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ToXicD

xr650r Motor Re-Build

10 posts in this topic

hey guys, i have read alot of posts on here about different engine builders and i just wanted to get your guys opinions on them. What i wanted to do is start a poll to see who is the best, but if this site has a poll submition somewhere i cant seem to figure it out. Anyways it seens barnums and xr's only seems to be all i have been able to find. I was wondering if there were any other good engine builders out there you guys can recommend. I have had motor work done by Allen Knowles of CT racing, and they are the guys that did the motor work for the xr650 quad raced at this years baja that placed 4th.

Since i have never had any 4stroke motor work done by anyone else i was wondering what i can get for about $2000?? I would really like to get a new rod which i know is about 250, and the crank rebuilt and balanced, have no idea what that would cost. i would also like to get the 680 big bore kit and have the cylinder re-plated. I am also thinking about getting bigger valves, 1mm over, with new seals, retainers, and springs with a new cam. Any ideas if i can get most of this done for that price?? may not do the larger valves, but i will be running a 43mm fcr carb so i figured maybe i could get some more horsepower with the larger flowing carb.

Also i havnt read anything about people running stroker cranks. is this just not a common practice because of the already high torque numbers the xr makes?? i know back in the 2smoker days we would stroke the hell out of those things and ever run 1/4" cylinder spacer plated to run up to a 5mm longer rod.

My last question is on the xr cams i have looked at it always has an *which says something about the factory decompression lever. I dont know exactly what that means.

I know this is kind of alot to throw out at once but my motor should be here tuesday and i am really anxious to get this thing together :banghead:

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You could always give Precision Concepts a try for the motor work. They might be kinda spendy, but its what the 1x team has gone with in the past.

As for the cam, the reason it usually says the * is because with aftermarket cams like the Hotcams, they delete the auto decompressor all together. My auto decomp went out, so that gave me a good excuse to go with the Hotcam.

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ok i guess i am way off here but i thought that the 650r had a lever-cable decompression system and not an automatic decompression system like the 450r. there is a lever on the left side of the cylinder head which i thought was the decompression lever, if its not then what is it???

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ok i guess i am way off here but i thought that the 650r had a lever-cable decompression system and not an automatic decompression system like the 450r. there is a lever on the left side of the cylinder head which i thought was the decompression lever, if its not then what is it???

It's got both, auto and manual decompressor. I never use my manual 1.

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oh ok, so my auto decompressor will be gone but i can still use the manual one?? if thats the case then that is totally fine with me. also i see they make hard faced rockers, but i cannot seem to find a hard faced cam. does anyone know who makes these and where i could get one??

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Millennium technologies did my 102.4mm overbore and nikasil plating they did a really good job, and their service was great. For the cylinder work, wiseco 10:1 piston, and gasket kit it was $450. I put it together myself, along with putting in a stage 2 cam and an eddlebrock, i also lapped the valves, i havent quite got it dialed in perfectly, but it runs pretty good. If you have an 8,10,12,and 17mm socket, and some screwdrivers, you can pretty much build it, i did, and im no mechanic.

I would not split the cases myself though, too many gears and bearings.

good luck

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+1 on the Millenium Technologies. I had my cylinder replated a number of years ago, and when I got it back from them, it looked better than new. They really do amazing work.

I'm pretty sure that Megacycle makes a hard-faced cam, but the only problem is that you might not be able to use your stock valves and rockers with the Megacycle cam. I don't know if the hotcam is hard-faced or not?

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