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I recently picked up an ‘03 XR80R for s good price. It needs a top end, clutch, rear spokes, tires and some love.
Searching around I didn’t find much info on the 80. So we’re gonna add a little to the little that’s out there.
The plan is
CB400F piston
Bigger carb
Cam
Intake
Xr100 clutch
And eventually suspension after its rippin again. I’m 6’ and weight 160lbs, so I want to add some height and springs or shocks to handle my weight. Right now I’m thinking xr100 forks, swingarm, and wheels/tires.
I haven’t decided if I want to do exhaust or not yet for noise concerns.
After a good cleaning I brought the bike inside and started tear down. The bike had been sitting outside for a while so was filled up with water from the exhaust not being plugged. I still need to pull the engine off the frame so I can tear down further, had to leave town for a week long work conference so that got put on hold for a minute.
When I pulled the cam I wasn’t exactly pleased. The cam journals don’t look all that great. There are grooves on both that I can catch a fingernail on and material knurled out where the caps meet. Cam looks the same. If it weren’t for this situation the stock cam would likely go back in
My friend is a machinist and thinks he can get them right. Worst case I’ll have to source another head.
Doing A LOT of sleuthing all over the inter webs I found a few posts talking about cb400f pistons as a possibility for use as a big bore xr80 piston. They have a 13mm wrist pin and we’re supposed to be 51mm std bore. I liked the idea of being able to still have room and piston options if I needed a rebuild, and 92ish cc sounds better than 80.
So,I ordered some 1976 CB400F pistons off of eBay. Got all 4 with rods and wrist pins for $20 shipped. I arrived home from my work trip today to them at the door. They seem to be in good shape. I put lime green grips on everything with handle bars, so I also picked up some Oury waffle grips. anyways pics
I was seeing conflicting posts about the size of the cb400f pistons. Some said 51mm and some said 54mm. Thanks to someone on one of the posts for this Honda piston chart
4-stroke.net
It claims 51mm as well. However, I still wasn’t for sure until today. 1976 CB400F std pistons are 51mm
I need to order some rings now and figure out what tires I want/can afford. I’m not sure if I should just do the xr100r rear setup first thing instead of putting money into new spokes and a tire for the 80 setup.
Off to the machine shop Monday. More to come

Searching around I didn’t find much info on the 80. So we’re gonna add a little to the little that’s out there.
The plan is
CB400F piston
Bigger carb
Cam
Intake
Xr100 clutch
And eventually suspension after its rippin again. I’m 6’ and weight 160lbs, so I want to add some height and springs or shocks to handle my weight. Right now I’m thinking xr100 forks, swingarm, and wheels/tires.
I haven’t decided if I want to do exhaust or not yet for noise concerns.
After a good cleaning I brought the bike inside and started tear down. The bike had been sitting outside for a while so was filled up with water from the exhaust not being plugged. I still need to pull the engine off the frame so I can tear down further, had to leave town for a week long work conference so that got put on hold for a minute.
When I pulled the cam I wasn’t exactly pleased. The cam journals don’t look all that great. There are grooves on both that I can catch a fingernail on and material knurled out where the caps meet. Cam looks the same. If it weren’t for this situation the stock cam would likely go back in


My friend is a machinist and thinks he can get them right. Worst case I’ll have to source another head.
Doing A LOT of sleuthing all over the inter webs I found a few posts talking about cb400f pistons as a possibility for use as a big bore xr80 piston. They have a 13mm wrist pin and we’re supposed to be 51mm std bore. I liked the idea of being able to still have room and piston options if I needed a rebuild, and 92ish cc sounds better than 80.
So,I ordered some 1976 CB400F pistons off of eBay. Got all 4 with rods and wrist pins for $20 shipped. I arrived home from my work trip today to them at the door. They seem to be in good shape. I put lime green grips on everything with handle bars, so I also picked up some Oury waffle grips. anyways pics

I was seeing conflicting posts about the size of the cb400f pistons. Some said 51mm and some said 54mm. Thanks to someone on one of the posts for this Honda piston chart
HONDA PISTON SIZE LIST
HONDA PISTON SIZE LIST This is a fairly comprehensive list of Honda Piston Sizes and only apply to 4-stroke engines. In case you need the sizes for 2-stroke en
It claims 51mm as well. However, I still wasn’t for sure until today. 1976 CB400F std pistons are 51mm

I need to order some rings now and figure out what tires I want/can afford. I’m not sure if I should just do the xr100r rear setup first thing instead of putting money into new spokes and a tire for the 80 setup.
Off to the machine shop Monday. More to come