Guidance rebuilding the XR650R top-end, please...

And when your riding in the sand look up the painty hose trick to keep it extra clean in there.

Dont forget that cam chain.

Hello,

I've been lurking here for some time, and am using my 1st post because need some guidance with my XR650R...

I purchased it 3 months ago (it's an '01), knowing the compression was a little 'soft'. I'd planned to rebuild it next winter, but after a trip to the dunes, some sand made it past my filter and apparently went through the cylinder... because now it's burning a considerable amount of oil (like a quart in 125 miles of street/trail riding), and the compression is ka-poot.

So... because I'm quite sure I sucked sand through it, I'd like to bore it out and have a new piston in it.

I went to the Honda shop this afternoon, and they were adamant that the XR650R cylinder cannot be bored.

So... that leaves me with 2 questions:

1.) Why not?

2.) What are riders doing then they're moving up to a larger piston? New sleeve?

I’ll likely stay with the 10:1 compression because I’ve read that the 11:1 requires machining to fit correctly? (Is this accurate?), but I’ll move to the stage 1 hot cams.

Please forgive me if I've posted this in the wrong forum, or if there's already a great thread on this subject (please direct me to it)~ I did several searches and couldn't find the answer...

Ryan

PM me when you get it done,maybe we can hook up out in the owhees and compare power.(Iv'e been needing a "reason" to make mine faster)..yes i'm married,I always need a reason.
PM me when you get it done,maybe we can hook up out in the owhees and compare power.(Iv'e been needing a "reason" to make mine faster)..yes i'm married,I always need a reason.

Sounds great. :bonk:

I ride the Kuna desert right now, since most of the Owyhee's are closed to motorized travel.

You should check out these guys, too:

motoidaho.com

:prof:

Sounds great. :bonk:

I ride the Kuna desert right now, since most of the Owyhee's are closed to motorized travel.

You should check out these guys, too:

motoidaho.com

:prof:

Cool!
Ruin a boring bar???

Yeah, a boring bar is what is used to bore a standard non-plated cylinder. I guess I see what your saying; it wouldn't ruin the boring bar, but rather the cutter tip on the end of the bar.

I have the steel sleeve and would NOT do that again. I would have the stock cylinder bored and re-Nikasiled. Millenium Technologies does great work as does Lukes Racing.

With a Nikasil cylinder you can run less the .0025" of piston to cylinder clearance but, with a steel sleeve you have to run at least .004" and you lose power, and the chance of a cold seize ( Barnum cold seize mine after the rebiuld) is not cool. Mike Powell's bike is Nikasil 680cc and you can tell it is much, much better.

Compression is 80psi ~ ouch.

I'll start ordering parts this evening. :prof:

Thanks for all the input!

Was that with the decomp pulled or without?

Page 8-4 Service manual

87psi (decompressor applied)

160psi (decompressor not applied)

If thats with the decomp pulled your perfect.

If not...she's cashed.

Decomp out ~ which means she's 1/2 of what it's suppose to be.

Ouch...wow that is really bad.

Even when I had 25% leak down through my rings I still could get 110-120psi with decomp out.

That is one seriously sick motor.

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