Slipping Clutch! On a four day trip!

[David Allaband]

Hi everyone! I'm having a problem with a slipping clutch. I'm visiting a friend in DC so I'm hopping I can work this out before the ride home. Yesterday I finally got the carbs balanced, but since then whenever the bike gets hot the clutch starts to slip. It gets worse and worse until it's hard to go over 25mph or up hills. It's fine on longer highway rides. I'm using Rotella T oil as was advised on this forum, I don't remember the weight.

Here's what I'm thinking. Maybe now that the bike is pulling evenly on all pistons it has more torque so when the oil heats up and gets thinner the engine is able to spin the clutch? Maybe? Could a different oil fix this?

Any thoughts?

One more thing, I just replaced the slave cylinder on the clutch. It was hard to get into gear before because the clutch would not disengage the tranny. Now the clutch is able to disengage but I have this new problem.

Help help! Before my ride home! Thanks!

[David Allaband]

Okay I just read the thing on slipping clutch that's right above my post. I see that the sugestion there is that my clutch needs new plates. I can't do that right now, or even pull it apart to imspect it because I don't have a new seal. But could this really be a bad clutch? The only thing that changed between my clutch working and not working was synching my carbs! Should I de-synch them so I can ride it home?!?!?!

Why can I not ride this bike for more then a couple hours before it breaks down!

[FJmonkey]

I had some slipping issues when I switched to full synth oil. Not like you described, mostly in the higher RPMs,. The friction pads need time to adjust, My clutch had sticking problems when cold and they seem to be gone now. My 86' also has the 2nd gear issue that feels like a rev limiter as it pops in and out of second gear under hard load. Adding a second spring will help but you might want a 14 mm master or some really strong left hand grip.

[racerrad8]

The clutch spring was weak and now that you got the carbs dialed in it is showing. You need to get it home then install the second spring.

Randy - RPM

[Arnie]

Did you replace the clutch slave at the same time you got the carbs sync'ed ?
It is possible that you have a combination of faults that are causing your slippage.

It is likely that the clutch disks are somewhat worn at least partially due to your old slave not pushing the pressure plate far enough out to fully disengage them.  Now that you have a new slave, its not able to retract enough to allow the clutch pack full engagement.

I wouldn't be too afraid to open the clutch up and inspect or replace some parts.  Even if you tear the gasket and don't have a new factory one, you can cut one out of (thin cardboard/thick paper) that will work just fine.  Just use the clutch cover and the old gasket as your form.

I'd be very surprised if the very slight additional power from sync'ing the carbs is the cause of your difficulties.

And, Washington DC is only what, 250-300 miles away from NYC ?  You can just about paddle the bike for that short a distance 

Cheers,
Arnie

[David Allaband]

Thanks for the advice everyone! I'm still confused about the slipping though. Why does it only happen when the bike is hot and get worse as it gets hotter? If I start out riding in town and then go to the freeway I don't get any slipping. If I ride on the freeway for a while it won't slip, but when I get into stop and go traffic it will start slipping... BUT when I get back on the freeway the clutch will stop slipping after a few minutes! This is temperature related right? Why does it slip when the engine gets hot? What does being hot have to do with it? Does the.... engine case change shape and allow the clutch plates more space to slip? Do the plates heat up and defy the laws of physics and get smaller? Does the spring heat up and get weaker? What's the difference between stop and go traffic and the freeway here? All I can think of is heat!

[weymouth399]

The clutch spring was weak and now that you got the carbs dialed in it is showing. You need to get it home then install the second spring.

Randy - RPM

Ya what he said.
Mine did the same thing, double up the spring. I like the double spring way more than the upgraded pressure plate w/individual springs. Even in the race cars.

Bob W

[andyb]

To contrast, I thought the coil spring conversion was infinitely better than doubled springs.  But that was with a stock master cylinder.   The coils get a little stiff in stop and go, but much better than the doubled ones did.

On the bright side, that's how you know an FJ is running well.  The clutch finally starts to give up!  Good job on the motor work, the clutch is much much easier.  If you keep riding it with a slipping clutch, you will probably need to take the time to clean the oil pickup screen as well as rapidly destroy your clutch plates.

[racerrad8]

Does the spring heat up and get weaker?

You have answered your own question.

There is some wear in the clutch pack which has changed the thickness, thinner than stock and the spring looses tension after it gets hot. So, once it is engaged on the freeway you are good to go, stop & go...not so much.

That tune up really boosted your torque and creating some of the issue as well.

Randy - RPM

[SlowOldGuy]

Also, make sure you're not building up pressure in the clutch fluid when hot.  If the lever is not returning fully, it can block the return port in the master and the heat could be building up pressure that's trying to engage the clutch.

DavidR.

[fj1289]

How old is the oil in it now?  If it's been there a while it may have thinned out quite a bit.  Some fresh oil may help the clutch a little.  

Also, try to reduce the amount of torque you put through the drive train.  Instead of detuning the engine, detune the right wrist a bit until you nurse it home.  

Unfortunately it will take a little while to work all the bugs out, but it's worth it!

Also, if you need to service the clutch, you should be able to lean it to the left pretty good (put the sidestand on a slight downhill) without having to drain the oil.  You can also try cleaning the gasket surface with brake cleaner and use some case sealer (like tri bond, yamabond, etc) to seal it up.  USE A VERY THIN LAYER!!  If you think you have enough on there, it is probably too much!

Good Luck!

[andyb]

Also, if you need to service the clutch, you should be able to lean it to the left pretty good (put the sidestand on a slight downhill) without having to drain the oil. 

Or use a 2x4 or other scrap bit under both wheels to get the bike to learn farther on the sidestand.  IMO though, I'd just drain it first, if the clutch is slipping hard, the friction material is being worn down and it has to go someplace, so into the oil it ends up.  At the least, you'll want a new filter and oil, but I'd still press you to check the pickup screen in the sump, those very fine screens don't take much to plug, and the motor goes away if they do.

[David Allaband]

Thanks everybody, this is all great info. I'll nurse it home and yank the clutch. I'll let you know how it goes!

[markmartin]

At the least, you'll want a new filter and oil, but I'd still press you to check the pickup screen in the sump, those very fine screens don't take much to plug, and the motor goes away if they do.

Andy, what is this pickup screen you speak of?  Where exactly is it located--and/or is it hard to get to?
Thanks.




David, sorry for hijacking the thread.

[andyb]

Mark:

Part #2 as listed in the fische is the oil pickup screen.  It's snapped over the end of #1, which is the oil pickup itself, and the screen must be removed to gain access to the two bolts (3) that hold the pickup in place.  There's a gasket (17) between the pickup and the lower crankcase.

To get access, you have to remove the oil pan (15) by taking out a zillion screws (18, 19), and probably should have a gasket on hand for when you reassemble things (16).  When you're taking it apart, take note of the direction that the screen is facing, iirc there's a big arrow on it or some other obvious indication.  It's just a cap with a spot-welded screen on it, and it's the first line of defense against nasty crap going through the oiling system.

IMO, it should be checked every time you put a new clutch in, and/or any time you find any strange particulate matter in your oil (at which time, probably you should check the clutch pack for wear!).

I'd take a picture, but I'm tired.  <edit>  Correction, I see Randy has a picture of one of them.