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
MountainMax

Engine surging at low throttle cruising

15 posts in this topic

when im on the road cruising on the road say around 80-90 km/hour and light throttle the engine surges up and down a bit, almost like it's still a bit lean. I have done the free type mods and done the jetting as per the sticky here but it's just not quite right. Also on a decel wnen hearing down i still get a scattered backfire. I also get a backfire if i hit the throttle and rev up the enginge quick and let go of the gas i get one backfire. finally if im at idle and hit the throttle fast she will stall out or bog,bog, bog then rev up. Any ideas, this is not a problem just some fine tuning i think will make it better, so im wondering where to go now, anyone have similar issues on their 06 WR450 ???

P1010004.jpg

Share this post


Link to post
Share on other sites

surging is caused by the TPS sensor. Unplug it and it will go away, but you will lose a minimal amount of performance.

The sputtering is most likely a "too lean" condition.

rejet accordingly.

Share this post


Link to post
Share on other sites

Thanks, i know it's a jetting issue but to what part, maybe move up the needle (drop the clip one slot)??

Share this post


Link to post
Share on other sites

it's about 1/8 throttle and worse in top gear around 80/90km/h on the road it feels like it starves for gas then cuts in again,

Share this post


Link to post
Share on other sites

Try a larger pilot jet or disconnect the tps. The tps is the eaisest to try.

1/8th throttle position isn't enough for the main jet.

Share this post


Link to post
Share on other sites

I was told the surging was from no flexable coupling in the rear like most bikes have? is this possible? I only notice it when I ride it on the street

Share this post


Link to post
Share on other sites

It is the TPS flipping back and forth from two different timing maps.

You can verify that by unplugging the TPS and see if it goes away.

Share this post


Link to post
Share on other sites

If your referring to the flex coupling in the rear hub on allot of DS bikes its more to protect the drive train from the shock of 50 hp hitting and very little tire spin.

Share this post


Link to post
Share on other sites

Well i already have the 48 pilot but still have the stock starter jet, would that matter? the specs here said it should have a 72 stock starter jet and they recommended a 70 so i left it alone, then i found mine only had a 68 (i think or 60 something) starter jet. I have the grey wire mod done and would not like to leave the tps disconnected but i can try it to verify if it's the culperate or not.

Share this post


Link to post
Share on other sites

As stated try the TPS first. My guess is it wont entirley cure the surge you feel.

Ride the bike and find where the surge is in the speed range and throttle setting. Pull over and unplug the TPS. Ride the same stretch of road under the same conditions - compare?

The TPS will improve the surge, no doubt. My experience with it was around half the surge was attributable to TPS, the other was ACV induced and related pilot circuit. I found the TPS was needed for smooth running at smaller throttle settings, so mine is reconnnected. The ACV also influences the circuit when there is any change to vacuum. If you still have problems post TPS then do a search for ACV and see what turns up. It had been a much talked about subject earlier in the year.

PS. The bike will improve with age and after all the mods are DONE :ride:

Share this post


Link to post
Share on other sites

Mountainmax, Try lowering the needle to lean it off. You are most likely running a bit rich. I had this exact problem and solved it this way without touching the TPS. The TPS is needed to map the ignition (RPM vs TPS).

Share this post


Link to post
Share on other sites

I was thinking it may be a lean condition not rich......... thought a rich condition would just make it burn more gas

Share this post


Link to post
Share on other sites

If you twist the throttle to quick it will bog for a second. Just turn it with more of a smooth rythem, as the acelerator pump is more of a squirt, and quick flicks of the throttle dont work. Even though mine seems very quick, and only notice it on very seldom.

How serious is the surging? Is it just changing rpms, or is it missing and sputtering?

Its probally the pilot circuit

What kind of back fire is it? is it a gun shot or is it more like a crackle? Crackeling is normal but explosions are a sign somthings amiss :ride:

Share this post


Link to post
Share on other sites

Yep, I thought it felt lean too, (used to that surging feeling in a car) but rich causes it to do this under light throttle. It probably gets worse when you go higher or it gets hotter? If so, definitely rich.

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