Non-linear throttle response at very low throttle opening

[Cosmin]

Hello everyone,

I'm asking your help with an issue for which I didn't find similar topics on the forum: my bike started for some time showing a rough throttle response especially at starting in first gear. It is 100% a different symptom from the classical GenII throttle on-off roughness; actually when I release the clutch the bike starts moving a little and after a few meters while very gently pulling the throttle it suddenly pulls harder, as if I suddenly open the throtlle wider. This issue can be sensed a lot also at gear change, generating a rough gear change when releasing the clutch lever and opening the throtttle after the next gear was engaged.

I repeat, it is not related to the Gen II on-off throttle roughness - in order to cure that - immediatly after buying the bike (5 years ago) - I filed with a dremel tool the throttle interior cam and everything was much better after that. This recent issue I'm describing started some 5-7.000 miles ago and seems to be more and more visible. I suspect the following:

1) perhaps a large mis-synchornization between throttle bodies, causing an initial engine slight reving at first degrees throttle opening (with only 1-2 flaps opened) and after gradually opening the throttle, all the throttle flaps open and the engine starts pulling suddenly at full capacity?

2) another theory could be an issue releated to TPS - perhaps it sends wrong reading at "close to idle" throttle flaps opening or non-linear signal while passing from idle to very low opening?

Could these be the causes, has anyone faced similar issues?

Thanks a lot.

 

[ANZAC]

This is a very common problem with our bikes. My 2003 does this to some degree but have chalked this up to normal low speed throttle response. I have tried the TPS, power commander 3, changed plugs, looked for vacuum leaks, checked TBS, replaced fuel pressure regulator, air filter and changed clutch fluids.

Check your bike over really well and add some fuel treatment as I wonder if the amazing additive me know as ethanol has not affected our bikes.

I came from a Street Triple which had better low end torque/throttle response than the FJR. Mine is better if I keep the revs above 2000 when in friction zone.

 

[bluesdog]

Possibly the injectors could use servicing. New filters and thorough cleaning may help. If you do go that route, make sure your service uses new o-rings and does not damage the 'donut' gaskets.

 

[Cosmin]

Thank you all for the replies. The filters and spark-plugs are new; I haven't added any cleaning fuel addtive till now, I'll try it in a first phase. Also I'll try a TBS.

What do you mean by additional injectors servicing - removing them and sending them to a workshop specialized in cleaning (with ultra-sounds etc) or there is any DYI method?

Thanks.

PS: the "sleeping clutch" gear change in order to avoid rough gear change concerns me a little in terms of clutch wear/lifetime