bad midrange stumble backfires

[hankohlson]

so ive got a 2000 800 non ves in an iqr cahssis thats got a real bad stumble in the mid range. its ported with reeds, custom fit gen2 slp pipe with a stinger silencer. no lights but i put the arctic cat 200 watt voltage reg in it. I rebuilt the motor top and bottom. ran great for the first tank or so but then got this problem. it has good idle and once you get it wide open it rips. it barely runs and back fires in the mid though. not rideable. went up on the neeld and pilot and cleaned the carbs. ran better for a minute but then it was back.

could it be electrical ? tach works fine?

ideas?

thanks guys!

 

[JET FUEL]

have you checked you TPS sensor?

 

[slash]

back fires out the pipe means to ritch , out the carbs means you are lean!! pos vac leak!

 

[hankohlson]

how do i check the tps?

it backfires out the pipe but it seems to get hot like its lean. dont have egt though.

the wierd thing is it ran great the first tank full and when i was goingback to the truck it did it just barely. next time out it was way worse. same place and temp. how would the motor breaking in make a difference. more compression?

if it were a vac leak wouldnt it pop out the carbs ? i split the cases and put new crank seals in so i dont think it could leak there and im using brads carb boots that look like they are sealed up very well.

 

[bigboy]

possibile air bubble

 

[RMK_Hillclimber]

A very rich condition looks almost exactly the same on your EGT's as a lean condition...sometimes its hard to determine for sure. Its dumping massive amounts or raw fuel into the pipe and the hot pipe is igniting it which is where you get your pipe backfire. Take a look at your piston wash and plug color to determine if its in your carb setup or it could very well be something electrical as well.

 

[farmervanny]

I have the same motor in my iqr and I chased the same type of problem for quite some time one morning at the trail head after a jetting change. Barely running, backfiring, super hot pipe because it was dumping fuel into pipe, once I got it wide open it would catch and rip. It ended up being the plug into the coil working its way lose. I would check all your connections, then maybe check the coil. Hope this helps

 

[hankohlson]

so I checked the voltage reg and there is not continuity between the two wires my arctic cat reg. The old stock polaris has cont. between the two so I figure ive got a bad regulator. pulgs and the inside of the pipe are black and oily so i dont thnk its lean related. it came on all of a sudden so im really thinkin its that regulator. ill change it out and see what happens.

 

[ggcustoms]

midrange stumble

Check the reed pedals, seen that happen with both stock and vforce3s, broken pedals suck

 

[hankohlson]

reeds look fine.

checked a new voltage reg and it didnt have conitnuity either, same as the one i was runnin.

could it be water in the fuel?

 

[bigboy]

possible but sounds almost like my friends sled and it was a air bubble in the coolant