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Freaky Clutch issue

C

Ciobulus

Joined Jun 2007
30 Posts | 0+
Hello,

I recently changed the fluid for my clutch. No issues here.

I dont know if this issue was present before the fluid change and I only noticed it now but...

When I pull the clutch lever 30% it makes a air squirting sound like I am pushing air with some water trough a small hole and its very light to pull than the rest of the travel after this 30% I can feel the fluid compressing and disengaging the clutch.

If i repeat the 30% travel at a very high pace I can see fluid jumping around in the reservoir.

The issue is that If i press the lever very very slowly and gently I can go all the way without even moving a part. Its like the lever is not connected to anything.

If I pull it harder the clutch works just fine engaging from 0% travel to 100% no problem. So I need to pump it from 0% to 100% fast or else I get no clutch action going.

When I pull it gently the fluid reservoir gets more fluid in it. So my master cylinder is pumping the fluid back up into the reservoir when I dont pull the clutch fast enough.

What do you think ? Is there a valve inside it that got stuck or partially blocked? Should I just change the whole master cylinder ?

Thanks
 
Hopefully its just air m8 give it one hell of a bleed making sure theres plenty of fluid in the resevoir
 
I cant imagine how air could make it push the fluid into the reservoir if I pull it really gentle. But I will try a super bleed tomorrow. Any other thoughts?

If my understanding of break systems is correct. There is a piston that when moved at some point it passes the opening from the reservoir fluid intake and starts compressing the heck out of the fluid. If fluid escapes it then why is it perfect if I pull it faster ? Pulling it faster will cause it to work perfectly. stupid issue.
I can only imagine a worn seal that if compressed slowly lets all the fluid past it and If its compressed with a jerk it makes it seal again and not let any fluid escape as long as there is pressure in the line.
 
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Does your clutch still work m8?the fluid might be coming back up because there is an air block before the slave cylinder thats why i was asking if your clutch was working if its not then it could be that or your slave is gubbed...
 
The clutch is working. It depends on how I pull the lever.

If I pull it fast ( like you would normally pull it in traffic or when you change gear ) It works Flawlessly Engages Disengages with no issues. I can ride it I can find neutral I can change two gears at a time etc.

If I pull it gently and slowly it wont do $hit. It just pushes all the fluid back up in the reservoir. If I pull gently 50% and then fast the last 50% it will disengage the clutch only 50% and make gear changes clunky like I just pressed the lever half way.
 
Have you bled the master cyinder? if not your problem might just an airlock in the cylinder, to bleed the brakes and clutch its best to bleed the master cylinder first then follow with the calipers or slave cylinder!
 
sounds like a seal in your slave cylinder on the bars is going...might be time for replacement. Try a good bleed first, but I doubt it will help.
 
There is only one bleed nipple for the clutch near the clutch cover. The only way to bleed the master cylinder would be to reverse bleed it I guess

I must have them switched. Which one is the master cyl ? The one on the bars or the other one?
 
ah now i see gen 1 not gen 2 gen2 has a bleed nipple on master cylinder on bars i think with gen 1 you have to crack the banjo on the master.but reading your last post it sound like the slave cylinder is sticking and only when you gi it welly it works could be worth whipping the slave off and checking the piston is free ....
 
Its not the slave cyl. I mean Its very clear that its the master cylinder ( the one on top of the bars ). Pulling on the lever with normal speed / force will make it work good. Now imagine pulling on it very very very very slowly barely moving it and very gently without any twich and it goes all the way without pushing any fluid trough the lines just up in the reservoir. :) I'm gonna have to do a video just to illustrate the issue. Writing dosent seem to do it.

Found some ways to figure out if the seal is gone. But I need to somehow keep pressure in the lines to see if it goes away. Thats a bit hard with a clutch :( Maybe I can keep it disengaged for 30 minutes and see if it will shift gears. Matter of fact I'm gonna zip tie the lever and check If it has pressure in the morning.
 
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yes the master cylinder is on the bars...thanks for the correction...but yes there in lays your problem.

I had a similar problem on my 01' 748 duc
 
Yep its the Master Cylinder. I found a small piece of rubber in the reservoir. This piece of rubber would leave a hole big enough to cause my issues 99%.

Do you guys know of a replacement piston kit for this Master Cylinder ? Or should I just buy the whole thing from the breakers ? I'd prefer a new piston and seals. Thanks
 
You have to get the ktm part as you can't get one from aprilia,and ive forgot the part number its basically the full piston kit i think its around the £50 mark but if its just the rubber cap thats away you can also just buy that and i think its about £4 there was a thread earlier this year about this with the part numbers on it m8 hope this helps...
 
Yeah I found the part number its 61002032000

The rubber cap has no way of ending up in the reservoir so its a bit from the piston itself.

How hard would It be to swap the piston I wonder. I dont see any way of taking it out other than pulling it with some pliers ?
 
i would not use a zip tie mate you will just damage your bearing on the clutch pressure plate its not made for long term use like 30 mins.the master is on the bars slave is the other with the nipple .put a big rag under the slave fill the master crack the nipple 1/2 turn hold your finger over the end of the nipple with some pressure then pump clutch lever untill you get some fluid scooting out then lock nipple fill up again and repeat again untill you get good lever pressure .you might even be better to screw in the wee screw on the lever all the way in (keep note of the turns in youve made)and set the lever to number 4 then try bleeding again ...... remember when your done reset the screw back to where it was ..i had to piss about with mine to get right but now its good..
 
mad biff said:
i would not use a zip tie mate you will just damage your bearing on the clutch pressure plate its not made for long term use like 30 mins.the master is on the bars slave is the other with the nipple .put a big rag under the slave fill the master crack the nipple 1/2 turn hold your finger over the end of the nipple with some pressure then pump clutch lever untill you get some fluid scooting out then lock nipple fill up again and repeat again untill you get good lever pressure .you might even be better to screw in the wee screw on the lever all the way in (keep note of the turns in youve made)and set the lever to number 4 then try bleeding again ...... remember when your done reset the screw back to where it was ..i had to piss about with mine to get right but now its good..
Click to expand...

lol im too slow at typing
 
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