I need some clutch learnin' (long-winded version)

[kdtrull]

Last weekend I was horsin' around trying to track down a scraping sound on downshifts and I over-did it a bit.



That thing flew out and hit me in the boot with enough force to make some of my pee pee come out.  Turns out, the previous owner had a 1 tooth over stock front sprocket, didn't grind the crush pad down, compounded by the sprocket was dang near worn out and too much slack in the chain.  The slack part is my fault, I had just reset it and left a little too loose.



Anyway, since I was gonna' have to order parts and spend money, I thought I'd try to solve a problem that goes all the way back to 2008 and spans 3 different XT250's.
I'm a little bit of a fan of the poppa-wheelie and a 16HP scooter only does that with a good bounce or a clutch dump.  I favor the clutch dump method 'cause it's easier for me.

The new XT's will hook up every time in 1st gear and provide you a right fine acceleration wheelie for about 20 feet....never could learn the balance-wheelie but I'm still trying.
Try it in 2nd gear and you'll get a big wad of slippage and disappointment....unless you're on a pretty good whoop.  3rd gear, forget about it...about three seconds off slippage.

I don't give much thought to material stresses 'cause I've been doing it since 1974 and I ain't broke nothing yet (except some ribs one time back in 2000 up at the Westpoint) from dumpin' clutches.  It's a long ride home from Westpoint with broke ribs.....dangit  :'(

Every other dual sport I ever had would immediately hook up even if the result was a proper wheelie or just a good surge forward....NO slip.
Three different year model XT250s have never done that....always hacked me off.

OK, back on track.  While I was already ordering parts, I thought I'd order some friction plates and some new springs.  I was hoping they'd be heavier springs but turns out they were almost identical to the stock springs.

So I bought these kevlar plates and some new springs, and a gasket, of course.  Props to Yamaha....their gasket material for the XT is like grafoil material and I don't think it matters if you scrape the old junk off or not.

Soaked the new plates in some old oil and flew into taking stuff apart in the dark on the back porch with just a POS utility light.



Please hang in here...the real question is coming.

The stock plates did not look distressed....no shiny parts and still reasonably thick.



I had heard/read mention of judder springs and was on the lookout for any such device.  I never found any information on the judders that I could fully wrap my mind around and, as I removed layers of plates, I didn't see anything that looked like the illustrations I had seen.

BUT....as I continued to remove layers of plates and steels, I found these two plates....right smack in the middle.



They were much thicker (less worn, maybe???) and have a different color and composition.

That there's the question.  Do any of y'all know what the crap that configuration is and what is the purpose of it?

The only thing I can imagine is that the XT250 is widely considered a beginner bike and maybe the slippery clutch is a "feature" to prevent new rider ground loops....although 1st gear will loop your arse just as expected if you over-do the clutch dump.

So, I got two questions:

What is the purpose of the two center plates being constructed of dissimilar materials?

And

How does it work?.....possibly 2 robust plates and 4 more that wear fast and slip???

I kain't figure on it.

Thanks for any ideas or proven knowledge you might have.

[Yankee Dog]

A little Google foo says judder springs are suppose to "smooth" out your shifting.  A little reading between the lines equates that to clutch slip.  Also did up a manual and make sure the plates go in in the proper order.  Google also says they don't always ship them in the proper order.  Some guys are apparently removing the judders and they get a more positive engagement and less slip. Your mileage may vary as diagnosis is not my strong suite. 

Further.  I would go back to the standard gear size.  That thing already has enough top speed right. : ).

[kdtrull]

A little Google foo says judder springs are suppose to "smooth" out your shifting.  A little reading between the lines equates that to clutch slip.  Also did up a manual and make sure the plates go in in the proper order.  Google also says they don't always ship them in the proper order.  Some guys are apparently removing the judders and they get a more positive engagement and less slip. Your mileage may vary as diagnosis is not my strong suite. 

Further.  I would go back to the standard gear size.  That thing already has enough top speed right. : ).

What little info I found came from the googles.  There was nothing in that basket but friction plates and steels.  Still don't know about the 2 brown plates amongst the black ones.  Maybe the two brown ones are the slippery ones

And I did put the stock 15t front back on.  16t may have been fine for a lighter feller but not for the fat man.  :)

[kdtrull]

Most of you probably already know this but the whole problem seems to be the weak springs.
Again, almost nobody makes performance parts for the XT.
So, I shimmed the springs to preload them a bit.
Now, finally, it hooks up solid in any gear.
Still don't have an answer to the brown v.s. normal stock plates but the shims did the trick.
As far as I know, there are NO judder springs in the XT basket....just puny main springs to begin with.

[Brian A]

Looking at the OEM clutch parts on Bike Bandit, I see what appears to be 1 judder spring located on outboard end of clutch stack. And aside from that, all clutch plates and steel plates are shown to be the same throughout the clutch stack.
No special plates in the middle like what you found.

Looks like maybe a previous owner was experimenting or didn't know what he/she was doing?

And I am guessing you already know this, but for the record, a larger than stock front sprocket can (and will) push a marginal clutch beyond its limits, causing it to slip (especially in higher gears when whacking the throttle).

[kdtrull]

Looking at the OEM clutch parts on Bike Bandit, I see what appears to be 1 judder spring located on outboard end of clutch stack. And aside from that, all clutch plates and steel plates are shown to be the same throughout the clutch stack.
No special plates in the middle like what you found.

Looks like maybe a previous owner was experimenting or didn't know what he/she was doing?

And I am guessing you already know this, but for the record, a larger than stock front sprocket can (and will) push a marginal clutch beyond its limits, causing it to slip (especially in higher gears when whacking the throttle).

I found no such part on the outboard end of the stack....so that may have been part of the problem "feature" on my other 2 XTs.   
All 3 of my XTs exhibited this same "feature"....this is just the first time I tried to solve it.  Two of them I bought brand new.
I'm certain the bigger counter-shaft sprocket on this XT compounded the problem.

Even the new kevlar plates slipped a little in anything but 1st gear...but only on clutch dump.
I had to craft the preload washers from...well...washers.  I sure hope my oil filter doesn't have little shiny metal stuff on it on the next change.  I should have used copper crush-washer material but didn't think of it at the time.

All things considered, I think the XT just does not meet (not necessarily) expectations, but desires.
It is, after all, just a moderately unique and somewhat overpriced 250.  I just really like the notion of very short wheelbase, combined with almost 11" ground clearance, and 32" seat height.
I cannot explain why I keep buying them.  I used to have the same defect with buying old Ford Bronco's.

Thanks for the feedback.
kdt

[Gam]

Most of you probably already know this but the whole problem seems to be the weak springs.
Again, almost nobody makes performance parts for the XT.
So, I shimmed the springs to preload them a bit.
Now, finally, it hooks up solid in any gear.
Still don't have an answer to the brown v.s. normal stock plates but the shims did the trick.
As far as I know, there are NO judder springs in the XT basket....just puny main springs to begin with.

Same thing for the xt225, I swear they put ink pin springs in there.

[kdtrull]

Same thing for the xt225, I swear they put ink pin springs in there.

I'm fairly sure you could find some alternate springs out there for some other make/model that would work.  I just took the lazy way out.  A couple weeks ago, I watched lazeebum change out his KLR plates and springs and almost asked him for his old springs to experiment with....but I didn't.  Now I wish I had.  I don't really like the drilled-out washer solution....but it works!

[Gam]

Same thing for the xt225, I swear they put ink pin springs in there.

I'm fairly sure you could find some alternate springs out there for some other make/model that would work.  I just took the lazy way out.  A couple weeks ago, I watched lazeebum change out his KLR plates and springs and almost asked him for his old springs to experiment with....but I didn't.  Now I wish I had.  I don't really like the drilled-out washer solution....but it works!

They make "heavy duty" clutch springs for xt225 but I don't know if that really means stiffer.