engine miss or surge at cursing speed

[dlbryant1]

Thanks again for everyone’s input on solving my last problem. Dead Cylinders.

Now that I can ride again I have noted a miss or surge at cursing speed, and it just don’t feel right. The bike idles fine and pulls good and don’t seem to surge after I get over 4500 RPM. It reminds me of a problem I had with my 1973 Bultaco. The problem was the needle & jet. The bike idled ok and pulled great but it was jerky at cursing speed. When I remove the needle you could see the wear. After replacing the needle and jet it ran great.

I did a search on this problem and noted that one other person had this problem but did he find the fix.

[dwales]

Quit cursing, and maybe it will quit surging. :-)

[Dennyz]

Surging could be timing or advance problem.

• A sticking advance plate or connecting the vacuum advance hose to the manifold port (instead of the carb) can cause pulsing of the vacuum advance.
• Having the timing too far advanced.
• It is also possible that you have a broken pickup wire.

[dlbryant1]

Thanks for the laugh. I be cruising not cursing!!

[Mike Hart]

"cursing speed" is the speed that RV's campers and boats go at on curvy roads!~

but seriously, is this problem at steady throttle? It could well be a pickup wire or advance prob as Denny says. If it IS carbs, surging is usually a lean condition - any air leaks at the intake can cause that.

[TopCatGr58]

Cursing at Cruising Speed

Hey Mike and Denny,
He posted in his other thread that he had found he had bad pick up wires and replaced them. Did you check the action of the vacuum advance unit, spin it by hand, if it didn't turn easily and return quickly, could need cleaning/lubricating. Also, check the hose going to the vacuum unit, your intakes for leaks like the gurus stated.

Isn't that RPM around the point of transition from idle circuit into the mains?? During your carb cleaning and bench eyeball synching, did you check out the rubber diaphragms of the slides?? They can get pinholes in them which cause them not to perform as well. I'm not a guru, but sounds like you're on the right track with the fuel supply process being the culprit. Hope others will chime in with more helpful words!

T.C.

[dragxs11]

I've been going through the same exact thing. Had bad pick-up coil wires, and now I got the miss too. I do have a stage one jet kit in it, but it was running good before all this started. My fuel filters are dirty, so I suspect that to be my problem. Since I'm running lean I have even more reason to suspect fuel starvation.
Because the main jet is further down in the bowl, I still get full on accelleration, but at 1/4 throttle I'm on the pilot circuit still for the most part. I'll let you guys know.
Matt

[dragxs11]

New fuel filters werkd 4 me. I guess after you have your tank painted you should change those.