250ES Backfiring???

[82ATCsuperswamp]

I've got a problem right now with my 86 BR. It won't start and when I turn the engine over, it backfires. I've got a new carb on it and even took it back off and put the old one back on and still does it. Anyone have any suggestions?

[Mr_RPM]

was it running before? i have had this happen before when my timing was off, maybe? was it running recently?

[82ATCsuperswamp]

It was running two weeks ago when I last had it cranked. I had to choke the crap out of it for it to stay running. I rode it for about 3 minutes and shut it off and haven't gotten it to crank since. It'll spin a little then backfire spin a little then backfire. I know my neighbors really hate me right now with all the backfiring lol

[Mr_RPM]

well that backfiring is caused by a gas build up and then BAM! it fires and causes the back fire. when u say crank what do u mean? like the engine is spinning over with the electric start? why did you have the choke out of it?, like im just a little confused on the story of this trike lol i wanted to say carb problems but if its the really loud kind of back fire (since the neighbors can hear it lol) gas isnt burning properly, hmmmm i will get back to you on this, unless someone else figures this out for ya before then.

[82ATCsuperswamp]

Yeah I'm turning it over with the electric start. It'll turn over for about 4 to 5 seconds and then BAM. I can never get it to start. I don't know if it could have jumped time or not. It wouldn't run with the choke off when it was running. It would always have to be on full choke to run. It won't crank with choke on or off now.

[Mr_RPM]

well the trike needing the choke on tells me 2 things, your running lean and if its a fuel enrichment type choke (i will have to check) then your carb is dirty. but you said u have used 2 diff carbs and im hoping both arnt dirty lol. but be sure your jets are clean anyway. but i dont think thats your whole problem (not the back firing anyway) now the running lean would make it pop and kinda backfire like, when running. but since its not running now and yet u still have backfire. when your cranking it that 4 or 5 times then it back fires, will it keep turning over if u hold the button? or does it kind of stop or kick back on the starter? like i said i will get back to you on this, feel free to add details. ill hopefully have your problem in about 4 hours where i can talk this over with my father.

[Thorpe]

^^^ Gotta agree with RPM... Sounds like you are having dirty/plugged carb issues... You pulled the oem carb off and replaced it with what? A ebay carb? I would order a rebuild kit for the oem carb, and go through it...

[Mr_RPM]

your problem is your running super lean, to the point that it wont run. you have a intake airleak, check everything from the airbox to the cylinder and everything inbetween. air is getting in somewhere. also make sure u are running the correct size jets, download a manual here if u havent already and check your jet sizes. so basically your either getting to much air or not enough gas, but im betting on the to much air. all the rubber seals are probably dry rotted and stuff. also make sure your exhaust isnt leaking from the head, that wont cause the problem fully but it will add to it.

[82ATCsuperswamp]

The OEM carb is shot. I've been through it about 5 times already. I've got one jet that won't come out. I got an eBay carb but it was like 140 bucks. It was running with that carb on there. I've checked for air leaks and checked spark.

[Mr_RPM]

are the jets the right size? u cant trust ebay carbs to have the correct settings

[82ATCsuperswamp]

Yeah they're the right size. I've got a manual and it matches it. It's stumping my brain. I haven't got to take it to the trails yet and I'm getting bummed ha.

[Taiser]

Easy check for the manifold leak, spin her over while spraying carb cleaner around the carb, if she tries to fire or runs for a few seconds, it's a leak.

[82ATCsuperswamp]

Found out what it was this afternoon.......bad plug. It's like 2 weeks old. I had cleaned it and put it back in but never thought it would have went bad that quick. I put another one in it and it started right up. I guess it would not fire and then all of the sudden BAM it would fire enough to backfire. Anyways got to figure out why it's running super rich now.