banshee running on one cylinder ?

[450rJam]

my friend has a 2000 banshee, he was hitting a large double when it started to miss.
now its got problems.
its only running on one cylinder. we changed plugs,swiched the plug wires,checked-cleaned the carbs,checked the reeds, it all looks good............?
the compression is 125 psi. on running cylinder and
127 on dead one.
if we spray carb cleaner while running it smoothes out so It seems its a fuel problem.
Im not sure what to try next. he is going to tear the top end off this weekend but I dont think that is going to help.
oh at about 3/4 throttle it will kick in and run but fall when you let off gas.
any ideas ?

[GPracer2500]

Sounds like something came loose or is otherwise amiss in the carb of the offending cylinder. I'd remove that carb and and inspect it before tearing into the engine.

[450rJam]

he has pulled it off twice and cleaned everything.
he is flipping the reeds now from one side to the other.
everything he has done has same result exactly.
even when he swiched plug wires the same cylinder was dead.
maybe he should try trading carbs between cylinders

[GPracer2500]

Whoops--I see now in your original post you mentioned the carbs have been checked.

Hmmm...I don't know then. Could there be an obstruction somewhere in the exhaust of the bad cyclinder?? Just a stab in the dark...

[450rJam]

changed reeds and same result,
carbs are diff. so wednesday he is going to try changing the major components of the carbs.

[scruff_mcruff]

if the motor has compression and fuel, the only other thing is spark. id say either a coil is getting weak or the cdi box is going haywire. and check all the grounds to make sure there is good contact.

[450rJam]

when we cross the plug wires over (#1 to 2nd cylinder and #2 to first cylinder) it runs exactly the same. the same cylinder is still not running. at 3/4 throttle it kicks in.
is there a hose that could be collapsing ?
if we spray carb cleaner the cylinder will kick in but everytime we take the carb bowl off its full.
I think we have it narrowed down to the carb but its been off and cleaned 3 times.
shooting carb cleaner through all the passages,jets,etc.
I dont claim to be a mechanic but I can usually get a clue and this thing has got me baffled.
it has comp. for sure by tester/ it has spark outside cylinder and when we trade wires and new plugs/ the fuel is the 3rd requirement for explosion, I just cant find why or where its not getting through.

[osmond.mark]

If you say you spray carb cleaner on the base of the cyclinder and it seems to be better than I would think your base gasket may be bad? It seems as if your not getting fuel.

Is it like it all the time or only when hot or cold? Did he try it with the choke on? You say he cleaned the carbs and everything apeared fine?

[450rJam]

yes he cleaned carbs and it all looked ok
its not when we spray base its when we spray the back of carb with air filter off.
there has to be something in that carb.
they are not the exact same (choke hose)
he is going to try to take both carbs off and trade as many parts as possible I really think the carb is the only thing it could be
but not sure what part would cause this.
it is dead at low rpm but at about 3/4 throttle it kicks in.
there has to be something simple im just overlooking.
when it does kick in and run it runs as good as it ever has.
just under low rpm it runs on one cylinder

[humblesquirel21]

i have an idea

he might have already checked it but it sounds to mee liek his throtle cables are messed up if its kicking in at 3/4 throtle then maybe sometihng in the linage or cable system to pull that cylinder have gone bad or become miss aligneed

it might be the floats to

now trhat i think some more about it the floats could be nocked out o tune by a big jump id put money on the floats

[osmond.mark]

If it cuts in at 3/4 throttle is it cutting in like normal or is it just starting? At 3/4 it would probley be switching to the main jet. I no you said he checked the carbs but I would have a second look at the starter and pilet jet. It sounds like when it is switching to the main its working fine? Just a suggestion.

[450rJam]

I will try both tomarrow and let you know, thankx alot for the input. I was at a loss for ideas

[red2004 TRX450R]

on the side that does not work try loosing the 2 outer reed cage bolts so that it will suck in a little air! and try running it in a non dusty place.
sounds strange but i worked on mine. if that works then put the bolts back in and buy a new carb!!!!!

[450rJam]

KICK @SS
she is back and now its raining outside.
it was one of the smaller jets, he had not taken them out but just spayed cleaner in them.
he took them out (took a really small screwdriver) and cleaned them good then when he put it all back she fired up and started running like a champ.
osmond.mark you did it man and I thank you
thanks to all of you who helped with info.
this site is great and I knew someone here would help me out.
thankx again, we may go ridding/mudding this weekend anyway.

[osmond.mark]

No problem man, glad to help a friend out.