My clutch slips sometimes

[cnap504]

Strange but true, my 1986 GS1150’s clutch slips in 4th and 5th @ w.o.t. in the upper rev range.  It’s a stock bike with pipe and carb jetting.  The clutch works great until it hits higher r’s in the higher gears.  I’m using dino motorcycle specific oil.  Thought about putting in some Barnett springs but the site has two spring sets for the 1150, one with no particular description and the other set denotes heavy duty application. Low mileage bike with stock power, what to do?

 

 

Edited May 1, 2021 by cnap504
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[Isleoman]

The builder that did my engine swears by stock Suzuki clutch parts and stock springs.    How low is low mileage?   I wouldn't open up the clutch without changing everything that needs changing,   I'm doubtful heavier springs will cure the issue on their own once it's slipping. 

 

[krazy kat]

Try to re adjust like in the manual . Pay extra attention to the adjustment at arm coming out of case .If you have proper freeplay up top.

They can be finikey have found the problem usually at that lower arm.Never needed heavy springs for basic stock.

[cnap504]

10,000 miles, but I have only had it for 1,500 miles and the clutch issue has just recently shown up.

 I am going to check the arm alignment and it’s free play, cable adjustment also.  I am most familiar with those clutches that use an adjustable “worm gear” that have you run the adj screw in and back out 1/4 turn.  So maybe I’m missing something on the GS setup.  Thanks for the responses

 

Edited May 1, 2021 by cnap504

[Dezza]

Personally I would avoid heavy-duty springs like the plague. They make the clutch lever action very heavy. When you say 'motorcycle oil' this is pretty vague. Semi-synthetic?

[no class]

one thing I have noticed about every efe I’ve owned ..... the clutch packs never really get enough oil saturation . Take a look at your plates and steels .... soak each fiber plate in oil and adjust cable freeplay.... take a test run . use a good quality mineral oil or semi syn blend .....and like  @ Dezza stated , no need for heavy springs on the stock set-up . 

[cnap504]

I have recently changed oil and filter, and I don’t know what oil was in it prior.  Now using  Valveoline mc, half 10/40 dino, and half 20/50 dino, not synthetic and not synth blend.

Edited May 2, 2021 by cnap504

[Gixer1460]

The GSX engines are pretty torquey even stock and a 20w/50 oil isn't the spec oil - should be 10w/40 mineral or semi. I'd suspect that could be upsetting the clutch grip. Some like heavier springs, but they are a moderately heavy clutch anyway, so i'd try oil first.

[cnap504]

A bit aggravated.  I removed the clutch plates and there wasn’t any damage.  The main shaft nut that sometimes gets lose was fine.  I staggered 3 Barnett heavy springs with new oem springs and reassembled the clutch.  Now it drags, won’t shift until warmed up and neutral is hard to get at a stop.  From intermittent slipping to incomplete disengagement.  Also changed oil to Motul 10/40 mineral.  Something aint right

[Gixer1460]

You haven't mentioned whether the fibres are OEM or aftermarket . . . . . general advise is OEM even for extreme use's! You say the plates are fine but are they in spec for thickness?? Other thing to check is notching of basket and hub - will cause symptoms described also a dry or frayed clutch cable won't help! If it was working and has got worse over time its liable to be wear / oil related, if its suddenly changed then something has broken or failed and if symptoms have changed after work then its something in the assembly that is different.

[cnap504]

Thanks everyone for the tips.  Both of my clutch “fixes” haven’t worked. The 82 Katana still slips after replacing broken friction plates and a new main shaft nut (the original had gotten lose).  It also got three heavy Barnett springs staggered with three new oems.  Everything looked to reassemble correctly sept it slips.

The 1150 too would slip just like the Katana the clutch would completely surrender without warning 2/3rds the way up the rev range, so took it apart and no apparent damage.  So I thought this one will be easy, put three hd springs with 3 std’s, now it drags won’t shift cold and no neutral at a stop.

I’d like to measure the stack height? of the clutch pack?  What exactly is that, how do you do it and what measurement should I look for?  I don’t race or ride the bikes hard so I could get along with a temperamental clutch but I don’t want to quit just yet.  Thanks again 

[Blubber]

It is very odd that 2 of your bikes have clutch issues.

 

Are they both running the same oil and is it the correct oil as per manual?

[Gixer1460]

28 minutes ago, Blubber said:

Are they both running the same oil and is it the correct oil as per manual?

As a couple of posts up - Motul Mineral 10w/40 so that's pretty well ruled out although not entirely ! I still want to know about the fibres and clutch metal parts wear ?

[cnap504]

2 hours ago, Blubber said:

It is very odd that 2 of your bikes have clutch issues.

 

Are they both running the same oil and is it the correct oil as per manual?

They both were non running bikes one with a known history of proper care until 10 year storage and the 1000sz unknown history.  The sz had the broken plates and a lose main shaft nut.  The 1150 clutch I couldn’t find any mechanical damage so to cure its slippage I tried 3 heavy Barnett springs.  Seems to have cured the slip but it now drags (no shifting when cold, no neutral when hot).  Motul MC mineral 10/40 oil filled to the correct level.

[cnap504]

2 hours ago, Gixer1460 said:

As a couple of posts up - Motul Mineral 10w/40 so that's pretty well ruled out although not entirely ! I still want to know about the fibres and clutch metal parts wear ?

I’m going to remove the plates on both bikes and measure the thickness of both the metals and frictions.  My main riding buddy is a retired motorcycle mechanic from one of the most competent mc service departments in this area and he tells me the clutch “stack” height is very important to the proper function.  So much so that Suzuki sent their dealerships a specific weight to place on a workbenched clutch so they could be consistently measured.  He no longer has access to these measurements.  He also tells me to achieve the correct stack height Suzuki had different thickness steels available, I will post my plate measurements when I get them, but does anyone know more about this “stack” height situation.  As always, thanks 

[Arttu]

While you are checking the plates make sure that the steels are straight and flat. Warped plates can cause all kind issues from slipping to dragging.

As far as I know the stack height shouldn't be very critical for stock clutch. As long as it's at right ball park so that the release mechanism can work and you still get enough pressure it should work. Meaning that if you have correct amount of plates and the plates are even remotely within thickness spec it should be good.

[Zenerdiode]

Have you knocked any glaze or shiny spots off the plates with a bit of emery?

[cnap504]

The plates looked good but since they were out I figure “eighted” both sides of the steels on 220 wet/dry sand paper.  Also very very lightly did the fibers also