Stutter problem on low revs

[ToreB]

Hi from Norway!
My completely stock '99 1200 145hp V-max has developed a stutter,especially when warm. I cant feel this when the engine is cold.
When I cruise on low revs the engine stutters and makes it very uncomfortable to ride. When I run on high revolutions I can't notice the problem. When I accelerate hard it can stutter a couple of times, then accelerate normally.
This seems to be a problem on the road only, and I can't replicate the problem in the garage. It runs a bit rough around 2000rpm, but I guess this is normal and due to the firing sequence.
I've got new spark plugs, checked all the plug wiring and have synchronized the carbs, same result.
For me, this feels like a electrical problem, maybe in the ignition module since pulling the spark plug caps all have the same degrading effect in idle. But, I have not very much experience with the V-max engines.
I've seen notes tht this can be caused by too lean mixture? Pressing the choke a bit don't change the behaviour.

Any tips?

Cheers from Oslo,
Tore

 

[jfeagins]

How is your voltage when at idle speed? The Vmax CDI box does not like low voltage, and will play tricks if your charging system isn't keeping up @ idle speed.

 

[sdt354]

For me, this feels like a electrical problem, maybe in the ignition module since pulling the spark plug caps all have the same degrading effect in idle. But, I have not very much experience with the V-max engines.
I've seen notes tht this can be caused by too lean mixture? Pressing the choke a bit don't change the behaviour.



Too rich, not lean. Rich is tolerated well, when cold. Do a shot gun cleaning to start. Check the air filter also.
Steve

 

[ToreB]

Thanks guys.
Battery voltage is fine, 13,7 at idle and above 14V on 4000rpm. I've also done the recommended mods to the wire splices in the loom to avoid bad GND. The air filter was changed a year ago, and I blew it clean this spring, almost no dust.
What is a shot gun cleaning?

I was out on a short run today, and the stutter is really annoying. The bike shakes and rattles at low RPM when driving, and I have to keep quite a high rpm to avoid unpleasant stutter when starting on green light. At higher RPM the phenomena is almost gone. I'm finding myself rolling around in third to avoid this.
Cheers,
Tore

 

[Cybergrizzly]

Shotgun Cleaning: http://vmax.lvlhead.com/tips/shotgun.htm

I had a similar problem and when I finally took the bike to a motorcycle shop, the mechanic showed to me sparks arching at the spark plug cover making ground with the engine. He placed a screwdriver between the engine and the spark plug cover and the engine idle speed went a bit rougher. He said that the cover was deteriorated. I am still waiting for the call from the shop to see if they have had time to work on the bike. Just my 2 cents. I hope that is the fix.

Either way, I already purchased a COPs Conversion Kit from "G" and should be getting it in about a week or so. So, if the cover is the one to blame and the mechanic replaces it with something from another bike temporarily, I will just change the whole hot wire + coils pretty soon. Crossing my fingers the problem is there.

Regards, Al

 

[naughtyG]

+1 to the COPs conversion from Gannon, it's a first rate mod and does away with OEM coils / HT leads / plug caps problems.

In the meantime, try pulling your HT lead from both the rear coils (front are a lot more difficult to reach) and from all four spark plug caps. Then cut off about 4-5mm off the ends of the leads and reinsert into coils and plugs. This will get rid of any bad connections due to corrosion, and may help if your problem is spark related.

 

[ToreB]

Thanks naughty G, I don't think this is plug wire related, as I get the same lowering of rpm at idle when I disconnect one plug at a time. As far as I understand, this means that all the spark plugs are working well.
Cheers,
Tore

 

[ToreB]

I've now done the shotgun procedure and the result was pretty good! I might have had some dirt in there. The stutter on cruise is now gone.
However, I now have a problem with hesitation at mid range rpm when accelerating.
I of course noted the four mixture screw settings at disassembly: 8, 13, 11 and 9 1/8-turn on these. (8 is a full turn) Is it normal that the idle mixture screws have different settings?
I've done a lot of engine work before, but have little experience with multi carb engines.

To sum up, these pages has helped a lot in this so far:
http://vmaxoutlaw.com/tech/cleaning_pilot_jets.htm
http://vmax.lvlhead.com/tips/shotgun.htm
http://vmaxoutlaw.com/main.html

Any tips for further investigations?
Cheers,
Tore

 

[Traumahawk]

Yes the stock settings were different on each plug. here was mine when I drilled out the brass plugs on the carbs, and counted the turns. (now these were complete turns)

Cylinder 1-2.5
2-2.75
3-1.75
4-2.75