auto decompressor cut off at rocker

Can someone post a pic of where the lug/tab is that gets cut on the exhaust rocker to disable my auto decompressor on a 2001 XR250? Thanks alot

Why make a permanent mod when all you have to do is press the decompressor cam off the camshaft, which is reversible if someone later wants to re-enable it.

Edited by Trailryder42

less complicated. New rocker arm cheap. need ready in 1-2 days for a ride

What logical reason would you have for removing part of the auto decompression mechanism in the first place? 

I don't think it is working correctly or as designed. Hard to start and requires tons of kicking. It pisses off my son trying to start it and I don't blame him - it is too finicky. Difficult to find TDC. Would rather determine TDC myself. Basically I don't like the system and the starting difficulty. I really just would like a pic or diagram if anyone has something. Thanks

TDC doesn't change with disabling of auto decomp.

I guess I don't get the thought that disabling the system will make the bike easier to start, when the purpose of it is to do just that.



Rocker Decomp Lug.JPG

No good reason to remove the decom. If the valves are adjusted correctly and the decomp cable is not to tight it should work fine.

Be sure the decomp is releasing before adjusting the valves or you get a tight one and it will be very hard to start.

Kicking it over with out the decomp will wear you out if you stall when warm.

Here are some other posts so you can see what I mean. I don't normally go hacking up my bikes. I've had this one for a couple years and I've always hated the starting. I bored it out slightly and installed new piston and rings as I was getting poor compression last winter for an unrelated issue.  I was hoping it would also help with the starting procedure. It did not.

I did a compression test and the thing just doesn't start making significant compression until you kick it 8-10 times. There are alot of others with this problem in the posts I attached if you want to check it out.

Trailryder, I appreciate you posting that for me. Even though you don't agree with it you still helped me out. You are a stand up guy!

4stroeridertt: the manual decomp would still be enabled if you dump the bike when it's warm - just not auto decomp

Edited by dogeddie

Just disconnect the cable that goes from the clutch cover to the head. That's the auto cable. The other cable is for the handle

4 hours ago, Lombardim21 said:

Just disconnect the cable that goes from the clutch cover to the head. That's the auto cable. The other cable is for the handle

You're thinking of an earlier model bike. A 2001 has its own auto decomp cam on the camshaft. Not cable actuated via cable from the clutch side cover.

Oh ok. Yup, your right. Sorry about that

OK so I ground the lug off and reassembled. Kind of late here but initial results are great - started first kick as long as I used specific starting procedure. Find TDC, pull in manual decomp for 1/4 kick or so more, release all, kick from the top. Bike still kicks very easy using this method, but it starts right away.


One thing I am wondering is how the manual decomp works as opposed to the auto decomp? I mean exactly what is engaging mechanically when using the manual decomp? I should have spent more time futzing with checking all that out while it was apart but it is late and I am tired and wanted to get it done to try it out. I attached a pic of what I did. I am wondering how/what the manual decomp engages? Initially I presumed it was the lug I cut off and said Oh shit, but that can't be the case, as all is working as planned. So I am having trouble visualizing what connects to what when it is all together. Anyone care to explain? Not sure how the auto decomp used to engage the lug either for that matter. I guess it doesn't really matter as it worked out well, but I like to know how stuff works and have been searching online for an hour with no results. Thanks




Edited by dogeddie


Edited by dogeddie

The 'tab' you need to (probably shouldn't) grind off is the little ear just to the outside of the rocker pad. 

The little pecker opposite of the right side cam lobe bumps it during the compression stroke.

Are you pretty confident with your jetting and valve lash? Good luck! 

sorry I got these so messed up I give up

Oh crap. Is that the before picture? 

That tab has nothing to do with auto decomp on the 96+ XR250R. 

The auto decomp is inside the cam on your bike.  It bumps the tab on the pad side of that same rocker.  

Seems like your auto decomp was never the problem though.  So that's good news.  


Mikerbike - I already did the mod and wrote on the photo what I did. What do you mean by the "pad"?  Photo is before I ground it off.


Edited by dogeddie

redo.jpg.3334d1325d8152e148bdb88c18c472f2.jpgI hope I ground off the right one?

You kinda made it sound like you already had an understanding of how the system worked. And that's why you decided on grinding the ear off instead of removing the decomp cam on the camshaft.

Unfortunately, the manual doesn't state which decomp lug that is, and I didn't study the dark picture long enough to see how the rocker is situated in the head, before I posted it. For that I apologize. But your pictures make it clear that the lug you ground off is for the manual decomp. The auto decomp lug would be centered under the cam since its activated by the decomp cam on the shaft.

When you pull the decomp lever on the bars, it pulls the small lever at the head, rotating the cutaway into that lug and pushes down on the right exhaust valve to unseat it, releasing compression. So I don't see how your manual system can be functioning now. I'm wondering if you're experiencing a placebo effect. The way you described your start routine is how you  should have been starting it all along. Any starting kick made from anywhere in the stroke besides TDC is a wasted effort.

The auto decomp cam on the cam shaft works via centrifugal force.

8 minutes ago, dogeddie said:

redo.jpg.3334d1325d8152e148bdb88c18c472f2.jpgI hope I ground off the right one?

It would seem the lug that is centered under the camshaft would be the one to grind off. Kinda looks like it has some wear in the face of it from something like the decomp cam contacting it.

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