Sputtering at low rpm

[Ben10]

Hey ya’ll im finally finishing up my 74 chopper build but am running into a hiccup and would appreciate any help i can get. I recently replaced my headlight since i noticed my last one went out and now my bike is sputtering and feels like it wants to stall at low rpm. It was running fine for the most part before i replaced this headlight so right now im assuming its an ignition issue. Im running hughs complete cdi system with a capacitor. Starts up one kick, tail light and headlight both are on when idling and super bright, and the bike accelerates fine past the low rpm stutter. I have to keep giving it throttle at low rpm to prevent it from dying. Carbs have been cleaned multiple times but will spit gas every once and awhile on startup. Plugs are good but they are new and I haven't ridden pass a few miles. Old plugs were very VERY black. Im thinking its either ignition or an overly rich mixture. Any thoughts?

Specs:
- 2-1 intake with a single vm34 with 2.0 slides
- 17.5 pilot
- 165 main
- 6f9 needle
- 159 p-5 needle jet

 

[Its been a long time]

In my opinion - If it was previously running fine and all you did was change the headlight, that suggests the carburettor is OK. Carburettor could be rich but I would get it running how it was before the headlight change. Sounds like an electrical gremlin resulting from disturbing wiring in the headlight bowl. Once it's running consistently again you can then think about mixture.

 

[Ben10]

Appreciate the quick reply! The headlight only had two wires so i just chopped them and soldered on a new headlight (ground and light wire). Headlight is on at idle and stays on while riding. Im guessing it could be a charging system issue?

 

[Its been a long time]

Appreciate the quick reply! The headlight only had two wires so i just chopped them and soldered on a new headlight (ground and light wire). Headlight is on at idle and stays on while riding. Im guessing it could be a charging system issue?

Ah OK. I have no experience beyond stock type charging and ignition systems. Good luck working out whatever has happened.

 

[Wingedwheel]

I dunno, maybe check and see what the charging system puts out at an idle? What is it as it wants to die?

 

[Ben10]

This might be a dumb question but how do I check what the charging system puts out when it dies cause it only dies when the rpms die down while riding not when idling?

 

[Its been a long time]

This might be a dumb question but how do I check what the charging system puts out when it dies cause it only dies when the rpms die down while riding not when idling?

I installed a temporary voltmeter I bought off eBay to monitor the electrics on my back from the dead 650D. Just mounted it on the side of the speedometer with a couple of cable ties. I will remove it once I have confidence in the system. But meantime, you get to see real time voltage on the bike. You could do similar.

 

[Jan_P]

Yes I would try to disconnect the light se if the Spluttering goes away
If battery one can measure across the battery with a Voltmeter

 

[JJames]

Yes I would try to disconnect the light se if the Spluttering goes away
If battery one can measure across the battery with a Voltmeter

Hugh's CDI with capacitor. Battery or no?

 

[Wingedwheel]

Appreciate the quick reply! The headlight only had two wires so i just chopped them and soldered on a new headlight (ground and light wire). Headlight is on at idle and stays on while riding. Im guessing it could be a charging system issue?

I’m not sure of the light you used but IMHO it should have three wires. Ground, Hi, Lo. Is it possible since this is a chopper that those two wires would be Hi, Lo and ground is the mount?

 

[Ben10]

Appreciate all the help fellas! I figured out the problem. There was a dead spider inside my gas tank partially blocking fuel to the petcock . I removed it and bike ran normally. I didn’t ride the bike for over a week before experiencing the stutter so it was a combination of me being dumb and not giving it enough throttle and a fuel obstruction.

 

[nj1639]

That might be an historical first for the forum, a spider in the gas tank problem.

 

[Jan_P]

That might be an historical first for the forum, a spider in the gas tank problem.

When I was Young there was a tiger in the tank not as a problem though