back fire and flames.

[kawi_rider_97]

So I've been trying to dial in my 440 and nothings working. as soon as I let off the throttle it pops real loud and shoots fire. I already shimmed the new cams and those are good now. the plug is nice and tan so I don't know whats wrong. is this just something that it does? if it helps any heres a list off all the "performance" parts: L.A sleeve 440, 13:5:1 94.5mm piston, HotCams, 40mm FCR carb, UNI filter with lid off, and ProCircuit full exhaust. Any help appreciated, Thanks.

[the Z Man]

TRy a new exhaust donut at the head..

[drzoo2]

Not sure about jetting n FCR but a few things......

Exhaust leaks

Intake leaks

Plug chops don't tell the whole story. Plus your suppose to look at the bottom of the porcelin which means cutting the thread off to look.

Your pilot is lean

There are a ton off threads on "another Forum" about jetting an FCR on a Z. There are some recent ones.
z

[kawi_rider_97]

well I think I might have found my prob. I decided to take my valve cover off and one of my intake valves only had .003" clearance. Would this cause it to backfire and shoot fire? When I tried going through different jets it still performed the same no matter how it was jetted it backfired when I let off the throttle. So is the clearance possibly my issue? thanks.

[Sforza919]

my quad is doing the same thing, back firing and shooting fire, it has a full trinity stage 4 exhuast and the kid that put it on tried jetting it but i don't think he really new what he was doing, the kid also put a new head on it and i'm not sure if he adjusted the valves right, and he said he took the carb off to clean it and it doesn't look like he hooked it up right, what would you say my problem is

[NRPkfx400]

Mine did that and i adjusted the Pilot screw and went up a jet size and it stopped the backfiring

[kawi_rider_97]

Thanks for all the input guys, I think I've got it figured out. I'm gonna go test ride it right now.

[Sforza919]

i took mine to the shop the other day and he thinks it may be out of time, but he hasent checked yet