High Speed Stutter

[stepthrutuner]

Ok, I don't want to get into a long story but since my carb and then K&N air filter worked their way off due to cargo bulging out the bottom of the seat bucket on a recent camping trip I have a high speed (9500-10,000 rpm) irregular stutter as if fuel flow is not consistent. It is similar to the stutter that developed with stock PHVA 17.5 that I could not cure through doing everything possible to insure consistent fuel flow. Finally I switched to the PHBG 21 and the problem went away. The stutter is there whether I run an air filter or not. I've thought I might try an iridium plug but I really doubt that will help.

It runs as strong as ever otherwise. Any ideas, guys? :stumped:

[90GTVert]

I dunno what to tell you that you wouldn't ahve checked already, but here are some ideas...

A good carb cleaning is never a bad thing. Worth a shot if not done already.

Maybe it's just enough fuel supply that it can't keep up at that point? Float level? Check all lines, filter, and petcock if so equipped.

I think the iridium is a good idea. Not sure it'll cure it, but good to have anyway. Along the same lines, check the condtion of your ignition components and their connections. If you have subjected the scoot to agreat amount of moisture of some sort it could make the ignition act weird. I had similar symptoms not long after I got my first scoot and a new coil cured it.

[stepthrutuner]

Haven't cleaned the carb yet and it's hard to imagine moisture being a problem with our drought conditions of late but I guess I'll get around to doing it if I don't find anything else first. A good while back I thought I had damaged my cdi/coil but I went out in a day or two and it started right up and ran fine??? Probably everyone should keep a spare ignition though. I do need a new battery. Replacing that would probably be a good place to start.

[2strokd]

Battery and a plug sounds like a good start. Maybe a bad tank of fuel?

[90GTVert]

Sorry, I barely keep up with weather conditions here sometimes, let alone anywhere else.

I've read other people's posts where a new battery has cured their problems, but I don't really see how. I have no battery in the Venus and it works just fine. If it were a different style of ignition I could see it, but not with the CDI ignitions on these things. The ignition system powers itself as long as the crank is spinning and we don't have any sort of engine management. What is the battery doing? I'm not saying it won't work, but I don't understand how a battery would cause engine trouble on these scoots. If anyone knows why, please explain it to me. Either way, it's always nice to have a working battery so I guess you can't really go wrong.

Having intermittent issues in the past would make me even more suspicious of an ignition component or connection.

Good call on the fuel too.

[2strokd]

With all the lights on the stator has got a heck of a load on it with a dead battery compared to a good charged one. Wouldnt the extra load on the stator cause a lack of performance? Am i wrong here?

[90GTVert]

The stator has separate coils and separate wiring from charging system though to my knowledge.

[Fox]

I'm thinking the plug wire/cap might be the issue...

A cracked wire can cause the spark to jump to the frame occasionally. Same thing goes for a bad cap. The spark can jump from the cap to the head.

[stepthrutuner]

I doubt that a new battery will help either but it will be good to have. What Fox said could be happening but I think it would happen under heavy load like going up a hill, etc. I do have a heavy load on my lighting coil (45 w. in place of a 25 w. headlamp) but as B. says, the ignition uses a different coil. Setting a closer gap on the plug might help (0.55-0.60 mm) high speed spark performance.