# 06 Brute 750 leaking fuel from rear carb



## sportdog (Dec 28, 2012)

Guys told me to check out MIMB for help..so here I am.

Background on my issue: quad sat for 2 years. It started but barely ran. Bone stock quad.

Removed and cleaned carbs very well. Jets were clogged and nasty. Installed rebuild kit. Flushed fuel tank, added new fuel and adjusted valves while plastic was off. New plugs with spark. Quad started right up, warmed up on choke noticed a lil stumbling. Took choke off and noticed popping in rear carb and occasionally backfiring out exhaust. 1/4 to1/2 throttle stumbles. Wot runs great. Noticed fuel leaking from rear cylinder where exhaust meets. My floats are not stuck...needles are new and everything appears clean. Stock size jets in rear 158. Dropped to 152 and same problem exists. Where is the excess fuel coming from?

Please help before I freak out!


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## NMKawierider (Apr 11, 2009)

That much fuel would fowl the plug. Is it? Because it is more common for the valve seals to fail on the exhausts letting oil run down the falve stems and out the exhausts and by the gaskets. It would be extreemly rare for that much fuel to be pulled into the intake unless there was there was either a. stuck or very miss-adjusted float ot bad needle & seat or b. a stuck open choke plunger.

For "a." to be the case, it would also run out the overflow..unless it got plugged somehow.


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## sportdog (Dec 28, 2012)

It does not come out the overflow. The overflow is not clogged. Seat looks good, needle is new and appears to function fine. I lightly sanded the choke plunger too make sure it was operating smoothly and applied a little wd40 to make sure it went in smoothly. The plug is running rich. It is definitely fuel leaking out rear cylinder. Not alot, spitting slightly but makes it wet on the case, 3" diameter spot.


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## NMKawierider (Apr 11, 2009)

Could there be...a jumped cam chain maybe?


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## sportdog (Dec 28, 2012)

It ran fine when it was parked. Valves are all good. WOT screams like a lovely v-twin should. The sputtering on lower throttle has to be from too much fuel. Once it clears out it runs good as long as I keep RPMs up high. Let off and it burps and farts all over (most likely from too much fuel). Still dont see anything that would make it spill fuel out the cyl/exhaust joint. Has to be in carb but, I dont see it. I even submerged floats to see if they had a hole in them.


Im pretty decent with this stuff but am kicking my own butt now!

---------- Post added at 01:44 PM ---------- Previous post was at 01:42 PM ----------

Thanks alot for you imput by the way!!!


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## dman66 (Feb 20, 2011)

Well looks like you got some checking ahead of you-yeah it 's a pain,but most of us been there. The burping and farting at idle - mid throttle could be to much air from air leaks on air box lid,carb and intake boots leaking,choke plunger o rings or rubber boots at cable to plunger,or o ring at air/fuel screws. Some of us added a # 4 washer under each slide needle to correct this problem. As far as the gas leaking,maybe the enrichiner valve diaphragm on the side of the carb?


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## sportdog (Dec 28, 2012)

I have checked for air leaks, sticking chokes, inspected enriching valves everything. I was watching the fuel as it came up from the bowl (quad running) and noticed the fuel from front carb atomizing in throat. Rear carb was more like spilling into throat and running into the intake.


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## sportdog (Dec 28, 2012)

I've been studing carbs. See what you guys think. Carb valves are not in sync. Front valve moves and fluctuates as it should with throttle. Rear valve does not move at idle, doesnt move til almost quarter throttle. Im watching fuel trickle into intake. Try giving more gas and it will backfire small flame out of carb. Too much fuel. I do not believe the carb valve is bad. Ive checked for tears and holes. I even swaped front to back to see if that made a difference, nope. I've cleaned every oracfice in the carb an d soaked it. Since the rear jets were plugged solid I'm guessing there is something still plugged and it cant be cleaned?

I'm ready for new carb at this point. What do you guys think?


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## dman66 (Feb 20, 2011)

If you have a compression tester kit,check the front and rear cylinder compression,then compare the two readings.Then if compression is good,and you're positive the slide diaphram is seated correctly and the little brass orfice is installed in the slide diaphram,then try a carb sync - you can make a homemade one for about 15 bucks with vinyl tube - I found instructions on you tube.


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## brianbob (Jul 11, 2017)

*2006 750 King Brute rear cylinder is not working, leaking gas into cylinder*

Sport dog, did you ever find the issue you were having with excess gas spilling into the rear cylinder?

I have a 2006 750 King Brute that is having a similar issue, except the rear cylinder is not firing at all. It has good spark, it has around 55 psi compression, and the carbs have been cleaned. When trying to start, the front carb slider moves back and forth, but the rear doesn't. You can hold the throttle in and the rear will try to kick off, but goes right out. I have the front plug off while trying so it wont start. When I put the front plug wire on, it will kick right off, but spits gas out of the tail pipe, and the rear cylinder is cool to touch.

Any ideas out there??

Thanks


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## NMKawierider (Apr 11, 2009)

brianbob said:


> Sport dog, did you ever find the issue you were having with excess gas spilling into the rear cylinder?
> 
> I have a 2006 750 King Brute that is having a similar issue, except the rear cylinder is not firing at all. It has good spark, it has around 55 psi compression, and the carbs have been cleaned. When trying to start, the front carb slider moves back and forth, but the rear doesn't. You can hold the throttle in and the rear will try to kick off, but goes right out. I have the front plug off while trying so it wont start. When I put the front plug wire on, it will kick right off, but spits gas out of the tail pipe, and the rear cylinder is cool to touch.
> 
> ...


This is a 5-year-old thread. I wouldn't think the OP is even around anymore. Check the float levels and the float valve. Then check the valve timing, then the coil voltage. And *** is a "King Brute"?


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