Exhaust Backfire Help!

[davidninja]

Hi, I'm having a terrible time trying to get my quad running right. The problem is that it backfires really bad. It starts easy with the choke on, but it bogs when I give it throttle and it starts to backfire when the choke goes down (on its own). I took it into a local shop. He had it for 5 months, replaced the stator with an oem part, charged me 500$ and said it was either the cdi or the crank was twisted. I bought another oem cdi and it didn't help. Is there a way to check if the crank is twisted without tearing the motor down completely?

I checked out all the wiring with an ohm meter, replaced the coil, checked the woodruff key, checked the exhaust and intake for leaks, cleaned the carb, and still no good.
Could this be a carb. issue? Is there a way I could test the pulse generator?

'86 CT 310 (I think)
CT Etched in the head
VForce3 carbon reads (do I need the spacer?)
PT 2003 Race Exhaust/Fat Boy silencer
38mm PJ Carb
DGK Needle 4th clip (also have DGH and DGJ)
170 Main (also have 150, 180, 190)
55 Pilot (also have 50, 58, 62)
110 Race gas 32:1 (also tried pump gas)

I'll post a cell phone video of the quad trying to run, you can see flames out of the exhaust at one point. I have to kill it or the header will come off the head.

For now I'll just post a pic

[davidninja]

Sorry it's a crappy cell phone video, but you get the idea... http://www.youtube.com/watch?v=aiuW1Tpr4eI

[deathman53]

what??? does this guy know anything?? I've never heard of a twisted crank. If its backfiring its way too rich. Popping is usually a sign of way too lean. However, these are usually things that happen with 4 strokes. I've never had a 2 stroke pop or backfire. Bogging is usually a sign of too rich, it has too much fuel and can't burn it. If it revs high quickly and popson deceleration or top end, its way too lean.

[IGOTSAND]

It sounds like a carb issue...
I had the same thing happen to me, the dang backfire blew the pipe off....so I replace the carb with a new one, and it has been fine ever since....
Try another carb if you can, that might be it...

[Aceman]

Originally posted by davidninja
It starts easy with the choke on, but it bogs when I give it throttle and it starts to backfire when the choke goes down (on its own).

This right here makes me think it's running lean, the choke is helping the lean condition until you stop choking it, then it starts backfiring. When you cleaned the carb, are you positive you blew out all the passages including the jets, specifically the pilot? Set your float height correctly?

[86 Quad R]

i'm thinking its lean aswell but with but with a 55 pilot i dunno. i'd deffinately pull the carb back down and flush it out with carb cleaner, followed by compressed air. if that doesnt solve the problem, i'd focuss on the pilot as well as the choke. reason being is that the pilot, choke and idle speed are controlled by it. the pj's are a beee utch to dial in for that reason.

generally, one can gage which way the pilot needs to go by how far the choke knob has to be turned to get it to idle. if the knob needs to be turned "all" way to the left(and still no change) or close to it, then its too phat....... you get the idea?


on rare occasions, the lil brass "orfic" that the needle slides up en down through will get wollered out and you'll never get the carb dialed in. i 'ont care who you are. lol

[davidninja]

Thanks for your help guys, really appreciate it. I cleaned the carb again today especially focused on the pilot and and choke. I also went through the wiring harness and cleaned or replaced all the connections. It's running better now, no more crazy backfires. Idle is prety good, although sometimes it revs up real quick. The real problem now is that it bogs down when I crack the throttle and feels like it has no power.