Author Topic: Bucking and Jerking  (Read 5365 times)

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jmalona

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on: April 18, 2013, 05:36:53 am
Hi folks, so far so good with the "new" G5 delux. I have about 750 mi on it and there is only one niggling issue I have. When I am in a low gear, say 2nd or 3rd and roll off the throttle I get a bit of bucking and jerking when the throttle gets close to the closed position. I assumed this was part of the charm of the enfield but I have a friend that would suggest that it is not. I read a few posts that this might indicate a need to adjust the TPS but nothing confirmed. The bike runs a little lean (bluing around the header) I installed an unrestricted silencer about 100 mi ago but this problem existed from the start. I know others have experienced this but there was no clear resolution on how it was fixed. It is the ONE thing I have to complain about with the bike, and if it were gone, it would be literally perfect.


Arizoni

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Reply #1 on: April 18, 2013, 06:04:42 am
If you have a US import, the O2 sensor living just outside the cylinder head exhaust port tends to restrict the exhaust a bit.
This rapidly causes the area to blue from the heat and is nothing to be concerned about.

If you are riding a bike without the O2 sensor, what can I say?  All of the big singles will blue (or gold) their chrome exhaust pipe as the mileage builds up.

As for the bucking/jerking that might be due to the fact that the engine at 750 miles still isn't totally broken in.
I would be hesitant to mess with the TPS and just try to avoid the throttle positions that seem to be causing the problem.
Jim
2011 G5 Deluxe
1999 Miata 10th Anniversary


High On Octane

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Reply #2 on: April 18, 2013, 06:09:23 am
Does your bike still jerk if you pull in the clutch?

Scottie
2001 Harley Davidson Road King


BRADEY

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Reply #3 on: April 18, 2013, 07:11:35 am
I beg to be different, and I think this bike may be running too rich.
This could be an issue with the sensors or the injector. Pls have the
dealer check it, rather then shooting arrows in the dark !


Ducati Scotty

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Reply #4 on: April 18, 2013, 01:46:57 pm
Have you checked the chain adjustment?  Spin the wheel and check it at several locations.

Scott


Pauly

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Reply #5 on: April 18, 2013, 05:37:52 pm
My 2010 G5 does this too. I just pull the spark plug, scrub it off well and put it back in, then I'm good for a while.
2010 G5
'84 Honda VF45


barenekd

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Reply #6 on: April 18, 2013, 05:50:47 pm
Have you guys put in the NGK BPR6ES plug yet? That has been known to cure these kinds of problems. The stock Bosch is not the worlds finest plug in an Enfield. Ya know, lowest bidder and all!
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Pauly

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Reply #7 on: April 18, 2013, 05:56:04 pm
Yeah. That made a huge difference, the problem now is that I'm just commuting around town and the plug really doesn't get hot enough, oh and it's 25 degree f outside
2010 G5
'84 Honda VF45


Ducati Scotty

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Reply #8 on: April 18, 2013, 06:33:23 pm
Are you running a BPR6 or BPR7?  In NGK lower numbers are hotter.  You could look for the next lower number plug (hotter) while the weather is still cool.  Change back to the cooler plug as the weather warms up.  The ES standard plugs work just as well as the IX iridium ones and only cost $3 each.

Scott


jmalona

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Reply #9 on: April 18, 2013, 09:48:08 pm
Hey folks, to answer Scottie J, no, when I pull the clutch in it's fine. I switched out the spark and I'm running an NGK BPR5es for the spring time. The recommended plug from NGK is the BPR8ES, but everyone suggests the 6ES. When I changed out the original bosch it was pretty sooty, this is before the open exhaust, don't know about this one. The chain is fine and I pulled out the volt meter, 0.67 at idle and 3.8 at full open. This is usually not a huge issue but parking lot maneuvering can be iffy and even in 4th, it lurches when you back off the throttle (which feels different than engine braking when I go down from 4th to 3rd, that is smoother). Let me know if you have any tips or ideas. I'm all ears.
J


mattsz

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Reply #10 on: April 19, 2013, 01:44:13 am
I wonder if this is similar to what I'm experiencing?  I wouldn't exactly call mine "bucking and jerking"; close, but it's much more subtle:

If I ride on a level, or slight downhill, and hold the throttle to keep a constant speed where the engine isn't really pushing the bike, but just keeping up with it, it feels like it's cycling between power and none, almost as if I was rolling on and off the throttle, even though I'm not.

I wonder if some EFI or sensor deal is automatically adjusting the fuel - too much, then not enough, then back to too much.  It isn't too often that I find myself riding in this state; usually the engine is either pushing or braking, but when I hit that "coasting" sweet spot it likes to push me around a bit...


Ducati Scotty

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Reply #11 on: April 19, 2013, 01:58:25 am
At steady rpm and throttle position the EFI cycles lean to rich and back again over and over.  With a closed loop and a narrow band O2 sensor it's the only way the system can work.

Scott


gremlin

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Reply #12 on: April 19, 2013, 02:32:39 am
..........I wonder if some EFI or sensor deal is automatically adjusting the fuel - too much, then not enough, then back to too much............

Yes.  Narrow-band O2 sensors work like a switch (near) stoich.  they detect O2 (lean) and raise the flag.  then the ECU widens the injector pulse until the O2 sensor stops detecting (rich).

O2 sensors are temperature sensitive -and- differing ECU's have more or less processor realtime available after managing each injector and spark event .....  so usually this process (fuel trim) operates with a good deal of hysteresis (time lag).

as shampoo instructions say :: wash-rinse-repeat .....
« Last Edit: April 19, 2013, 02:35:42 am by gremlin »
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