Air/Fuel Mixture Questions

Prasinos · #1 06-06-2009, 10:22 PM

I just thought i would start a thread on this because the subject is brought up in several others.

Anyway,
Ive been checking my spark plug several times and it has stayed a nice light brown for the entire life of the engine. However, since removing the head gasket and changing to a synthetic oil (20:1), a thick layer of carbon has built up on the inside of the cylinder and on the head. The spark plug is still the same color. Im not sure what caused the problem. Should I try to go leaner? Has the higher compression caused the engine to require a higher octane fuel? Too much oil? Other?

Thanks
-Phil

misteright1_99 · #2 06-07-2009, 12:54 PM

This is a common thing with 2 strokes. You will get carbon buildup as the oil is burned in the fuel. I use synthetic oil and run 32:1 You could try "leaning" out the oil to gas mix and see how it runs.

Prasinos · #3 06-09-2009, 11:38 AM

Thats whats so weird, i just started to use synthetic oil and went from 16:1 to 20:1 and i just started noticing the buildup. I just got some new gas i mixed it 32:1 and got 91 octane just to be sure. Il let you know when this tank runs out and i try out the leaner mixture.
Maybe its just that the synthetic oil is made to be mixed 50:1 so like you said, leaning it out would help. Thanks and il let you know how it works.

-Phil

misteright1_99 · #4 06-09-2009, 02:03 PM

Quote:

Originally Posted by Prasinos

Thats whats so weird, i just started to use synthetic oil and went from 16:1 to 20:1 and i just started noticing the buildup. I just got some new gas i mixed it 32:1 and got 91 octane just to be sure. Il let you know when this tank runs out and i try out the leaner mixture.
Maybe its just that the synthetic oil is made to be mixed 50:1 so like you said, leaning it out would help. Thanks and il let you know how it works.

-Phil

1) Keep an eye on your plug "leaning" the oil/fuel mixture you MIGHT have to adjust the needle to lean or richen the fuel/ air mixture.

2) I have read in posts that high octane fuel is a waste, I dont know I always run the "cheap" gas.

Keep us posted.

George...............

**Bikeguy Joe** · #5 06-09-2009, 02:20 PM

Carbon build up is normal and can be removed with wooden dowel, or even a piece of 1"x1/2" piece of hardwood. Resist the temptation to use a screwdriver or other metal tool.

**Bikeguy Joe** · #6 06-09-2009, 02:21 PM

Usually a lean(er) oil to gas mix means a richer fuel to air ratio. Your plug may darken slightly...

matt167 · #7 06-09-2009, 04:54 PM

run a bit of seafoam in your gas according to directions for small engines.. it'll smoke a little white for that tank, but it'll end up free of carbon

Prasinos · #8 06-10-2009, 01:48 AM

Thanks matt il try that when i get home. I mentioned this before but my spark plug seems to indicate a good mixture (light brown). It was only when i took off the head that i realized that there was so much carbon buildup in the combustion chamber.

Also this build up was only from about 100 miles of riding, that cant be normal right?

misteright1_99 · #9 06-10-2009, 12:57 PM

Quote:

Originally Posted by Prasinos

Also this build up was only from about 100 miles of riding, that cant be normal right?

20:1, I imagine, it could build up that fast......

Prasinos · #10 09-16-2009, 11:24 AM

Ive noticed this with a few of my engines...

My engine runs great for about the first 10 min, but after crawling up a long hill or just riding for a while it loses alot of power. I cant decide if this is normal or if it means that my engine is overheating because it is running too lean. Or if it is running too rich after it warms up the crank case. Any suggestions?