Topic: Need some advice on white smoke from exhaust after top end rebuild - cb350f

[craywm]

hey all,

i recently decided to rebuild/clean my cb350 motor and replace the rings. my oil started to smell like gas and one cylinder was not opperation correctly (tried to do a compression test but the adapter that i ordered started eating up my threads and i decided not to do so) But while syncronizing the carbs i noticed that my #1 cylinder gage was moving WAY behind the other 3 cylinders, i double checked the gage by switching a good cylinder to it and it operated normal. so i came to the conclusion that my #1 rings must be bad and i started tearing her down to clean her up and replace the rings.

after finishing all that, i went to start her up and she was spyewing white SMOKE everywhere. i let it run a bit to see if it persisted and it did so. i am now replacing the gassy oil and will give her another go. im pretty sure i installed all the piston rings the correct way (with the exception of the oil ring because mine didnt have any sort of markings but i dont think this one has a right side up) while putting the pistons into the cylinders i snapped my 2nd ring on my #1 cylinder. so i had to reuse an older 2nd ring that was still in good condition. i also reused my Cometic CFM-20 Head gasket after cleaning it up. no leaks there. the only thing i didnt check was my valve seals. since i didnt have white smoke spyewing out before the rebuild i figured my valve seals were fine and i just needed new rings.. but now i have caused a problem with trying to solve one.

one other side note on this too, while i was reinstalling the cam chain, somehow i installed it slightly off (the lines paralell with the top face of the head thing, you know) and i caught this when i started trying to turn the engine from the points cover when i felt resistence then if i pushed a little it would move normal, anyway i tore the top off again, readjusted the cam and it didnt hang up anymore. i was worried that i maybe pushed a valve into a piston and put a hole in the piston but, i didnt start it that way. anyways, anyone have ideas on why im getting a very large amount of white smoke now?

NOTE: THIS ISNT CONDENSATION. ITS SMOKE. IN LINGERS IN THE AIR

[trueblue]

A quick run through of smoke colours:
Blue:-Oil smoke (can look whitish depending on oil type)
Black:-Caused by an overly rich condition, it is fuel that has partially burnt.
White:-Can be one of 2 things, either coolant (not applicable in this instance), or unburnt fuel.
I would guess when you felt that bit of tightness when you tried to turn it over, you touched a valve to a piston and bent the valve.  Most of the time when a valve meets a piston the piston wins.  The only time I have seen a valve hole a piston is when the valve head dropped off at high rpm and it bounced around and embedded itself into the piston crown. 

[craywm]

I was going to change out the valve seals so ill check the valve stems too. It seemed to run fine after that it was just burning oil. It was the head gasket btw. is it possible to reuse a bent stem if it operates normal and seals well? I was only 1 tooth of on my cam chain so it shouldnt have bent that badly.

[craywm]

I dont think that it bent a valve seal. When i pulled the head cover off t stopped snagging and i noticed there was a chip right where a boss for the cam was in the head cover. I figured it was snaging there. But i guess it could have been both. Pistons and valves dont look like the came in contact ( atleast it doesnt look that way)

[trueblue]

I'm no expert on the 350 but I think when you lift the head cover off of them you remove the rocker gear as well which will stop the cam having any effect on the valves because they are no longer connected.  If the valve is bent even a couple of thou the valve won't seal properly.  I'm not sure on how far out the cam has to be on the 350 for it to touch valves but on the 500-550 they need to be 2 teeth out, but with the 350 being such a small engine it may not be so forgiving.