Carbs Popping

[bassgoat1979]

I got my bobber pretty much toghether and it runs out nice, but at idle it sound really good the evey one once in a while it pops out on or the other carb. Mainly when warmed up. You can actuly see a little pop of smoke out the air filter too, then dies. If it idles at 1500 it pops, but doesn't stall. The run down of what I've done is below. I tried to hook up a battery too, still does the same thing just doesn't completly stall, just heasitates when the pops happen.

any ideas?

-Points ignition with pefect .013" gap. New condeser.
-VF500 stator and regulator
-Banshee flywheel
-ACCEL harley battery eliminator capacitor
-Stock single coils (tried a differnt set, exactly the same problem)
-Carbs sync perfect.
-One size up on the pilot jet and two sizes up on the mains. Screws 1 1/2 turns out. (doesn't change when changing settings on them.)

 

[yamaman]

Carbs might need a clean, there's some very small orifices in there!

Pilot jet may still be too small, std BS 38's?

What air filters you running? What exhaust?

 

[inxs]

Screws 1 1/2 turns out. (doesn't change when changing settings on them.)

- this is a good indication that the idle or pilot circuit isnt working

- as yamaman says, the rest will depend on what youve done with filters and exhaust

- while youre checking, you could also look for air leaks in the exhaust, rubber boots, throttle shaft

 

[bassgoat1979]

The carbs are squeaky clean as far as spraying to carb cleaner through and how it look coming out. Yes stock carbs 38mm vaccum diaphrams. I only up'ed the pilot jet one size. I have the XS performance air filters and shotgun straight pipes to about the rear axle. Sorry I forgot to add that.

Is the pilot sytem the only cause for a popping? I thought it was a lean pilot condition, but wanted to make sure befor I got into something.

 

[yamaman]

No guarantees in this life, I'd up the pilot 1 maybe 2 sizes if it were mine & I knew the carbs were clean & definately no vacuum leaks!

 

[retiredgentleman]

It might be a good idea to adjust the mixture screws using the "dead cylinder method".

 

[KevC]

No guarantees in this life, I'd up the pilot 1 maybe 2 sizes if it were mine & I knew the carbs were clean & definately no vacuum leaks!

Probably need to go up more on pilot jet with those pipes & pod filters, if your sure there are no vacuum leaks, what are your carb mounts like? mine did the same when they went only a few weeks ago. When my pilot was too small it also popped thro the exhaust when you shut off the throttle while riding

 

[bassgoat1979]

What is the dead cylinder method? I have no popping through the exhaust, so it looks to be lean. I'll have to ty the bigger pilot if adjustments don't work. It's really close to being bad ass though!

 

[inxs]

- adjusting one side pilot screw for idle while the other side has been incapacitated either by disconnecting the vacuum or earthing the spark to the cylinder outside...swap sides then do the other...reconnect both and adjust idle setting...here post #8

 

[bassgoat1979]

Could it be possible from a rich condition? Look at the plug (both the same) only idleing. Both plugs were new. I never had a real backfire (through the carbs) be a rich condition, but I learn something new every day. Maybe run the stock pilots? It does see to do fine when cold, then pop after a couple minuets.

 

[Sundie]

Definitely looks rich. Running open pipes, i would expect to see them much leaner. How much do you run the engine up past 3 or 4k? I've found open pipes guys tend to keep the rpm's low, so the plugs don't get a real chance to warm up and blow off the carbon.

 

[bassgoat1979]

It had a few good revs on them. Basicly those plugs have about 10 minuets on them. I just tried reving again and coming off idle it has a little black smoke. I'm going to lean the pilot down and see what happens.

 

[retiredgentleman]

With a plug that colour and puffs of black smoke, you may very well have a leaking head gasket. Oil being sucked from the camchain tunnel into the cylinders. Has the head been off lately? Have you checked the torque on the head studs?

 

[bassgoat1979]

Never seen black smoke when oil was burning. Oil fouling has build up too or oil on the plug. Oil is whiteish blue. Black is rich fuel. I thought it may be something that was out of my league that someone knew about. I know the common cause for carb popping is lean. I guess it's I'll just keep going on what i know. I checked for lean already and found it was rich. I know it ain't buning oil.

 

[bkmarsha]

i got a popping carb too im guessing maybe an air leak on mine though