1998 MZ Mastiff, Yamaha XT660 YDIS

**Trent in Colorado** · #1 8 Nov 2008

I just got this bike a couple weeks ago. Great Bike,

I ride winding mountain roads here in Colorado USA. the bike corners great and has excellent low end horse power.I'm getting backfire when I let off the gas, I'm not sure about how it should be jetted, I live in Evergreen 8,000ft. Elev. and ride to Golden 5,500ft. Elev., for work. Can anyone tell me if my backfire is a fuel-air mixture or jetting, or timing??

Trent in Colorado

**Warthog** · #2 8 Nov 2008

The times I've had back-firing on the over-run, is when the bike is running lean.

Can't say if timing would affect it though. At a guess, I think mixture is probably more likely to be out (due to aftermarket airfilters put on, new end cans, your altitude etc) than timing on a modern bike IMHO....

HTH

**ourade** · #3 8 Nov 2008

I owned a MZ Skorpion and it backfired, especially when rolling the throttle off then back on hard. The problem was the exhaust joint between the front pipe and silencer. The sealant blew out after about 2500 miles and the join is not a tight fit. The only time it did not backfire was while riding in France, during 2 trips and nearly a 1000 miles not one bang.

Cheers
Ade.