# Backfire and no power unless choke on



## KMKjr (Jan 9, 2009)

2006 BF650i No snorkels, mods, etc....

Brute idles and starts great.

Has no power, backfiring out exhaust and out front carb.

You can drive it fine but have to have open choke completely open to stop backfiring and restore power (still slight backfire a bottom end acceleration but not severe).

Started last week when we were replacing front end parts and winch contactor (negitive battery terminal was hot/arching due to bad contactor to winch). Did nothing that should have effected the running, just front end parts, rear bearings, etc...

Started after repairs and was misfiring but cleaned carb (did mistake carb clean and brake clean when flushing.....but thats another story) last week and was ok that night. Next morning, back to misfiring again. Belt light was tripped and slight noise from belt area, removed and inspected belt, ok. Reset light and didn't come back on. Drove it for 126km trip with choke on and never cleared.

Flushed carb last night and made no difference. Does seem to pick up power and backfire less when spraying front bowl. Have it soaking in Seafoam now and will try after work.

Thinking its a carb issue (dirt or vacuum leak?) and have a run tonight and no time to remove plastics, etc... to completely inspect carbs, etc...

And ideas?


----------



## dman66 (Feb 20, 2011)

I think it sounds like it's running lean on carbs.What I would do is,first check your spark plugs - they don't last forever.Then open up the air box and remove the filter - filter cage - and backfire screen - make sure it's clean in there,put air box lid back on,start up bike on full choke,open airbox lid so you can watch the slides move from idle to say 1/2 throttle - they should move up and down with the increase in throttle the same mirror image - watch your face incase a flame were to shoot out.If one is not responding properly - check carb boots for cracks or check the slide diaphrams to see if leaking vaccum.Other than that it would be clean your carbs and jets - then reinstall.This is assuming things ran proper before.There's alot of other stuff,but this is where I would start.


----------



## KMKjr (Jan 9, 2009)

Did all that and all the new I can tell you is that its only backfiring out rear carb and exhaust. Front is ok. 

Removed and re-gapped plugs. No change.


----------



## blue beast (Feb 16, 2010)

your choke maybe messing up ...those things are notorious for messing up...delete it , then when you need to choke it cover up snorke holes halfway


----------



## KMKjr (Jan 9, 2009)

No snorkels.

Choke appears to be working fine.


----------



## Leardriver (Feb 21, 2012)

Sounds like the pilot jet is plugged.


----------



## redrumredrum89 (Apr 12, 2012)

I had the same thing ,no balls ,no wheelies, popping when you hit the gas it bogged down right? 
1 changed the gas --nope 
2 cleaned the carbs then had a pro clean them---nope 
3 changed the plugs (well Dale from DSC did it) ---nope
4 put a dynatek cdi --bingo it goes like hell 
still pops a litle but it a commn thing with the ddynatek cdi


----------



## NMKawierider (Apr 11, 2009)

Might be a failing CDI but check all the other signs first. It sounds like its very lean so check that the tank vent check isn't stuck, the pump is putting out what it should, the tank screen isn't blocked, no water or crud in the bowls, the CV diaphrams are working, no splits on the carn boots..which happens a lot, the upper vents are not blocked...stuff like that.


----------



## KMKjr (Jan 9, 2009)

What years will the CDI's work from? Have a few I can swap out from friends bikes.


----------



## dman66 (Feb 20, 2011)

I think you are limited from the 05 - 07 750's for swapping the cdi's.


----------

