2003 stumble when launching

[ANZAC]

Everyone

Well, I finally got my 2003 FJR and it's a great bike. I do have one question though:

I have to feather the clutch and keep the revs above 2,5k to prevent stumbling/bucking when launching from a stop. This happens either warm or cold. TPS was done in 2007 and diag range is 18 to 101 with throttle twist.

I have put in Lucas fuel treatment and bumped up the idle to 1100. Shifting and performance is great except when getting the bike rolling from a stop.

The bike also has a high beam intermittent connection problem coming from the wire bundle down by the steering head and under the cluster. Need to get under the tank to check things out as well.

Any ideas or comments

Thanks

 

[Fred W]

2500 rpm is not really that high. I may ordinarily rev the engine that high for a launch, I don't know... I guess what I'm saying is don't be afraid to rev the engine a little. The inline 4 in these bikes, while torque-y compared to a 600cc crotch rocket, ain't no v-twin cruiser.

I've found if I try to launch at too low an rpm I get a knocking/pinging and valve clatter that I do not like. I do not do that any more. Of course some of that depends on how aggressively you are releasing the clutch.

 

[FJRBluesman]

JATO may help.

How about last tune up etc? You may have other minor issues with TBS, air filter, plugs, etc. If all are okay etc, then not really sure.

One also must define "launch." You racing? I can easily and consistently let the clutch out with little to no twist of the throttle. Do it all the time just mellow commute riding. I bet my throttle rarely goes above 1800 RPM, probably average 1500 RPM when taking off.

 

[ANZAC]

Thanks guys

Well, this bike is used as a commuter so you know my dilemma I am on and off the throttle a lot. No - launching in therms of starting out from a stop not drag racing

This bike will buck as the clutch is slowly released unless I kick the revs up to around 2.5k

 

[ahchiu]

Have you tried to flushed your clutch fluids?

 

[garyahouse]

When you say it's bucking, are we talking clutch or the engine itself? I assume you can tell the difference... the clutch will have a very even, pronounced pulsating. If you have the beginnings of a clutch issue, the clutch will indeed buck at low RPMs, but not hardly at all if you keep the engine RPMs up around 2500 or higher. If you let the clutch all the way out and THEN play with the throttle at various RPMs in 1st gear, does it still do this? If it still does, you just eliminated the clutch as a source of this problem. Is it any different when the bike is hot vs cold? FWIW, my clutch has done this same thing for years, but ONLY when the engine is cold, and only at lower RPM's when I first begin engaging it on a cold morning. Solution for me? Higher RPMs when engaging clutch first thing in the morning. Cures the problem. Many on this forum have done a clutch soak and cured the problem that way.

Google search site:fjrforum.com clutch soak

By the way, just curious, how many miles on your bike?

Gary

darksider #44

 

[Pepperell]

On a first gen there is a largish connector under the tank behind the steering head that is known to be prone to corrosion. It can cause any manner of bizarre problems, including drivability issues. May also be a contributing cause for the headlight issue. Oh yeah, check your battery terminals for corrosion/tightness.

 

[ionbeam]

On a first gen there is a largish connector under the tank behind the steering head that is known to be prone to corrosion. It can cause any manner of bizarre problems, including drivability issues. May also be a contributing cause for the headlight issue. Oh yeah, check your battery terminals for corrosion/tightness.

Find that connector here. I'm not a fan of packing connectors with dielectric grease, it was never intended to be used like this.

Also check for intake leaks between the throttle bodies and the intake ports on the cylinder head, missing TBS caps and the hoses connected to the throttle bodies. The band clamps on the rubber tubes have been known to become loose. For the dull & uninspired you can spray WD-40 in the area and look for idle speed drop or the adventurous, hot-chili types can spray the area with starting fluid and look for idle speed to rise.

 

[ANZAC]

Awesome information guys - thank you

The connector makes sense as this is a PNW bike which probably has picked up moisture in the connections. This weekend I am going to give the bike a full service including bleeding clutch, brakes, changing oil, checking coolant etc... The previous owner has installed a power strip under the seat which has some leads taking off into somewhere so need to sort that out as well. Many questions to be answered under the tank. We all know that water and electrons don't mix well

 

[FJRBluesman]

Does the bike ride smooth otherwise? If it lurches or bucks at steady throttle I'm going to say you may have another problem electrical in nature. ionbeam hit on it, or maybe a loose battery terminal.

 

[ANZAC]

Does the bike ride smooth otherwise? If it lurches or bucks at steady throttle I'm going to say you may have another problem electrical in nature. ionbeam hit on it, or maybe a loose battery terminal. ;unsure:

The bike runs fine and smoothly at all speeds other than starting out - letting out the clutch - under 2500 rev's. My hopes are linked to this connector or other cables as well.

 

[Intech]

What is your idle set at?

 

[ANZAC]

What is your idle set at?

I have it set to 1100. I can make the bike move off by just very slowly letting out the clutch WITHOUT feeding throttle. Any slight throttle other than over 2500 will have the bike jerking/bucking moving off.

 

[ionbeam]

If you are saying that your issue happens in only one small rpm range, regardless of gear then we need to walk you through a TPS troubleshooting that goes beyond diAG. Rough engine operation that happens in a very narrow rpm range in any gear is a classic symptom of a bad TPS. It is possible to have more than one bad rpm band, but each will be narrow, separate and well defined. Link.

 

[ANZAC]

This is what my bike does as quoted by Ionbeam:

"As I passed from .750 to .850 volts it would go: .760 .780 .120 .120 .810 When the voltage dropped to .120 volts then went back up to .810 volts it was violent!!! First it would pitch me & pillion forward then slam us back. This was followed by hammering on my helmet to quit f'kn around. If the TPS voltage were to drop fully to 0 volts I'm sure the engine would stall."

When releasing the clutch the bike tries to pull off idle then begins to stall/choke. If I feed in more throttle the engine recovers too quickly and throws you back - that's why I have to feather the clutch.

Humm, I wonder if a new TPS will have an improved design or better quality control

 

[ANZAC]

Placed an order for a new TPS which is now part #3P6-85885-00-00 (The old part number was 5PS-85885-01-00) Amazon carries this part too. I called the local dealer who ran my VIN and they confirmed the TPS was done back in 2007 so that means mine is 7 years old.

Perhaps this new part is an updated/improved part or adapted for use across multiable platforms (bikes, watercraft)

 

[ionbeam]

Did you actually confirm a TPS voltage glitch with a volt meter? The new updated TPS seems to be pretty reliable and 31k miles is pretty low for a wear-out type component. Crossing my fingers!

 

[ANZAC]

Today, I checked the vacuum hoses and electrical connectors (large white and red). Connections looked clean but shot them with CRC electrical cleaner anyway. This sorted out the high beam intermittent connection problem.

I also checked the battery and found the positive connection on the loose side and a little bit of the red terminal covering laying under the cable. Got that sorted as well but I still seem to have a throttle hesitation under 2000 when pulling away.

TPS was checked and cleaned connections. Resistance measured 4.26k and upwards when twisting throttle. Did not notice any jumping around of the readings. Perhaps it's a different story when a bias is applied and engine running.

So, fingers crossed for the TPS sensor which will arrive next week. Oh well, at least I got to know the bike better working on the panels, t-bar and tank.

 

[ANZAC]

Did you actually confirm a TPS voltage glitch with a volt meter? The new updated TPS seems to be pretty reliable and 31k miles is pretty low for a wear-out type component. Crossing my fingers!

How did you measure the voltage on the TPS?

I double checked the TPS range again after I was done playing around and it's now 17 - 101.