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Discussion Starter · #1 ·
Hi all, just put a nice new piston, rings etc in and were still white smoking :( if i drive it round the garden gently its fine for 20 mins. as soon as i open it up down the fields or it has the trailor on, it starts white smoking alot! if i turn it of, and back on it fine! any ideas? cheers guys!
 

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OK - Let's review "engine troubleshooting 101".

You may have rebuilt the engine when it wasn't necessary, but regardless, you didn't hurt anything by installing the new parts.

My first question is; did you install the proper size piston and did you install the rings correctly? While there is no "up" side to the oil ring there is an up side to the compression rings and a difference between the top ring and the second ring.

I have to presume you had the identical problem before you installed the new parts. First, "white smoke" (that seems to disperse quickly) is usually raw fuel. Oil smoke usually is slightly blue and rather hangs until carried away by the wind. Sometimes raw fuel collects in the exhaust and is vaporized by exhaust heat causing a white smoke. Depending on the location of the "fuel pool", it may not vaporize at low speed (when just the head pipe gets hot), but if the muffler is full of gas, then at high speed (when the entire exhaust system gets hot) you will see it. Extended high speed operation may clear up the problem.

My guess would be that you have (or had) a fuel control problem. This might be caused by the carb or the petcock or both. With the petcock in the off position, pull the fuel line off the carb and check to see the petcock is stopping fuel flow. If you are not shutting the petcock off when parking the machine, start doing so. If this does not solve the problem, check the carb for proper float level and that the main jet is in place and of the correct size.

Final thought; I presume you changed the oil when you rebuilt the motor? If not, it is possible a fuel control problem filled the crankcase with gas and when running, the crankcase ventilation system is drawing fuel evaporating out of the oil into the air intake and causing the white smoke. At low speed only a small amount of vapor enters the system and no smoke is visable. At high speed, both fuel vapor and some oil may be drawn into the intake causing the smoke.

There are other possibilities, but these are the most common.
 

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Discussion Starter · #3 ·
Re . .

Thanks for the reply! piston and rings were done by the local engine refurb shop and honned at the same time, carb is a aftermarket american one of ebay and i am wondering if this is the problem, as i am struggling to get it to idle for more than 20 secs after been on a run, idles peeeerrrrfect on choke tho! so would make me think its to lean - but white smoke in the exhaust means fuels getting into there?? also . . . i am wondering about the decompresion valve as i found the cable had come off, so i thought bingo reconnected it and it was abit better :) but still white smokes under strain. i do use the fuel shut of valve all the time also cheers!
 

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Look at the carb - kind or type does not make a difference. The carb is only a mixer. It mixes fuel with air. Properly set up, any carb will work.

Fuel in the exhaust was just a guess. Another guess is; too much fuel at full throttle.

Sometimes (with the original carb) the main jet would fall out and cause a problem like you describe.
 
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