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new top end, still smokes

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rebuilt my 100 several months ago but havnt really had time to ride it. last night i rode it and noticed it smokes. it only smokes after idling and then revving the engine, usually im doing this in neutral. if i continue to rev the engine it clears up, but will smoke again after idleing for a bit. while riding it i dont see any smoke. what should i look for first? my first thought was valve seals but they are new. could it be the rings just havnt seated yet? the rebuild consisted of new bb120, new oem head/valve seals, and a web cam. i also replaced odd and ends like timing chain and what not. any ideas? thanks

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How much time is on it? The rings do need to seat. The valve seals could be damaged maybe? Take a compression reading and see if it's normal. If it is, then you can rule out the rings.

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bike has about 2 hrs on the new motor. its a street ride to almost all of that was at 40-60mph, i would think the rings would be seated already. valve seals was my first thought, i just dont understand why with new honda seals and honda valves. thanks for the replies.

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The amount of oil that causes smoke is very very small so if a seal popped of the guide or a seal lip was nicked during installation you will have a smoker. Orientation of ring end gaps during assembly can allow more oil to get by to the combustion chamber. Last is a oil control ring that is not properly installed.

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Yea, the rings would be seated by now. Chuck gave great info. I wouldn't worry too much. If it runs good, go with it.

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What Web Cam? You need to machine the guide a bit, because the rocker will smash the seal and make it break, which causes the seal to leak.

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it the web 68/69 i believe. when turning it over by hand it looked like i had room on the valve guide/seal. looking through the spark plug hole while turning over the motor the backsides of both valves look clean (no oil residue) which makes me think the rings didnt seat right. grrrr, guess it just needs to be taken apart.

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The exhaust seal always breaks whenever you run a 68/69 cam. You reallly don't need to fix it, unless it really bothers you. Tou need to take off about 20% of the guide....not too much.

Edited by socalxr

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i just did the same kit on my xr100 but i used the cam that came with it mine smokes to when i rev it but i havent ran it maybe 20-30 min could it be the rings havent seated yet

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Great info above!

Comp test?

and Leak down

If you guys brake your kits down. I would also check piston to wall clearance, ring gap, piston and cylinder true-ness. Don't assume that it's new- and it's perfect. Ya never know.. The kit could be out of spec from the manufacture...

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i just did the same kit on my xr100 but i used the cam that came with it mine smokes to when i rev it but i havent ran it maybe 20-30 min could it be the rings havent seated yet

It's possible that the rings haven't seated yet, but I would think that they would have. IMO, the best way to seat the rings is to ride it hard. I'd ride it pretty hard for a good ride then see what it's doing.

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i went out for a night on the town sat nite. probably around 2-3 hours of riding. it got worse the longer i rode. after taking off from a stoplight i would leave a pretty decent smoke cloud.

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WTH-Slow600-talk about some bad luck with your last two kits!

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haha i know! guess im the only common factor. i did check ring gap on the bbr kit and it was fine. should have spent a little more time checking the cylinder and piston. the only other thing i can think of is that if it was too rich at idle maybe the rings didnt seat properly, but hell i barely let the bike warm up and went and ripped on it.

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I was just thinking about your valve guides.. Its possible that the guide it's self is passing oil (between the head its self and the guide)

Something else to inspect

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