Wr450f smoke at high rpm

[RiderDeAzul]

Just recently got a 2007 wr450f and it has the Athena 480cc kit on it, and I have noticed that it blows a little bit of blue smoke, but only at the higher rpms, is this just the valves needing to be adjusted or is the engine getting ready to go kaboom?

[CRFRida1605]

Blue smoke is oil being burned, it could be from the valve guides leaking but im not sure if it would do it only at high rpms. Someone else will chime in with some more detail hopefully. I doubt its getting ready to go kaboom in the short term, but you need to get it straitened out quickly or it will just get worse and worse, and eventually it will blow.

Edited August 23, 2015 by CRFRida1605

[FORMA MOTO]

More than likely you have blow-by past the rings.

If the motor was not broken in agressively when new, the rings never seat properly.

It could also be the valve guide seals going out from lack of use/sitting.

 

Are you testing it on the stand, or under load?

[SteveThe Snakes]

If it doesn't have a million miles on it and doesn't show oil loss on the dip stick it's likely okay. If you lose too much oil in a ride you've got a problem.

[RiderDeAzul]

I'm just noticing it when I am looking for it, no one when riding behind me can see it, I can only see it when I'm sitting in neutral somewhere and give it a decent amount of throttle

[SteveThe Snakes]

Okay stop looking behind you?

[RiderDeAzul]

Okay haha, so you don't think I should mess with it until it starts losing power or smoking more?

[SteveThe Snakes]

Okay haha, so you don't think I should mess with it until it starts losing power or smoking more?

Or losing oil.

[RiderDeAzul]

Okay, so update, it blows the smoke when coming off of the higher rpms, and today after revving the bike some on the stand, it shot a small flame out the exhaust after I turned it off, but it didn't make a loud bang like a backfire normally does, and the smoke is more of a white smoke than blue

[FORMA MOTO]

Why the hell are you reving it out on the stand to begin with.  

You don't ride a bike that way.

That's a really good way to float a valve and bend it.....

 

 

You are chasing ghosts.  

 

Burning some degree of oil is normal. If it is a measurable amount between rides, you are passing oil where you shouldn't be, and it's not a big deal unless it's more than 10cc or so. 

 

You have not metioned the durations of the rides, how harsh, oil changes, fuel quality, last spark plug, carb tuning, or pretty much anything else that might affect your 'smoke' issue.

 

Follow the service manual and do all the scheduled maintenence.

[SteveThe Snakes]

And also remember a big bore takes a smaller main jet not a bigger one.

[RiderDeAzul]

Okay, thanks, I think I'm just going to tear it down and put a new piston in just to be safe

[FORMA MOTO]

Okay, thanks, I think I'm just going to tear it down and put a new piston in just to be safe

 

Yeah, but don't just 'put in a new piston'.....you need to check the service limits of the cylinder, and the old piston to see if they are evan worn, and where.

You need to check the valves for sealing...you can do this by just pouring gas in the upside down head and see if fuel leaks out faster than a drop per minute...

Check the ring gap of the new piston and rings, and properly orient the rings relative to each other.

 

 

You need a SERVICE MANUAL!

[RiderDeAzul]

I'm probably just going to take it to the Yamaha shop, any idea where I can get a manual other than from Yamaha? They want $85! Do you think that I should just buy a stock bore cylinder since I'm at a 480 already? Sorry for all the questions, I'm just used to the simplicity of my banshee.

Edited August 25, 2015 by RiderDeAzul

[toten]

Ebay for a manual.

[SteveThe Snakes]

The easiest thing to do is look at how much oil the bike consumes. If it is nill just ride the bike.

[stainless601]

Got a few service manuals for that model, $ 40.00 shipped. If you want to know what's up with your motor, do a Leak Down Test. There's an article on this on thumper talk. It's possible you see dark smoke that's related to over rich condition. People commonly over jet when a big bore kit is installed.

If you need hard parts I've got a new factory Yamaha cylinder and piston for that model as well.

[RiderDeAzul]

Got a few service manuals for that model, $ 40.00 shipped. If you want to know what's up with your motor, do a Leak Down Test. There's an article on this on thumper talk. It's possible you see dark smoke that's related to over rich condition. People commonly over jet when a big bore kit is installed.

If you need hard parts I've got a new factory Yamaha cylinder and piston for that model as well.

How much for the cylinder and piston?

[RiderDeAzul]

More than likely you have blow-by past the rings.

If the motor was not broken in agressively when new, the rings never seat properly.

It could also be the valve guide seals going out from lack of use/sitting.

Are you testing it on the stand, or under load?

Okay I tested it out again today and it burned quite a bit in about 2 hours, it blows it only when letting off of the gas, as the people riding behind me noticed it, the oil went from the top of the crosshatches to where my thumb is pointing in about 2 hours of normal trail riding, it still feels like it has quite a bit of power, but I've never really messed with 450s before, should I just get a new 450cc stock piston and sleeve? Or can I buy rings and a piston from Athena for my current cylinder?

[FORMA MOTO]

Yeah, but don't just 'put in a new piston'.....you need to check the service limits of the cylinder, and the old piston to see if they are evan worn, and where.

You need to check the valves for sealing...you can do this by just pouring gas in the upside down head and see if fuel leaks out faster than a drop per minute...

Check the ring gap of the new piston and rings, and properly orient the rings relative to each other.

 

 

You need a SERVICE MANUAL!

 

Not sure why this doesn't register with you........