Cobras running rough

[localyokel]

Just installed 6/6 cobras and I'm not sure it was the right move. Super loud is one issues, but they seem to be running  really rich. Heavy gas smell and boggy performance around town. Carbs were just reworked a few months ago and ran fine with stock pipes.

Others here said no jet kit was needed with cobras, but maybe so? I May have a new set to sell here soon...

Anyone have experience with supertrapps?

[KY,Dave (AKA Misunderstood)]

If I'm not mistaken (others please correct me if I'm wrong) Cobras would cause a slight LEAN running, not rich.

Why were carbs done recently? Were they gunked up? I have heard of ones having to do them more then once as more stuff lossens up and affects jets depending on how bad they were before cleaning. Just a thought. I'm sure others will chime in, but they will want more details/info if you want help diagnosing. 

[9Ball]

Dave is right....installing the Cobra 6x6 typically causes issues with running too lean rather than too rich, but there seems to be a wide variation of experiences.  Need to know a bit more about your setup...any other mods such as air filter?  The Cobras have less restriction than stock which means you can get more air flow through the system if you can get more air into the engine.  Rejetting kits allow you to enrichen the fuel mixture by shimming the carb needles and installing larger main jets.  If you get the mixture too lean, then symptoms such as a stumble, rough running, severe popping, or rapid loss of engine power when you really jump on the throttle can occur.


What did you do with your airbox?  Did you install or re-oil a K&N air filter?  I've often seen issues with over-oiling (filter should be on the pinkinsh side, not bright red).  Too much oil can restrict air flow and may lead to a rich running condition you describe.

The best way to diagnose this problem is with a dyno and exhaust analyzer.  When I installed the Cobras, K&N, and jet kit on my bike we did dyno runs to dial it in.  What ended up happening is that I got a smooth running, louder bike that only lost 2 hp instead of 7 or 8 hp over stock.  My final dyno run was 90 hp/ 90 torque.

[Chrisj CMA]

My bike ran good with cobra pipes and no jetting but it too was a little rich.  Sooty exhaust and all.  I added a K&N air filter and with the pre-filter it seemed to bring the mixture to where it needs to be.  No more soot and runs crisp and clean