smoke on start up

[Dr89]

so just wondering if i have a problem? my yfz has very few hours on a brand new rebuild....everything was taken care of, piston, rings, cylinder, crank and rods, gaskets, the whole bit. anyways if its been sitting for a while, as in over night or days at a time, and i go to start it up it will back fire some and throw out puffs of white smoke. this only happens when the engine is really cold and needs to crank a few times to start, when its warmed up i just hit the button and it starts up instantly no smoke etc...when it does smoke a little however it only lasts for a few seconds, maybe 30.

im not losing any coolant or oil what so ever that i can tell, even after hours of riding. so i was wondering if it could just be some left over oil etc. that they might have used while rebuilding it? i also just repacked the pipe but i dont think its coming from there. the guy who do the work is extremely knowledgable and incredibly experienced so im hoping this is just common with break in??? it runs like a champ btw! :)

[Ride1Rob]

From the way you're explaining it, it seems that your rings are letting oil get by when the bike is cold. Once it warms up it burns off the oil and the bike stops smoking. When it sits, it repeats the process all over again. If it's a new topend they didn't seat correctly or the bike wasn't broken in properly. If it's been awhile it's time for new rings and piston.

[Dr89]

sounds like a really good possibility...but i'm still in the break in stage and haven't been hard on it at all...is there still chance that the rings will seat yet? as long as i keep an eye on oil is this gonna be a problem?

[Ride1Rob]

Well if you're going through the breakin they probably haven't seated yet. What does your breakin consist of? When I rebuild my bike I take it through 4 heat cycles of about 15mins. First crank for one minute and listen for anything unusual. Ater it cools the 2nd crank for 5mins. Repeat up until 4 cranks and cooldowns. I putt around on it the 5th crank for 10mins. Let it cool completely, change the oil and ride it hard. That's my breakin ;)

[Dr89]

yep bout identical to the process im going through...im at the "riding it hard" stage and am loving the switch from my kfx to a yfz :D

[Ride1Rob]

Originally posted by Dr89
yep bout identical to the process im going through...im at the "riding it hard" stage and am loving the switch from my kfx to a yfz :D

What was the deal with the KFX?

[Dr89]

oh, i just used to have a modded out kfx that i tried forever to sell on here...i ended up finding the yfz i have now for sale somewhere else and traded my kfx to the guy straight up. it really was an awesome bike but i love the yfz, i could never go back to a 400. not to mention it was an awesome deal, it ended up needing rebuilt just a few hours after i got it but the guy ran a nice little shop and did the rebuild for free so i cant complain.

my old kfx