Backfiring Banshee

[Antwon]

Okay need some help, i just had my banshee in the shop, they put in all new main seals and case seals and re-jetted my carbs they also re-sealed the intake manifolds and repacked the toomey silencers, i also just put in a brand new modquad cdi box cause my stock one went out. The bike was running great and i took it out for the weekend. The second day of riding i took it up to the drags and opened her up, i did like 3 back to back races down the drags and the bike ran fine except the last race when i was fully pinned out, the bike stalled out but i started it back up instantly, we then headed out for some duneing and while i was riding the bike started backfiring from the left cylinder. so i swapped out the left plug in the dunes and rode back to camp. But the backfiring still kept happening so i parked it for the weekend and when i got back home i check a couple things that i read in topics about backfiring like: Split flywheel, plugs, spark, obviously jetting is good i just had it done, and i check for any visible leaks around the intake manifolds and exhaust. Is there any way a reed cage could be broke or could i have blown a head gasket or is there a leak some where? I am going to start with a compression check and if i find nothing i am going to do a leak sown test. but i am new to banshees and am not too sure what is going on. Does anyone have any advice or ideas as to what is going on?

[SAVAGE420]

Honestly, YOU need to know what the jetting is, mains, pilots and needle and the position they are in. + list your mods and temp and elevation. To me you sound lean on your top end. Could have a small leak also. Did they or you do a leak down test? But i have really no idea because YOU didn't list ANYTHING. But back firing "usually" means lean.

 

Your shop might not have taken your bike out and ripped it around to jet it in the "field". You need to jet it according to your mods temp and elevation. It takes a few minutes for you to do out where you ride. With help here, you will have NO problems.

 

Do a plug chop also. http://www.dfn.com/benkaren/plugchop.html

 

Read this twice http://www.dfn.com/benkaren/jetfaq.html

 

Also go through lots of people setups here also http://bansheehq.com/forums/index.php?showtopic=99361

[Antwon]

Honestly, YOU need to know what the jetting is, mains, pilots and needle and the position they are in. + list your mods and temp and elevation. To me you sound lean on your top end. Could have a small leak also. Did they or you do a leak down test? But i have really no idea because YOU didn't list ANYTHING. But back firing "usually" means lean.

 

Your shop might not have taken your bike out and ripped it around to jet it in the "field". You need to jet it according to your mods temp and elevation. It takes a few minutes for you to do out where you ride. With help here, you will have NO problems.

 

Do a plug chop also. http://www.dfn.com/benkaren/plugchop.html

 

Read this twice http://www.dfn.com/benkaren/jetfaq.html

 

Also go through lots of people setups here also http://bansheehq.com/forums/index.php?showtopic=99361

 

well Jasons and I did a compression test and found the left cylinder to be only 40 psi. So we pulled the top end to discover a very melted piston and rings. So I'm in the process of rebuilding the whole top end. New modquad head, weisco piston kit. Cylinder bore and port adjustments.

[KickStartMyHeart]

Yeap, u were too lean and got it hot. I would take it back to whomever rebuilt it and tell them to fix the shit right and parts and labor are on them! Thats fuckin bullshit in my books. What jets were in it when u burned it up?

[Antwon]

Yeap, u were too lean and got it hot. I would take it back to whomever rebuilt it and tell them to fix the shit right and parts and labor are on them! Thats fuckin bullshit in my books. What jets were in it when u burned it up?

 

350 mains. Not sure on the pilots. I'll have to check.

[KickStartMyHeart]

350 mains. Not sure on the pilots. I'll have to check.

 

 

WOW!! 350 mains with your mods should be plenty!! Hmmmm. I had a major leak in mine and the dealership just kept puttin bigger jets in it to overcompensate for the air leak and they ended up putting a 420 main in a relativley STOCK bike! I was livid pissed when I got it back and burned it up. I tore it all apart and built it from nothing and have never had a problem since. Im running real aggressive ported cylinders, +4 timing, milled head, t-5 pipes, 30mm carbs, v-3 reeds. 350 mains should be plenty good. Im curious as to what ur pilot jet is. But im almost positive it got hot from being lean and burned it up.

[Antwon]

WOW!! 350 mains with your mods should be plenty!! Hmmmm. I had a major leak in mine and the dealership just kept puttin bigger jets in it to overcompensate for the air leak and they ended up putting a 420 main in a relativley STOCK bike! I was livid pissed when I got it back and burned it up. I tore it all apart and built it from nothing and have never had a problem since. Im running real aggressive ported cylinders, +4 timing, milled head, t-5 pipes, 30mm carbs, v-3 reeds. 350 mains should be plenty good. Im curious as to what ur pilot jet is. But im almost positive it got hot from being lean and burned it up.

 

Maybe. I think what might have happened is that when i had it in the shop we took a look at the top end and we saw some scaring on the left pistons exhaust side. I asked if we needed to rebuild it and they said it would have no problem making through the season. I think the rings were worn and it was letting air through because the piston has black down that skirt side. i only had a problem when the bike got hot after running down the drags a couple times in a row. Either way i am rebuilding the whole thing with Jasons (from the forum) he is a mechanic. Then we will adjust the mains and pilots. Ill post up all mods pretty soon. but i usually ride in the imperial sand dunes, ie glamis, gordons, super, buttercup, oglby, ect.