Clutch Mod

I read about a clutch Mod on the WR side that uses lock washers on the clutch spring bolts to give the clutch plates a little more clearance. I just did it and the clutch feels much better and could even start it in gear. Anyone else tried this? I'm wondering about any long term problems this can cause. I can't think of any, but maybe I'm missing something...?

It reduces the clamping pressure of the springs.  May lead to slipping and reduced clutch life.

That makes sense, what do you think about drilling additional oil holes in the hub?

I've got an 09 YZ250F but seem to be having the same troubles. Can't find neutral, hard to shift into second etc. Disks and plates look good, minimal wear on clutch bosses.

I took the inner clutch boss off last week and drilled about 12 new holes in addition to the 4 or 5 that are on there from the factory. I can't tell any difference. I might try the washer trick next but I was looking at the bolts that I have and there's already a small washer on there.

I'll try to attach a pic of one of my bolts. Does yours look like this?

image.jpeg

I've got an 09 YZ250F but seem to be having the same troubles. Can't find neutral, hard to shift into second etc. Disks and plates look good, minimal wear on clutch bosses.

I took the inner clutch boss off last week and drilled about 12 new holes in addition to the 4 or 5 that are on there from the factory. I can't tell any difference. I might try the washer trick next but I was looking at the bolts that I have and there's already a small washer on there.

I'll try to attach a pic of one of my bolts. Does yours look like this?

Mine does not have the second smaller washer. I am guessing someone already tried it on yours but used a flat washer instead of a lock washer (which is a little thicker).

That is an OEM bolt. I ordered them from the dealer.

They changed part numbers in 09 then went back to using pre 09 bolts in 2010. Not sure if the pre and post 09 bolts have the extra washer.

Anyway my bike apparently has the "washer mod" from the factory and it still shifts hard.

This is for 250F's by the way. Not sure about the 450's

Edited by Thumbster21

 what do you think about drilling additional oil holes in the hub?

 

Kind of a waste of time.  The boss (hub) already has a fair number of oil hole in it already.  The only oil that ever actually gets to the clutch in the YZF is the amount that leaks past the clutch push rod.  The trans shafts are pressure fed from the left end, and the oil that reaches the clutch is metered by the fit of the clutch side end of the push rod and the 4 small grooves cut into it, so there isn't a lot of it in the first place.  

 

The thing that causes an inadequate clutch release is almost always that the plates are not flat enough.  If each steel plate was only .008" out of compliance, that stacks up as a total of .064", over 1/16" of pressure plate movement that would be negated.

 

 

 I was looking at the bolts that I have and there's already a small washer on there.

I'll try to attach a pic of one of my bolts. Does yours look like this?

 

Bought the bike used, didn't you?  That isn't the original bolt, for one thing, and someone has already done the washer trick. 

Bought the bike used, didn't you? That isn't the original bolt, for one thing, and someone has already done the washer trick.

Yes I did get it used but I just bought these bolts a couple months ago at the dealer. (Snapped off one of the heads when I tightened it up) Had to order them from Yamaha. Came just like pictured.

Part #90159-06049-00 for the 2009 only .

Part #90159-06092-00 for 2008 and prior and 2010 thru 2014.

I used this site to look up part numbers

http://www.accelerationps.com/OEMpartfinder.htm

Kind of a waste of time.  The boss (hub) already has a fair number of oil hole in it already.  The only oil that ever actually gets to the clutch in the YZF is the amount that leaks past the clutch push rod.  The trans shafts are pressure fed from the left end, and the oil that reaches the clutch is metered by the fit of the clutch side end of the push rod and the 4 small grooves cut into it, so there isn't a lot of it in the first place.

In the case of my WR clutch hub, that fair number was 6 holes, and I added 12. I don't know how different the YZ oil/clutch system is, if at all for '09-earlier on the 450, but I did notice less drag in the clutch and an improved (smoother) clutch engagement feel, and if it's worth anything, many people have reported easier (or the gained capability of) starting in gear. I didn't have issues with that, in any gear, hot or cold, to begin with. Yeah, I know I have my little how-to thread over in the WR forum, but it's an easy and free modification that might make a difference for some. FWIW, I have noticed in product pictures that aftermarket clutch hubs come with more holes than the stock six that my WR had.

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