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JOHNDOE83
06-24-2012, 12:21 PM
Ok, Im new to 2 stroke tunning and 2 stroke technical stuff.

I built a hybrid 2 stroke quad with a 250r based motor, it seem's like it smoke's an awful lot on start up.

Like more then I would expect, once its warmed up a lil bit it doesnt smoke like that at all.

Is alot of smoke a sign of bad rings or is this normal for a 2 stroke motor, I built this for drag racing, I would hate to annoy people with huge amount's of smoke in the pit area if I can avoid it.

I came here because my motor is essentially a 250r motor, its a cr250 motor.

b0rn c0nfused
06-24-2012, 01:30 PM
Not sure what causes it but my cr250 was the same way.

89trx250r
06-24-2012, 04:33 PM
What color smoke? Does it smell like coolant or trans oil burning? Did you do a leakdown test of the engine and cooling system?

wilkin250r
06-25-2012, 02:45 AM
I've also seen other 2-strokes (not my 250r) that smoke significantly at start-up because the fuel bowl fills up with gas and oil, and a lot of the gas evaporates, leaving a mixture that's really heavy with oil in the carb. It will smoke bad at start-up, but then clears up when all that extra oil is burnt up and you get a normal mixture in the carb bowl.

My little LT80 is notorious for that, because the oil injection system will leak into the carb. It smokes like you wouldn't believe for the first few minutes.

Motofool250r
06-25-2012, 05:10 AM
what oil are you using?

which mixture?

are your floats set properly in the carb?

if your rich and leaking into the carb like what wilkin stated it will have to burn that oil off when it starts up.


try this set your floats and checkout your float needle tip.

then next time you shut the bike down turn the fuel off and let it run till the bowl is dry and the idle starts getting higher then kill it.

next time you start it turn the fuel on for a few seconds before you start kicking so it can fill the bowl back up.

Motofool250r
06-25-2012, 05:10 AM
what oil are you using?

which mixture?

are your floats set properly in the carb?

if your rich and leaking into the carb like what wilkin stated it will have to burn that oil off when it starts up.


try this set your floats and checkout your float needle tip.

then next time you shut the bike down turn the fuel off and let it run till the bowl is dry and the idle starts getting higher then kill it.

next time you start it turn the fuel on for a few seconds before you start kicking so it can fill the bowl back up.

JOHNDOE83
06-25-2012, 08:34 PM
The smoke deffinetly smell's like 2 stroke oil and not rad fluid or trans fluid.

It makes sense that evaporated gas left a heavy oil mix in the carb making it smoke, after it's had a good couple minute's to warm up it almost disappear's.

I also recently aquired a stock cr80 and it "kinda" does the same thing but not as much. I think Im gonna try the run the bowl dry thing a few times and see if it calm's the start up smoke.

Both ride like a bat outa hell and have good compression by kickstart feel, I havent done a compression or leakdown test on either one yet but they deffinetly feel plenty powerful and smooth for now anyway.

I checked the float height when I took the carb apart to check the jetting and all seemed ok.