no spark on top two cylinders

[sprouticus]

Re: not firing on one cylinder

Re: not firing on one cylinder

i'm pretty sure I got those, but I'll go take it off and have another look.


thanx for the tip.

 

[sprouticus]

Re: not firing on one cylinder

Re: not firing on one cylinder

ok, I took the carb apart once more. I put a single strand of wire through every oriface I could see. every jet was sufficiently clog free, I am quite sure. re-assembled everything.........................same problem. I even changed spark plugs just to be sure.


so now I have a question. I am assuming that my motor is not running correctly because when I pull the plug wire off the top left cylinder (when behind the boat), I hear no change in the motor. when I pull the plug wire off of any other plug, there is a noticable change, and it immediatly picks back up as soon as I even bring the plug wire close to the plug. this does not happen with the top left plug. I believe my assumption to be correct, that if I bother to bring my boat to the lake, I will have no power, and risk doing more damage to my boat as there will be no lubrication in the top left cylinder.



so...........to sum up my situation,

I believe spark to be fine, as there are one inch long lightning bolts going from the spark plug wire to my pliers when I pull the wire off, and spark is nice when tested on the plug.

I believe compression is fine. although it hasn't been tested in a few weeks, the motor hasn't been out of the driveway in that time, and there is no reason to expect different numbers (105 on the "bad" cylinder...between 103 and 110 on the rest)

I believe the carb is clean...........I've taken it apart twice now, every brass tube in there has had a wire strand passed through it, i've used compressed air at work, and i've personally used my lips to blow thorugh them.

I am running a carb cleaner in my gas tank, and I have used 2 cans of the aeorsol stuff.

Gas has to be my issue, but only on the top left cylinder. and I believe all jets are clear inside the carb.

I'm stumped now.

 

[rupertmja]

Re: no spark on top two cylinders

You first said you had a problem with the cowling. Sometimes, if a plug lead is disconnected and the engine runs, it can damage a coil, one that might still work intermittently. Also, any shorts on the plug leads? New plugs?

Is the petol pump working OK? Undo the carb drain plugs and see if petrol comes out. Or, is the choke operating properly / sticking on? Linkages all in unison etc?

 

[CharlieB]

Re: no spark on top two cylinders

My question,

When you remove the float bowl drain screw, does gas come out?

How much?

As fuel is used the float lowers, pulling open the needle off of its seat, thus allowing more fuel to enter.

A stuck needle or plugged fuel inlet will not allow fuel into the carb giving you the symtoms you describe.

 

[iwombat]

Re: no spark on top two cylinders

You might try pumping the bulb REALLY HARD when it's running. That'll force fuel past the float. If that works, you've got a stuck float.

 

[sprouticus]

Re: no spark on top two cylinders

plugs are new, and i've even changed them.spark is not an issue.

can't imagine it's a short as I can get a spark off the boot to ground.

when I removed the carb both times, it was full of gas, and the other cylinder that shares the carb is working fine. approx 1/5 cup of gas.

I don't know why a choke would effect one cylinder.


I will try that idea of priming the bulb..sounds like a good one.


thanx for the ideas.


this question makes me sound like an idiot.but I have to ask anyway............air can only come in through the carb right??? there is no other airway???

and is there any safe way of checking for gas in that cylinder???

maybe pulling the plug and starting it, and seeing if a mist comes out the spark plug hole??? obviously, don't have the spark plugs anywhere near that hole, but i'm starting to think it's getting gas now too.