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

[zimak]

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.

[scalejockey]

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.

[RyanWilliamCantrell]

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.

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

[scalejockey]

Sounds great.

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

Cool!

[Thumpmeister]

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.

[BWB63]

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.

[RyanWilliamCantrell]

Compression is 80psi ~ ouch.

I'll start ordering parts this evening.

Thanks for all the input!

[zimak]

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.

[RyanWilliamCantrell]

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

[zimak]

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.

[BWB63]

Some cam timing web pages for the XR650R:

http://www.scott-world.com/XR650R/engineering.htm