XR600 Rebuild 628/660 kit.

6 replies to this topic
  • 600ish

Posted February 08, 2005 - 02:07 PM


I have a '94 XR600 that has just about everything new on it but the engine and tranny, and I plan on running Vegas to Reno this year and even though the bike runs well, but burns a lot of oil, I don't feel comfortable running a 10 year old engine that I have no Idea how many miles it has in a 500+ mile race. The rest of the bike and suspension is up to date and in good shape but I'm looking for info on the 628 kit, cost etc. and I've looked at Thumper-racings 660 BAJA kit for use with pump gas. I have never been inside this engine other than to just adjust the valves, and any help is appreciated. What about the transmission? It too has never been touched. Thanks, Walt :cry:

  • Moredesert

Posted February 08, 2005 - 03:34 PM


Walt, The XR600 transmisions are known to go out. I had to replace 6 gears when I had mine apart. What I did is build the motor stock bore and spent my money on the head and trans. Get the head ported and new valve maybe a cam. Re-ring the thing unless the bore is out of speck go the next size over. You can build the motor out to 660 but just remember it's and air cooled motor and over heating it in a race is not something you want to do. My XR ran real good with 94+ octang. I added Lead Boost to my gas which helped when I ran hot in Baja. I went to a 436 kit on my DRZ and I find the bike over heating easyier than before. It's faster but some of my desert races are in 95* weather and I over heated then so I don't know what I well do this summer.

  • mr660

Posted February 12, 2005 - 07:53 PM


go with the thumper 9:1 racing kit but get the hrc cam through service honda. I replaced valves, valve springs, cam, rockers, sub rockers, cam gear and chain. also kevlar clutch. also had head port and polished. I road the $hit out of mine and it never over heated. (jetting is important) I never had a single problem with trans either. I loved the difference it made. the bike felt 100lbs lighter after the work related to the power increase. call thumper racing and these guys know what the hell they are doing and tell them what you want and they will not steer you the wrong way!

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  • gnnova

Posted February 13, 2005 - 06:06 AM


I've got a JE 628 big bore kit, gasket set and Hotrod connecting kit for your bike. PM me if interested.

  • michaeln

Posted February 13, 2005 - 09:30 AM


I have an XR650L. I wish someone made a piston with a moderate compression ratio for it. Stock is 8.3:1, Wiseco is 10.25:1 and JE is 10.5:1. I'd like something around 9.5 to boost the compression a bit without the overheating problems you can get with the higher ratios.

  • mr660

Posted February 13, 2005 - 07:11 PM


thumper racing. 9:1 comp 102.5mm reliability is the name of the xr game

  • Old_Man_Time

Posted February 13, 2005 - 07:28 PM


You might call Baja Designs and talk to their Techs. They used to specialize in the XR600. They made it very clear in their catalogs and when I talked to their techs that the bike looses it's reliability at a certain point. They will will advise you away from getting too radical or big on the bore.

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