Triumphrat

T120rdog · 12-21-2009, 10:52 AM

Just fitted a 2-1 exhaust on my 71 bonnie cafe project. And now there is a distinct popping from the exhaust on the decel.

There have been quite a few threads on this but I couldn't find an answer to my primary question.

Is the popping a symptom of something harmful to the bike or just a harmless side effect of a tuning or exhaust problem?

I don't want to run her if I'm doing damage.

Also to fix the popping on the advice of some trusted members of this board I adjusted the carb floats and cleaned and synched the carbs. Popping is still there, what should I try next?

Thanks in advance

TxTiger · 12-21-2009, 01:24 PM

Seems I remember reading on a similar thread that this could be caused by an exhaust leak, where the pipes fit to the head. If it didn't pop before and now it does, I would check for proper fit and tightness of exhaust.

68TR6R · 12-21-2009, 03:02 PM

Could be due to timing or too rich/lean low speed circuit.

thekeyman · 12-21-2009, 03:14 PM

lf the 2-1 is a solid welded unit there is a good chance that the pipes are not entering the exhaust port at the exact angle and allowing it to suck in air. Although the adjustable down pipes do not look so good as the solids, they are easier to line up with the ports. So as previously advised, check your exhaust for good seals before messing around with needles jets ect.

jimmy bush · 12-22-2009, 04:31 PM

Many times, newer exhaust flow better than stock exhaust neccesitating a change in the mixture. Freer flowing will usually cause a leaner mixture. when you close the throttle, the mixture is sometimes too lean to burn in the combustion chamber. The unburned fuel collects in the header where it ignites and pops when there is enough fuel in the mix to combust. Try richening the mixture a bit. You should also do a plug chop to see if it is rich enough on top.

Snakeoil · 12-22-2009, 08:25 PM

Quote:

Originally Posted by jimmy bush

Many times, newer exhaust flow better than stock exhaust neccesitating a change in the mixture. Freer flowing will usually cause a leaner mixture. when you close the throttle, the mixture is sometimes too lean to burn in the combustion chamber. The unburned fuel collects in the header where it ignites and pops when there is enough fuel in the mix to combust. Try richening the mixture a bit. You should also do a plug chop to see if it is rich enough on top.

Yup, gotta agree with you, Jimmy. I run a V&H propipe on a FI Harley and the mixture was set on a dyno by Fred Eno. The FI puts out just enough fuel to make it pop on a decel. What's better though is the vicious growl when I redline it and chop the throttle to shift. I get more compliments on that sound than I do on the bike itself.
regards,
Rob