[whiskerfisher]

On my '94 300, I have rebuilt the topend about a year ago and now it is starting to smoke on cold start ups. Smoke goes away after a minute or two. I replaced the valve stem seals and it still smokes. What else could be causing this, bad valve guides maybe?

 

[shadetree]

has it ever been sunk ???.

 

[Manny]

When you rebuilt the top end did you just re-ring it, or did you have the cylinder bored?

 

[ktriebol]

Is the smoke blue, black, or white?

 

[whiskerfisher]

has it ever been sunk ???.

Nope never been sunk.

 

[whiskerfisher]

When you rebuilt the top end did you just re-ring it, or did you have the cylinder bored?

Cylinder was bored .5mm with new Wiseco piston and rings.

 

[whiskerfisher]

Is the smoke blue, black, or white?

.

It's blue smoke and smells like burning oil.

 

[shadetree]

was the crank inspected at the connecting rod BEFORE you put another top end back on ?. change the oil lately installing the oil filter backwards ??. ( yes..ppl do it !..lol ).

 

[whiskerfisher]

was the crank inspected at the connecting rod BEFORE you put another top end back on ?. change the oil lately installing the oil filter backwards ??. ( yes..ppl do it !..lol ).

The oil has been recently changed and the oil filter is in correctly.
Not sure what the Conn rod has to do with it but ING oil on start up.

 

[shadetree]

was the crank inspected at the connecting rod BEFORE you put another top end back on ?. change the oil lately installing the oil filter backwards ??. ( yes..ppl do it !..lol ).

The oil has been recently changed and the oil filter is in correctly.
Not sure what the Conn rod has to do with it but ING oil on start up.

the connecting rod has a ton to do with it !..lol. if the top end of the rod is out of spec's ?, when you put a new top end piston kit back on the engine, if the rod is bad ?, the piston won't track straight up and down, which means..your new piston, bore job, rings wont last any time at all !.

 

[fishfiles]

Not sure what the Conn rod has to do with it but ING oil on start up.

if there is play in the upper connecting rod bore , then the piston will wobble in the bore and tear up the cylinder walls fast , doing a upper with a bad rod don't last long at all -------- usually smoking on start up is oil coming thru the valve stem seals , maybe the guides are worn , maybe the valve stems are worn , maybe the stem seals were damaged during installation , maybe the engine ran hot from a carb adjustment and cooked the stem seals

 

[ktriebol]

I agree with the stem seals too. I know you said you replaced them. I was wondering if the valve stems themselves may have a little carbon build up on them which would tear up the new seals.

 

[whiskerfisher]

but if the rings are bad wouldn't it burn oil all the time and not just at startup?

 

[whiskerfisher]

new valves and valve seals were installed when I rebuilt the top end. After I got back from a WV trail ride. I changed the oil and that's when it started to smoke at cold start up. Checked oil, not over filled or anything like that.
I purchased a new set of valve seals from Honda and installed them. It still smokes at start up. Sometimes its so light you can barely see the smoke then sometimes it smokes worse but clears out after a minute or two.
Checked compression, it is good. When I installed the last set of seals, I check for excessive play in the guides by wiggling the end of the valves, didn't feel any play at all.

 

[fishfiles]

new valves and valve seals were installed when I rebuilt the top end. After I got back from a WV trail ride. I changed the oil and that's when it started to smoke at cold start up. Checked oil, not over filled or anything like that.
I purchased a new set of valve seals from Honda and installed them. It still smokes at start up. Sometimes its so light you can barely see the smoke then sometimes it smokes worse but clears out after a minute or two.
Checked compression, it is good. When I installed the last set of seals, I check for excessive play in the guides by wiggling the end of the valves, didn't feel any play at all.

...right after changing the oil = did you put the oil filter in correctly ? what do you call good compression , ( 200+ on a fresh rebuild ) ----- you rebuilt the upper , what did you do , hone ? standard rings ? new jug ? bored over size ? who did the boring ? what piston and rings did you use ? Chinese/ ebay , OEM ? how was the connecting rod bore ? so many questions come to mind

 

[mac102004]

Usually smoke on start up is valve seals. But you said they were replaced. Only thing I can think of is maybe the valve stems were scored or something and it ruined the new seals.


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[shadetree]

it's posb one or both of the valve guides are cracked ?.

 

[Manny]

I would just tear it down again, pull the bore, have it measured and start back again from scratch. having the parts in your hands is going to provide ya with real hard data not just speculation.

 

[wheeler]

You say u replaced the valve stem seals & new valves. Did you have a shop install them & get them lapped to match? If it only smokes on start up I’d lean towards either of the two.. did u put the right oil in the quad? Very ironic this happened after an oil change as well...