UK Bridgestone 200 racer

[Gerrit]

I think that apart from reduced friction the nikasil coating offers another advantage: better heat transfer. Heat destroys power. I was merely wondering how far one could go with a DT engine towards a full 250, as Bridgestone never built a full 250 engine. The stock castings obviously place a limit on what can actually be achieved.
The TD2 was 56 x 50.6 (ditto the RD56) so oversquare isn't necessarily bad.

[craig641]

Vince - I've got a couple of questions for you if you don't mind.  I also race a 200cc Bridgestone in AHRMA here in the states and mine is a long way from your 40hp.   What brand of pistons are you using in your bike?  You mentioned you're using X7 connecting rods,  what is the benefit to using these rods?  I've experienced the common broken crankshaft, so  I'm very interested in learning more about your four bearing conversion for the crank.  Also, if you're willing to share,  what are your expansion chamber measurements?

Craig

[vinny g]

Hi Craig..Sorry for the delay,ive had computer issues for a few weeks and im playing catch up.The Suzuki X7 rodkit is cheap,available and of a decent quality.I only use Suzuki parts or those made by the Long corporation.The actual amount of roller in the big end bearing is far superior to the original Bridgestone big end and the bearing as a whole is lighter.I remove 1mm from inside each crank wheel and thats the only mod. There is a Suzuki RM100 rodkit that will fit straight into the Bridgestone from i believe 1977 but its unobtainable here.You may have more luck.
I have center pins made for the crank that i fit after boring out the old shaft one side..opening out the other side.These are 20mm pins with no step.I cut woodruff key slots in the pin and wheels at 180 degrees to make alignment simpler.
I run the Suzuki x7 piston at 54mm,we are allowed oversize here,that fits straight in.I also use the KX100 piston (Wiseco) at 52.50mm in the ceramic coated cylinders.The piston is shorter so i skim the cylinder base and recess the heads into the cylinders to run those.Very good reliable set up once done..its a forged piston and i run just a single ring.

Il do a diagram of the pipe design over the next couple of days and post it up.I was on the dyno on Thursday and the bike produces peak power at 11750rpm.

Cheers,Vince

[bsracer]

Hey Vince,

I just had a couple of questions on the crank. Do you use the shims with the X7 rods? Have you had one crack between the 20mm pin and the rod pin? That looks like it would be pretty thin between them (3.25mm?). I just broke another crank (which hasn't happened for a long time!) the last race outing. I think it was going out over the course of two race weekends. Impressed that I was only off my times by 15 sec with a single!

paul

[vinny g]

Ooops! Playing catch up a bit.
Hi Paul,no i dont run thrust washers on the crank at present and(so far!) no cracks.I appreciate that,as you point out,you are left with a pretty thin "wall" the straight through pin stiffens the whole crank up that much it hasnt been an issue.Il work on some other crank ideas over the winter and report back.

Important stuff!! Exhaust dimensions..im not clever enough to do a schematic diagram of the pipes that i run with (Dyno proved) but have had a measure up and can tell you:

Exhaust flange is 30mm id..35mm od..length 25mm.
First section= 375mm long going from 30mm upto 77mm.
Second section=72mm long going from 77mm upto 90mm.
Third section= parallel 99mm long 90mm diameter.
Fourth section=200mm long going from 90mm down to 20mm.
Tailpipe=170mm long @ 20mm diameter.
     ALL LENGTH MEASUREMENTS ARE MEASURED THROUGH THE CENTER OF THE PIPE!!
You can choose to either add a silencer to the stinger,see attached pics,or run a silencer built over a perforated tube stinger.Not much to choose other than looks.
If someone wants to add those dimensions to a pipe drawing and post it up then feel free.
Not much else to report at the moment though il keep you upto date with any mods i feel may be of benefit.
We have had success with lined cylinders running the Wiseco Suzuki RM100 piston Type 454 which needs just the top ring peg moving a few mm.If you break these pistons or rings something is seriously wrong.Available from 50mm upto 52mm so worth a look.
Il be putting a set of the pipes you see up for sale shortly on the board along with a set of cylinders and wiseco pistons.Nothing wrong with any of it but im planning a season of standardising my engines/bikes for next year to cut down on the amount of different parts i carry and simplify development.
Thats about it for now..any questions just ask,Vince

[bsracer]

Hey Vince,

just wondering if you used the straight 20mm pin with the original bearing and seal setup with success? I found some Honda bearings (91005-KCN-003) for a CRF250 transmission that were also used on a non US market GL200 single on one side of the crankshaft.  They are 20x55x11 and with a 9mm labyrinth seal, two will fit perfectly in the center case. I was thinking of setting up one crank with standard bearing and seal (no mods to the case necessary) and try another with these Honda bearings, a lab seal and of course the cases modified to lube the bearings.

paul

[vinny g]

Hi Paul.Didnt run it again this year as the engineer that helps me out with bits and pieces hasnt been so well.Its a goer for next year though.Id say give it a go..my only worry being that 9mm is wide enough for a lab seal..really..im no expert with them.We run manufactured labs on our cranks but from memory they are 15mm wide.Can you find a load rating for those bearings? I cant see why i wouldnt work if im honest..the load is obviously taken on the balls and race..for the rest of the bearing they just seem to increase the surrounding thicknesses when going larger.Ive even thought about trying running two bearings back to back that have sealed inners with the sealed sides running in the center.Once the engines up and running the compression forces fight against each other in much the way a lab seal works so i may experiment.Keep me upto date and il do likewise.

   Very best...Vince

[vinny g]

Hi all..not much to report..no real mod's to report.I'm pushing on with the four bearing crank conversion but taking a slightly different route.I'm going to use two of the original roller bearings sandwiching a lab seal and slim the two inner crank wheels to compensate for the width.I'l then plate inside the crankcases to keep the volume there or there abouts and support the bearings.Well thats the plan...

I've just bought another Bridgestone racer from a friend of mine that's retiring as i wanted the replica chassis so will be putting some spares up for sale on the classifieds board shortly..i'm quadrupled up on some parts now as the engines are identical.I shall sell turned from billet disc housings for 28mm carbs you see in the pics..a set of the four straight cut primary gears from Nova that we run..a pair of SR175 factory disc valve covers..a couple of pairs of pipes..a pair of lined 175 race cylinders with Wiseco pistons that are new..possibly a close ratio Nova 5 speed gearbox..nothing wrong with any of it but they wont get used here.

Keep you upto date with mods.

   Vince

[bsracer]

Hey Vince, I'm interested in some of those parts.

If you want to shoot me an email, bridgestone67@yahoo.com

paul

and p.s. who's bike did you buy?

[vinny g]

Will do Paul.I bought Rob Lusk's bike.I'd built and ran the engine,and continued development, for a couple of years anyway so it made sense.The chassis is a lightweight replica with 35mm GP Ceriani's that i could never have afforded new so i had to buy it.I'l build it up with my best 6 speed engine for next year and it should be quite a few pound's lighter.I think at the moment mine weighs 180lb.It's buying this that has free'd up the parts as i'l only run two bikes.
 Cheers..Vince

[hmmmnz]

awesome stuff.
if you ever have one of those cranks going spare let me know.
im currently doing a rebuild on my 200 now,   any hints or tips greatly appreciated.

[bsracer]

Thanx Vince, looking forward to hearing from you. I think mine weighs in at 225lbs so that's a big difference.


paul

[vinny g]

We had a bit of a top end (11000rpm+) misfire recently and started looking at the ignition as being the culprit.As those that have followed this thread will know i run a one-off ElextrexWorld ignition.One off's are great...until you need another.They couldn't manufacture me a new one as the stator was a complete one off..they can't even remember what it was off..so i looked at what was available from the shelf.

This is the Yamaha TD1/2 ignition they supply that drives the correct way,clockwise,and it's a bit of a squeeze but i got it on.Totally self generating..and with a nice curve.

I'll report back on how it performs.The extended housing is required to take the unit into the space between the cylinders/crankcase...should you want to use it on a 350 it will run up against the crankcase flat as there's much more room.For that application you'd use the Yamaha TZ350 ignition as it drives anti-clockwise.

I have these units on a few of my other bikes and they've always been faultless in use...and pick up midrange nicely.

[vinny g]

Unit complete.

[bsracer]

Looks interesting Vince. Send a shot of it in position. The new one I started working on will hopefully fit in the orig generator housing.

paul