Stumble, Hesitation, Stall

Hi all,

I've read through this forum and found quite a few folks with similar problems.

Problem: A quick throttle blip at low RPMs will cause the bike to hesitate or even die if not in gear and idling and cause a brief hesitation/stumble if moving in a lower gear. Worse when cold.

Mods: FMF Mega Bomb, FMF Q4, FMF FI Programmer, Flapper Screwed down, K&N air filter (clean), IMS 4.7 Gal tank (Has the vacuum system hose connector).

It's a 2008 and I have put a new fuel pump on recently. After reading suggestions elsewhere in this forum, I've tried a multitude of suggested and my own FMF FI settings and none seem to help including taking it out of the loop. This started soon after I put the tank on, so I've checked the vacuum hose connections and even unhooked and plugged the line to the tank. No difference. The fuel pump was also replace after the tank install. I've also tried it with no air filter door and even without the air filter. I've visually checked, cleaned and reseated the FI electrical connector.

Here's a video of the problem off idle. http://rjudge.org/forsale/WR250R.wmv

Also, rarely, when going through the gears, usually under hard acceleration, it will go through a "missing" episode. It sounds like it is hitting every other cycle. Letting off the throttle and reapplying throttle will fix it. Very rarely, it will completely die when going from one gear to the next under hard acceleration. Again, letting off the throttle and reapplying throttle will fix it.

I'm now thinking: dirty fuel injector, FI module screwed up.

Any other suggestions?

I hate to admit it, but I'm about ready to take it to my most trusted dealer and let them have a go at it.

TIA!

Rick

See below from another thread in the Forum.

Make sure you check all of the electrical connections for the FI and FMF programmer. A loose connection can give you fits when you are riding.

MotoJunkie wrote:

I got out for a good day ride yesterday and I may have found the problem.... Spent a few minutes the night before checking some of the electrical connections. Everything looked good except for the positive terminal on the battery ... it was barely finger tight.

Rode the bike all day long and never had any issues at all. I hope that was it.

rsteiger wrote:

Just as a sanity check you make want to look at your ground connection to the FMF programmer.

Make sure it is tied to the battery and not another 'ground' bolt on the bike. I haven't had the pleasure of experiencing this issue on my bike yet but in a past life designing, building, and troubleshooting cars has taught me that a bad ground connection can create a lot of weird transient issues.

The only other thing I would look at is to make sure the FMF wiring is not running along a high output electrical device such as an ignition coil.

Make sure you haven't got a pinched fuel line. It's a common problem with aftermarket tank installs.

I do not even have a programmer on mine it is like yours..I have spent time around 2 more wr250r they do the same mine an 09 the others 08 with or without tank changes///Yamaha has a problem they will not address..dealers tell you they just run lean you pull the plug it's black sure sign of adequate fuel it is not pinched lines it is not electrical it is common to otherwise a great but expensive bike///oldman has said his say...

oldman65 wrote:

I do not even have a programmer on mine it is like yours..I have spent time around 2 more wr250r they do the same mine an 09 the others 08 with or without tank changes///Yamaha has a problem they will not address..dealers tell you they just run lean you pull the plug it's black sure sign of adequate fuel it is not pinched lines it is not electrical it is common to otherwise a great but expensive bike///oldman has said his say...

Stuttering when cold is pretty normal agree... mine does it as well. You get used to letting the bike warm up a minute or two.

"Also, rarely, when going through the gears, usually under hard acceleration, it will go through a "missing" episode. It sounds like it is hitting every other cycle. Letting off the throttle and reapplying throttle will fix it. Very rarely, it will completely die when going from one gear to the next under hard acceleration. Again, letting off the throttle and reapplying throttle will fix it."

However... sounds like there is an issue. Mine has never given me those symptoms and if it was a common issue we'd have seen it more frequent. The FMF sometimes causes a similar cutting out issue, but he's already tried that (verify that setting 4 or 5 is above 6, I'd have to go back and look).