Jump to content
Sign in to follow this  

Im Back !! Stuttering problem Carb. Maybe!?

Recommended Posts

Ok when im on the gas it pulls fine..whenever i let of there is no decel pop or nothing but when im just cruising it has a little stutter or pop is this carb. related?:banana:

Share this post


Link to post
Share on other sites

i read that its from the tps. thats normal. if you want it to go away you can unplug the tps or just get used to it

Share this post


Link to post
Share on other sites

The stuttering will not change if the TPS is disconnected. If the TPS is out of adjustment, the bike will be down on power. I have done extensive tests both with a yz and a wr that have a stutter. You must first eliminate jetting as the cause. If you still have a stutter after careful jetting, then a different CDI is called for. I have yet to see a YZ that needed the CDI fix.

Share this post


Link to post
Share on other sites

it seems this is normal...check JD jetting site, theres a speil about that stutter in there ! its a cdi/yamaha settings thing...not carby related..

Share this post


Link to post
Share on other sites

didnt know they were that different in that dept ??? i'll watch this closely to see whats what ! thanks !

Share this post


Link to post
Share on other sites

the wr and yz use the same cdi so the studder will be there on the yz as well. hence cut the grey wire and now its a yz cdi

Share this post


Link to post
Share on other sites

No, they are not the same CDI, they are similar. The map you get with a WR CDI with the grey wire cut is 'YZ like" and not the same.

I have never seen a properly jetted and adjusted YZ do the stutter.

On a WR, Grey wire cut, TPS disconnected, the stutter is less pronounced but it is still there. If you re-connect the grey wire, the stutter is less pronounced but you can have the TPS connected. With the grey wire cut and TPS plugged in, the stutter is terrible.

Share this post


Link to post
Share on other sites

mine doesnt stutter at all ? 2005 wr and all free mods and yz pipe... it flies ! only stutter i had was knackered 5th gear lol...so(off topic), would swapping a yz cdi sort the so called wr cdi stutter ?

Share this post


Link to post
Share on other sites

I'm not so sure the infamous "WR stutter" is a 100% thing experienced by everybody. Agreed, my 05 had a nasty stutter when jetted too rich, but the stutter was gone once I dialed the jetting. Something very important to consider- my 05 also had the coast enrichment circuit disabled.

This might be wrong, I think the WR stutter could very possibly be caused by the coast enrichment circuit.

Share this post


Link to post
Share on other sites

The stutter is almost never noticed off road. It is noticed by those that have plated thier bike and hit the pavement. Your thought about the CE has merit but with the throttle open past 1/3, the CE should not be operating at all as it should only kick in with the throttle closed/high rpm situations that generate high levels of vacuum.

James Dean ran some exhaustive tests. He had an ocilliscope connected to a bike on the dyno. You could see the spark/cdi misfiring. It is pretty definitive and unarguable pictures. A search on his web site will produce them.

Share this post


Link to post
Share on other sites
mine doesnt stutter at all ? 2005 wr and all free mods and yz pipe... it flies ! only stutter i had was knackered 5th gear lol...so(off topic), would swapping a yz cdi sort the so called wr cdi stutter ?

It should be it is not as easy as that. The two CDI's are not interchangeable. It would require wiring harness changes and changes to the stator. Much simpler to buy a aftermarket CDI.

Share this post


Link to post
Share on other sites
The stutter is almost never noticed off road. It is noticed by those that have plated thier bike and hit the pavement. Your thought about the CE has merit but with the throttle open past 1/3, the CE should not be operating at all as it should only kick in with the throttle closed/high rpm situations that generate high levels of vacuum.

James Dean ran some exhaustive tests. He had an ocilliscope connected to a bike on the dyno. You could see the spark/cdi misfiring. It is pretty definitive and unarguable pictures. A search on his web site will produce them.

Good info, I'll have to take a look at that. I was thinking on those exact lines of "if only I could put it on a scope", the same way someone had done back in the early WR days with & without a gray wire connected.

My 05 was plated and I did ride it on the road, but only just so much. A WR250F really isn't the coolest street bike, and the plate was more for taking the short cut back to the truck type of thing.

Share this post


Link to post
Share on other sites

That is exactly how my WR is ridden on road. Once a year to get inspection, then the rest of the time it is to connect trails, get gas or lunch if it is close. In three years, I have maybe 100 miles of street use on it.

Share this post


Link to post
Share on other sites

ok i just put a fresh post up because my bike is doing this but its really bad and i put 1500 miles on the road last year and never had a problem with it studdering... now i have the air cut valve blocked off a yz needle and both the free ac pump mods and it started studdering.. usually less than 1/4 throttle and doesnt wanna idle.. i have yet to mess with the jets more though

Share this post


Link to post
Share on other sites

i thought popping and what not was because of a lean condition and jus a lack of power was a result of a rich one?

Share this post


Link to post
Share on other sites

Pulsator,

I sent you a PM. But also, to answer your Q in the previous post. You will have some lean popping with the air cut valve disabled, but you may have a different problem here. Which approach did you take to disabling the ACV?

There is two (or more) approaches to disabling the ACV- one opens the ACV and then jets to match that always open condition. The other approach is replicate a YZF carb. I went with attempting to be like the YZF carb.

With the YZF carb approach, I removed the spring, and plugged up the passage between the air cut diaphram and the air box passage. This makes the carb behave like the YZF carb which has no ACV. (it takes a bunch of head scratching to figure out what is happening). If you block off the passage to simulate the YZF scheme, then you should use the YZF air jet (located in the carb bell on the air box side). Without this larger ID YZF jet, the pilot and fuel screw circuits won't be quite right at different rpm ranges.

Share this post


Link to post
Share on other sites

Stutter, no pop. Spent a ton of tim e and a good chunk of money chasing it with jetting; even bought a different bike to ride around with my kid on his 50 (now 90) because I just could NOT ride the WR at steady small throttle openings, the stutter was so bad.

Then I unplugged the TPS and all of a sudden, the bike is tolerable to ride at those speeds.

Try it--it's not hard to do as tests go. Supposedly I'm down a little power on top and getting worse mileage, but I really haven't noticed.

Steve

Share this post


Link to post
Share on other sites

well being that it ran with no studder until i changed to the yz needle and yz paj along with blocking off the acv im sure its something to do with that. ill tinker with it tomorrow. my problem today was i didnt bring tools with me when i went out and my gf was sleeping at home so i came in the driveway as quietly as possible and didnt wanna go back out. for the acv i flipped the diaphram around and blocked off the o ring passage. i am going to check to make sure i put the right pilot jet in... because i had four of them laying there.

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

Reply with:

Sign in to follow this  

×