jerking under constant speed - Yamaha FJR Forum : Yamaha FJR Owners Forums
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post #1 of 16 (permalink) Old 07-16-2020, 09:10 AM Thread Starter
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jerking under constant speed

Hi All,
I have a 2009 with 17,000 miles on it. The bike jerks under constant speed but not during acceleration or slowing down.

John
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post #2 of 16 (permalink) Old 07-16-2020, 09:29 AM
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Constant, low-load throttle and it surges and lags? Probably right at the "cusp" between 2 parts of the fueling map (and is jumping back and forth). The fuel cut off programmed into the OEM map can be an issue. Remaps or Power Commanders can address that by resolving the extra-lean cut. A less "elegant" patch is to enter into diagnostics mode and chance the CO setting a little (but it's not precise and really hit-or-miss on if it makes a difference).

Ridden wet. Put up hard.

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post #3 of 16 (permalink) Old 07-16-2020, 10:12 AM
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Has it done this for as long as you've had it or did it start suddenly, or gradually?

Seems unlikely to me that it is jumping across a "step" in the map because a) decent calibration doesn't have steps and b) ALL FJRs should have the same issue, which they don't. I'm thinking more along the lines of running too lean (O2 sensor off?) or something worn or sticking in the cable/linkage. Standing by for other opinions.

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Last edited by slowdave; 07-16-2020 at 10:16 AM.
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post #4 of 16 (permalink) Old 07-16-2020, 10:41 AM
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jerking under constant speed

Quote:
Originally Posted by mrwiggly View Post
Hi All, I have a 2009 with 17,000 miles on it. The bike jerks under constant speed but not during acceleration or slowing down.
John
John,

I would want to check the Throttle Position Sensor using the FSM procedure, or a better test if available. Look for loose or flaky connections, especially for the engine sensors, battery wiring (a battery cable has two ends), and of course, run a can of fuel injector cleaner through the gas tank, mixed per label directions.

Have you seen any odd electrical glitches there?
.

Cheers,
Red
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P.S. Life is too short, and health is too valuable, to ride on cheap parade-duty tires.
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post #5 of 16 (permalink) Old 07-16-2020, 11:48 AM
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Important if just started or whether it's always been there, not always easy to interpret what you're seeing vs. what we imagine....... need clarification.
I'd start by run some Seafoam through it and ensure water in fuel isn't an issue, then put in fresh fuel.
Doesn't sound like Map Sensor vac. line/nipple clogged, but EZ to check (remove MAP sensor, then vac line and check.
At 17k, kinda hard to imagine TPS issue as well, but never know with those. Hard to diagnose. Go with what red says......

Ray
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post #6 of 16 (permalink) Old 07-16-2020, 12:51 PM
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Quote:
Originally Posted by RaYzerman View Post
Important if just started or whether it's always been there, not always easy to interpret what you're seeing vs. what we imagine....... need clarification.
I'd start by run some Seafoam through it and ensure water in fuel isn't an issue, then put in fresh fuel.
Doesn't sound like Map Sensor vac. line/nipple clogged, but EZ to check (remove MAP sensor, then vac line and check.
At 17k, kinda hard to imagine TPS issue as well, but never know with those. Hard to diagnose. Go with what red says......
Ray. I sent you a message on this
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post #7 of 16 (permalink) Old 07-16-2020, 01:16 PM
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...jerking under constant speed....
Variable speed sometimes helps 😄 😄

... sorry couldn't resist 😜

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post #8 of 16 (permalink) Old 07-16-2020, 05:33 PM Thread Starter
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Sorry guys i should have clarified more info. Engine sounds find to me anyways. I'm hearing a clucking sound when I let off the throttle and then speed up. I also put the bike on the center stand
with it in 1st gear. I then was able to rotate the back tire 1/4 to 1/3 of a turn and heard the same sound.
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post #9 of 16 (permalink) Old 07-16-2020, 06:23 PM
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Ok probably normal then, normal driveline lash between trans gears and middle drive. If you want to get anal and reduce it, there is a two-piece large washer type shim between middle gear housing and tranny... I believe 0.030" thick. reducing it will reduce the gear lash.... procedure in the service manual on how to set gear lash, but yammie was generous with it. Technical name "middle driven pinion gear shim". Yammy doesn't offer other thicknesses, and I know of only one owner who did it. PITA job anyway.


The only other area of concern is the cush drive rubbers in the rear wheel hub. At 17k they are nowhere near worn, wouldn't worry about that at all.
With bike on centerstand and in gear, not abnormal to see tire rotate roughly 2"... mark it and your floor, rotate it and you'll see that. Normal. Ride it worry less.

Ray
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post #10 of 16 (permalink) Old 07-17-2020, 02:55 AM
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Quote:
Originally Posted by slowdave View Post
Seems unlikely to me that it is jumping across a "step" in the map because a) decent calibration doesn't have steps and b) ALL FJRs should have the same issue, which they don't. I'm thinking more along the lines of running too lean (O2 sensor off?) or something worn or sticking in the cable/linkage. Standing by for other opinions.

Under low load and constant speed, the system goes into closed loop mode and the surging is well documented in at least Gen 1 and 2 (with it being addressed in stages with a misstep in the 2007 fueling and throttle cam).

Ridden wet. Put up hard.

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