who knows something about 2 stroke engines?

[Guest bearcat123]

Check fuel pump diaphram. If the diaphram splits, it will flood the cylinder that is suppling the vacuum to the fuel pump.

[hipshot]

hate to disagree but it takes more voltage for a spark to jump a given distance under compression than at atmospheric pressure. a plug can fire out side a cylinder and not fire under compression this is due to the fact that as you compress air, the molecules are forced closer together and the resistance between the electrodes increases.that is why racing engines use high voltage ignition systems in access often times of 40,000 volts or more.an orange spark, which is a very weak spark will usually not jump a spark plug gap at all under compression.this is one of the reasons the new cars start so much easier in the winter than they once did.they have a much higher voltage output on the secondary side of the coil than the older cars to fire the ultra lean mixtures being used now.

i have to agree with this,as i have seen it many times.

never worked on a "snowmobile, as there are none down here.but i would strongly suggest changing plugs AND fuel!

just jt

[bisquit]

Might as well run the gammit. Change the plugs and fuel. Check the air filter to make sure its clean. Check the gap between the flywheel and magneto. Make sure theres no rust on the flywheel. Do all these simple things first to eliminate any obvious reasons that it wont fire. I dont know about the exhaust having a whole lot to do with it. I've seen lawn mowers with a straight pipe on em an no muffler to create any back pressure.Hopefully you can get her up and running before ya actually need it..............Don

[yamastar4]

You have got some very good advice in here, but it sounds like the reed valves to me. There might be some trash in them or the reed plate might be warped. If its warped you might can smooth it out on a face plate with fine emery clouth.. That happened to me on a 50HP johnson outboard, and I was able to fix it.

[pegscraper]

I finally got a chance to do a compression check on my sled yesterday. I'm getting 130 psi on both cylinders. So that's not it. On to something else.

[Snarley Bill]

I finally got a chance to do a compression check on my sled yesterday. I'm getting 130 psi on both cylinders. So that's not it. On to something else.

it's not the cylinder compression you need to worry about it is the crankcase compression.crank case compression is very critical in a two stroke engine.the main causes of low crankcase compression are,warped reed valves,bad crankshaft seals,to much skirt clearance on the piston.leaking rotary valves if it has them.if crankcase compression is even slightly low on a two cycle it will not run.one sign of low crankcase compression is backfiring in the crankcase.if you have reed valves start by replacing them.this is the most common problem on twocycle engines.hold the reed plate up two a light and see if you can see any light around the edges.

[Redneck]

The problem is that two strokers won't run without the exhaust pipe on them. The expansion chamber in the pipe somehow greatly increases exhaust flow, which is really needed when the exhaust and intake stroke are the same thing and the engine won't generate its own exhaust flow. Without the expansion chamber keeping the exhaust flow up they won't run.

 

If exhaust heat distorting and breaking a cylinder is an issue on a sled, I wonder why it isn't on our bikes. What's the difference?

A two stroke engine will run without exhaust it won't make peek power but it will run. The expansion chamber does not increase exhaust flow it restricts flow like every other exhaust system. Its not the heat distorting and breaking the cylinder its the engine moving and the exhaust stationary that causes the the problem. The difference in the sled and our bikes is night and day. On a 2 stroke engine the exhaust mounts to the cylinder when you distort a cylinder it changes piston clearance and scores the piston and breaks the cylinder. Our bikes are 4 stroke the exhaust mounts to the head the head is mounted to a very solid block so stress on the head has little or no effect on the cylinder.