1976 340 TNT

Hey I am a 1976 340 tnt. It runs for about 30 minutes and if you let off the throttle it'll die out and quit. It'll start right back up and if you hold wide open it sounds like blaahhh no power what so ever. I've put new points and condensors in. new coils, set the float, cleaned the carb, checked the fuel pump and cleaned it, new fuel filter. Im out of ideas. Anyone else have an idea what it is thanks.

curtludwig

You've definately got spark on both sides? Definately got 12v at both coils?
I had that same sled and put points and condensors into it twice and never got it to run right. I dunno what I was doing wrong but I just didn't have the skills required on that one.

When it dies out pull the plugs, what color are they? Are they covered with gas? Is one wet with gas and the other dry?

__________________
Raising sleds from the dead in north central MA.
'70 Ski-Doo Olympique 12/3 - The Yellow Bullet
'71 Arctic Cat Panther 303 - Wankle Panther
'80 Polaris TX-L - Hers
'81 Arctic Cat El Tigre 5000


www.deadsledwrenchers.net

1976 340 TNT

I pulled them out when it died they seemed more blackish. When your sitting on it the right one seems a bit wetter. I thaught crank seal i've sprayed either in the seal and no change. Yes both plugs have tons of spark and coils have 12 volts going to each checked that all.

curtludwig

Spraying ether is not the end all be all for crank seal testing, especially since you can't really test the mag side. Another test is to pull a vacuum at the impulse port on the case. I've never had much luck doing that but I think my MityVac just can't pull enough vac at any one time.

I don't think the problem is your carb, I've never seen a carb that would work fine for 30 minutes and then quit. Have you replaced the gas lines and the impulse line from the engine to the fuel pump? Have you cleaned/rebuilt the fuel pump?
I'm sort of grasping at straws here, my TX-L is doing something similar.

Ohh, heres another idea. On my TNT the plastic T for the primer line had cracked and was leaking. On that sled when it sat for awhile the gas would drain out of the lines and it would be hard to start. I wonder if maybe yours gets warm and a crack opens and it starts sucking air... If you haven't done it recently new lines and that T wouldn't be a bad idea. Another one would be the pickup in the tank, maybe its covered with crud. You might be able to see it if you shine a flashlight in there. You can pull it out with a hooked wire to get a look at it.

__________________
Raising sleds from the dead in north central MA.
'70 Ski-Doo Olympique 12/3 - The Yellow Bullet
'71 Arctic Cat Panther 303 - Wankle Panther
'80 Polaris TX-L - Hers
'81 Arctic Cat El Tigre 5000


www.deadsledwrenchers.net

1976 340 TNT

I have put a new vacume line on it from the engine to the fuel pump. I am not sure if the lines are suppost to be bigger or smaller? As most these lines are smaller. I also notice that the line in the tank doesn't have a check valve on the end of it. Could this be throwing me off also??? I dont know how it'd make a difference though. Let me know thanks.

1976 340 TNT

I haven't changed the lines yet waiting on a reply to say if they should be thicker or smaller lines. Also does the check valve make a difference? The line the goes to the tank and fuel filterr are all new. the vacume line is new. The lines off the primer are new. When it runs it runs excellent. Im also having a hard time with getting it to just idel. Always seems to drop below 2 grand and shut off. Deffintley heat related I am out of ideas anyone else have any??

GP396

Since the plugs are not reading lean I wouldn't think it's a cranks seal issue. If this is the sled that may have the Mikuni carb conversion on it, it may just not be jetted correctly (way rich) and you're just fouling plugs if they are black as you say. Another thing to check, since this sounds like a conversion, is that the choke cable is properly seating in the carb. If not, it's letting extra fuel by, which is fine when the engine is cold or you're on the throttle.

Pull the cable out of the top of the carb. Make sure the cable moves freely in the sheath. There will be a plunger on the end, make sure it's there and not cracked or brittle. Make sure there is nothing where it seats in the carb that is binding it up. I've seen them rusted in pretty good. When the choke is on it's up, letting extra fuel in. When off it's down blocking that fuel flow. If it's not seating down all the way when off, you'll get what you describe.

No gaurantee it's the issue, but worth a check.

1976 340 TNT

How do you know if the jetting is right where do I start with that. Is does have the Mikuni carb and seems to be
running way to rich.

1976 340 TNT

Also I have bin told that my setting in the seat of the carb that little piece where the needle goes and there is settings that it was set 1 setting lean. I have never changed it and was told not to but could this maybe be part of the problem?