time you get to the end of the fork tube it was easily noticeable.

Since I couldn't find a shop willing to straighten them. It was time to buy a small press. I would encourage anyone with this issue to "do it yourself". The process was super simple. Plan the tube on a set of v-blocks ($40 on eBay). Get out a dial indicator to find the high/low spot - slowly rotate the tube in the v-blocks and keep an eye on the indicator. My bend was just below the lower triple clamp. When you identify the true high spot, start pressing - gently. I would put a little pressure on the tube. Release. Then rotate the tube to see how much bend I took out. Keep repeating the process until you get the bend out.

It's a good idea to put something between the tube and the ram - v-block made out of wood, strip of wood, thick gasket material, what ever. You just want to keep the ram from making the chrome.

So tubes are now 0.009in and 0.008in out. Or to make it sound better, on side pushes in 0.0045" in, and the other side sticks out 0.0045in. I can live with that.

Now back to aligning that rear tire. Spring is going to be here soon, right. I'm dying to start this thing.





Al Pritchard
Highlands, NJ

BS175 Racer

Offline al_pritchard

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Re: Racer Resurrection
« Reply #222 on: March 11, 2019, 03:15:34 PM »

Not a lot to report on. Everything is finished, just need to add oil and fuel. So stay tuned for warm weather and an update on the starting front.



I added a set of quick disconnects for the fuel lines. Will probably replace then once the big gremlins are worked out. I couldn't work out a tidy way to have both the quick disconnects and a T connector. I'm currently assuming that the tank will be on and off a lot in the beginning, and the quick disconnects will be valuable.

Al Pritchard
Highlands, NJ

BS175 Racer

Offline Jeff Bar

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Re: Racer Resurrection
« Reply #223 on: March 11, 2019, 03:59:19 PM »
Al. You really do nice work, everything looks so good I am pretty decent at general restoration but wish I do you level of fab work thanks for posting I really enjoy looking at your post. Jeff bar

Offline anotheroldtrailrider

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Re: Racer Resurrection
« Reply #224 on: March 13, 2019, 01:26:42 PM »
Ditto the appreciation for all the build information.  I just stumbled into a Mach II RS that's just bad enough off to justify some customization instead of pure restoration, and although I've been around bikes all my life (I'm an old guy - 75), this is my first BS.  It's really nice to see what's available, what works, etc - I've wanted to add a little two stroke to my garage, and this was the perfect candidate.

Offline Mike Anderson

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Re: Racer Resurrection
« Reply #225 on: March 13, 2019, 03:47:00 PM »
Pictures as it goes. Good luck with the project
Later Mike

Offline anotheroldtrailrider

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Re: Racer Resurrection
« Reply #226 on: March 13, 2019, 10:22:59 PM »
I just happen to have a couple Kehein PE26's from KX100's and am contemplating how they might be mounted to custom disc covers with the shortest inlet tract possible (I have a very nicely equipped machine shop focused exclusively on motorcycles) - anyone experiment with other carb's this large?  Also, the factory Tune up manual provides dimensions for a couple variations of expansion chambers for 175's, do you happen to have this info for 200's?  A few years ago I hydroformed a megaphone exhaust for a project and have wanted to try making a pair of expansion chambers, ever since.  The bike has great compression on both cylinders and shifts perfectly, but I plan to take it down to the crank, anyway - this bike will get used regularly so I'd like to start from the inside out - especially if I'm going to lean on the engine.

Offline bsracer

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Re: Racer Resurrection
« Reply #227 on: March 14, 2019, 11:23:42 AM »
You might be able to run some 26's but there's a lot of other work to be done. I run 22mm because AHRMA has a restriction on the Bridgestone for the class I run. The info in the tuning manual is a bit outdated these days for expansion chambers.

paul

Offline OldSwartout

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Re: Racer Resurrection
« Reply #228 on: March 14, 2019, 11:51:29 AM »
You might be able to run some 26's but there's a lot of other work to be done. I run 22mm because AHRMA has a restriction on the Bridgestone for the class I run. The info in the tuning manual is a bit outdated these days for expansion chambers.

paul
I agree with Paul, the expansion chamber info in the tuning manual is outdated, although it worked OK back in the day.  Modern chambers are larger diameter, with tapered head pipes, multiple tapers on the cones, etc.  The first set my brother and I built for my racer based on Bell's Two Stroke book seemed to work OK, but I found out later the  power curve had a BIG drop in the 8-9000 range.

There are a couple issues with 26's: space in the housings and difficulty getting a matching port area going into the crankcase.  It's difficult getting a corresponding passage to match the 22's, the radial distance you have to work with is limited.  I think you would end up with a 26mm carburetor feeding the engine through the equivalent of a 22mm orifice in the crankcase wall.
Karl Swartout
Mooresville, IN
BS175 Roadracer
BS350 GTR

Offline anotheroldtrailrider

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Re: Racer Resurrection
« Reply #229 on: March 14, 2019, 07:29:42 PM »
Beautiful valve covers, I hope I can produce something along that line.  I was a Suzuki Can Am Vespa dealer in the 70's and had fun building rotary valve Can Am's, so this is a blast from the past in more ways than one.  Yeah, I agree about the carbs - I just happened to see them lying there, alone, waiting...  Anyway - like I said, I want a bike I can have fun with while I'm dodging Buick bumpers.  It'll stay a 'sit-up standard' but tucked in a little, solo seat, etc with slightly updated suspension hidden as best possible.  Any links to the expansion chamber dimensions with comments about their power characteristics would be greatly appreciated.  Obviously related, since the stroke is the same as the 175, is the porting info reasonably useful?  Since this bike doesn't have to meet race or show class restrictions I'm guessing I might have a few more choices throughout the build - I just want to stay somewhat faithful to the basic bike and was delighted to find this group of enthusiasts.  Thanks, guys...

Offline anotheroldtrailrider

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Re: Racer Resurrection
« Reply #230 on: March 24, 2019, 09:00:43 PM »

Yea!!  Looks like the title is no problem, so I'm ready to start on the 200 project.  I'll pull the motor completely apart for at least a fresh top end and porting & intake rotor trim along the lines of the scrambler section of the tune-up manual.  I also like ceramic in exhaust ports & combustion chambers, so maybe that as well.  After reading the discussion about the stepped center pin, if my crank needs anything I'll do that mod, and am very interested in the recommendation for RM100 rods and pistons.  The KX100 26mm carbs I mentioned earlier will physically fit in both sides (I wasn't sure about the right-side case), so now I need to decide if a mildly ported motor with only a moderate compression increase use that much carb.  In the meantime, I'd like to start fabbing the pipes - I see several discussions about pipes and how they've evolved, anyone willing to suggest dimensions for something oriented towards mid and upper mid-range?

Thanks, Art

Offline vinny g

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Re: Racer Resurrection
« Reply #231 on: March 25, 2019, 06:13:24 PM »
Hi Art. I did a post a couple of years back, on here, about the specifications of my 175/200 racer including the spec of my pipes. I'm on my phone and unable to find it for some reason, but type UK 200 racer into search and it may help you. Alternatively, search via my name. Anything you need to know, tune up wise, is on that post and tried and tested.

Cheers, Vince

Keep up the good work, Al! Bike is looking good!

Offline anotheroldtrailrider

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Re: Racer Resurrection
« Reply #232 on: March 26, 2019, 05:11:42 PM »
Hi Vince - thank you very much - I'll do update posts & pic's once I finally start pulling things apart, but should the top end need drastic work, anyone care to comment on the maximum safe overbore (again - no race rules, this is a street bike)?

Offline OldSwartout

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Re: Racer Resurrection
« Reply #233 on: March 26, 2019, 05:31:44 PM »
Sounds like a fun project and Vince's specs should make a really fast bike.  As far as overbore, since those had a chrome bore, Bridgestone didn't make oversize pistons for the 200, so you'd have to look for something from another brand. You would have to consider piston pin size, deck height, crown and overall length. Vince's post said he ran modified Suzuki X7 or Kawasaki KX100 pistons, so start there.
« Last Edit: March 26, 2019, 05:39:30 PM by OldSwartout »
Karl Swartout
Mooresville, IN
BS175 Roadracer
BS350 GTR

Offline anotheroldtrailrider

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Re: Racer Resurrection
« Reply #234 on: March 27, 2019, 09:05:16 PM »
Hi Karl - I was referring mostly to minimum cylinder wall thickness prior to re-coating in the question about overbore limits and doubt that's needed.  Obviously I haven't done much research on piston dimensions yet, but the KX and RM suggestions included head and cylinder deck mods to accommodate them.  Your mention of overall piston dimensions fits right into their discussion about port timing changes when the cyl is trimmed on the bottom vs on the top - obviously depends on piston dimensions like you said...hmmm, I gotta lot to learn on this one...

Offline al_pritchard

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Re: Racer Resurrection
« Reply #235 on: May 06, 2019, 10:01:02 AM »
With a small window of sun shine on Saturday, we drug the bike out of the workshop for it's first start. Unfortunately it didn't go completely to plan.

Set Up
Pilot Jet: 20
Main Jet: 230
Air Screw: 1 1/4 turns out
Float: 25mm
Fule: 112 octane / VP C12
Oil: 28:1 / Castor 927

I did manage to get it turned over twice, but immediately bogged and died after hitting 4000 RPM. I think a lot of this is due me being to heavy on the throttle as it would start to catch.

I checked the timing was at 0.09" / 24° BTDC, and I had good , strong spark. As an aside, make sure you ground the spark plug on the side of the head, or it will ground through you. Ask me how I know.

Im thinking of stepping up to the #25 for the pilot jet, and stepping down to the #220 main jet. And turning the air screw 2 1/4 turns.

The good news is that my drive way has a slope. So pushing is not that hard. And I get a good long 50 foot for two, or three attempts per push.

Questions / Thoughts
This is the first time I've set up a carb. Should the slide be resting on the floor of the carb, or should is be raised slightly? That didn't seem clear to me. Nor did the air screw. Some set ups from the carting world talked about 2 1/2 turns to start with. And I think the Sudco book stated 1 1/4.

Al Pritchard
Highlands, NJ

BS175 Racer

Offline al_pritchard

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Re: Racer Resurrection
« Reply #236 on: May 07, 2019, 11:15:01 AM »
A short video, sound will help. It catches and then dies.

Click on the image to view the video
Al Pritchard
Highlands, NJ

BS175 Racer

Offline BRT-GTR

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Re: Racer Resurrection
« Reply #237 on: May 08, 2019, 08:59:01 AM »
          Bike looks great.
       Here's a link to a good carb tuning guide that I found helpful when setting up my GTO carbs from scratch.
                http://kawtriple.com/mraxl/carb/carbadj.htm

    Put the 25 pilots in (airscrews 1 1/2 turns out) and raise the carb slides a turn or two to see if you can get her to stay running. Leave the big main jets in until you are happy with the pilots/carb slide cut outs/jet needle postion. Main jets are the last items to tune.
Unspoiled by progress.

Offline bsracer

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Re: Racer Resurrection
« Reply #238 on: May 08, 2019, 12:27:07 PM »
Hey Al, what needles do you have and what position are the clips in?
These carbs seem to be very finicky. If the needle is a 4L6 it may be too rich. I typically run the mixture screw barley a 1/4 turn out. I just tried up to 35 pilots at Willow. It would be fine on start up and slower running but anytime the throttle was closed from WO it was too rich. I ended up back to my almost regular carb settings. I did leave a 25 pilot in (I'd usually run a 22.5). You can turn the idle screws up so it will idle then adjust mixture screws.

paul

Offline al_pritchard

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Re: Racer Resurrection
« Reply #239 on: May 09, 2019, 01:18:19 PM »
Thanks for the link Brian. I think this might help a bit with the learning curve.


Available Jets
Pilot
17.5 ( VM22/210)
20 ( VM22/210)
22.5 ( VM22/210)
25 ( VM22/210)
27.5 ( VM22/210)
30 (Original)

Main
230 HEX ( 4/042)
240 HEX ( 4/042)
250 HEX ( 4/042)
300 (Original - although one seems much smaller)

The carbs were set up with a 30 pilot just, and a 300 main when I got the bike. But with a blown engine, I never ran it with that setup. I swapped them out because the pilot head screw slot looked like my dog chewed on it. And one of the 300 mains looks much smaller than the other - even the carb cleaning wire didn't open it up. So it might be miss labeled, or just hopelessly clogged.

I don't know what the needle is. I'll swap out the pilots and check the needle. Stay tuned...
Al Pritchard
Highlands, NJ

BS175 Racer

 


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