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Slow clutch return

PostPosted: Fri Sep 20, 2013 4:57 pm
by 661
When doing speedy changes, 3rd to 4th as an example, even though the clutch pedal has been fully released to the upright position the engine over revs as you try to apply power for about half a second as the clutch appears to fully engage. It just seems to need some help to spring back. Any thoughts most welcome .
Graeme

Re: Slow clutch return

PostPosted: Fri Sep 20, 2013 5:33 pm
by twincamman
Try a stronger return spring

Re: Slow clutch return

PostPosted: Fri Sep 20, 2013 6:51 pm
by oldelanman
There are a number of things which could cause your problem........

Check that you have clearance between the slave cylinder pushrod and the clutch release lever. This clearance is essential to ensure the clutch engages fully and it diminishes as the clutch wears so the pushrod length needs to be adjusted periodically to compensate - the workshop manual gives the correct setting. If your clutch bite point is at or near the top of the pedal travel it could indicate a lack of this clearance - or if the clearance is OK - that the clutch disc may be in need of replacement.

If the clearance is OK then, as Ed says, check the return springs. There should be one on the slave cylinder and one on the pedal itself - Check they are both present and have not become overstretched and weak.

If your clutch fluid line includes a rubber flexible section it could be failing internally and creating a sort of non-return valve. If you have a one piece nylon line check that it's not kinked or damaged by heat from the exhaust.

Check the pedal itself is not partially siezed on the pedal box cross shaft.

If all of the above are found to be OK then it's likely to be the master or slave cylinder pistons themselves sticking in their bores.

There may be other factors but that's all that comes to mind at present.

Re: Slow clutch return

PostPosted: Sun Sep 22, 2013 10:45 am
by 661
Thanks for the replies. I'll take a look at the points you raise. It's something fairly new so I don't know that the existing springs would lose their tension in this kind of way and I'm pretty sure I replaced the master and slave cylinders about a year ago. Plenty else to check.

Re: Slow clutch return

PostPosted: Sun Sep 22, 2013 1:37 pm
by collins_dan
Is it possible that the problems with both the clutch and brakes are related to your change from silicone to DOT 4? I always thought these were highly incompatible, so changing from one to the other required completing changing the lines to ensure completely removing any remnants of the old fluid. Just a thought. Dan

Re: Slow clutch return

PostPosted: Sun Sep 22, 2013 8:31 pm
by 661
collins_dan wrote:Is it possible that the problems with both the clutch and brakes are related to your change from silicone to DOT 4? I always thought these were highly incompatible, so changing from one to the other required completing changing the lines to ensure completely removing any remnants of the old fluid. Just a thought. Dan

Interesting thought. I got rid of the silicone at least 3 years ago and the systems have been flushed a number of times. I just don't get the feeling that's the issue

Re: Slow clutch return

PostPosted: Sun Sep 22, 2013 9:19 pm
by vxah
I had the very same thing! It was the flexi hose that had failed internally! It felt a little soft from the outside so i replaced it with a braided hose and the problem was solved!

Re: Slow clutch return

PostPosted: Mon Sep 23, 2013 7:52 am
by rgh0
The clutch cover diaphragm spring is what returns the pressure on the clutch plate once your foot is off the pedal. The other springs just stop the pedal and clutch release arm and release bearing from rattling around when your foot is off the clutch pedal and are not critical for the clutch return itself.

A clutch that slips for a very short period after engagement may just be getting near the end of its life. It can also be due to just a too slow release clutch foot movement combined with a too fast accelerator foot movement. I find myself when racing that if my footwork timing is a little off in the heat of a corner or a passing manoeuvre that I can end up with a slipping clutch for a half second like you describe.

If the return is truly slow then you have an hydraulic blockage or mechanical drag somewhere in the system as described by others.

cheers
Rohan

Re: Slow clutch return

PostPosted: Mon Sep 23, 2013 7:30 pm
All good suggestions for that slow return syndrome and I'll add just one, the "foot" valve in the master cylinder.