Clutch problem when hot

[geetee]

Hi,

Looking for some ideas on this one.

Replaced the seals in my clutch master cylinder a couple of weeks ago as it was p1ssing fluid on my shoe.

Since then it's fine from cold, but once the engine is up to temp the gear change gets crunchy and/or impossible.

I thought the bite was too low to the floor so adjusted it up a bit last weekend - but still when warm it does the same thing.

In 1st and stationary it feels like the clutch is dragging on and off - but it still takes the same inch or so of pedal travel to disengage the clutch and move off.

Going to do some investigation at the w/e so some pointers on what to look for would be welcome.

I'm thinking:
1. The clutch fluid is crap. I used DOT3 that had been open for a while. So will replace that with fresh DOT5.1
2. Clutch release fork has bent or broken... but then why only a problem when hot?
3. Gearbox oil needs changing.
4. Clutch slave cylinder has gone... but then why only a problem when hot?
5. Flywheel has highspots or clutch plate is warped. Being hot means they expand and are closer together?


Any other ideas?

Thanks
Graham

 

[oap-r]

Think changing the fluid will cure the problem.

You're not supposed to use brake fluid from a container that has been open to atmosphere for any length of time and the grade is wrong too.The fluid has more than likely absorbed moisture.

 

[Major_Sarcasm]

^^ what he said. See my reply on the other forum.

 

[youngsyp]

And again. As oap-r say's, brake fluid is hydroscopic so, it will asorb moisture out of the air. If it's been open for a while, it will have absorbed one hell of a lot of water. This will start to evaporate when warm and produce condensation which, can be compressed. So, when you press your clutch peddle, it's not actually moving the slave cylinder that much and so, not disengaging the clutch. Sorry for trying to tell you how to suck eggs !!

If I open a bottle of brake fluid, if I don't use it all, I'll bin it as, it'll be no good the next time I come to top up the brake or clutch fluid.

Try to get some high boiling point DOT 4 fluid. You'll find that this will have a higher boiling piint than the DOT 5.1 plus, there is no advantage of using DOT 5.1 unless you use it for your ABS brakes as, that's what it was designed for !

 

[geetee]

OK.

Thanks guys.

I wouldn't have used it but I was stranded at home with no transport to go and get fresh fluid.

Does clutch fluid get that hot? It's not like it's sitting in roasting hot brake caliper cylinders. The only heat it could get would be transferred via the clutch fork and slave cylinder.

Sounds like the most likely cluprit (and also the easiest to sort out thankfully) - so fingers crossed!

I'll let you know how it goes.

Thanks again.

Graham

 

[oap-r]

OK.

Thanks guys.

I wouldn't have used it but I was stranded at home with no transport to go and get fresh fluid.

Does clutch fluid get that hot? It's not like it's sitting in roasting hot brake caliper cylinders. The only heat it could get would be transferred via the clutch fork and slave cylinder.

Sounds like the most likely cluprit (and also the easiest to sort out thankfully) - so fingers crossed!

I'll let you know how it goes.

Thanks again.

Graham

The fluid absorbs the water/air and when they get compressed,they get hot.Also,when any water trapped in the fluid gets hot,it actually boils the liquid.

 

[geetee]

Replaced the fluid today with fresh DOT 4. Ran near enough a litre through it to make sure all traces of the old cr@p was flushed out.

Unfortunately - same problem. OK when cold, crunches and/or refuses to go into gear when hot.

1st, 3rd and Reverse seem worst.

Any more ideas?

Thanks
Graham

 

[oap-r]

Replaced the fluid today with fresh DOT 4. Ran near enough a litre through it to make sure all traces of the old cr@p was flushed out.

Unfortunately - same problem. OK when cold, crunches and/or refuses to go into gear when hot.

1st, 3rd and Reverse seem worst.

Is all the air def out of the system as it sounds as if the clutch is not completely disengaging when hot.Did the seal change cure all the leaks?

Have you had any rough changes before the crunching started? If you've done the synchro's i'd expect you to be crunching the gears all the time whether hot or cold.

 

[pulsarboby]

right first of all, its highly unlikely to be a fluid problem as the clutch is biting an inch or so off the floor, so clutch id dis-engaging and doing its job!

most likely cause is the selector fork is bent slightly or worn or as bruce above said, you have a worn syncro!

if any gear part is worn it will create excess heat due to friction which will show up as a prob when hot.

i would consider changing the oil in box for a good quality oil, and see if that improves matters, but if theres wear there at all, your only delaying the inevitable!

 

[geetee]

Time to get the box rebuilt by the sound of it then

Unless anyone has a good condition 2nd hand one going?

Thanks
Graham

 

[gunmetalgtir]

Exactly the same problems I was having with my last R! Turned out to be a warped clutch disc and broken release bearing.

What kind of clutch is it?

 

[geetee]

RPS Street Max.

I'm going to have to work up the enthusiasm to pull the thing apart to work out what's wrong now!

 

[gunmetalgtir]

Exactly the same clutch I had as well! :lol: I took it to 3 differnet garages who all said that it was faulty, as it had only been in for 1000 miles or so, phoned srb who I bought it off of and they didn't want to know about it!

 

[petebann]

i'd like to know when you solve this problem as i'm having exactly the same thing happen to me. Lovely when cold/warming up but after been running for a while or give it some, i really have to ram it in 1st gear at lights.
Keep us posted mate!

 

[Fusion Ed]

Had the same experience as this with other clutches as well. They get hot and warp or slip and then you can never get the things in gear..

 

[geetee]

Going to be a while before I have the time to do it. Saving up for some other bits and bobs to do to the motor whilst it's out this time as well.

Will let you know.

Cheers
Graham

 

[a11ova]

My fingers would point at either a selector fork aor the clutch itself. Either way the engine is gonna have to come out so if clutch is ok then new gearbox on the cards i reckon

 

[abyss]

if its an rps its more than likley the fork has bent causing friction trying to and get it into gears. im affaid a new clutch fork is needed not a rebuilt as some state. buy a new fork and strengthin it should fix your problem.

 

[geetee]

Not buying anything until I've got the motor out and found out what's buggered

Cheers
Graham

 

[Fast Guy]

1) Try to get some high boiling point DOT 4 fluid. You'll find that this will have a higher boiling piint than the DOT 5.1 plus,

2) there is no advantage of using DOT 5.1 unless you use it for your ABS brakes as, that's what it was designed for !

1) Not true. Dot 5.1 should have a higher boiling point than Dot4.(Motul RBF 600 being an exception) Dot 5.1 is realy incorrectly named as it's more of a Dot4.1, Dot5 is a different type (silicone based) of fluid to Dot3,4&5.1.

A couple of examples here

http://www.stealth316.com/2-brakefluid.htm
http://stason.org/TULARC/vehicles/motorcycle-ducati/5-Should-I-use-DOT-3-4-or-5-brake-fluid-when-replacing.html

2) True in the case of the clutch as there's no temperature involved which could cause the fluid to boil, so in theory Dot3,4 or 5.1 could be used. (In the brakes case it should have a higher boiling point and so be an advantage to heavy breakers against most Dot4s, just check the specs before buying)