Engine is "sputtery" at lower rpms

[norcal616]

Ok. I wondered if syncing the throttle bodies would help/alleviate this. Actually, my first thought was perhaps the throttle bodies being wonky. I know after I had the throttle bodies synced on my FJR1300, it was indeed smooth as silk.

Old thread but curious did TB sync or ECU flash helped your FJ? I have the exact same issue, seems to have developed slowly. I'm at 12k miles and tried tightening then replacing chain, but my rpms and travel are still jerky in the 2-3k range at constant speed. 3rd gear around 22 mph is the worst.

 
 
this little gem of a motor really doesnt like being "lugged" along in low rpms... im still in 2nd gear till 40+...

[betoney]

but my rpms and travel are still jerky in the 2-3k range at constant speed. 3rd gear around 22 mph is the worst.

 
I think you found the problem right there, 3rd gear around 22 mph the engine is fighting to stay moving.
I would expect that riding it like that it would be jerking quite a bit.  Too slow in too high of a gear.
 
 

[duhs10]

I think you found the problem right there, 3rd gear around 22 mph the engine is fighting to stay moving.
I would expect that riding it like that it would be jerking quite a bit.  Too slow in too high of a gear.
 

I agree... this motor has torque to allow you to pull through the low RPMs, but it definitely doesn't like to stay there.

[buz11]

I'm not usually in 3rd then, but even 1st and 2nd are jerky trying to hold a constant speed 20-40 mph. I'm always accelerating or decelerating or feathering to keep smooth, which is a pain in the city until I hit open road. At constant speed feels like engine can't relax, is always pulling or pushing, even on highway. New chain helped but can still feel it.

[jonno12345]

I have a slightly different issue - mine feels okay mostly, but almost like there's a small 'lag' if I am trying to gently rev up? Like the first few degrees of throttle movement don't really pull, but I can tell that the engine is doing *something* (and I've checked in diag and the numbers increment as normal, and I've done the APS adjustment). Then it'll lurch a little as I open the throttle slightly more. Is this normal? The only thing I can slightly think of is I might have slightly pinched one of the little caps that go on the vacuum ports when I did a throttle body sync, which may be letting some air through... Could it be that, or just a remap would help?

[skipperT]

I have a slightly different issue - mine feels okay mostly, but almost like there's a small 'lag' if I am trying to gently rev up? Like the first few degrees of throttle movement don't really pull, but I can tell that the engine is doing *something* (and I've checked in diag and the numbers increment as normal, and I've done the APS adjustment). Then it'll lurch a little as I open the throttle slightly more. Is this normal? The only thing I can slightly think of is I might have slightly pinched one of the little caps that go on the vacuum ports when I did a throttle body sync, which may be letting some air through... Could it be that, or just a remap would help?

 
Monkeying with the APS/TPS adjustment could cause this as well.
 
Are you in STD mode awhile riding? Stock ecm or flashed? How many miles? Replaced the chain yet? What tension are you running? Any trouble codes? Fuel fresh?
 
-Skip

[jonno12345]

I have a slightly different issue - mine feels okay mostly, but almost like there's a small 'lag' if I am trying to gently rev up? Like the first few degrees of throttle movement don't really pull, but I can tell that the engine is doing *something* (and I've checked in diag and the numbers increment as normal, and I've done the APS adjustment). Then it'll lurch a little as I open the throttle slightly more. Is this normal? The only thing I can slightly think of is I might have slightly pinched one of the little caps that go on the vacuum ports when I did a throttle body sync, which may be letting some air through... Could it be that, or just a remap would help?

Monkeying with the APS/TPS adjustment could cause this as well.  
Are you in STD mode awhile riding? Stock ecm or flashed? How many miles? Replaced the chain yet? What tension are you running? Any trouble codes? Fuel fresh?
 
-Skip

 
 
STD mode, stock, 7.5k, no, around 1 inch, no faults, fresh fuel. Aps I adjusted (from memory, might be other way around!) to be 12 - 97 in diag 14 and 13 - 97 in 15.

[buz11]

I'm not usually in 3rd then, but even 1st and 2nd are jerky trying to hold a constant speed 20-40 mph. I'm always accelerating or decelerating or feathering to keep smooth, which is a pain in the city until I hit open road. At constant speed feels like engine can't relax, is always pulling or pushing, even on highway. New chain helped but can still feel it.

I'm wondering if my issue could be due to rear sprocket unevenness.  I got a new chain when the old chain got stiff and its slack changed as I rotated rear wheel, but I'm seeing the same slack change with the new chain and it's definitely related to the sprocket rotation not the chain section.  It isn't much--a difference of 3/16" vertical travel in the middle of the bottom chain--but could that be causing some hitchiness?  The hitchiness also goes away at a given rpm if I'm applying rear brakes while keeping throttle on, just like it does when I'm accelerating, indicating the engine or chain are ok if there's enough load.

[dbeau]

I'm wondering if my issue could be due to rear sprocket unevenness.  I got a new chain when the old chain got stiff and its slack changed as I rotated rear wheel, but I'm seeing the same slack change with the new chain and it's definitely related to the sprocket rotation not the chain section.  It isn't much--a difference of 3/16" vertical travel in the middle of the bottom chain--but could that be causing some hitchiness?  The hitchiness also goes away at a given rpm if I'm applying rear brakes while keeping throttle on, just like it does when I'm accelerating, indicating the engine or chain are ok if there's enough load.

 
 
Interesting consideration. I too notice the hitchyness and I also have a slightly warped sprocket but never related the two.

[buz11]

Just ordered rear sprocket, I'll report back after installing!  

[dbeau]

While I do notice the hitchyness, it's my belief that it is just characteristic of the CP3 motor and some people are just more sensitive to it than others. My experience outside the yamaha triple is a Honda inline-4 (F4i) I had before and my friends Africa Twin (parallel twin) which from what I understand are very smooth motors. I've accepted that the CP3 triple is a quirky motor and you take the good with the bad (mostly good).

[skipperT]

I’d agree - the crossplane crank definitely has a “feel” to it at certain rpms, usually lower IME.
 
But yes, chain/sprocket wear could absolutely be causing that “uneven” feeling. Every time the tight/loose spot rotates over the sprocket it can cause it to feel almost like it’s speeding up/slowing down momentarily. Difficult to describe, but noticeable.
 
If you did the APS/TPS adjustment some time ago and didn’t notice anything different about the bike at that point, then I would say it’s not your issue.
 
Good luck, hope the new sprocket fixes it. I would consider a chain as well to keep everything wearing together.
 
Also be aware of tightening the 6 nuts evenly so that the sprocket rests evenly on the hub. Those nuts won’t usually take factory torque specs the second time around as they should be replaced once loosened.
 
-Skip

[buz11]

Thanks for the tip about sprocket nuts. I haven't installed yet because further digging has convinced me the problem is O2 sensor, which a "kev mod" can address as well as an ECU flash.

[buz11]

Thanks for the tip about sprocket nuts. I haven't installed yet because further digging has convinced me the problem is O2 sensor, which a "kev mod" can address as well as an ECU flash.

First ride with Kev's O2 Controller, low rpms and constant speeds are much smoother in all modes.  Highly recommended!  

[huck]

I have flashed my bike as well, and it was a significant help, as everyone knows... But it did not fix the bad off idle lean fueling. a friend recommended the Booster Plug
Go here:
https://www.boosterplug.com/shop/frontpage.html
 
If you go to the site, there is a free 40 page book offered for free that explains everything you ever wanted to know, and more, about bike fuel injection, and how and why Fi bikes are delivered running very lean in aid of meeting certain standards. Because they are set so lean, and because bikes have relatively light weight fly wheels... The off idle and rapid shifting fueling is terrible. This is particularly bad on our FJ-09s. The Booster plug is a gadget that works along with the air intake sensor (Not effected by flashing) to correct the the fueling issue-all explained in the free book. And it is easy to instal. There pieces of body work, and one connector.
What I once thought of a a pretty good bike with crap off idle fueling, is now a very good bike with no... NONE, off idle stumble. It is like riding a carburetor bike. I can now ride calmly at walking speed without using the clutch, shifting in tight corners is smoothed out, and now, all three modes actually make sense.
The unit is unconditionally guaranteed so they do a refund if you are unsatisfied. I was skeptical of course, until I hooked it up and went riding... this is really a fantastic change for the better. In fact, I was very close to simply selling the bike and going to something else because of the frustrating low speed stumble and difficulty in riding slowly... But that is now simply gone. The bike runs better all around as fueling is now so smooth.
One thing... Because this unit effects the way the air temp sensor works, your dash meter thermometer will show 35 degreed F low. I simply bought a small stick on unit to take it's place.
I am not affiliated with this company, but the product is so good I wish I was!
Seriously, if the off idle stumble is as frustrating to you as it was to me, give this unit a try. It simply works as advertised.