Author Topic: 400-4 Clutch slip when cold  (Read 411 times)

Offline Erwin83

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400-4 Clutch slip when cold
« on: March 12, 2018, 09:36:55 AM »
Hi fellows,
looking for some advice. My 400-4 has a lot of clutch slip when the engine and oil are cold.
When warmed up, everything is fine.

I'm running Bel Rays 10w40 mineral oil, and the clutch isnt worn out.

In what direction should I be looking for a solution?

The fact that the slip disappears when all is warm, is just opposite of what I would expect...
CB350f with 400f engine

Offline Nurse Julie

  • 1973 CB750 UK K2.1977 CB550/4 Mongrel Brat. 1978 CB400/4.
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Re: 400-4 Clutch slip when cold
« Reply #1 on: March 12, 2018, 10:14:11 AM »
I had the same problem with a 400/4 I owned many years ago. Even though the clutch plates measured within spec, after fitting new plates, the problem went away. Trig also had it on a CD250u last year, once again all measurements within spec but fitted new and problem resolved.
Im a Nurse, trust me, this won't hurt.....much !!!

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Offline K2-K6

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Re: 400-4 Clutch slip when cold
« Reply #2 on: March 12, 2018, 06:49:29 PM »
The oil is thinner when warm so it disperses from the clutch plates more easily when hot.

The 10w and the 40 viscosity specs are two different scales so it looks confusing.

Offline Erwin83

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Re: 400-4 Clutch slip when cold
« Reply #3 on: March 14, 2018, 09:08:20 AM »
thanks for the responses!

I changed so many parts on the bike last year that I forgot, but the friction set is a new one, by Gecko. I also changed the clutch springs.

The 10w40 mineral oil is the right spec, so i'm now thinking about adding another steel plate (basket-steel-steel-friction-steel-fric..etc).
If I remember correctly, this is also how I took this 400 clutch apart, although I'd still like to understand why a clutch, with everything in spec, can still slip.
CB350f with 400f engine

Offline K2-K6

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Re: 400-4 Clutch slip when cold
« Reply #4 on: March 15, 2018, 08:42:18 PM »
Would adding another steel plate just increase the preloaded pack size?

Have you any way of checking spring length/rate? As all other thing's being equal, then spring loading will control the clamping pressure.

Offline Erwin83

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Re: 400-4 Clutch slip when cold
« Reply #5 on: March 16, 2018, 08:50:09 AM »
Would adding another steel plate just increase the preloaded pack size?

Have you any way of checking spring length/rate? As all other thing's being equal, then spring loading will control the clamping pressure.

Yes, it's a fairly safe way of increasing preload. Another method is adding rings under the springs. I added rings on my Aprilia Falco after having modded the clutch basket to counter slip...

I installed a new Gecko clutch last spring, with new Gecko clutch springs as well...

I'm a bit lost why I would need more preload, other than I could imagine the steel plates being worn a little... Or maybe something wrong in the clutch lever mechanism integrated in the right cover?
CB350f with 400f engine

Offline ka-ja

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Re: 400-4 Clutch slip when cold
« Reply #6 on: March 16, 2018, 09:39:26 AM »
Hi,
    Try searching out a set of "race" clutch springs, the standard clutch will handle a yoshi 460cc with road/ track cam fitted, or question the   new friction plate qualities.
nice bike,nothing in the bank

Offline Erwin83

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Re: 400-4 Clutch slip when cold
« Reply #7 on: March 16, 2018, 09:50:48 AM »
Hi,
    Try searching out a set of "race" clutch springs, the standard clutch will handle a yoshi 460cc with road/ track cam fitted, or question the   new friction plate qualities.

Hi. I fitted the "heavy duty" version of Gecko springs and (by feel) checked the compression force on the new springs versus the old. It really seemed quite OK.

So assuming this is all in order, is there another possible thing I'm missing?
CB350f with 400f engine

Offline ka-ja

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Re: 400-4 Clutch slip when cold
« Reply #8 on: March 16, 2018, 08:17:31 PM »
Recheck position of clutch plates, especially rear clutch disc spring/disc spring seat is in the right position and the thin friction plate is in its right place.
nice bike,nothing in the bank

Offline TrickyMicky

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Re: 400-4 Clutch slip when cold
« Reply #9 on: May 27, 2018, 04:13:25 PM »
Have you tried the very basic approach first? As the engine warms up, the free play in the clutch cable increases, and some people have been known to set the lever with minimal play when the engine is hot, meaning that when it cools you have no play in the cable whatsoever. Set the free play with a cold engine, try this first, much easier than pulling a clutch apart! Be Lucky!