what are the differences between the xr80 engine and the xr100 engine

what are the differences between the xr80 engine and the xr100 engine

I see most of the go fast stuff is for both.

are the cases the same?

I think I read somewhere that the tranny is close ratio on the 80

whats interchangeable and what bolts up to what ?


case is different because the cylinder and the case hole(were oil is sent though) are off a bit or to say they don't line up

hey a couple things u can do for the 100 is and exhaust i got a fmf powercore 4 fpr mine,bbr rev box,bbr frame cradle, really need that,K&N filter and jet the carb to 102 main jet and 34 pilot jet


looking at what stock parts are same /different

Mainly, the cases, cylinder, crank and rod. This means with an xr80 you can't use a big bore kit that is made for a 100. Some xr80 trannys are interchangable, but some aren't. I don't know the year that the tranny changed. But the early 80's use a really short kick starter shaft.

ya any thing excapt like the motor and case cant mix match thoughs parts but as far as exhaust tiers rims, air filter plastic, graphics that stuff u can buy for on bike and put on the other but ussally it says crf/xr80/100.

The short kickstarter shaft and countershaft will still work with the Miller frame conversion.... I was discussing that with him today, coincidentally. He said the tranny ratio's were the same? I don't usually question him.... but he might be wrong. :applause:

I have a set of 100 cases and a couple of 80 bottom ends. I'm going to put one of the 80 clusters/etc in the 100 cases and see how it looks. I'll let you know.

As I mentioned somewhere else, I also have 3 or 4 XR 75 bottom ends that someone could have real cheap.

My CR 85 conversion is coming along steadily. Waiting on a cam chain to finish assembling the engine - a 9mm Powroll stroker that I've had a few years but hasn't been in a frame. My existing KX conversion (one of the Team Green bikes Miller did) is getting a new Kitaco 145 kit... the folks on here spoke highly of them, but after Miller telling me how good they're doing in the 6-7 they've built, I'm convinced. 10.5-1 and no kickstart shaft problems? Hooray... no push starting like the Powroll.

Pics when I get things finished up.


thanks for the answers guys

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