I've got a Nightster with pipes and an A/C and sometimes when I'm coming up to a stop and I'm downshifting I'll blip the throttle to match the revs and once in a while when I do this the revs dont come up and the bike will make a "ccchhhh" sound. I'm not sure if its running to rich and can't ingnite all the fuel or if there isn't any fuel there to ignite. I basically did a "plug and play" with my TMax so I'm set at all the default settings. Any suggestions?

 

In the basic module settings you may need to increase the value for accel fuel. For what it's worth, on mine it set to 10.0
Normally the decel function is set to 0 and not functioning but if your's is set to 1 it is. In this case the decel low number may be set too low, or the post decel fuel enrichment may be low also. Again, mine is set to 16.08 default, but I don't use the decel part. You may need to juggle the numbers to fix yours. Check for an intake leak first before doing anything.
Ron

 

This "ccchhhh" sound.....is it like a cough or pop sound? From the right side? If so, then it's probably backfiring through the air-cleaner. Link to the ECM and remove some Accel Fuel. The default for map 390 (Sportster 1200 motor) is 12.0. Lower it to 11.0 and see if that helps. Page 63 in the TMax manual has all the info on Accel Fuel...

If that sound isn't a pop in the intake then give us more to go on with the sound....

 

Duh, I didn't pick up on the fact it was a Sportster, so my numbers will not apply,however spitting back through theTB is lean. At least we both picked the same area to work on
Ron

 

I second this notion. I had some similar issues with my Dyna and by lowering the Accel Fuel value, they all went away. I'm actually down to "6" from "10". No negative changes in throttle response/performance.

 

Thanks for all the replies. Yeah it's more like a cough.....like its gasping or wheezing or something and it is from the right side. It's not a pop. I used to have a PCIII so I know what decel popping sounds like, lol. I'll link up to it tonight and see about removing some of the Accel Fuel.

 

Lowering accel fuel will have a positive impact on your fuel economy too...

VicW.