Engine builder needed

[Jeff Bar]

Its a shame some of the old bridgestone guys will not join us on this site, I really do not know how much help you will get from them. Jeff Bar

[drtracr]

Vince Gunning is being very helpful. He says they are way ahead of us on engines over there. Very nice guy or chap as he says.
JM

[Jeff Bar]

JM, Its great you are getting some help. I wish I knew tech too.   Jeff Bar

[ztnoo]

Jimmy,
Since you have made contact with Vince, why don't you invite him to join us here.
Might be a great discussion (it already is) if he'll chip in his two cents worth.
Steve

[drtracr]

Will do.

[vinny g]

Hello chaps,Jimmy has been in touch and sent me a link to this site,thanks Jimmy,so here i am.Whilst in no way pretending to be a Bridgestone expert i have had a mess about with the 175/200 engine with a little success at times.I hide nothing so if you have a question that you may think i have the answer to just ask.As Jimmy pointed out we seem,unfortunately sometimes,to be a little in front of you in engine development.Classic racing in the UK is very competetive and developement constantly on going.Ive read through the previous posts from your goodselfs and,for now, will list a few things that i know to be true with regard to my own engines.I daresay some of you would also have some experience of some of these things.
 Carbs, I thought that when i changed from 22mm to 28mm carbs the bike would transform from mediocre to missile.Wrong,the main benefit was that i was able to get the bike to carburate better with the bigger carbs.You can put this down to the assymetrical inlet timing,running around 220 degrees gives plenty of time for fuelling regardless of carb size.Remember,the mixture has to go somewhere and we know how limited we are on port area.
 Power. 36/37 bhp is about it and for that your engine is trick and expensive.32/33 bhp at the backwheel is hometuneable at nice revs,ie 10000.This keeps reliability uptogether.
 Ignition. I have back to backed the fixed timing Dyna S system and a self generating unit with a curve in it.Peak power and revs were identical though midrange was superior with the curve.
 Cranks.Yes they will snap,Im convinced that this is an age/use issue rather than a power issue.The cranks we have snapped have been on our slowest motors.I now run a straight pin between the wheels doing away with the step where it always snaps.Bridgestone rods,pins and bearings are surprisingly good and in 10 years have never suffered a failure.I have just modded a crank to run the Suzuki rod kit from an x7.The Rm125 kit is the same with a silver plated cage.i will report back.Ideally the crank needs to convert to 4 bearing with a lab seal but the space is tight.
 Clutch.We have no issues with the standard clutch but you will break the odd plate.I run straight cut primary gears and slightly heavier springs.I am trying some kevlar plates this year and will report back.
 Gearboxes.We do run modified boxes.These were converted by Nova transmissions and were quite adequate.We also went on to made from scratch 6 speed boxes from Nova that are faultless but horrifically exspensive at around £2000.
 Pipes.Various designs tried and to be honest it all seems to be about what you want the bike to rev to.
 Heads.I gave up trying to weld and mod standard heads and cheated by using heads from a Yamaha Rd200.You could look at the ycs1 head also.Plug the stud holes,re drill to suit the Bridgestone stud spacing and hey presto,factory squish heads with the benefit of a long reach plug.I run .6mm squish with i think 9cc volume giving me 12.5-1. The stud spacings are very close and as we say in this part of the world its a piece of cake to do.
 Porting.Nothing special here,i think my timings come out at around 198 exhaust,132 transfer and 135 rear trans.Spot the tip? Open the rear around 1mm before the main.
 Well i must go as its Sunday and as you know us folk over here like to spend our days off drinking tea and moaning about the weather.I hope that the above may have been of help if only in a small way to someone.I shall be a regular visitor so anything you think i may of come across before,feel free to ask.My email address is as posted elsewhere vincegunning@hotmail.com.
Very best wishes to you all that side,Cheers for now Vince

[ztnoo]

Vince,
Welcome aboard! Great to have you here at the site.
Thank you for the wonderfully informative thoughts you have given us in your first post.
We look forward to hearing much more from you.
Regards,
Steve

[OldSwartout]

Very interesting and useable information in your response, Vince.  I'm in agreement with you on the crank breakage, although I had (wrongly) assumed it would be worse at higher RPM, so that lead to my thinking that a highly modified engine would be more likely to break one as the operating RPM range would likely be higher.  I had guessed that a straight center pin would help as that eliminates the stress riser as you have found, but hadn't tried it. It's good to know that works. I had built a couple crankshafts with an improved center pin (4350 hardened to RC48 with a much improved corner radius design). That didn't last significantly longer than the stock pin. I think the real cause is a resonance of the crankshaft/crankcase with the crankshaft bending into a wave shape at some RPM range, flexing the center pin until it cracks at the shoulder.  All failures I've seen over the years (many) have obviously been rotating bending failures, not torsional failures.  Have you tried balancing the crankshaft assembly to different specs than factory?  If the resonance point could be moved out of the operating RPM band or the forces just reduced by better balancing, the problem should go away. It would take a couple  accelerometers and decent recording/analysis equipment to sort this out, though. 

Do you make an attempt to  enlarge the transfer ports significantly?  I think everyone here matches up the transfers with the crankcase, smooths them and takes out some material, especially at the entrance.  Unfortunqtely, the 175 transfers are smaller than the 200s and it's pretty difficult to get very much material out.  I do open the exhaust significantly and raise it 1mm.

[drtracr]

Karl you and Vince are so far over my head I am lost. I am a race car driver and builder and bike racer, not an engine builder. That is why I desperatly need some one to build my motor.

Jimmy

[drtracr]

hey guys, spoke to Richard Taylor and he has done some port work on B/stones. His specialty is Hodakas. He also sent me to Jemco for pipes, might screw around and find enough stuff to do this.

I still would like to buy some new parts if they exist. New cyclinders, heads, pistons, rotary valves, gaskets, seals, piston rings, pins and bearings, crank bearings.Clutch plates and springs. Anyone got anything, let me know.

JM

[ztnoo]

Jimmy,
You might check with Richard to see what he specifically has in the way of 175 parts.
He may have way more than you even dreamed about.

Also, there is some other stuff floating around. Keep an eye on eBay
I noted NOS 175 SR fiber clutch plates and a NOS 175 crank on eBay this morning.
http://motors.shop.ebay.com/i.html?_nkw=Bridgestone%20motorcycle%20&_sacat=6028&_odkw=Bridgestone%20motorcycle%20parts&_osacat=6028&bkBtn=&_trksid=m194&ssPageName=STRK:MEFSRCHX:SRCH

There are a few parts here: http://bridgestonemotorcycleparts.com/index.php?action=classifieds;cat=
and here: http://bridgestonemotorcycleparts.com/index.php?board=13.0

btw I've looked at some ECTA and SCTA stuff as far as motorcycle classes.
Looks like there is a category for about anything anyone would care to run.
What class or classes are you shooting for?
And what are the records in those classes?

Regards,
Steve

[drtracr]

Steve, shooting for PMG 175/2 and the record is 81 and PMF 175/2 and it is 84.

Basiclly the non pushrod 175 2 stroke production based chassis with slight mods.

[ztnoo]

bsracers reference Schurgers to got me to thinking and remembering and researching.
Fascinating stuff......really.
* reference: http://www.yamaha-classic-racingteam.nl/site2/index.php?page=team_jos
"Jos Schurgers was however especially known for his Bridgestone 125 racer, a machine he build him himself because it was to only way to get a competitive racer with a small budget."
"He bought a Japanese 125 cc Bridgestone road bike which he tuned together with the legendary Jörg Möller. Jos build his own fairing and the result was the number nine position in the final GP standings. In 1973 he even managed to conquer the third overall position in the final ranking."
"1. What was, in your opinion, your single biggest achievement as a roadracer?
To win the Belgian GP in 1973 on Francorchamps and the third place in the final ranking of the world championship that year with my Bridgestone 125 cc racer. No mean feat with a very limited budget that was compensated by an enormous passion, both in developing the Bridgestone and in racing it."
"3. What was your favorite racing bike, favorite track and favorite public?
As a rider my 125 cc Bridgestone, as my dream de fourcilinder 125 cc Yamaha used by Read and Ivy before my own racing career took off. I loved fast tracks such as Francorchamps and Sachsenring, but surely also Assen."

And then I found some absolute fantastic pics of Schurgers' Bridgestone:





How about them apples???
 

[drtracr]

Awesome bike.

[ztnoo]

Jimmy,
Yes, it an amazing example of what GP privateers in the 60's and early 70's could turn out.
Their individual machining and engineering skills were at a level right with the factory teams.
The big difference.....and it always comes up when one is trying to reach the top.....is resources.
Bucks, pounds sterling, guilders, swiss francs, whatever.
Money is always an issue...it was then and it is now, particularly in a depressed economy.
The Dutch were especially skilled in developing the lower displacement classes.
When you eye-ball Schurgers Bridgestone......it looks like a slightly larger Kreidler 50cc GP machine.
That's gotta be a copied Kreidler fairing and gas tank.

That was an amazingly innovative period.
Too bad that isn't possible today.....

So privateers now go for LSRs, right???
 

[drtracr]

Gentlemen, it appears as with many people's help I have located or found a source for everyting I need. Between Karl and Richard I have the motor parts located. All I need is some pipes. If anyone knows of any SR pipes laying around I sure could use them to send to JEMCO for a pattern Or if there are any good  pipes for sale anywhere in the world, let me know. Found a very knowledgable B/stone engine man 20 miles from me and he will do the motor assembly. I am getting very exciting about this. Also if anyone knows how to get in touch with Cory Moore, tried his email and it didn't work.
Thanks to9 all.

Jimmy

[drtracr]

Almost forgot. Steve got any 22 or 24 mm carbs laying around.

[ztnoo]

Jimmy,

That's great news.....the parts and a Bridgestone guy close to you (how fortunate is THAT???)
Keep us updated!
When do you think you might be ready to make an attempt this year?
Steve

P.S. There are expansion chamber dimensions for the 175 Dual Twin here:
http://bridgestonemotorcycleparts.com/PDF/BStuningUpManual.pdf
See page 13.
You might check with Karl to see if this is what he's running, or maybe if he's made a few dimension changes.
With dimensions like in the diagram, any competent pipe builder should be able to fab these for you.
Scott Clough comes to mind.

[drtracr]

I am shooting for July.

[OldSwartout]

The expansion chambers Paul, Craig Hirko and I are using are all of later, more modern design (all from different people) than the factory design pipes from 1967 (shown in the Tuning Up for Performance book).  Those would work, but will provide less peak HP and a narrower powerband.  Craig Hirko's pipes were made by Karl Smolenski (Google him), I believe.  You can probably get Scott Clough to make a set although he won't have an engine and frame to set them up on.  With mine, Harry Barlow made the head pipes and cones, I welded them together to fit the bike and made the brackets.

Sudco sells 24mm Mikuni VM's. http://www.sudco.com/CatalogJPG/107.jpg  Not certain of the price.
Richard sells 26mm 350 carbs for a good price.
Most of us racing them run the 22mm carbs from the Kawasaki A1, as they are very similar to the BS racer carbs, except they have enricheners, whereas the racer carbs didn't. They're pretty easy to find used.