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XR80 carbon build up question SEE PICS

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85 XR80 Down on power but I found some serious carbon build up and the exhaust port looks restricted. SEE PICS BELOW. Dirtrider188 suggested to torch the pipe and I will do this. He also recommended when it was time for a top end to glass bead it. This makes sense as well.

I found this on the web but its discussing a small 2 stroke " The exhaust port is also a place to look for carbon buildup. You should be able to look into the exhaust port with the muffler removed and see the piston. The light coating of carbon that lines the port is not the carbon to be concerned with.

If there is a buildup, it will be right next to the piston, and in fact acting as a part of the cylinder, so the hole the piston is seen through is much smaller than the hole at the end of the port the muffler is mounted to. It is possible for an exhaust port that should be a 1" diameter all the way to the piston be reduced in size to 1/4". Most times this carbon can be removed by chipping it away with a small screwdriver or file, being careful not to scratch the piston. "

This is a 85 XR80 and it is really a fixer upper for the kids and pit bike. It seems to run fairly well considering its age. Keep in mind that this is a 20 year old well ridden/ worn XR with what is apparently on the stock top end. Do you think it would be safe to attempt to scrape the carbon out of the exhaust port using a tool and shop vac ?? This seems dangerous as the valve sits down from the port. I am just looking for a low cost fix to see it the kids stick with it before I do the top end work.

P1010007.jpg

P1010005.jpg

Thx

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Go for it!! It would be best to disassemble the valve train, the valves will probably need attention too.

I would use a wire brush on a bench grinder for the valves. Dental pick screwdriver [old], dremel wire brush for the exhaust ports and piston top.

Be careful around the valve/head seal, but you should lap the valves regardless. Be careful around the head gasket sealing area. Run the dremel around the weld on the exhaust pipe.

Robert :)

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i dont see anything that is bad, looks normal to me but those pictures just show the edge of the exaust port. that description does not apply to 4strokes.

check the compression to see if you are getting any valve leak. if it just seems low on compression and your an experienced mech a topend rebuild should be done.

not too sure on jetting those bikes but it may be a bit rich if its a reoccuring problem

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I'd say to just put it back together, and let the kids ride it. As fiveO stated, it doesn't look all that bad, at all. It does appear that the old exhaust gasket is still stuck in place (it's a common thing), just keep that in mind when you do any top end/cylinder head work. It will need to be removed, and you usually have to work at it.

When the time comes to do the top end, ob1 is right on the money for doing the cylinder head properly. Better to take the time to do the job right the first time, than to do it half-a$$ed, and have to do it a second time.

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I'd say to just put it back together, and let the kids ride it. As fiveO stated, it doesn't look all that bad, at all. It does appear that the old exhaust gasket is still stuck in place (it's a common thing), just keep that in mind when you do any top end/cylinder head work. It will need to be removed, and you usually have to work at it.

When the time comes to do the top end, ob1 is right on the money for doing the cylinder head properly. Better to take the time to do the job right the first time, than to do it half-a$$ed, and have to do it a second time.

I think that is what I will do for now. I will just let the kids ride it!!

If I do the top end I will pull it send it out and have it done right. Jetting seems to be pretty good based on the plug that I put in the bike. Thx

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