76 cyclone 340 wont start

jasoniowa · Post by **jasoniowa** » Mon Oct 20, 2008 9:44 am

I just bought a 76 cyclone 340 my first snowmobile. My son and I have cleaned the carb, fuel pump, and gas tank. Put new spark plugs in and cannot get this thing to fire. I have hooked the plugs up outside touching the engine to make sure I have spark and I do. They are wet so I know I am getting fuel. We have even put fuel in the spark plug holes and cannot get it to fire. I am not sure what to do at this point. Any suggestions we be great.

Thanks

JDT · Post by **JDT** » Mon Oct 20, 2008 10:07 am

You have fuel and you have spark. The third thing you have to have is compression. Have you tested that? Without enough compression it will never fire.

Borrow a compression tester/gauge and test each side. They should read fairly close to being the same(even) and at least 115 lbs psi maybe as high as 165.
If they are not even or one, or both test low, you will need to fix that problem first.

Asuming compression is ok then you can go on to the next step below. But never assume compession is ok. Test it first.

-------

The plugs may be too wet. I dribble of gas in the plug hole is enough to make it pop.

With the key off and the plugs out pull the rope several times to remove excess fuel in the cylinders.

Then try a set of clean dry plugs and see what happens.

jasoniowa · Post by **jasoniowa** » Mon Oct 20, 2008 10:32 am

I will have to check compression, I will need to find a gauge.

Also, I noticed there is a black wire coming from the CDI box that is not hooked to anything and a wire coming from the key switch not hooked to anything. I found a wiring diagram on jdsleds.com , it appears that those to wires hook together, but even after that it still would not start.

One other question. There is a red kill switch, should that be in or out for this to start?

JDT · Post by **JDT** » Mon Oct 20, 2008 7:13 pm

The black wire on the CDI is the kill wire. It connects to ground when the key is turned off or the kill switch is pushed in and shuts off the spark.

luvzvintage · Post by **luvzvintage** » Mon Mar 10, 2014 10:07 pm

well, i redid the ohms checks and all checked out excellent! I removed the main harness receptacle thats attached to the engine with 2 small screws and found one black wire blade backed out a little. I popped it back in and just for the heck of it checked for spark...i got spark back! What sense would this make, a blade/wire backed out of its place in a plastic holder kills my spark!?

I put the plugs back in expecting the sled to start rt up and it wont fire. Best it does is pop back thru the carb. seems i've got excess fuel as applying choke increases carb back-pop. And i've got raw fuel leaking out of the exhaust manifold/muffler joint. Pouring fuel into the cylinders also didn't cause the engine to fire. i took the plugs out and pulled the engine over more than a dozen times to clear excess fuel, getting only a brief puff out of one plug hole on the first pull. Repeated checks for spark are good adn i tried multiple fresh/dry plugs to no avail! This thing started 2-3 pull every time before the loss-of-spark adventure!! My compression is good at 130 and 125.

Is my crankcase now badly flooded with fuel because i pulled it over so often when i had no spark??

luvzvintage · Post by **luvzvintage** » Mon Mar 10, 2014 11:37 pm

i came across alot of good info under "76 cyclone still won't start" I''ll try those suggestions.

JDT · Post by **JDT** » Tue Mar 11, 2014 7:49 pm

If your crankcase is full of fuel it will not start.

Remove plugs, turn off ignition, unhook gas line and pull it over a couple of hundred times.