I need help. Chain drive issues I can’t diagnose

[Kgermanton]

Hey Guys, I’ve owned a Jedi formula car converted to a prototype for about two years and I still haven’t done a lap under full power. I bought the car supposedly in good running order and I found my first track test, I would pull out of the pits with full power then on my first hot lap I would start losing forward drive like the clutch was slipping and it would progressively get worse to the point where I almost can’t make it back into the pit. Once the car cools down I can repeat the same issue. I took the clutch out of the spare engine and replaced it and it did the same thing. I bought a 3rd new clutch (genuine Suzuki) with heavy springs and that didn’t fix. The motor runs strong. Fires right up. Gears work. Sprockets seem fine. I also replaced the slave cylinder thinking that could be it. Many might think it’s the diff... the car rolls very nicely while turning with no sounds or grinding. Any help would be hugely appreciated and if you know a mechanic in the NJ area that could diagnose it that would be also great.

[RussMcB]

To determine if the problem is with the clutch or with the differential, maybe mount a camera looking at the chain. If, when it starts slipping, the chain is spinning rapidly, the problem is with the diff. Conversely, if the chain is going the correct speed for how fast you are traveling, the slippage is with the clutch.

Do you have a chassis dyno near you? Someone could observe the chain speed as you start experiencing the slippage.

I wonder if it might be an engine oil issue. The wrong oil might cause a problem with the clutch.

Make sure your clutch slave cylinder is allowing the push rod to fully engage the clutch. In other words, make sure, like in a car, you aren't driving with your foot applying pressure to the clutch pedal, causing it to slip.

Good luck. Let us know what you find.

[cjahn]

Hey Guys, I’ve owned a Jedi formula car converted to a prototype for about two years and I still haven’t done a lap under full power. I bought the car supposedly in good running order and I found my first track test, I would pull out of the pits with full power then on my first hot lap I would start losing forward drive like the clutch was slipping and it would progressively get worse to the point where I almost can’t make it back into the pit. Once the car cools down I can repeat the same issue. I took the clutch out of the spare engine and replaced it and it did the same thing. I bought a 3rd new clutch (genuine Suzuki) with heavy springs and that didn’t fix. The motor runs strong. Fires right up. Gears work. Sprockets seem fine. I also replaced the slave cylinder thinking that could be it. Many might think it’s the diff... the car rolls very nicely while turning with no sounds or grinding. Any help would be hugely appreciated and if you know a mechanic in the NJ area that could diagnose it that would be also great.

Rob's suggestions are spot on. The oil has friction components for the clutch as well, so I run the appropriate MC Redline oil. I have also seen the bolts not torqued properly and they backed out.... (not my engine) but ugly consequences when the metal was shaved off the cover.

But your symptoms are very similar to when my diff failed in a prior car I owned. The diff was buried in a structure so not completely in view or accessible. What happened is the diff bolts holding it together and the sprocket carrier sheared.

It was a generic Quaife that was grease packed. SO it would work fine at low speeds and low torque but as soon as power was applied it would free wheel.... From now on with any car that doesnt have easy access to the diff for service or inspection I create an access panel. (Disclosure - not a JEDI)

If I need to clarify let me know
Thx
Cj

[Kgermanton]

To determine if the problem is with the clutch or with the differential, maybe mount a camera looking at the chain. If, when it starts slipping, the chain is spinning rapidly, the problem is with the diff. Conversely, if the chain is going the correct speed for how fast you are traveling, the slippage is with the clutch.

Do you have a chassis dyno near you? Someone could observe the chain speed as you start experiencing the slippage.

I wonder if it might be an engine oil issue. The wrong oil might cause a problem with the clutch.

Make sure your clutch slave cylinder is allowing the push rod to fully engage the clutch. In other words, make sure, like in a car, you aren't driving with your foot applying pressure to the clutch pedal, causing it to slip.

Good luck. Let us know what you find.

every point is great thank you. I do have a friend with a dyno. We had it there twice with the body off watching to see if the rear wheels are at a different speed from the chain and couldn’t really tell. It’s harder than you think to see what’s going on. I may try marking a dot on the chain with paint and a dot on the tire.

I used Motul racing motorcycle oil two or the three failed track tests. The first was on the previous owners oil. What oil do you recommend?

Is there a good way to know the slave has full engagement?

thank you again for the help

[Kgermanton]

Rob's suggestions are spot on. The oil has friction components for the clutch as well, so I run the appropriate MC Redline oil. I have also seen the bolts not torqued properly and they backed out.... (not my engine) but ugly consequences when the metal was shaved off the cover.

But your symptoms are very similar to when my diff failed in a prior car I owned. The diff was buried in a structure so not completely in view or accessible. What happened is the diff bolts holding it together and the sprocket carrier sheared.

It was a generic Quaife that was grease packed. SO it would work fine at low speeds and low torque but as soon as power was applied it would free wheel.... From now on with any car that doesnt have easy access to the diff for service or inspection I create an access panel. (Disclosure - not a JEDI)

If I need to clarify let me know
Thx
Cj

now I’m thinking about opening up my diff. I called Jedi when it first happened and they suggested pulling the CV axles out of the diff and inspecting them. I don’t know the first thing about chain drive differentials but I’m willing to poke around and open it. Jedi won’t return my emails so I can’t even find out what type of Diff it is.

so you use a redline oil for wet clutch motorcycles?

I also just stopped at a Suzuki dealer and begged them to let me hire one of their mechanics to come and inspect my clutch to verify I’m installing them correctly. I’m crossing my fingers one of them calls.

[cjahn]

now I’m thinking about opening up my diff. I called Jedi when it first happened and they suggested pulling the CV axles out of the diff and inspecting them. I don’t know the first thing about chain drive differentials but I’m willing to poke around and open it. Jedi won’t return my emails so I can’t even find out what type of Diff it is.

so you use a redline oil for wet clutch motorcycles?

I also just stopped at a Suzuki dealer and begged them to let me hire one of their mechanics to come and inspect my clutch to verify I’m installing them correctly. I’m crossing my fingers one of them calls.

I use redline 20w50 motorcycle oil but may not be your issue.... Is your diff open or locked?

I am sure there are tons of resources to help! Great community here.

Cj

[Mike B]

so you use a redline oil for wet clutch motorcycles?

Only use motorcycle oil, which it sounds like you are. I always use Mobil 1 4T motorcycle racing oil.
Aside from the already spot-on suggestions, take a look at your oil temps. Overheated oil will make the clutch slip but it usually damages the clutch so it wouldn't be any better once it cools down.

[Kgermanton]

I use redline 20w50 motorcycle oil but may not be your issue.... Is your diff open or locked?

I am sure there are tons of resources to help! Great community here.

Cj

its 100% limited slip I don’t know if it’s clutch or gear type.

[Kgermanton]

Only use motorcycle oil, which it sounds like you are. I always use Mobil 1 4T motorcycle racing oil.
Aside from the already spot-on suggestions, take a look at your oil temps. Overheated oil will make the clutch slip but it usually damages the clutch so it wouldn't be any better once it cools down.

great point. It does get better when it cools so maybe it’s not the clutch. I’m starting to think it may be the splines on the CV’s going into the diff or possibly the diff. I did call a race car trans/diff builder and was about to pull out the diff and send it to him and after explaining the issues he said you’d hear grinding or clunking of it was something diff related. I’ve been chairing my tail for two years.

ive always used 4T oil. Usually the most expensive.

[sccadsr31]

This may be a master cylinder problem, what brand is it? We have had them the Gurling style that has a residual pressure valve in it which has caused the clutch to slip because it pumps up pressure and the residual valve prevents the MC from going all the way back to "0". The Tilton MC's have no residual valve.

David

[Kgermanton]

This may be a master cylinder problem, what brand is it? We have had them the Gurling style that has a residual pressure valve in it which has caused the clutch to slip because it pumps up pressure and the residual valve prevents the MC from going all the way back to "0". The Tilton MC's have no residual valve.

David

nobody has thought of this! I’ve had multiple mechanics hands on the car and none mentioned it. It’s not a Tilton. It’s a Girling brand. I’ll try to post a picture. I’m willing to buy a new one if you think this may be the issue. I’m hoping a Tilton will fit without modification

[Onebadbug]

I have seen many times with VW's where the master cylinder pushrod has no freeplay The more you drive it, the more it engages the brakes. Check that with your clutch master.

[R. Pare]

Definitely not a mechanical issue ( broken diff, slipping splines, etc). It is related to heat, and most likely the expansion of the clutch fluid is causing the clutch to partially disengage.

Another thing - with the reservoirs integral to the master cylinder, the vibrations from the engine can cause the fluid to at least partially "boil", which in turn will cause more air to be dissolved into the fluid, which in turn will cause it to expand more with heat. At the minimum, you should get reservoir extensions, and use a bellows in the reservoir to get rid of all of the air. On top of that, you can also try putting the fluid (while still in the can, of course!) in a vacuum chamber to get rid of any entrained air before bleeding the clutch hydraulic system.

[sccadsr31]

What is interesting is Wilwood makes what is essentially an exact copy of the Girling. Get ride of the Girlings and go all Tilton. I lost one of my early 2005 ZX10r's because of the Girling MC.
You just do not want any pressure build up in the master cylinders, I'm sure there was a good reason for RPV way back when but we certainly do not want any pressure in the brake and clutch hydraulics.
Why back around 2005 when I switched to the ZX10R and shredded a clutch clogged the filter and took out a rod and bearings the search for the cause took me to the clutch MC. At that point I learned the difference between some of the brands of MC's. At the time Tilton was the only one with no RPV, the quality was great and the cost was reasonable.
Also I need to give credit to Bob Fox in that search for answers, he had solved some GSXR clutch problems by going to the Tilton
David

[Kgermanton]

Definitely not a mechanical issue ( broken diff, slipping splines, etc). It is related to heat, and most likely the expansion of the clutch fluid is causing the clutch to partially disengage.

Another thing - with the reservoirs integral to the master cylinder, the vibrations from the engine can cause the fluid to at least partially "boil", which in turn will cause more air to be dissolved into the fluid, which in turn will cause it to expand more with heat. At the minimum, you should get reservoir extensions, and use a bellows in the reservoir to get rid of all of the air. On top of that, you can also try putting the fluid (while still in the can, of course!) in a vacuum chamber to get rid of any entrained air before bleeding the clutch hydraulic system.

makes me happy that you’re confident it’s the MC rather than mechanical! Thank you for the info. When I call Tilton Monday I’ll get a remote tank.

[Kgermanton]

What is interesting is Wilwood makes what is essentially an exact copy of the Girling. Get ride of the Girlings and go all Tilton. I lost one of my early 2005 ZX10r's because of the Girling MC.
You just do not want any pressure build up in the master cylinders, I'm sure there was a good reason for RPV way back when but we certainly do not want any pressure in the brake and clutch hydraulics.
Why back around 2005 when I switched to the ZX10R and shredded a clutch clogged the filter and took out a rod and bearings the search for the cause took me to the clutch MC. At that point I learned the difference between some of the brands of MC's. At the time Tilton was the only one with no RPV, the quality was great and the cost was reasonable.
Also I need to give credit to Bob Fox in that search for answers, he had solved some GSXR clutch problems by going to the Tilton
David

Im starting to get excited to finally get laps under power soon (just in time for the season too!). I’m calling Tilton Monday to get the MC. Do you guys recommend Castrol SRF for fluid? I’ll keep you guys updated.

[924RACR]

Sorry to be late to the thread.

I run Girling masters on my P2, but remote reservoir. I too would wonder about the clutch building up some preload over the course of a session.

Do you use your clutch on track? Left foot brake or right?

For sure, footroom in the pedal box can be in short supply, one does wonder if there could be an issue where you're starting to put pressure on the clutch... though I'd hope you'd be aware of that by now.

For fluids - any clutch/brake would work, I use ATE Typ200 'cause it's cheaper and is excellent.

For oil, I've recently switched to Mobil1 4T but the Redline bike oil worked fine too, ran that for many years, no clutching issues.

I am surprised to hear the thought that a slipping diff clutch pack could lead to this kind of symptom, not just one-wheel peels. In my experience, working with those (not in the P2, to be clear) across a wide range of engagement, the power goes to the rear wheels even if the diff is slipping 100% - it's just a normal open diff at that point. So having a progressing loss of power to the rear wheels doesn't make sense to me as a failure mode for that type.

Torsen style, though I have it in my car, not so certain on, though I'd expect similar results.

So my suspicion is still at the clutch, starting with actuation (MC/slave/pushrod).

I don't think switching to a Tilton is a bad idea, just not sure the Girling is necessarily the problem... unless as noted it is holding some pressure. That would in fact also make one wonder about if there's some issue in the plumbing between...

Good luck with your testing...

[Steve Davis]

I'm not 'up' on the engines nor chassis for your class, but might it be POSSIBLE to just DISCONNECT the clutch hydraulics for a test session? even on the chassis dyno? If you can crank it in gear (or push it off) and get it going, you should be able to shift it without the clutch .. I think.... I know I can on a motorcycle.

You didn't say whether you were CERTAIN it was a clutch slipping issue. I would think it would be pretty easy to tell if the engine was 'running away' from the clutch or not. Drag from other aspects .. like diff or brakes would NOT cause a properly operating clutch to slip I wouldn't think .. not if it was a proper clutch for the expected loads.

Just throwing out an idea for determining the source of the issue.. If I'm WAY off base, just ignore this post .
Steve, FV80

[924RACR]

For sure, these can be shifted without clutch. I only use my clutch twice a session, getting going and coasting into the pits.

Not a half-bad idea, pull the clutch slave and just be sure to remove the pushrod too (or you'll lose it on track and be hosed!)... will be obnoxious to start, plan on the push start, but if you could run a session like that you might learn something...

[Kgermanton]

Awesome idea guys. My friend has a dyno only an hours drive so I may swap to the Tilton MC since it’s only few hundred $ for piece of mind. If it doesn’t work I wonder if I can get the dyno rollers going without the clutch.... maybe two people pushing the tires.

[R. Pare]

Awesome idea guys. My friend has a dyno only an hours drive so I may swap to the Tilton MC since it’s only few hundred $ for piece of mind. If it doesn’t work I wonder if I can get the dyno rollers going without the clutch.... maybe two people pushing the tires.

Just put a T fitting in the clutch line somewhere, along with a length of hose that can be capped off after bleeding everything. Once the engine is running and the car in gear, pull the cap off of the t-eed line to release any possibility of residual pressure.

[Farrout48]

For sure, these can be shifted without clutch. I only use my clutch twice a session, getting going and coasting into the pits.

Not a half-bad idea, pull the clutch slave and just be sure to remove the pushrod too (or you'll lose it on track and be hosed!)... will be obnoxious to start, plan on the push start, but if you could run a session like that you might learn something...

If you remove the pushrod in the GSXR, engine oil will be pumped out of the hole left in the pushrod seal.

[RussMcB]

This is a pretty great community, isn't it? :-)

I know many of the people who have responded have many years of experience with motorcycle powered race cars and racing in general.



Hey, how about posting a picture of the car? And of the engine/chain/drive train?

[Kgermanton]

This is a pretty great community, isn't it? :-)

I know many of the people who have responded have many years of experience with motorcycle powered race cars and racing in general.



Hey, how about posting a picture of the car? And of the engine/chain/drive train?

it’s amazing. I’m still not getting my hopes up but I’m pretty sure it’s the MC. Yes thank you to everyone for the help and ideas. Can’t tell you how many mechanics couldn’t figure it out.

Jedi P2 car. Ran at Waterford Hills most it’s life until I bought it. It will run at NJMP, Limerock and the Glen. GSXR1000 pistons and rods. About 950lbs with me in it.

[924RACR]

If you remove the pushrod in the GSXR, engine oil will be pumped out of the hole left in the pushrod seal.

Derp.

I know this car well; watched Jim Lamb (RIP) run it quite a few years at Waterford. He (and my teammate) own the blame jointly for talking me into moving over from ITB to DSR! I had wondered if it was Jim's car you ended up with...

[Kgermanton]

Derp.

I know this car well; watched Jim Lamb (RIP) run it quite a few years at Waterford. He (and my teammate) own the blame jointly for talking me into moving over from ITB to DSR! I had wondered if it was Jim's car you ended up with...

yup this was Jim’s car. A local guy Zach bought the car from Jim and sold it to me.

[Mike B]

I’m still not getting my hopes up but I’m pretty sure it’s the MC.

A little more effort but you could convert to a cable-operated clutch to completely eliminate the MC.

[Kgermanton]

A little more effort but you could convert to a cable-operated clutch to completely eliminate the MC.

do most run cable operated? If so I’d love to know how. I can figure out how to fabricate a cable from the pedal back to the slave. How do you convert the slave to cable?

[RussMcB]

do most run cable operated? If so I’d love to know how. I can figure out how to fabricate a cable from the pedal back to the slave. How do you convert the slave to cable?

A clever one I saw had a backwards "L" shaped lever. The cable pulled on the longer arm and the shorter arm pushed the clutch push rod.

Clutch push rod --> 1|
L shaped Lever --> 11------ < -- pivot point
Cable pulled here. - - - - - |
Cable pulled here. - - - - - |

Yes, Formulasuper, I'm talking about your Ralt/Hayabusa. :-)

[924RACR]

PS - if you were to ever get the car over here to Waterford Hills for a race weekend, rest assured you would have a VERY warm welcome! Jim was much loved, and is missed, and we'd all be very happy to see the car again, if only for a visit!

[Shelly Sadwin]

Had a similar problem with a fb running a whirling mic. When fluid heated up the clutch would slip put s wilwood in and problem gone.

[Kgermanton]

Great news everyone. Changed to the Tilton MC and problem solved!! You have no idea how appreciative I am of everyone who tried to help and especially the the few who figured out it was the MC. 7 runs at my local autoX and it pulled strong. Next up is a NASA TT at NJMP. Finally enjoying the car!

[sccadsr31]

Had a similar problem with a fb running a whirling mic. When fluid heated up the clutch would slip put s wilwood in and problem gone.

My guess is you are eventually going to have the same problem with the Wilwood, IF it looks just like the Girling, then it also has a residual pressure valve, the Tilton does not.