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xr100r engine fouled badly

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so i got a xr100r about a year ago as a first bike, and after i got better at riding and mechanics i noticed it was putting out way less power than my brothers little 70. so i decide to tear it down and it turns out the whole valve and head was badly fouled and so was the piston. i also accidently stripped a bolt off in the process on the head. will i need to buy a whole new head assembly or can i just clean it all up and keep going? also how much do you think it would cost to get these parts cleaned and redone?

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looks fine to me, maybe running a little rich.

in your diagnosis for lack of power, what was your compression reading? Leak down spec?

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i dont have the right tools to check compression, but it was under what i would have expected for a 100 need in ways of compression. when i say "badly fouled", i mean its completely covered in carbon buildup and needs to be cleaned very badly but i dont no if i will mess it up if i take a wire brush to it and clean it off.

Edited by mxchri5

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looks fine to me, maybe running a little rich.

in your diagnosis for lack of power, what was your compression reading? Leak down spec?

ya i thought it was fine but i want to clean the head and i dont now exactly how to do that without damaging the actual valves, and i dont know if i can just take a wire brush or if i should take it in and have the dealer do it

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I looks absolutely normal to me, very little buildup. If you want to clean it up a little that is fine but unnecessary. Anything you want to use for cleaning is fine, just don't mar the gasket surface.

As long as you have it apart you might put a set of rings in it. Turn the head upside down and fill the combustion chamber with liquid and leave it that way for a while to see any leaks past the valves. If it does then you need to have the head looked at by a reputable mechanic.

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I looks absolutely normal to me, very little buildup. If you want to clean it up a little that is fine but unnecessary. Anything you want to use for cleaning is fine, just don't mar the gasket surface.

As long as you have it apart you might put a set of rings in it. Turn the head upside down and fill the combustion chamber with liquid and leave it that way for a while to see any leaks past the valves. If it does then you need to have the head looked at by a reputable mechanic.

okay, ya my dad kept saying that it needs a bunch of work but i keep looking and seeing it needs less and less, i still need to get the bolt out form the head cover that i accidently stripped out and do you mean rings for the piston or gaskets?

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I looks absolutely normal to me, very little buildup. If you want to clean it up a little that is fine but unnecessary. Anything you want to use for cleaning is fine, just don't mar the gasket surface.

As long as you have it apart you might put a set of rings in it. Turn the head upside down and fill the combustion chamber with liquid and leave it that way for a while to see any leaks past the valves. If it does then you need to have the head looked at by a reputable mechanic.

i tried that ricj to put water in and the water started to pour out of the intake hole in a pretty good stream, i guess when i get time ill have to go dowon to the dealer and have them look it over and see what i need to do

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I meant replace piston rings and check valves and seals while you have apart. Gaskets go wthout saying..

Judging from your pictures it looks like it was not burning oil excessively or looking anything other than maybe slightly rich on fuel mixture. But as long as you have disassembled it you might as well freshen it up while you are there.

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ya thats what i was going to do and maybe put in a couple of upgrades while its apart, but i dont know. i want to try and put the bbr big bore kit on it since its a good deal for how much i want to actually put into it and i also noticed the clutch cover had cracks that started to go all around the part where the clutch adjust lever would press on it and i need to replace that before it goes through the cover

Edited by mxchri5

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you could try lapping compound on the valves, about 6$ at an auto parts store, just need to take the valves apart(easy).

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Take the head to the bike shop you buy the rings and gaskets from, they will do the job for you.

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maybe, but i don't have the tool to get the valves apart yet and i don't want to do it by hand

look for homemade spring compressor ... basically you just need to bent a metal bar 2 time so it form a U shape then you compresse the spring and take out the little thing with a magnet how a pair of long nose

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