Intermittent billows of blue smoke on acceleration

So I can't figure this one out, I've had the engine apart so many times and thought I'd finally have it done, this last time is was because my timing chain slipped and smashed my intake valves, so I replaced the valves, timing chain and tensioner

The bent valves came out of the head very easily, my spare valves I had to hammer out of my extra head? But looked fine, putting them back in my other head, they wouldn't just slide in, I had to smash them with my palm to go in, but once in they would slide up and down freely, so something odd with the top of both valves.. I didn't replace the valve seals because they were done about 2300 miles ago

The jug and piston rings were replaced about 100 miles ago and I've been taking it easy to brake them in

My bike backfires pretty nice on decel, so I would think its lean, but my plug is back

The problem is this, when I start the bike, no smoke, if I rev it quickly it will puff some blue smoke while it winds down, and when I first ride it it'll smoke a little but when its warm it won't smoke

So I would think valve seals, the weird part is it will randomly blow blue smoke like crazy when its warm, not constantly its only happened twice now since the final reassembly, the first time it was after I tried a small clutch wheelie in first gear, then it started smoking like a 2 stroke, but still seemed to run fine, I wouldn't push it

This last time just now, I readjusted my valve clearances, and it seems to run leaner, pops more and louder, but plug is still black? Anyways stopped at store for 10 min, since its like 50 degrees F I started it with choke again, and when I took the choke off, is about the time I noticed it start smoking like a 2 stroke again.. I'm trying to give as much detail as possible, also the head gasket was reused, just copper coated it first, since my head gasket I ordered still hasn't gotten here.. I'm thinking the first thing I do is replace the new valve seals? I just don't know..

Sorry the valve seals were replaced 300 miles ago.. edit isn't working...

Sounds like you dicked uq the valve stems when you knocked the valves from the spare head. Then you forced the bad end in the guide and trashed it and the seal. Take the head to a machine shop for new guides and a valve job.

Well I scrupulously went over both these valves, there were no knicks, sharp edges or anything, at the most it would have had to been a little out of round if anything, but it was also just at the top of the valve, where the valve retainers go on, inside the head, one valve was solid, the other valve had a tiny bit of wiggle room, not enough that I could see it with my eye, but enough I could feel it, if oils getting past those then just replacing the seals would fix it right?

What worries me is last time this bike was blowing that much smoke was because my wrist pin retainer came out and gouged the cylinder. But it was blowing smoke continuously.. I've also been told that running a bike lean wont allow rings to seat correcrly

The valves should not have to be forced in the guide. Doing so scratchs the guide and allows oil to leak by. Take the head to a pro and get it fixed correctly.

Well I can get new valve guides on eBay for 8 bucks, so would I be better off gettin a set of those and poppin them out with an air hammer? They also may have been damaged when the valves bent.. does that also mean my valves are probably shot?

If you change the guides the seats will need to be cut also. An airhammer is not the tool for this job, it can swell the guide and enlarge the hole in the head.


So you can get parts 2 and 3 in the above for $8 each..seems darn cheap..What is your bike again???,,I've used the above as an example only as I can't recall what it is.


I'd get the head off invert it on the bench and fill the valve cavity area with some sort of free flowing liquid then look inside the intake and exhaust orifices for the liquid leaking through..Least I think that's the way it's done .Take it from there..


And as has been said getting valve guides out is a job for a pro..those things are tough to get out..

Edited by Horri

Valve guides can be removed with an air hammer by the way,,a special bit is designed for this job......


Installing is different the guides and heat the head then press them in...........


There are oil seals under the guides........i`ve seen perfect rebuilds burn oil because people overlook changing those seals/o-rings pressed under the is not common for them to pass oil unless the engine overheats and burns them


Most guides must be final reamed to size for the right fit..........though Honda is pretty decent with their guides if the valves aren`t hammered..


Who installed the piston/rings??????????


Were the rings gapped properly,was the piston measured and cylinder bored/honed to match.......


Rebuilding an engine,,,,,,,and having it work well,not burn oil,and last any time takes alot of knowledge/time to do correctly..RE-using a head gasket is asking for leaks usually..



Edited by brianhare

The problem you had with the valves is caused by the keepers for the retainer working the groove in the valve stem. You should have dressed them with some sand paper or equivalent. You now need to replace the valves,guide and seals. Never re-use valve stem seals. Always cut the seats after guide replacement.  Do it right the first time = cheaper. Do it cheap 2-3 Times = expensive ;)

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