Racing Bridgestone 200

[craig641]

Folks,

I've been building my 200cc Bridgestone vintage road race bike for a while now and have finally gotten it on the track.  My first event at Summit Point in WV was pretty unsuccessful.  My first race for the day was the 350gp race.  I had been having problems getting the bike started during the day's practice sessions and it wouldn't start at all for the race.  After some carb adjustments it was starting and running pretty good.  My second race, the 250gp race, I got a great start and was doing well until I got to the point that every time I gave it gas the clutch would slip.  By the fourth lap it was slipping very bad.  I ended up pulling in and calling it a day. 

At home I pulled the side cover and found a completely burned up clutch.  The clutch fibers were toasted.  The steel plates were black.  I got a set of SR175 clutch fibers and a new set of steel plates from Richard.  I put in motorcycle transmission oil and adjusted everything up to the specs. 

My next race was this past weekend with the USCRA.  The bike was running great.  Easy starting and plenty of power.  I raced in the 200 and 250 gp classes for this event.  I took a third in the 200 class against a very fast guy on a Bultaco 200 and another very fast guy on a Yamaha 180.  In the 250 class I ended up second behind the same Bultaco rider and ahead of the rest of the field of Hondas and Ducatis.  But during this second race I could feel my clutch slipping again. 

At home last night I pulled the side cover and again found the oil to be burnt pretty bad.  The steel plates were in better shape than the last event, only three being black this time.  The clutch fibers were also blackened, from the original green color of the SR fibers.  I did pre-soak the SR fibers before I installed them. 

So, any ideas on what I can do to make the clutch last?  I am making quite a bit more power with this motor than a stock bike with this motor that was built by Scott Clough.  Any of the other Bridgestone racers have clutch issues?  What have you done to work around this?

Thanks,
Craig

[OldSwartout]

Craig - I'm running some extra springs.  Paul Piskor came up with some that fit over the OD of the existing ones and nearly double the compressed load. I'm running them on three of the posts. I also shim the standard springs with some copper washers that are about .050 inch thick.  Even with that, the clutch wants to slip on the warmup lap until it warms up. But it doesn't burn the plates.  I should put three more of the extra springs in.   I think Paul has been running extra springs also.

[Toystoretom]

The only ideas I have are:

Get with Barnett's and have them make you up some racing clutch plates....

http://www.barnettclutches.com/products/clutch_plates_springs.aspx

Try to find a lock up clutch that you could fit up to your bike. Dirt bike riders use a pressure plate that has a series of ball bearings that ramp up when rpm's increase, and these ball bearings force themselves up against the clutch stack and lock the whole assembly up. If I can find a link to one of these I'll post it. Nevell Lush makes one of these for Rocket III's but you would need a much smaller version.

[Toystoretom]

Here is an interesting link but not what I was looking for:

http://www.motorcycle-superstore.com/1/5/87/22009/DPITEM/Street-Bike-Clutch-Plates-SpeedyMoto-Kukri-Pro-Clutch-Pressure-Plate.aspx

Ah Ha.... this is it. This size would be easier to adapt to your 200:

http://www.rekluse.com/z-Start-Pro.html

[bsracer]

Hey Craig,

since I started using some extra springs I've had no problems. If you send me your address I'd gladly send you a set. I'm curious to know what oil your using in the transmission? I only use Valvoline 30wt non-detergent.

I spoke with Barnett about clutch plates years ago and it seemed too costly (that might have been for 350 plates, I can't remember). Richard at Rave Motorsport has kevlar clutch plates for 175's however i think they are $25-30 each and he's in the UK.


paul

[OldSwartout]

Richard at Rave Motorsport has kevlar clutch plates for 175's however i think they are $25-30 each and he's in the UK.
paul

$25-30 each is still cheaper than Barnett, I think.  And, as Paul implied, don't use one of the modern friction-reducing oils in the transmission.  That's guaranteed to make your clutch slip.  I actually use ATF type F in mine.  The type F has an additive to increase the friction coefficient of clutch material (due to Ford screwing up years ago and underdesigning a reverse clutch in one of their transmissions).

[craig641]

Paul - I'd love to get a set of those springs.  I sent you an email with my address.

For the previous race I used Golden Spectro motorcycle transmission oil in the transmission.  The first race out I used Mobil 1 gear oil.  The second race had much less slippage than the first race, but there was still some.  I may give Karl's ATF type F a try for Mid-Ohio, my next race.

Craig

[bsracer]

Hey Craig,

got the email. I'll send you out some springs this week. I'll send six, but I only use three over top three of the existing springs. I was wondering if you might have used Mobil 1. I was at Portland and a bunch of the Honda guys were scrambling after they all had "upgraded" to Mobil 1. All of them couldn't even start their bikes because their clutches were slipping so bad.

I haven't had the bike out this year yet. I was supposed to race at Willow Springs in April to see if I finally worked the hole in the piston problem out but never got to. In an extreme case of stupidity, a couple of friends and I thought it would be great to cruz around the track on bicycles. Let's just say that after one of my friends plowed into me and I spent the next 18 hours in the hospital having surgery to repair the ground tip and chipped (missing) bone in my right thumb, I haven't raced yet this year. I'm hoping to shake down the bike at a track day or maybe a race (wera, ccs or afm) here on the west coast. If that goes well I'll start putting together another motor that will run the aluminum disc covers with some newer style dirt bike carbs that are rubber mounted.


paul

[craig641]

Thanks Paul.  I appreciate it.  I'm hoping to get the bike's clutch issues fixed before Mid-Ohio this July.  I won't get a chance to get the bike on the track before then though.  And the neighbors aren't thrilled with my going up and down the street.  I could tell them this is part of the plan to keep the mosquitoes here in NY under control.

Craig

[drtracr]

hey guys, I talked to the smartest mind in lubrication this morning. Forrest Lucas of Lucas Oil. He and I go back a long way. He tells me to run his Sure Shift racing ATF. Clutches will run cooler and engage better, and if he says it I believe it.

Jimmy Martin

[scrambler]

I have ran ATF in the transmission of quite a few 2-stroke engines. Never had a problem. I used ATF in my ice racing BS175.

[blue twin]

I have ran ATF in the transmission of quite a few 2-stroke engines. Never had a problem. I used ATF in my ice racing BS175.

i'VE HEARD OF THAT AND THE SYNTH SLIP PROBLEM, TOO.

I heard of something I think they call 'red ball" or "redline "that is supposed to be race proven. I'll ask for what the name is, but of course it's spendy.

[craig641]

I realize this topic was originally about my questions about a slipping clutch.  Which was solved very nicely with Paul's double spring trick and Karl's ATF type F transmission fluid. 

I've got another question for discussion.  With the fifth gear being an overdrive in the transmission I've found that my engine loses a lot of drive when shifting to fifth gear in a race.  Some solve this by using the transmission as a four speed and just using higher overall gearing to get the desired top speed.  I've done some investigating and found a supplier that would be willing to make a close ratio 5th gear replacement for our overdrive fifth gear.  The Honda CB350 guys are using a similar gear in their gearboxes and it seems to make quite a bit of difference.  The Honda guys get this gear from Nova.  Nova also makes a complete close ratio transmission but the price for the Honda is approaching $3000.  Nova doesn't list a complete transmission for the Bridgestone but I'd expect the full gearset would cost close to the $3 grand as well.  Is anyone else interested in a close ratio fifth gear for their bike?  I'm assuming the cost would depend on how many orders we can place.

Craig

[bsracer]

Hey Craig,

I spoke with Graham Dyson from Nova sometime in 2007 about Bridgestone transmissions. They made them for the guys racing Bridgestones in the UK. At that time he said they stopped making the 5 speed conversion and offered a 6 speed only. They were priced at 2000 GBP and he wanted a minimun order of five transmissions to make it worth while. I think the pound to the dollar was quite high at the time and I didn't think anyone was going to shell out that much ( me included) let alone find enough people for the minimum. Sadly Graham passed away last month.

I spoke with Ellis Moore of Moore Performance Engr in 2008 about transmissions and he said he could do a new fifth gear for about 80 GBP, which didn't sound too bad. He also said he could do a complete conversion set using existing clusters for around 800 GBP. These were quoted 5 years ago, but maybe still close in price.

paul

[craig641]

Paul,

Ellis Moore is the guy I've been talking to.  I think you were the one that told me about the Nova prices so I didn't bother going there.  Ellis has asked me to send him a gear cluster so he can come up with some options for us.  I'll keep you updated with what I find out if you're still interested.

Craig

[bsracer]

Hey Craig,

I'm still interested. Are you just looking into a new fifth gear? I'm probably not interested in a complete gear set at this time. I just pulled my motor apart. I was getting ready for Willow Springs and had just made some new cylinder base shims. The bike just didn't run right last year. I was about to assemble the cylinders and on closer inspection, I felt the right side connecting rod a bit loose for my liking. I decided to put in a new crank that I had. When I split the cases, I inspected the trans since it was jumping out of gear a bit last year. The two center shift forks are wasted again. I had the trans undercut a couple of years ago but I guess not enough. So I'm off this morning to see if I can get the shift forks (these were the last new ones I had) repaired and the tranny undercut a bit more.

paul

[bsracer]

Hey Craig,

give me a call when you get a chance. I think the transmissions are gonna need more than just a fifth gear. Karl, I'll call you later about it. I did some extensive modifications to the pins for the shift forks for this past weekend's races. The bike also had some motor mods that proved very good. However the transmision couldn't handle it and started jumping out of 4-5th gear. By the end Sat races the bike was jumping out of third as well. Graham from Nova said that when these bikes started to approach 30Hp the transmissions weren't up to to task. I will be looking into some fix for this if it means converting some other transmission or having new gears made that won't disengage so easily.

Craig, I just want to get on the same page as I might want to contact Ellis Moore. Did you send a gear set to him?

paul
619-675-4060