Smoke on startup

I have an 03 YZ450f, if I leave it sitting for a day and start it up (1-3 kicks) with the choke on it will blow a whitish smoke out of the exhaust for about 30 seconds and then it will blow out more smoke if I rev it but it goes away in about a minute. The whole smoking only lasts about a minute until the bike is warm i guess and goes away. Do i need rings, or what? the smoke has a smell to it but I dont know if it is oil or coolant.

Coolant smells sweet, oil smells like burnt rubber. Either way, teardown time. Its oil if you aren't losing coolant. Piston, rings and valve job coming up.

Coolant smells sweet, oil smells like burnt rubber. Either way, teardown time. Its oil if you aren't losing coolant. Piston, rings and valve job coming up.

Dang you think so, it only lasts for less than a minute then goes away, still starts on 1-3 kicks. I am pretty sure the smell was rubberish so what does that mean i need to replace? Shouldnt it smoke more if it needs rings, and the valves seem to be fine since it doesnt backfire and it starts easy

Pomoco is right, that is the first symptom of the rings starting to go. It goes away once it runs a little because thermal expansion. Do a compression test cold and warm, note if there is any difference. The bike may run like this for a long time or may not? It's a normal and just an indication not long before top end needs to be done.

Oil smoke on startup after sitting for a time, as opposed to just a few minutes, that goes away shortly after startup, is the fault of valve guide seals, not rings.

Pomoco is right, that is the first symptom of the rings starting to go. It goes away once it runs a little because thermal expansion. Do a compression test cold and warm, note if there is any difference. The bike may run like this for a long time or may not? It's a normal and just an indication not long before top end needs to be done.

Ok, I will do one this weekend, what ranges do you think i should be looking for. If they are pretty close when warm and cold then how long do you think I should have before I would really need to do the top end? I am going to have to save some money up

Oil smoke on startup after sitting for a time, as opposed to just a few minutes, that goes away shortly after startup, is the fault of valve guide seals, not rings.

Yeah yesterday i started it with the few seconds of smoking, and rode for a few minutes. Then let the bike sit for about 4 hours and when I went to go ride again there was no smoke. I guess it only smokes if it sits for over 12 hours. How much is it to replace the Valve seals and is it a major problem that would need to be fixed ASAP?

Most of us that ride hardcore will change the piston and ring long before the bike starts to smoke. Valve seals are typically the cause of cold start smoke. Either way, I'd freshen it up before it grenades and costs you big money.

Most of us that ride hardcore will change the piston and ring long before the bike starts to smoke. Valve seals are typically the cause of cold start smoke. Either way, I'd freshen it up before it grenades and costs you big money.

I dont think it needs a piston and rings though. and how do you replace valve seals? is it that bad if you dont replace them?

I think and most will agree, that a smoking bike is overdue for dome attention. If you're just play riding it and taking it easy, it'll run for a while, if you race or jump big jumps I'd freshen it up.

Some attention not dome attention.

Some attention not dome attention.

I think and most will agree, that a smoking bike is overdue for dome attention. If you're just play riding it and taking it easy, it'll run for a while, if you race or jump big jumps I'd freshen it up.

Some attention not dome attention.

Some attention not dome attention.

Just talked to my bike mechanic, He said since it is barely any smoke and it isn't bad then I shouldn't worry about it, especially since I don't race. He said I just need to replace them once I am actually due for a top end.

The downside of letting it go is that it will contribute to the amount of carbon and baked tar on the backside of your valves.  Not the worst thing that could happen.

Yeah i will probably just wait. Heck I started it up today after it sat for 2 days and no smoke....

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