Stuttering at 5k rpms

[drivera84]

hi guys,

kinda reviving this thread. Ive been doing alot of work on the bike. Ive changed the points plates, got new oem points and condensers. The carbs have been pulled, checked the float levels, they appear to be fine. Valve clearences were done again, checked the compression all 4 cylinders at 120.

The bike starts easily no choke, even on cold days. Idles excellent. But still stutters after 4000 rpm. Someone told me to change the needles, does this sound reasonable?

Carb #1 float always seem to be humid with fuel, no leaks, just humid.

Could a faulty petcock cause this?

[drivera84]

Anything guys?

[Who Dat?]

I am surprised that nobody has suggested trimming the spark plug wires.

Remove the wire from the spark plug. Unscrew the cap (the angled rubber piece that clips onto the plug) from the wire. Cut about 1/4" (6mm) from the end of the wire. Screw the cap back on the wire. Put the wire back on the plug.

Try this on your #1 plug, see if it helps. If it does, do the other three plug wires as a preventive measure. If it doesn't help, go ahead and do the other three anyway, but you will have to keep trying things to see why it's stuttering.

[Spyder]

If you can start it without the "choke" on a cold day, you are running WAY too rich. When you do start it up, does it smoke? If so, what color is the smoke? When you are sitting at a light for a minute or 2, does it puff some smoke when you take off again? When you pull the #1 plug out is it just black, or is it really goopy and black?

[drivera84]

Thanks for the help.

The plug wires have no more space left in them to cut some more. They have been cut in the past. Plugs are just black. Somewhat clean. I'll post a pic later.

Left sitting for two days had to use choke to start it. The battery is almost dead so I always kick start it. Can having a dead battery affect how the bike runs?

When it starts it blows some black smoke then runs clean. When sitting in neutral I can pull the throttle and notice some black smoke not too much. I can Rev it all the way up to the redline and it doesn't stutter, sometimes it backfires though.

Any ideas?

[OldVet66]

Where are the needle clips set? Try raising the clips one notch to drop the needles to lean out all the carburetors. It will require readjusting the air screws for highest idle. Look at a rebuild tutorial for the VM carburetors and insure your nylon washers are in place and in the proper position.