STP for oil smoke?

[Tkelly]

My high mileage SPNT is burning oil,not sure how much but not 2 stroke level.Compression is equal in both cylinders and it runs good.A friend suggested STP Smoke treatment.I am thinking of trying it,is there any harm?

[Ncdan]

My high mileage SPNT is burning oil,not sure how much but not 2 stroke level.Compression is equal in both cylinders and it runs good.A friend suggested STP Smoke treatment.I am thinking of trying it,is there any harm?

IMHO.
The STP probably won’t hurt anything however I’ve had several excellent motor builders tell me that only new parts can replace worn out engine parts, not oil additives.

[nc43bsa]

If it runs good and has good compression on both cylinders, one thing I'd do is pull the carbs and see if oil is drooling down the valve stems.

[kballowe]

STP

"The Racer's edge"

I remember that stuff.  It's like snot - and gets all over everything. 
It gets on your hands, your shirt, your tools, on the workbench, the floor...

[guzzisteve]

STP is OK but only makes oil thicker & additives.  I would do a leak down test to be sure what issue is. Most likely guides unless you been using cheap oil.

[moto]

If it runs good and has good compression on both cylinders, one thing I'd do is pull the carbs and see if oil is drooling down the valve stems.

Right! THEN put it back together and add STP.

If the STP works, you'll know WHAT it fixed and what you would need to do for a permanent, mechanical fix.

[Tkelly]

I’m thinking the STP would simply burn up with the oil,which is probably cheaper.Thanks for the commentary.

[ridingron]

Worn parts can only be fixed by new parts.

Before I tore down that motor, I would try a quart bottle of watercraft synthetic 2 stroke oil at 1 oz. per 5 gallons (doesn't have to be perfect measurement). Every tank full until the bottle is empty. It will help clean up any carbon in the combustion camber. May be with some carb cleaner in the same gas. What do you have to lose, $20? Has the oil and filter been changed regularly? My old riding buddy would probably say it just needs a good Italian tune up. Fresh gas, fresh oil and go run the snot out of it! For the PC in the group, he was a first born generation, in the US, with both his parents being from Italy.

[bigbikerrick]

I used something similar, on and old honda ATC  70 that smoked alot. It was called "motor honey" and was thick like STP. It did reduce the smoke some,and quieted the engine. Some old school mechanics  in the 70's swore by STP. They recommended adding  a can to old british car motors  that were a little "loose" , and it did seem to help in an old MG Midget I had.
Rick.

[Bisbee]

Check out Project Farm - a great site - on his trial of Seafoam. And a one year follow-up. Never tried it but might be worth a shot.

[Bulldog9]

Does it smoke at startup then clear up when at operating temperature, or all the time?

If the bike sat for a while, and oil rings are gunked up, adding Marvel Mystery Oil or Seafoam (I like to use 1/4 volume) to the crankcase and oil and running it for 10-15 miles and let it sit then run again 10-15 miles and fresh oil may free up and degunk the oil rings and clean things up, but as others have said, new parts will likely be in order.

[Moparnut72]

Restore is another product that had been reported to help in this area. It supposedly helps with minor scuffing on cylinder walls. It has been tested an shown to help. Not a permanent fix though. Does it smoke at continuous rpm or after idling a bit and then goes away. That tends to indicate worn valve guides.
kk

[Tom]

MMO to loosen up stuff.  Then run carb cleaner.  OR At higher rpm's spritz/squirt water into the carbs.     2stroke oil in the gas is a good one too. 

[mechanicsavant]

I’ll take oil additives for $400 , ken . What does STP stand for? Answer Scientificly Treated Petroliem !

[jhem68]

Gee Whiz TKelly, you're probably just driving too slow! LOL



John H

[larrys]

Well, fifty five years ago my high school shop teacher told us that if you put STP in your engine and it runs better, it's shot and needs rebuilding. I don't think that has changed.
Larry

[Moparnut72]

STP is a band aid. I have been told that it is a good assembly lube but I use Lubriplate.
kk