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JOE DIRT 88

XR80 stock vs over bore

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Doing a rebuild on a XR80. Due to a chipped exhaust valve that inbedded itself into the top of the piston. Weirdest thing. Was wondering about a 50 overbore. I have a cylinder. Would their be a noticeable difference in power and performance over just leaving it stock?  Is it worth the money over piston prices?  Kinda weighing the advantages and disadvantages before deciding.  Thanks.

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On ‎6‎/‎11‎/‎2018 at 11:08 AM, vintagemx said:

The piston from a '74-'77 Honda CB400F will work in the XR80 motor and up displacement to 92cc.

https://4-stroke.net/library/honda-piston-size-chart.html

I had a Powrol big bore kit in my XR80 back in the day but no one seems to package a big bore kit for the CRF/XR 80 any more.

There was one place that had one for like $250?

I do remember the CB400F pistons as an option.

Working on a 1974 XR75 project that I may put a points XR80 engine in so a big bore piston would be nice to source out that isn't too expensive or else I would just look for a 100 engine.

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2 hours ago, RBracing said:

I had a Powrol big bore kit in my XR80 back in the day but no one seems to package a big bore kit for the CRF/XR 80 any more.

There was one place that had one for like $250?

I do remember the CB400F pistons as an option.

Working on a 1974 XR75 project that I may put a points XR80 engine in so a big bore piston would be nice to source out that isn't too expensive or else I would just look for a 100 engine.

I still have that XR motor sitting in my garage. It’s got a few more goodies than just the big bore. I’m done building XRs, so if you’re interested send me a pm.

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Yeah I was debating between a xr100 or xr80 for my pit bike. I ended up getting an xr80 as the 100 felt just a tad more than a pit bike. Come time for mods- couldn’t find a thing about BBKs. I ended up swapping it with a 200cc motor and calling it a day lol

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On 6/14/2018 at 5:26 PM, vintagemx said:

I still have that XR motor sitting in my garage. It’s got a few more goodies than just the big bore. I’m done building XRs, so if you’re interested send me a pm.

PM sent

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7 months later lol

I have an xr80r with a locked up motor I need to build

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