HEADS UP!!!

Site upgrade in progress... Core site functions are working, but some non-critical features/functions will be temporarily unavailable while we work to restore them over the next couple of weeks.

Please post any bugs you encounter, but before you do, check to see if it's already listed.

Thanks for your patience while we work to improve the community.

Sign in to follow this  
Followers 0
bikejet52

2006 wr450 backfires and loss of power at high rpm/load

13 posts in this topic

I bought a 2006 WR450 a few months back.  

 

Took it for a ride today on the road.  I accelerated with moderate/heavy throttle.  About 3/4 throttle full load the bike basically fell on its face.  I did it a few more times with the same result. It also backfires after a hard take off.

 

It rides great with normal riding (fast but not under heavy load, blipping the throttle every now and then)

 

The bike has been uncorked (not by me, the previous owner).  I've recently got it plated, and put about 200 road miles on it just tooling around.

 

The problem is more noticeable while on the road.

 

-I changed the oil 150 miles ago

-I replaced the filter 3 days ago. (no off road riding since filter change)

- I have no clue if its been re-jetted

-still has stock silencer on it, not sure if its been modified

 

Any ideas?

 

Thanks,

Gary.

Share this post


Link to post
Share on other sites

Is this a new problem?

If it is a new problem....

 

Maybe  a bit of crap in the carb bowl which under hard accel gets sucked up and blocks main jet then when you back off falls back out.

 

Maybe it is starving for fuel because of crap in fuel tank tap. Also tank vent hose can block causing a vacuum in fuel tank.

 

Maybe a stuck float....just tap the bowl lightly with a hammer might be enough to get it to free up.

 

My first course of action would be to take carb off (or at lease the bowl) and give it a clean. Then test and report back.

Share this post


Link to post
Share on other sites

Thanks, I'll try this as soon as I can. What do you think would be causing the backfiring?

Is this a new problem?

If it is a new problem....

 

Maybe  a bit of crap in the carb bowl which under hard accel gets sucked up and blocks main jet then when you back off falls back out.

 

Maybe it is starving for fuel because of crap in fuel tank tap. Also tank vent hose can block causing a vacuum in fuel tank.

 

Maybe a stuck float....just tap the bowl lightly with a hammer might be enough to get it to free up.

 

My first course of action would be to take carb off (or at lease the bowl) and give it a clean. Then test and report back.

Share this post


Link to post
Share on other sites

Backfiring happens due to a build up of fuel in exhaust which then detonates. If you get a starvation on one stroke and it doesn't fire all that mixture ends up in exhaust and might fire on next stroke. Also true for over rich condition.

Share this post


Link to post
Share on other sites

Backfiring happens due to a build up of fuel in exhaust which then detonates. If you get a starvation on one stroke and it doesn't fire all that mixture ends up in exhaust and might fire on next stroke. Also true for over rich condition.

I see.  

 

I will remove the carb and clean it out first.

 

I'll keep you updated.

 

Thanks.

Share this post


Link to post
Share on other sites

Have you checked your valve clearances? I'm thinking you have some tight intakes.

Share this post


Link to post
Share on other sites

Have you checked your valve clearances? I'm thinking you have some tight intakes.

Just called my local service center and they want $300 to check the valves.  Is that price high or about right?

Share this post


Link to post
Share on other sites

That is about right for a dealer

Find a tuner, or do it yourself

 

I would do a full carb service my self if I were you, as your symptoms are load and throttle position related more than rpm, which would mean carb more than valves

Besides, the WR valves don't fail, they just wear out after hundreds of hours

 

You keep saying back firing: do you mean that literally?: or do you just mean popping from the exhaust.

 

I would guess that you have most likely the usualy carb corrision and passage issues, especially the apump 

 

http://www.dirtrider.com/features/protips/141_0707_keihin_fcr_carb_rebuild/

 

You should also check the harness, coil ground, plug, plug wire, etc.

High load problems are usually attributed to arcing electrics, like a bad plug/cap/wire

Edited by TheKoolAidMadeMeSick

Share this post


Link to post
Share on other sites

That is about right for a dealer

Find a tuner, or do it yourself

 

I would do a full carb service my self if I were you, as your symptoms are load and throttle position related more than rpm, which would mean carb more than valves

Besides, the WR valves don't fail, they just wear out after hundreds of hours

 

You keep saying back firing: do you mean that literally?: or do you just mean popping from the exhaust.

 

I would guess that you have most likely the usualy carb corrision and passage issues, especially the apump 

 

http://www.dirtrider.com/features/protips/141_0707_keihin_fcr_carb_rebuild/

 

You should also check the harness, coil ground, plug, plug wire, etc.

High load problems are usually attributed to arcing electrics, like a bad plug/cap/wire

 

 

Thanks for the info.

 

I pulled the carb out yesterday.  Took the bowl off and it was filthy, and the pilot jet was (from I could tell) completely blocked.  i cleaned everything out, got the pilot jet clear and put back on the bike.  I havent had a chance to ride it yet but I did crank it up.  I sounds a lot better while giving it quick throttle blips no noticeable backfiring. I'll get the tank, plastics and seat back on today and test ride it.  If the problem is solved I plan on getting a rebuild kit for the carb.  I didn't realize how easy it was to remove the carb.

 

As far as backfiring or popping....  while riding and giving it full throttle then releasing a 12 inch flame shot out of the muffler.  (I checked it at night)  To me thats backfiring, but could be popping in the dirt bike world.

 

Also, I took note of the main jet size, its a 162.  After all the free mods is this jet adequate?

 

Thanks.

Share this post


Link to post
Share on other sites

Ok, took is for a test ride and it feels like a new bike.  

 

The power curve is smooth and zero backfiring/popping.

 

It feels better than when I bought it.   3rd gear power wheelies are much easier now, even with a 210lb rider.

 

Thanks for the help!

 

Time to go thru the carb the right way, I may even send it off for a complete rebuild.  I'd do it but my main problem is finding the time to do it.  I just barely have enough time to ride.  

Share this post


Link to post
Share on other sites

And it was solved by...

 

Read post # 10   Thanks for your help.

Edited by bikejet52

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