Sign in to follow this  
Followers 0
troyfisher123

Valves and a little smoke on start-up...

4 posts in this topic

Do they go hand in hand?

The bike is an '04 YZ450F. I bought it from a friend of mine with it having 38 hours on it. The bike now has 86 hours on it and sometime between 72 and 80 hours, it started blowing a bit of black smoke on start-up, but when it's been run and is hot, it doesn't smoke that I have noticed. Yes, I have looked. It has a WB Carbon Pro exhaust and a Lectron carb. I don't think that is really relevant, but the information is there in case someone asked. Is the smoke from the valves needing to be adjusted? I just had the valves adjusted but haven't picked the bike up yet, so I don't know if it still does the smoking or not. The valves were all in spec yet, with the exception of one, which they tell me wasn't far off at all and really didn't need much attention. So, if it continues to smoke, where do I look next? And from what I have read on here, Yamaha 's seem to keep the valves in check and not need too much adjustment, correct? I just want to make sure all my bases are covered before I take the bike home. If something needs to be addressed, I'd like to be able to tell them where to look. Thanks guys!

Share this post


Link to post
Share on other sites

Black smoke is from an excess of fuel, so yes, the non-OEM carb is a relavant fact. Valves being incorrectly clearanced don't cause smoke of any kind. A brief bit of white or "blue" (white, really) smoke on a cold start can be caused by the valve guide seals allowing a small amount of oil to run down one or more of the intake stems as it sits.

Share this post


Link to post
Share on other sites

Mine will puff some black smoke on start up too... I think its from the choke because it stops soon as it warms up a bit.

Share this post


Link to post
Share on other sites
Black smoke is from an excess of fuel, so yes, the non-OEM carb is a relavant fact. Valves being incorrectly clearanced don't cause smoke of any kind. A brief bit of white or "blue" (white, really) smoke on a cold start can be caused by the valve guide seals allowing a small amount of oil to run down one or more of the intake stems as it sits.

So with it being a jetless carb, I need to lessen the amount of fuel going in on the bottom end, correctomundo?

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0