399cc olympic?

[littleford68]

hi i have a 399cc olympic motor out of a 1970 skidoo and i cant find where the fuel line from the top of the carb goes, does anyone know? it has a tilson carb on it

[6X6]

Hi, that would be your fuel return line, should run back to the tank.

[littleford68]

that's what i thought but someone told me different, i have the line run like that now and it runs about 20 feet then shuts off, i cant figure it out, i rebuilt the carb an same thing happens

[countrycummins99]

thats not what richs book said sould have a pulse line somewhere

[6X6]

Some have a pulse line, some have a port in the flange that gets pressure thru the block at the mounting flange. I am not sure which setup was used on that motor. If you unbolt the carb (be careful of gasket) you would see a small port on the engine just below the intake opening, and a port that lines up with it on the carb's mounting flange. If the gasket is just the slightest bit damaged or the port is partly/fully plugged, you'll have issues like you described (If you can get a replacement/make one, replace that gasket, no gasket sealer, especially around the port, you'll plug it). If you have a port in one side, but not the other, then it's the wrong carburetor, but I doubt it, if it starts up and runs more than a couple seconds, it's pumping at least some fuel. (If you're priming it then it's just running off the prime and stalling)

*edit* Tillotson carbs can be finicky if the gaskets are not 100%. If it's been sitting for the past 30 years, I would rebuild it, as long as you feel comfortable doing so, before it drives you up the wall. Rebuild kits are not expensive, just make sure it's for your model carb (# should be stamped on the top edge of the mounting flange)

[littleford68]

i just rebuilt it an im still having the issue im going to have to take the carb off and look for that hole but it does have all new gaskets.

[6X6]

If you installed the intake manifold gasked backwards (Top to bottom) and the hole in the gasket is not lined up with the hole in the block/carb flange, that right there would be it. (Also if you used Gasket sealer and it got into the hole)

[littleford68]

i don't remember a hole and i didn't use gasket sealer ill have to rip it apart and see

[6X6]

If not then you have to have a pulse line, if just not in the gasket, then wrong one, but you can cut a hole with a leather punch or similar, just be careful not to rip it, and check alignment twice (Sorry if I'm covering stuff your already aware of, just don't want to leave any info out )

[littleford68]

haha no its fine im just trying to get a second or third opinion because it giving me trouble, next time i get a chance to mess with it ill look for that hole but i don't think it has one so i might have to make one if it needs it, because when i got it, it had sat and did this same thing then i rebuilt the carb an still no luck but, the people before me could have done the same thing with replacing the gasket with one with out a hole in it i dont know well figure her out

[06chops]

i had the same snowmobile and it had a pulse line on the carb and went to the motor if you kneed help tell shawn to call me and i can run up to his house and help you out Rich

[littleford68]

haha i cant find the nipple where it would go do you know where i should look on the motor? thanks for the help

[ericood]

Did you get the problem sorted out? 1970 399's did not have a pulse line. If it will idle and run at low power you have fuel supply problems. Common troubles are the gasket that's on the screw on filter, the filter it's self and so on. those carbs can be pretty fussy you have heard. If it does run for just a short burst the high speed screw may need be opened up some. I have also found that if you run the fuel level a little higher they run better. I have 2 of them sitting on the floor in may basement one was in a attex I have. If you need parts let me know.

[littleford68]

i have been at school an haven't had time to look yet unfortunately but this week end i would like to tear in to it a little and ill let u guys know what i find, does any one know carb adjustments for it?