Smoke on Startup - Normal?

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Nick1994

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I've got a MTD lawnmower with a Honda motor, I think it's a 5.5hp. On the first startup it blows out some smoke, seems white-ish but definitely has blue. I've been changing the oil with Valvoline NextGen MaxLife 10w40. The mower has always run great and starts on the first or second pull, even after sitting for 2 months. It's got a new plug too. Should I run anything through it or keep on with it?
 
If the oil level is correct, provided that your valve guide clearance is still within spec, then it's either your valve stem seal hardened or worn.

It's a very simple, 10min job if you have the parts on-hand and the right tools.

(*ref GC135 series)

Q.
 
Not on a Honda,cant be.lol. Unless MTD is dictating a Chinese-made Honda instead.
 
Smoke on start is not normal on any modern ICE, ESPECIALLY a Honda. It's something you did to it such as using some fad product you read on BITOG or that junk oil you have in it. Switch to M1 10W-30 HM and see what happens.

Better yet, leave it and fix your mother's car [From another thread for those left scratching their heads].
 
No, it's not normal. The only small engine that I have (and I have a number of them) that smokes a little on startup is a 40 year old Kohler in a John Deere 210. Other than that none of them smoke on startup.
 
Make sure its not overfilled with oil. It doesn't take much to get oil into the horizontal cylinder.
To test, just store it with the cylinder facing up a little. If it doesn't smoke thats how oil is getting in.

Its not uncommon with any air cooled horizontal engines with larger ring clearances to puff a little oil smoke when cold.
Many old VW Käfer gave a nice puff of blue smoke every morning with the engines totally within spec. Don't sweat this, its nothing worth worrying or doing anything about.
 
Originally Posted By: Trav
Make sure its not overfilled with oil. It doesn't take much to get oil into the horizontal cylinder.
To test, just store it with the cylinder facing up a little. If it doesn't smoke thats how oil is getting in.


I think Trav is dead-on correct.

Check the oil level and how it has been handled re: cylinder orientation. I've got a Briggs and Stratton push mower that will smoke on start-up when it has been tipped with the cylinder down and I've got a little too much oil in it. Runs fine and doesn't smoke under load. No smoke at start-up otherwise.

thanks,
ben
 
Originally Posted By: Trav
Make sure its not overfilled with oil. It doesn't take much to get oil into the horizontal cylinder.
To test, just store it with the cylinder facing up a little. If it doesn't smoke thats how oil is getting in.

Its not uncommon with any air cooled horizontal engines with larger ring clearances to puff a little oil smoke when cold.
Many old VW Käfer gave a nice puff of blue smoke every morning with the engines totally within spec. Don't sweat this, its nothing worth worrying or doing anything about.
I well remember that puff from the bug motors I had.
 
Originally Posted By: kd5byb
Originally Posted By: Trav
Make sure its not overfilled with oil. It doesn't take much to get oil into the horizontal cylinder.
To test, just store it with the cylinder facing up a little. If it doesn't smoke thats how oil is getting in.


I think Trav is dead-on correct.

Check the oil level and how it has been handled re: cylinder orientation. I've got a Briggs and Stratton push mower that will smoke on start-up when it has been tipped with the cylinder down and I've got a little too much oil in it. Runs fine and doesn't smoke under load. No smoke at start-up otherwise.

thanks,
ben
My Honda lives in the basement all winter and is carried up some stairs in the spring. It smokes a little bit on the first start since we tilt it a bit getting up the stairs. Doesn't burn any T6 all season though.
 
Originally Posted By: AZjeff
The real question is why you'd even need a lawn mower in Phoenix??
Have you been to Phoenix? At least half of people's yards are grass.
 
As someone else said, horizontal cylinder, slightly over filled, the oil will seep past the rings into the cylinder giving you a bit of smoke on start-up. Change the oil and fill it up to halfway up the dipstick and report back. No need to use a multi-weight in your climate, use SAE30.
 
Horizontal cylinder + little wear + mineral/semi syn oil = smoke!!!

Use 5w40 synthetic and smok will be gone
wink.gif
 
I would bet if you remove the head after it has sat,you will find some oil has seeped by some sightly worn rings.
 
The real question, neither asked nor answered, is "Does it use any oil between changes?" If the oil is checked before each use, and no oil is required to be added between changes, then the consumption is minimal. It is normal for all engines to consume a bit of lube, it would be abnormal for an engine to not consume oil.
Were it mine, I would ignore any startup smoke if the oil level remains consistently in spec. If the oil level rises, be concerned for gas contamination due to carburetor needle & seat failure.
 
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