I have a 09 KX450F that I just bought with roughly '30' hours on it. When I rev the engine hard, a puff of white looking smoke comes out. I realize it is more of a blue smoke to be concerned about, but is this normal? Does it just burn away a little oil or something?

 Chandler789, on 16 March 2012 - 01:44 PM, said:

So, how is it that you can see this puff of smoke when you are riding?

Oh, you mean on the stand? Before it's even warmed up?

Now you are guaranteeing that it will need to be replaced more often..............

ya its not totally abnormal to blow a little smoke when its still cold.   It shouldnt smoke at all once its at operating temp.

To answer you question, you should follow the manual's recommendations to the letter, but checking parts spec's.

The only way to be sure of you top-ends condition is to pull the head and jug, and start mic'ing parts.

Then you know, you aren't guessing, and will be able to gauge how many hours before YOU need top end work done.

The last time I pulled my head,  I decided to check my piston and rings, and they were past the service limit, but every valve measurement was in spec, so a new piston and rings were put in.

That was 70 hours that I put on, and an unknown amount by the previous owner.

If you ride 35 times a year, you should be pulling it apart every year.

 Krannie, on 16 March 2012 - 02:55 PM, said:

I do not have a stand at the moment, but for all intensive purposes, yes, it is when it is idling after start up, maybe 30 seconds afterwords.

Why would that guarantee that it need more replacing? because the oil has not headed or circulated enough? I should have said a little throttle, not revving it like a two stroke, just to pull on it a little, maybe just over a fourth a turn, but for this bike that is harnessing a lot of power.

 stlavsa, on 16 March 2012 - 02:57 PM, said:

That is what I have always noticed with any of my bikes, but I have never owned a newer bike with <30 hours on it, or it having been raced by the previous owner.

 Krannie, on 16 March 2012 - 05:22 PM, said:

I know I need to pull it and check the specs, I am just wondering if I can go a couple more rides before having to do that, I was planning on checking valves after my ride tomorrow and next mondays, so I would be doing it then.

If you go by the manual, it reads change oil every 15 hours of operation and replace piston at 15 hours.

To answer your question, it depends on several variables... the more time it spends in the upper RPMs the more often it will need serviced.  The more often you change the oil, the less often it will need serviced.  I do mine at about 40 to 45 hours, but I find the piston, rings, and cylinder are ok, it's the bottom end that fails first for me.  The majority of guys I ride with and around can get 80 to 100 hours before needing major service.

A little puff of smoke is acceptable at any engine temp.  When you start getting more than just a puff it's time to look inside and find the culprit.  You will also need to make sure what the puff is, oil, coolant, or fuel.

As far as the valves go... I have destroyed several bottom ends before I got my timeline down for rebuilds.  I have never hurt a head, valve, guide, or seat on one of the green big bikes.  On the last three bikes I have only changed valve lash once on each head and that was only because they were close to the bottom of the spec.  I currently have 130 hours on my 11.  I'm getting parts ready for the 4th rebuild and the valves are still in spec.

Edited by kx450f63, 21 March 2012 - 10:32 AM.

 kx450f63, on 21 March 2012 - 10:24 AM, said:

Thanks for that, I thought valves were more high maintenance then that, so that is a relief. I will be looking at a top end soon enough then anyway. I change my oil every other ride if not every ride.

i have 140hrs on my 450 and havent done a piston or rings....never had to adjust the valves either. GREAT BIKES!
i used to have to shim my 04 crf250's valves every lap damn near....