[Jmike001]

Im thinking about doing a couple engine upgrades to my xr80 and looking for some suggestions. I was thinking of boring to 49.5mm(86cc), polishing the exhaust port and combustion chamber, smoothing out the intake port, stage 1 hotcam, and exhaust. I have seen other posts with guys talking about using pistons from different bikes and was wondering if boring the stock 80 cylinder more than 49.5mm is ok. I ask because the biggest oversize I've been able to find for an xr80 is 49.5mm. I also don't want to have to change anything with the crank to make a different piston work. Also looking for input on cam and headwork, any information will be helpful. Or should I ditch the 80 engine for a 100(if it will bolt in)?

 

[Jarret53]

The 100 motor will Bolt in.

 

[vintagemx]

I had an XR80 jug bored out for a 51.25mm piston from a Honda CB400F, roughly 95cc. Lightened flywheel, ported head from Stormin' Norman, Hotcams Stage 1 camshaft and XR100 carburetor. It will run with a stock XR100, but can't hang with a 120 kitted XR100.