tombo46 Posted June 4, 2009 Report Share Posted June 4, 2009 I have posted about this problem before in the past however I have tried a few solutions to no avail and wanted to give people an update and hopefully get some fresh idea's... My bike is a 2008 Gas Gas 300 and a strange clutch problem started happening a while back.... When the clutch is under load the clutch slowly starts to bite more and more (resulting in me having to pull the lever in more and more until it is against the bar and the clutch is fully engaged and the bike is driving forward) To try to explain it more clearly here is where its giving me problems.... lets say I have a very small run up to a rock and I have to put the front wheel against it. to balance I will drive the bike into the rock face with the front brake on, obviously because the bike cannot go forward the engine is being labored. while im doing this, the clutch is being slipped so the bike is trying to drive up the rock but It cant because the front brake is on, whilst gaining some composure and using this method to balance, the clutch plates will grab more and more as time go's on, resulting in me needing to pull the clutch lever in more to keep the "bite point", eventually (10 - 15 seconds or so depending on how hard the engine is working) the lever is all the way into the bars and the bike will drive like the clutch lever isnt pulled in at all. after releasing the clutch lever the bike rides normally again almost straight away. Heres a video to help make things easier to understand.... http://www.youtube.com/watch?v=UJMsjLrqT4A This problem first happened when my water pump seal broke, there was water in the gearbox for anything up to 2 hours before I noticed so I changed the water pump seal and put fresh oil in. thats when the clutch problem started, I thought it must be because of the water, and the clutch plates must have swolen taking them close to their tolerance, so when heat started to build it the clutch pack, it was expanding and running out of adjustment. So naturally, I bought a new clutch pack and a gasket. after fitting both and expecting it to be fine, I quickly found that it wasnt and that the problem was exactly the same as before. I then thought it may be a hydraulic problem, So I changed the slave cylinder seals and the master cylinder seals. this still didnt solve it... It was then reccomended to me that I try using mineral oil instead of DOT4 as it may be the DOT4 thats expanding and causing problems when the clutch gets hot. so I cleaned the whole hydraulic system out with compressed air etc and put fresh mineral oil and fresh mineral oil seals in. and yep....you guessed it! still not working! so, after racking my brain I came across a sudden realisation! when I bought the water pump seal, I also asked for some oil (Motul Dexron II ATF) however the lady said that they didnt have any and that there was a "new" oil they were using in the bikes and instead gave me a bottle of Motul Transoil. Suddenly I thought that must be the problem. So I quickly flushed the engine out and replaced the oil with some new Motul Dexron II ATF but the problem was still there. I also tried 2 other types of oil with no luck. I then decided that the oil may have done something to the clutch plates so I bought yet ANOTHER clutch pack, fitted it with fresh oil (The Motul ATF). and would you believe it, the problem still persists! Im out of Idea's now, So im turning to you guys for some inspiration. the only other detail is that I have a Venhill hose on the front, But I cant see why this would pose any problems as I dont know of anyone who has had trouble with them. Heres hoping! Tom Quote Link to comment Share on other sites More sharing options...
paul w Posted June 4, 2009 Report Share Posted June 4, 2009 when you changed the clutch did you change the steel plates as well? Quote Link to comment Share on other sites More sharing options...
ksv Posted June 4, 2009 Report Share Posted June 4, 2009 Definitely sounds hydraulic to me. Have you tried doing the biting point thing with the cover removed from the clutch master cylinder, if there was hydraulic fluid leaking back past the seals you may be able to see it returning into the cylinder. Just a thought.... Quote Link to comment Share on other sites More sharing options...
max1956bikes Posted June 4, 2009 Report Share Posted June 4, 2009 got to be hydrolic problem.change the hose it could be balloning. Quote Link to comment Share on other sites More sharing options...
blocky Posted June 4, 2009 Report Share Posted June 4, 2009 I'd put a tenner on it being a hydraulic problem. If the fluid level in the master cylinder is going down then you have a leak somewhere. If not then it must be creeping past the seals either in the master cylinder or slave cylinder. I see that you have replaced the seals in both so the next stage would be to borrow a master cylinder from a friend and try it. If the fault is corrected then you know the fault is with the master cylinder. If not its almost certainly in the slave cylinder Quote Link to comment Share on other sites More sharing options...
andysv1k Posted June 4, 2009 Report Share Posted June 4, 2009 i know next to nothing, but if fluid was passing the seals in the slave, wouldnt that be just leaking into the clutch housing and therefore the fluid level would be dropping. Andy. Quote Link to comment Share on other sites More sharing options...
tombo46 Posted June 4, 2009 Author Report Share Posted June 4, 2009 Definitely sounds hydraulic to me.Have you tried doing the biting point thing with the cover removed from the clutch master cylinder, if there was hydraulic fluid leaking back past the seals you may be able to see it returning into the cylinder. Just a thought.... Tried this and there isnt anything going back into the master cylinder, and im not losing any fluid through the slave seals either. If the clutch is pulled in and the bike is in gear, no matter how long its pulled in for, the clutch doesnt start to bite, it is only if the engine is under load. also, there is no visible swelling of the clutch hose, I find it really hard to believe it could have gone wrong after just a year and it would be a hell of a coincidence if It happened after I had worked on the bike. Still, everything else has been tried so I might aswell give it a go. In the mean time if anyone else has any thoughts on it, please post them! Cheers, Tom Quote Link to comment Share on other sites More sharing options...
tombo46 Posted June 4, 2009 Author Report Share Posted June 4, 2009 when you changed the clutch did you change the steel plates as well? yep, put a whole new clutch pack in, they come measured up to the correct thickness. Tom Quote Link to comment Share on other sites More sharing options...
tombo46 Posted June 4, 2009 Author Report Share Posted June 4, 2009 got to be hydrolic problem.change the hose it could be balloning. Just changed the hose over to the original standard one and its still the same =( Tom Quote Link to comment Share on other sites More sharing options...
b40rt Posted June 4, 2009 Report Share Posted June 4, 2009 Got to agree that it sounds like hydraulics, fluid passing back into reservoir. Quote Link to comment Share on other sites More sharing options...
tombo46 Posted June 4, 2009 Author Report Share Posted June 4, 2009 Got to agree that it sounds like hydraulics, fluid passing back into reservoir. if this was the case, wouldnt it also pass into the resevoir if the clutch was just held in and the clutch wasnt being slipped? Tom Quote Link to comment Share on other sites More sharing options...
lowbrow Posted June 4, 2009 Report Share Posted June 4, 2009 Tom, I had a similar experience and it was the bore inside the master cylinder that was damaged/worn. Most of the time you only pull the lever in part way and this is where the bore wears. When you hold the lever fully in the seals reach part of the bore that its not so worn and hence they actually seal. Can you borrow a master cylinder that's known to be good to eliminate the problem for yourself? Dave Quote Link to comment Share on other sites More sharing options...
copemech Posted June 5, 2009 Report Share Posted June 5, 2009 I think most all has been said. If the fluid pressure is relaxing going to release the clutch, yet there is no fluid loss externally, then eith the hose is balloning under pressure or you have an internal loss in the MC. If you give it another quick pump, then it holds, I might further suspect the hose, yet if same thing happened, might further suspect the MC. Thoughts, MC Quote Link to comment Share on other sites More sharing options...
tombo46 Posted June 6, 2009 Author Report Share Posted June 6, 2009 Im going to swap master cylinders with a mate on sunday, hopefully it will sort it, thanks for the input people, ill keep you posted. Tom Quote Link to comment Share on other sites More sharing options...
jse Posted June 6, 2009 Report Share Posted June 6, 2009 I think most all has been said. If the fluid pressure is relaxing going to release the clutch, yet there is no fluid loss externally, then eith the hose is balloning under pressure or you have an internal loss in the MC. The hose expanding under pressure seems highly unlikely (I don't ever remember seeing one do it in a newer bike) but a problem with the M/C bore seems to be the most logical explanation, based on info given. It's easy for a small piece of dirt to enter the reservoir during regular servicing and work it's way into the bore where it can scratch the wall enough to provide a small channel that fluid can pass through, past the seal lip. It could also be caused by a remaining piece of swarf in the bore left over from the machining process. I'll be interested to see if a different M/C solves the problem. Jon Quote Link to comment Share on other sites More sharing options...
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