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Old 05-29-2019, 02:33 PM   #1
monkeewrench
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Missfire on light load

Hi everyone, this is my first thread on 1130cc, and although I've been checking the old threads for "misfire", I can't find the exact problem I have - hope someone can help...
I have a 2010 VRSCF, bought it a year ago with only 6'000 km. When I first got it, it seemed to run OK.
After a couple of months (1500 km) it started to have a very intermittent misfire only on very light load (cruising).
Didn't think much of it and had a set of J&H slip ons fitted.
Although it was supposedly "flashed" after having the pipes fitted, the misfire progressively got worse (still only at light load).
Had no joy with the shop that fitted the pipes, they just said I should ride it harder!!
Last month I decided to go to a different shop who has a good name for tuning.
They put the bike on their rolling road to tune it, but last week told me that they are also seeing this misfire, but can't place where it's coming from.
It's definitely intermittent between both cylinders - and only during light load.
They're having trouble pinpointing where it can be coming from.
Any one had a similar problem?

Hope someone can help; this could end up costing a fortune if the shop just starts swapping electrical parts until they find it

Thanks in advance - from sunny Switzerland
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Old 05-29-2019, 03:06 PM   #2
Elgavilan
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Make sure all 3 grounds are clean and good and tight. Also, sometimes the coil wire in the extension that connects the coil with the spark plug can get pushed into the tube and not quite reach the spark plug. It can be fixed by lengthening the coil spring in the tube with a couple pair of needle nosed pliers.


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Old 05-29-2019, 03:41 PM   #3
monkeewrench
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Quote:
Originally Posted by Elgavilan View Post
Make sure all 3 grounds are clean and good and tight. Also, sometimes the coil wire in the extension that connects the coil with the spark plug can get pushed into the tube and not quite reach the spark plug. It can be fixed by lengthening the coil spring in the tube with a couple pair of needle nosed pliers.


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Thanks for the tips - I'll pass this onto the shop and see if it helps. I'll get back to you and let you know what happened.
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Old 05-29-2019, 04:17 PM   #4
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Quote:
Originally Posted by monkeewrench View Post
Thanks for the tips - I'll pass this onto the shop and see if it helps. I'll get back to you and let you know what happened.
Ignition breakdown always happens under higher loads. Your issue is the mixture is either too lean or too rich in that area of light load. The person that tuned it should be able to see exactly what TPS, KPA and what RPM it's happening and work that area. Generally a dyno tune will make this area too rich for steady state light cruising. It's not part of there methods and why many bikes, while they pull good numbers often run like shit on the road in real conditions.
Ron
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Old 05-29-2019, 05:12 PM   #5
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Quote:
Originally Posted by monkeewrench View Post
Hi everyone, this is my first thread on 1130cc, and although I've been checking the old threads for "misfire", I can't find the exact problem I have - hope someone can help...
I have a 2010 VRSCF, bought it a year ago with only 6'000 km. When I first got it, it seemed to run OK.
After a couple of months (1500 km) it started to have a very intermittent misfire only on very light load (cruising).
Didn't think much of it and had a set of J&H slip ons fitted.
Although it was supposedly "flashed" after having the pipes fitted, the misfire progressively got worse (still only at light load).
Had no joy with the shop that fitted the pipes, they just said I should ride it harder!!
Last month I decided to go to a different shop who has a good name for tuning.
They put the bike on their rolling road to tune it, but last week told me that they are also seeing this misfire, but can't place where it's coming from.
It's definitely intermittent between both cylinders - and only during light load.
They're having trouble pinpointing where it can be coming from.
Any one had a similar problem?

Hope someone can help; this could end up costing a fortune if the shop just starts swapping electrical parts until they find it

Thanks in advance - from sunny Switzerland
I have this same issue. Thought it was the tune, it isnt. Getting ready to replace coils with Energy Coils and upgrade injectors. I have done the following

Switched to 2-1 from slip ons - less noticable but still there
Replaced exhaust gaskets - no change
Replaced Plugs - no change
Replaced IAC - Did this more for testing stall at first start when cold.
Removed PCV and Autotune from equation - no change
Changed to Power Vision with Target Tune - No change

Its odd too, it is literally at cruise, regardless of gear and rpm. Its more throttle position related. If I give it a bit more gas to accelerate, no issue.
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Old 05-29-2019, 06:04 PM   #6
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Originally Posted by darendt View Post
I have this same issue. Thought it was the tune, it isnt. Getting ready to replace coils with Energy Coils and upgrade injectors. I have done the following

Switched to 2-1 from slip ons - less noticable but still there
Replaced exhaust gaskets - no change
Replaced Plugs - no change
Replaced IAC - Did this more for testing stall at first start when cold.
Removed PCV and Autotune from equation - no change
Changed to Power Vision with Target Tune - No change

Its odd too, it is literally at cruise, regardless of gear and rpm. Its more throttle position related. If I give it a bit more gas to accelerate, no issue.

That's because the ve's are more inline for accel or more of a load then steady state lighter load rpms. It boils down to how you ride or the dyno guy collects the data during autotune runs. It is also dependent on what afr is chosen for this process for that area.
Ron
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Old 05-29-2019, 06:18 PM   #7
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Originally Posted by rbabos View Post
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That's because the ve's are more inline for accel or more of a load then steady state lighter load rpms. It boils down to how you ride or the dyno guy collects the data during autotune runs. It is also dependent on what afr is chosen for this process for that area.
Ron
I would have agreed with you had that not been the first place I looked. I also went complete stock and had same issue.
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Old 05-29-2019, 06:25 PM   #8
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Sounds kind of like you have a small air leak in the intake. Make sure the rubber cap is on the vacuum inlet tube on the left side of the throttle body, and check the throttle body boots for cracks, and make sure the injectors have good o-rings on them. Also make sure the coils are good, a coil going out can be difficult to diagnose, might want to buy one and swap it in to see if it makes a difference, they are pretty cheap.


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Old 05-29-2019, 07:49 PM   #9
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Originally Posted by Elgavilan View Post
Sounds kind of like you have a small air leak in the intake. Make sure the rubber cap is on the vacuum inlet tube on the left side of the throttle body, and check the throttle body boots for cracks, and make sure the injectors have good o-rings on them. Also make sure the coils are good, a coil going out can be difficult to diagnose, might want to buy one and swap it in to see if it makes a difference, they are pretty cheap.


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Agreed. I checked all of the above. I also called HD for the Injector O rings but they only sell them with injectors. Ill be getting some higher flow ones shortly with new o rings. Then Coils.
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Old 05-29-2019, 08:01 PM   #10
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Hate to say it it, ....
have you put any spark plugs in it? Coils and/or the coil spring would be my next step.
Elgavilan knows his stuff and been around. I agree check the boots i would also check the throttle body gasket.They are very thin and get pinched easy if it was ever removed.
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Old 05-29-2019, 09:27 PM   #11
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One more thing to check, there is a small screw on each head half way between the throttle body and the bottom of the head, it fills a hole into the intake tract that guys use to hook up vacuum lines to sync the throttle bodies, make sure they are there and tight.


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Old 05-30-2019, 07:47 AM   #12
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Any intake leaks, where ever can be identified by an major change in the IAC steps at idle. If they have dropped a lot, the engine is getting air from somewhere it shouldn't. It might also show up as out of spec MAP sensor readings. End result will be the calibration will be off, in regards to amount of fuel based on the TPS %

Ron
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