[canuck19]

Having some trouble getting my bike dialed in, its a '71 T120 with dual Amal 930's. . I'm getting a steady popping and black smoke out of the left pipe. Right side running perfect.

Been through the carb a couple times, cleaned the hell out of it, cleared the pilot jet with a guitar string. Strobe timed at 38 btdc, running a Hunt magneto for ignition.

Carbs were low mileage when I bought them, so I had them honed/brass slides installed to take slide slop out. Would a worn needle jet cause this?

Thanks for any ideas on what check out.

 

[Tony the torch]

you can verify your carb suspicion by switching the right and left carbs, but yes we just had a brand new Amal 930 that we couldn't get to run right, we started changing everything, re-jeted it, change the slide, change the float and bowl. finally we put a used carb on it and it ran better. so I took the needle jet out of the new carb and put the one from the old carb it it and it runs great. when you look at it you can't see any difference but it sure runs better now.
Needle jets are widely overlooked when looking for carb problems. cost me 2 hours labor, Big mistake to assume if it's new it's good.

 

[canuck19]

Thanks Tony I'll give that a try.

 

[Glider]

Whenever you're sure it's a carb problem, it's usually the electrics.....

 

[Rob Axel]

single or duel points? electronic? single or duel coil?

 

[canuck19]

Whenever you're sure it's a carb problem, it's usually the electrics.....

Yeah I agree, but ignition is supplied by a Hunt mag so there really isn't alot that can go wrong. It has new condenser and points. . I also checked the points gap and checked I have consistent fat spark.

Gonna swap carbs left for right tomorrow morning and swap out the NGK plugs for Champions.

Anybody running velocity stacks with baffled cocktail shaker mufflers? Any recommendations on jetting are also appreciated.

Thanks.