High RPM Miss/Stumble

[silent1]

My bike recently started running weird. When I am heavy on the throttle (usually 80-85 mph at a steady speed), the engine will cutout and stutter as if it's out of gas - maybe pop a little out the exhaust. But it doesn't die. If I let off the throttle a bit and cruise back down to 70, it smooths out and is ok again.

I have no issue accelerating from a stop or from any other gear and the bike still feels strong for the most part. It starts up no problem, and has no problem idling, or cruising at the speed limit. But the minute I start acting like a hooligan, I have issues.

It doesn't happen all the time, so it's pretty hard for me to duplicate the issue.

I haven't done too much riding yet this year. I've gone through 3 tanks of gas since last year, so I don't think it's an issue of bad gas. I checked the connections on the battery and they're good. I think I'm running a 48 slow jet and a 205 main jet in the carb, so I should be getting enough fuel.

What else do I need to look for? Fuel filter? Plugs?

[SafetyMan]

I told you that engine shake was going to give you trouble.....

Sent from my brick-sized SAMSUNG GALAXY Note II using Tapatalk 2...
It's a phone AND a weapon. Much better than a concealed rock.

[vafatboy]

Dirty carb from deposits left behind after gas evaporates. Bad acceleration pump/diaphragm. Dirty needle and seat in the float bowl. Float bowl out of adjustment (not likely, but maybe).

Did you do anything to pipes, engine, cams etc that might change jetting needs?

[silent1]

Originally Posted by vafatboy

Dirty carb from deposits left behind after gas evaporates. Bad acceleration pump/diaphragm. Dirty needle and seat in the float bowl. Float bowl out of adjustment (not likely, but maybe).

Did you do anything to pipes, engine, cams etc that might change jetting needs?

Smart Dave did a lot of work to it last fall. I basically rode it home, took it out a few times, and parked it for the winter.

[Fe Butte]

Something (dirt other gas crap) maybe getting into main jet circuit (?) I don't know if Harley Carb has a power jet circuit (?) Loosing vacuum to the tank shut off?

[dzlfitr]

What do the plugs look like?

Popping out the exhaust is prolly rich. Might be loseing
spark for just a bit.


Usually going lean will pop out the intake.

[silent1]

Plugs look ok and are tan in color.

When I mentioned popping, it only happens during the stumble if I stay in the throttle. It doesn't do it in any other circumstance. I don't think it's a tuning issue.

[d j]

Does it still have the original plug wires?

[silent1]

Yup.

[d j]

Originally Posted by silent1

Yup.

They are pretty easy to change out and not a ton of money. Mega had a similar issue with his bike a few years back down a Josh's. Plug wires.

[vafatboy]

My brother sold his bike after it sat for a while. Doing the same thing....hard on the throttle and it would cut out. I cleaned the jets and needle. Fixed.

[y2kflhr]

Warren knows stuff


Sent from my phone

[Bluetoys]

Somebody installed a momma module on it to monitor and deter you from being a hooligan.

It reports back what you are up to, momma hits the cut-it-out button.

[dynageno]

I'd run some clean power in your tank and see if it clears up.
I'm not sure they sell it where you live, but they have it here in Cali.
Great stuff. Has Vinyl Toluene in it.

[Fe Butte]

Not naga hyde?