Viper mcx270 backfire...

[Martens199]

Hey guys, I have been riding out in the prairies and have found my sled to be backfiring when I let off the throttle, or when the sled it boosting up in the higher end. Sled seems to be over reving, seeing my revs up in the 9000 range. Possibly because I would get a lot of track spin with not alot of load.
In the mountains it ran fine in the heavy snow. What could this be and what is it hurting? Could over boost cause a backfire

 

[Boostd]

Your hitting your rev limiter

 

[Martens199]

They will backfire like that if they are hitting the limiter. I noticed it was hitting the limiter. But even when I let off before I hit the limiter, it would backfire

 

[Martens199]

Yeah one help me out here? I know it's hitting the limiter but if shouldn't backfire everytime.

 

[yamahajohnson220]

Martens, are you using an afr gauge? I think you might be running lean at a certain throttle position. However if you need weight in the primary or have a secondary that needs attention, can also affect your fueling. And usually mcx has the fueling down perfect.

 

[Martens199]

No I unfortunately do not have a afr gauge. I will get the info on what weights I'm running. Secondary is stock. Primary just has new weights and rollers nothing done with the spring. I will get you numbers. Could this not be a too rich problem?

 

[Boostd]

If your secondary is stock it's the rev limiter. You have to increase spring pressure and angle. The stock helix is a 37 and has a spring a bravo could max out. It can't upshift fast enough to load the clutches so the primary is winging up and and revving before you gauge could ever read that fast.

 

[Martens199]

Boostd, your on to something.. sounds exactly what it's doing. If I full throttle it, it revs up so fast a cant even tell what it revs. Only when I hook up real good on the snow I can almost give it fu ll throttle. So what can I try? I'm not the greatest with clutching

 

[Martens199]

I know lots of people have been having problems with the MPI kits and hitting the limiter, but I have never heard them backfiring like my mcx270 does. I don't even here the limiter just the backfire.

 

[Boostd]

I know lots of people have been having problems with the MPI kits and hitting the limiter, but I have never heard them backfiring like my mcx270 does. I don't even here the limiter just the backfire.

Muffler design is different, power, turbo setup ect can all lead to why yours sounds different. If your running a 270 kit I would at least start with a 45 degree helix and a cat Snopro green spring. This will load the motor more and get your track moving.