Topic: added a mac 4/1, will it run lean or rich?

[carl550k]

 hey all, i've had my mac for a couple years now with no problem. recently i cleaned my carbs especially the pilot jets. the idle issue has been solved but now the bike(76 550k) seems to be running very rich.does going from a 4/4 exhaust to a 4/1 make the bike run lean or rich?the bike always ran lean because of the clogged pilot jets. i run a uni foam oiled air filter, this and the exhaust are the only non-stock parts. if you clean the plugs which are carbon fouled, and put them back it will run great with good throttle responce, but after a few miles the responce deteriorates and you have to keep the rpms up to keep it going. thanx in advance carl

[Loudpipe]

4/1 would mean there is less flow than a 4/4 (read: more backpressure), so it would start running rich, like the symptomes you describe.  The reason for this is the extra backpressure causes the unburnt fuel/air mixture which is in the cylinder after the intake down stroke of the piston to travel BACK into the carb during valve overlap (since the exhaust valve doesn't fully close until the piston is a little ways down on the intake stroke), and get loaded down with a second load of fuel.  Just adjust it and you should be fine.

[seaweb11]

Excellent.!
   You now have the perfect set up to put on pods.   Add some air and OFFFFFFF you go!

[ProTeal55]

My bike had velocity stacks and a 4 into 2 when i bought it.
When i made the switch to the MAC un-baffeled 4 into 1  ,the bike ran 10 times better..
I still have yet to touch my carbs, besides messing with the idle