premature clutch failure

Clutch on my 2008 wr450F went a while ago. I got dragged out the desert (thanks pembell!), replaced friction and steel plates (including the 2mm WR ones) and it was fine. It then failed again about six months later, and I got dragged out the desert (thanks ADVRider808!), and replaced friction plates and it was fine. It then failed again just two weeks later with less than 5 hours on it!!! (and I got dragged out the desert!)

Checking the friction-plates they're all at or above 2.85mm and some are >3.00mm. Spec is >2.92 and wear limit is @2.80.

I'm thinking energy conserving additives in the oil out here might be to blame.

I had been using fairly low cost 20W-50 motor oils thinking these would most likely be free from additives. These are all SL/CF, without any energy conserving or similar in the lower half of the donut.

I understand that for 20W-50 they don't need to list if the oil is energy conserving or not in the donut, but should 20W-50 SL/CF oils generally be OK for a wet clutch, or was I too optimistic?

Pictures:

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To be safe I'll try to find specialist motobike oil - it can be hard to get here so could reduce oil changes. Doh!

Thanks.

Al

I understand that for 20W-50 they don't need to list if the oil is energy conserving or not in the donut, but should 20W-50 SL/CF oils generally be OK for a wet clutch, or was I too optimistic?

You can't assume anything about automotive oils one way or other. 20w-50 oils will never be marked as ECII compliant because their viscosity is too high to qualify them. The same is true of most 40 weights. That doesn't mean that they don't include friction reducing additives that might possibly affect the clutch.

But I doubt that oil is your problem (although it's not impossible). Are you certain that you've kept the clutch cable slack at the recommended minimum while you were riding?

You can't assume anything about automotive oils one way or other. 20w-50 oils will never be marked as ECII compliant because their viscosity is too high to qualify them. The same is true of most 40 weights. That doesn't mean that they don't include friction reducing additives that might possibly affect the clutch.

But I doubt that oil is your problem (although it's not impossible). Are you certain that you've kept the clutch cable slack at the recommended minimum while you were riding?

Thanks for the quick reply :cry: .

- I did have trouble getting the free play set to spec, but I assumed it was just because it was a new clutch.

That said, given that when I measured the failed friction plates all were above the wear limit, and some were well in spec, could that happen if lack of cable slack caused premature wear?

If it's mechanical rather than oil, could it be weak springs?

Thanks!

Al

I will say the oil is the problem, engines with wet clutches must have JASO-MA oil which has the correct friction modifiers or lack of (I'm defintly not a oil chemist). Look for oils that meet this rating (Shell Rotella is a popular one and can be purchased almost anywhere).

Plus I'd be scared of 20W-50 weight oil as thats pretty thick on start-up. Yamaha recommends Yamalube10W-50 semi-syn or equilivent which would be Shell Rotella T5.. Chain auto parts stores here are selling Lucas oil for motocycles at a reasonable price also.

I would probably replace the friction plates after flushing the engine with a couple quick oil changes using correct oil then plan on finishing a ride without a tow rope!

Riding as he does in Saudi Arabia, I don't see 20w-50 as being a problem. Remember, it's a 20 weight on startup, and he might have a 60 degree morning there during a 20 year cold snap. :cry:

Besides, I run 20w-50 in SoCal for 4 months of the summer, and sometimes longer. Never an issue. Reviewing the manual will show that Yamaha recommends 20w-50 for use in the range of 10-45 ℃ (about 50 - 125 ℉), so no problem. Personally, if I rode in Saudi, I'd run nothing else.

I think, however, that oil, while it is important, is not at the heart of this problem. The '08 WR has a reduced size clutch relative to '06 and earlier models, so there are two things things that became more important along with that. That is first the quality of the clutch plates. Avoid low cost aftermarket replacements and use only OEM or a premium replacement like Hinson. The second issue ties in with the first. The shorter clutch stack gets hot quicker, meaning that you have to keep an eye on cable free play while you ride, as it will loosen up on you and make the clutch hard to use. You can, of course, tighten it on the fly, but you have to remember to loosen it back up when the clutch cools off again, or you won't have any slack. That will lead to an early failure from slippage. Cheaper clutch plates exaggerate this problem because they often expand with heat more than the good ones do.

You might also try a set of OEM clutch springs from an '07-'09 YZ450. They're a bit heavier.

Haha, Didn't catch the location till after the fact. I'd still look for a good diesel oil that meets JASO-MA if moto specific oil is hard to come by. I looked in my manual and sure enough it does say 20w-50 for 5-50 deg C but I can't imagine that being great for cold start reguardless of amibent air temp.. But in a case where no 10W-50 is available it should work great as long as it does not have friction modifers.

I would defintly measure the springs esp if the clutch has been hot from slippage. And I agree with grayracer do OEM plates if possible and check the metal plates for warpage on a surface plate or replace all the friction, drive plates and springs if in doubt.

Also make sure your push rod is in good shape and working properly.

Most importantly drink plenty of water! I don't do temps over 100 deg!

20w50 is fine, if it meets the specs (SG or higher except energy conserving and meets JASO T-903 MA and no friction modifiers)

I would suspect those oil's you show, to have friction modifier (molybdenum), moly is no go for clutch, for gear and crank good, like in car.

Maybe you can try cleaning with some fine emery cloth, on the plates, to get moly out of the surface, and then use Jaso-ma oil, and se if it's stil slips. :cry:

Regards Carsten

Edited by hjorth

Thanks for the replies.

never found the Rotella T5 here, there is loads of shell rotella SAE40 but I understood monograde oils have less stable viscosity vs temperature at both high and low temps, even though I never need the 'winter ' viscosity.

I.e. this time of year it will be 40C when i start it, so maybe 10x the thickness as for 100C and so poor flow / too high pressure until it warmed up, but as I suffer from overheating (me and the bike) i'd be doing most of the riding with the engine above 100c and i'd loose viscoinsity at the high temps and damage the engine.

What do you think? The monograde is available everywhere as all the trucks use it.

Al

Edited by ACM

Thanks guys,

On the plates, it's always been OEM plates from Yamaha dealer. I'll try new springs, as I really cooked it first time it went, next two times I recognised what the problem was so just gave up and looked sheepishly at my buddies!

I'm keen to pin it on something mechanical, as I put the same oil in my wife's wr450, so if it is oil I'll be changing two clutches!

What really puzzles me is that the plates were not warn down much (all above wear limit, some well in spec), is this possible if it was overheated or warn down e.g. due to cable slack? Confused!...

Thanks!

Al

Your not running a hydro-clutch are you?

Maniac

Have you been replacing the springs with the plates? I'm a self proclaimed clutch abuser (old 2 stroke habits I can't break) I have found my plates last 2 to 3 times as long as my springs. I use Pro-Circuits labeled springs and replace them about every 20 hours and will get 40 to 50 hours out of a set of stock frictions.

I went as far as also shimming new springs for added grip. It definitely works, but plays havoc on other parts. Clutch does not disengage as well due to increase pull weight and pressure plate flex, but man does the clutch hook up!

So basically I don't think it's your oil or your style. If your set up is accurate and you use oem plates and Hinson or Pro-Circuit springs you will be fine.

You might also try a set of OEM clutch springs from an '07-'09 YZ450. They're a bit heavier.

I managed to get hold of some 2006 YZ450 springs (90501231E9). This appears to be a different part number to the '07. Anyone know in what way their different, and if they'll do the job above??

Thanks!

Al

The springs and pressure plate are both different between '06 and '07 because the '06 and earlier models have a 9 plate stack, whereas yours has 8. You should use '07 or later springs.

Regarding single grade oils and viscosity stability, you have been misinformed. They are generally more stable. That's because multi-grade oils are made from the lighter of the two marked grades (20 wt in the case of a 20W-50, for example). Additives are used to prevent them from thinning out with heat as much as they otherwise would, but with the exception of those more expensive additives found in multi-grade gear oils and an increasing number of motorcycle specific oils, these additives break down very rapidly in a transmission. That leaves you with a lighter grade than you paid for in a sometimes alarmingly short time. Because straight grade oils are made from a heavier base stock to begin with, they are much less subject to that.

The one thing that would be true along those lines is that it is very rarely that you will find any straight weight synthetics, and synthetics are generally tougher against heat than natural petroleum bases.

Thanks!

Springs: right on - just downloaded a 2006 YZ manual, they're way to short, 47.8mm rather than 50. (If anyone in Riyadh has a 2006 YZ your welcome to them!). Replacements coming by post from UK/US.

Oil: Given I wasn't using synthetic anyway - Are you saying that the monograde SAE40 diesel oil might offer better or no worse protection than an equivalently unsophisticated non-synthetic 20w-50?

- The SAE40 is available everywhere, so I could change the oil after every ride.

- What about it being too thick on start up (even at 40 degrees C ambient)?

Cheers

Al

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