Runs for a minute then stops - lights pulsing - 'pop' on next ignition on

[Molly]

My 78 has been parked up for a month. Previously fine. Will run for a minute then stop. Not sure if it's relevant but after it last cut-out I noticed the headlight was pulsing in and out. When I turn the ignition off and back on I get a loud pop through the pipes.

Assuming the simplest answer which would be dirt in the fuel line / carb. Just those other details kind of has me wondering.

Thanks.

[Hossamania]

What is the battery voltage, standing before start, and running, if it starts? Check for loose battery cable.
Dirty float bowl/stuck float, causing flood? The pop is excess fuel being lit in the exhaust. Do you still have points? If so, check them, maybe replace the condenser.

[Molly]

Thanks. I'll check through that lot. Appreciate the response and guidance.

Worst of it was that on one occasion it cut out outside a busy pub teaming with fans of the Manx GP that's underway here at the moment (I'm in the Isle of Man). They thought the loud pop was hilarious...

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[Hossamania]

Start with the loose cables, easiest and quite common issue.
Often when I fire my Twin Cam it will "Pop" when it starts, quite startling to bystanders, good humor for me.
And I'm really jealous you're at the Manx and I'm not!

[Molly]

Start with the loose cables, easiest and quite common issue.
Often when I fire my Twin Cam it will "Pop" when it starts, quite startling to bystanders, good humor for me.
And I'm really jealous you're at the Manx and I'm not!

Thanks again. I'll check through it all.

Just in from a practice session. I'm a marshal so get a good view and a chance to chat with riders / see the bikes up close when they flag the session / break down.

Not relevant to the thread but here's a beautiful example of a visitor's bike I saw the other day.

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[Excalibur]

Loose or poor connection. Perhaps a wire almost broken off and only connected by one strand. Symptoms indicate poor or erratic voltage. Check battery voltage, preferably load test it.

[drifter]

That is a nice Vincent, you are in a good place.  Enjoy!

[crock]

There is a quick connect behind the headlight for the kill switch on the handle bars. That will give some head scratching gremlins, ask me how I know

[72fl]

Thanks. I'll check through that lot. Appreciate the response and guidance.

Worst of it was that on one occasion it cut out outside a busy pub teaming with fans of the Manx GP that's underway here at the moment (I'm in the Isle of Man). They thought the loud pop was hilarious...

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What I'd pay to come there and watch those amazing people ride that race. I am so intrigued by their riding and capability at SPEED.

Oh sorry you had a tech question Check Battery Voltage I concur with Hoss, make sure your Ground under the seat is attached firmly also.

[Molly]

Just a quick follow-up. Put the battery on the Optimate overnight and also drained the float bowl. Lots of dirt in the bottom of the carb.

Took it for a run and it seems Fine again. Guess I should've done each task individually so I'd know which was responsible for the problem.

I'm also going to run through the advice given for peace of mind and as a learning thing.

Thanks guys.

[fbn ent]

Thanks for the update. Glad you got it figured.

[david lee]

Just a quick follow-up. Put the battery on the Optimate overnight and also drained the float bowl. Lots of dirt in the bottom of the carb.

Took it for a run and it seems Fine again. Guess I should've done each task individually so I'd know which was responsible for the problem.

I'm also going to run through the advice given for peace of mind and as a learning thing.

Thanks guys.

did you drain the tanks.dirts coming from somewhere

[Molly]

Just a quick follow-up. Put the battery on the Optimate overnight and also drained the float bowl. Lots of dirt in the bottom of the carb.

Took it for a run and it seems Fine again. Guess I should've done each task individually so I'd know which was responsible for the problem.

I'm also going to run through the advice given for peace of mind and as a learning thing.

Thanks guys.

did you drain the tanks.dirts coming from somewhere

No. Not yet. Carb's a Super B which has a handy drain bolt. Going to put a good quality in line filter in there.

Thanks again folks. I do appreciate you giving me the benefit of your experience. 

Sat in my garage after an evening ride, listening to the Evo cooling down. Life is good.

[david lee]

Just a quick follow-up. Put the battery on the Optimate overnight and also drained the float bowl. Lots of dirt in the bottom of the carb.

Took it for a run and it seems Fine again. Guess I should've done each task individually so I'd know which was responsible for the problem.

I'm also going to run through the advice given for peace of mind and as a learning thing.

Thanks guys.

did you drain the tanks.dirts coming from somewhere

No. Not yet. Carb's a Super B which has a handy drain bolt. Going to put a good quality in line filter in there.

Thanks again folks. I do appreciate you giving me the benefit of your experience. 

Sat in my garage after an evening ride, listening to the Evo cooling down. Life is good.

most will say do not fit an in line filter

[Molly]

Why's that? Do they inhibit the flow of fuel too much?

Was just about to buy one.

Thanks.

[crock]

I've heard the same thing, but I have ran a glass "aircraft style" forever without issues

[Hossamania]

In general the screen on the petcock (if present) catches most of the dirt. Often an in line filter can cause flow problems, but many do run them with no issues. Finding room for it and still keeping good flow is the main issue. It may be worth a try.
You could try draining some fuel out of the tank into a catch can and check for excessive dirt as well. No smoking!

[david lee]

I've heard the same thing, but I have ran a glass "aircraft style" forever without issues

ive got a glass 1 in the garage for yrs got talked out of fitting it. i agree with hossamania

[bump]

I ran an inline filter on my shovelhead mounted between the cylinders. Bike acted like it was running out of gas when everything got warmed up. Removed filter and problem went with it. This was with a S&S B that I ran for almost 40 years.

[thumpr54]

I ran an inline filter on my shovelhead mounted between the cylinders. Bike acted like it was running out of gas when everything got warmed up. Removed filter and problem went with it. This was with a S&S B that I ran for almost 40 years.

I had the same setup with an E....worked OK til I got down around the Salton Sea on a hot day then acted similar...took a peek and I could see the fuel bubbling inside the filter...removed the filter and it was fine. Bubbling in the fuel line equals fuel starvation....

[Molly]

So, I'm guessing I've found the problem. Carb's about to get a thorough clean.


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[Hossamania]

Yep, that might cause a few problems!

[bump]

You might also want to clean out gas tank.

[JSD]

Run a pingle filter close to the fuel tap away from heat no issues!