750 brute force

[STEVIE D]

i took carbs off an cleaned them found trash in front carb cleaned an reassembled cranked up ran for sec then died out , now i cant even get it to start with carb cleaner . anyone have any ideas , i am fixin to ck valves to see if got dirt are valve stuck open spits fuel out of carbs when turning over to start ,,,,,,,,,,,,,

 

[HagmanMod1]

check your jets to see if pluged

 

[STEVIE D]

No tits but do you have an answer

 

[STEVIE D]

I CLEANED ALL JETS AN IT IS GETTING FUEL JUST SPITS BACK THROUG CARBS LIKE VALVE NOT CLOSING

 

[fmx]

make sure none of you carb vacume lines are not plugged or kinked, also make sure that your overflow lines are also not plugged or kinked. Have you checked if you are getting spark? maybee something electrical got pulled and unplugged while you where in there.

Good luck with it!!

 

[leonard]

heh something similar to this happened on my grizz one time.. turned out the valve on my gas cap was stuck closed and was causing a major vacume which actually stalled my engine over and over.

 

[BIG_BRUTE750]

check the in take valves had the same thing.

 

[STEVIE D]

Thanks that is next step i am use to repairing honda an rebuilding them blindfolded this is whole different animal do you know if have to pull engine to get to front head off

 

[BIG_BRUTE750]

no i dont think that you have to pull the motor to cheak your valves.

 

[Garryese]

Put yor air box back together and try again. Proper vaccum at the carb throut is essential, and that will only happen with the air box in place.

 

[redlineguy]

Did you pull the floats off and take the needle out?? The new gas will make them stick open or cloesed.

 

[Bruteskeg]

did you get her runnin ??? I was going to ask if you wear runnin a stock cdi or if you installed a dyna tech ?? If your runnin the dyna tech try takin it out and swappin with you stock one.. if your not gettin and spark....

 

[STEVIE D]

No but i read where they are famous for shearing timing gear pin an causing no comp on both cylinders which is what i also have so i think that might be the problem cause i have 0 compression on either cylinder ........

 

[Gunny]

I was think'in maybe needle & seat ... but the timing gear pin shearing ... that sucks !!!!

Keep us up-to-date on what ya find.

Good Luck ....

Later ....

 

[STEVIE D]

Garry how does decompressor work i cant get compression in either cylinder an i did not touch them i just cleaned carbs so i am wonderin if one of vacum lines is wrong so they want open to build compression in cylinder to start it

 

[Bruteskeg]

iv hear of this problem happening b4 on the brutes, expecialy if you have not started it for a long time for some reason the rings get sized in the piston and when you crank it over you dont get any compression what iv heard of some guys doing to unstick the rings was take out your spark plugs and pour some oil in the cylinders and crank it over......... a good place to post about this is
High Lifter can bee a really helpfull site, if you dont allready know about it .

 

[Garryese]

Garry how does decompressor work i cant get compression in either cylinder an i did not touch them i just cleaned carbs so i am wonderin if one of vacum lines is wrong so they want open to build compression in cylinder to start it

Decompressor operates off of weights on the end of the camshaft. When the cam is turning slow the weights holds the exhaust valves open longer then normal. As the engine reaches full cranking speed the weights open and allow the exhaust valve to follow the cam profile. Over simplified version, but you get the idea.

Proper way to do a compression test is to hold throttle wide open while manually turning engine over. Pulling the rope turns the engine over faster than the starter will.

I do not think your problem is with cranking speed or the decompressor as you mentioned that fuel spits backwards through the carbs. Generally, on a four stroke when fuel spits backwards the intake is being open, most often becuase the is no valve lash or the valve is bent. Burnt valves, broken rocker arms, and broken valve springs can also cause the same problem, but this occurance is rare in these engines. On the these Kawi engines they will spit alot of fuel back when air box is not full assembled, however they will usually start, just not rev out.

Did the engine back fire near the time this problem started? What was the reason for cleaning the carbs? How many miles on this engine. Has the engine been ran out of oil at some point in it's life or ran a very long time between oil changes? Is there any chance the exhaust system might be plugged? Is there any chance the carbs got re-installed in the wrong location (carbs are jetted differently, front to back)? Do you have the means to check pressure check the needle and seat in the carbs? Do you have the means to do a leak down test? ... at different crankshaft degrees?

It is really strange that you would loose compression in both cylinders at the same time. The only single part I can think of that might cause this on both cylinders at the same time is the timing chains drive sprockets.

 

[STEVIE D]

It was running the same day an i heard it running alil bad an so i pulled carbs off found alil trash in front carb , put back together sprayed alil carb cleaner an tryed it , it fired off an so i finsihed putting it back together an it only started one time since , i find it hard to believe myself because i work on bikes all the time an fix them from bottom up no problem but in this case i am fightin wiht it , i read about timiing gear key on web site an symptons are exactly as described i have fuel an fire just no comp on either cylinder , so i am ckin on key this weekend i cked valves they are not bent so i am in limbo till weekend so i can work on it again

 

[Garryese]

Yes, the key for the timing chains drive sprocket does shear off from time to time, however it usually results in a (or a few) bent valve(s). And, usually the valve train will not rotate, resulting in the no compression but this is pretty obvious when checking for bent valve stems or checking valve lash.

I suggest rather than checking the key itself, just check the cam timing at TDC. If the cam timing is off, then go through the work to check the drive sprocket key. If cam timing is correct, then a leak down test is in order. Actually, I would do the leak down test if the cam timing is off just so I would know if the head(s) have to come off before I put it all back together; Remember the cam sprockets have to be removed to get enough slack in the timing chains to replace the drive sprocket key. I would be pleasently shocked if the key is sheared off and there is no valve or/and piston damage.

BTW, if you are often working on engines, I recommend a leak down tester over a compression guage.

Keep us posted.

 

[STEVIE D]

SO YOU THINKING VALVE NOT CLOSING ALL THE WAY ON MAYBE EXHAUST SIDE , U SUGGEST DOING LEAK TEST ON VALVES TO SEE IF LEAKING DOWN , ALSO WOULD IT RUN ON ONE CYLINDER LIKE IF BACK WAS SEALING OFF AN GOOD WOULD IT STILL START , ALSO WHEN I GOT IT TO START THAT ONE TIME BY SPRAYING CARB CLEANER IN PLUG WHOLES OIL WAS BLOWING INTO HOSE FROM CRANKCASE TO BREATHER BOX ON BOTTOM , SO I TURNED IT OFF AN HAS NOT CRANKED SINCE THEN , BUT I FIND IT HARD TO BELIEVE KEYWAY IS SHEARED ALSO BUT I AM FRUSTRATED SO I AM JUST REACHING I GUESS INSTEAD OF STEPPIN BACK AN TAKING DEEP BREATH AN REEVAULATING , I HAVE NEVER NOT BEEN ABLE TO FIGURE ONE OUT , AN IT MAY BE SIMPLE , ALSO I DID HAVE ALIL DIRT FALL IN VALVE AREA ON FRONT CARB WHEN I PULLED OFF , BUT I VACUMMED IT OUT BEFORE I TURNED OVER , DO YOU THINK ALIL DIRT IN CYLINDER ARE VALVES CAUSING WHOLE ISSUE ,,, PS I APPRECIATE ALL INFO YOU HAVE GIVE ME SO FOR, IT IS 1.00PM ON 1/08/09 I WOULD LIKE TO TALK MORE ONLINE I HAVE EMAIL OF stevesmithoutdoor41@yahoo.com maybe i can get it running this weekend for my son ,,,,,,,,,,