Hesitation/Surging

[bikerschim]

For what seems like a long time - 2 years - yah, at least that, I have had a gradually increasing hesitation/surging situation with my '03 FJR currently with 18,800+ miles. It is still ridable, but it can get annoying to say the least.

The hesitation occurs typically at or below 4k rpm at any speed, only at a "neutral" throttle position (like when you are trying to match the speed of the cage ahead of you in traffic - no passing situation). If I gradually roll on the throttle the hesitation is more pronounced then suddenly the hesitation is gone and at the rolled-on throttle position the engine blasts off "surging". If in the same situation I roll off the throttle, the engine decelerates as normal. But at any time if I roll on I get the hesitation then surg. If I pull the clutch and watch the tach the engine drops to an idle at 1k rpm and stays there. I can rev the engine and it responds normally, when I slip out the clutch and roll on the throttle, hesitation and surging are present again. Gross, agressive throttle movements seem to have no hesitation or surging.

In attemps to evoke the hesitation/surging at RPM over 4k to 8k+, it is less noticable but present in lower gears (slower speeds) and apparently not noticable at higher gears (faster and oh $h!{% speeds)

Last summer (2005) after much consulting and discussions on this matter I installed a Power Commander III USB with the Wally Kilburg (a certified Dynojet Tech) "smoothess map". Results were positive, there was no longer a hesitation or surg, for a while. (OK I wasn't writing all this down at the time)

This year I have checked the TPS with on-board diagnostic and it is ok. I finally took my trusty steed to a local motorcycle mechanic guru (trying to avoid the 115 mi drive/trailering to the dealer I like going to) and he thinks it is fuel related. Like a pinched fuel line from tank to engine. He is waiting for adapters for a diagnostic tool to check pressures etc. During the week he had my FRJ we received a lot of rain and when I went there (a 26 mile drive) to pick up my bike to ride and disconnect the Power Commander for future tests, it was still wet following a brief rain. During the ride home, I tried everything to evoke the hesitation/surging with no success, my fjr was CURED!! It was soooo smmooooooth!! until I got to town, but then the sensation was so slight I would not have noticed it if I haden't been trying to cause it. This required another ride, right away. Over a total of 85 more miles I experienced NO hesitation NO surging. At about a mid point in the ride I went through a cloud burst, not a lot of rain but definatley a lot of humidity. Smoothness like I have never had. Was it this smooth when it was new, I don't remember.

For me, this humidity thing seems significant. But I can be classified as a non-mechanical type person when it comes to the workings of a sophisticated engine like the one in the FJR. I do understand the effect humidity and temperature have on internal combustion engines and with that the normal relative humidity we have here in central Washington is in the 15 to 25 percent range. I check it every once in a while. No I didn't think to check it the day of the smooooth ride. (I do some of my best thinking in my sleep, or just before sleep.)

So for all you more mechanical minded (genius types, in my eyes) do you have any suggestions? Is this humidity issue related to the problem? Should I trade the '03 in for an '06? :yahoo: No, actually, that isn't an option.

 

[Ronman]

To ask the obvious (though I don't think it was in your post) have you done a thorough TBS, including checking the synch at 3~4k rpm?

Before doing my first TBS, my bike was bad enough that I was considering a Power Commander, but after tuning the bike with a TBS (and honing my tuning skills with the TBS), my bike ran much better.

Some here have stated that their bikes ran quite badly before a TBS.

Humidity could have an effect on how the engine runs. Remember the water injection some guys added to their cars during the 80's? Made the intake much cooler and denser I think it was, therefore adding HP.

 

[bikerschim]

Yes I had just done a Throttle Body Synchronization.

Ya gotta love this forum.

After posting this Hesitation/Surging, I once again went surfing through the pages of this forum and found yet another thread about similar problems. When I read the posts, one of them mentioned performing the onboard Throttle Position Sensor diagnostic at a time when their bike was severely in the process of hesitating/surging. His results were much different than the same diagnostic preformed on a static bike. My initial TPS diagnostic was done on a cold engine, in my garage and all the numbers were as they should be.

As soon as possible (yesterday after work) I took my FJR out for a drive to do a TPS diagnostic when it was hesitating/surging. Sure enough the hesitating/surging started and I waited a while until it was really annoying, I pulled over and performed the test. When rolling on the throttle, every time I got to about 18 or 19 the numbers displayed would change spontaniously displaying all over the scale and when rolling off the throttle reaching 21 or 20 the same thing would happen. So it is the Throttle Position Sensor causing the hesitation/surging.

Returning home I performed a Google search for FJR OEM TPS and of the 4k plus sites found, the one in Muskegon, Missouri at Babbitt's Sports Center had the best price for $105.19 and $7.16 for the two screws and $9.43 for UPS Ground (1 week to WA) I called today to order the part ASAP and found the cost was $139 and change. I told the parts man that was significantly more than their web order price. He said that was the idea, to get people to order parts on line. I did, it will be here the 9th. :yahoo:

 

[bikerschim]

For more information about the purchase of a TPS (for $73.76 US) go to the post "Throttle position sensor, Throttle position sensor and error codes" under this same area "Technical/Mechanical Problems"