1993 Polaris Trailboss 350 not starting

[hawlinbass]

Hello All,

I am in need of a little professional help. I have a 1993 350l. The other day It was running great. I took it for a ride around the house and pulled back into the garage. This is when it all happened. It was idling fine for a few min when all of a sudden it back fired (sounded like a shot gun going off) I could not get it started. I left it for several days and tried to start again with no luck. The only way I could get it to even pop was to spray starting fluid in the carb. I figured it was a carb issue so I rebuilt it again with no luck. Tore top of engine down to discover a hair line crack in the bottom of the piston skirt. Rebuilt top end with a wiseco piston. Had it bored and matched to the new piston .5mm over. I have great compression 125psi. However the engine will still not start same simptoms. Is it possible that when the engine back fired it took out a crank seal? What else could be the issue. I have good spark, fuel, and compression.

Thank you

[DirtDemon]

Check the flywheel key, if it has sheared off, you can still have spark, but not at the right time. I suppose that the backfire blowing a crank seal out is feasable, it wouldn't hurt to check them.

[hawlinbass]

I removed the flywheel to replace the seal and all looked great, no issues seen. I am waiting on a clutch puller so I can remove the clutch and replace the seal on that side. Can anything else cause this issue?

Thanks

[DirtDemon]

It really sounds like a timing issue, but I think that the crank seals would be a good place to start, since they aren't too expensive. I had alot of hard starting that was cured when I replaced the crank seals. If the motor is sucking air in through the crank seals, it won't draw fuel in as well. However it should still show some life when you use starting fluid. Try pulling the plug and spray the starting fluid directly into the cylinder. What does the plug look like? Is it really oily? Another thought, if it has been sitting for a while, some gummed up fuel could have plugged up the carb while you were riding.

[hawlinbass]

I have been able to get it to sputter with starting fluid, the carb was completely rebuilt after this first started. Thats what I originally thought it was. When I pulled the flywheel and stator off, it all looked good, I didnt see where anything had moved or was loose. I am currently waiting on a seal and gasket kit to come in, I plan on replacing all crank seals (besides inner dont want to split cases) and the water pump seals and gaskets while I am in it. Please if anyone has any other ideas let me know. I will post the final outcome.

[DirtDemon]

New crank seals are a good idea at any time since it can't hurt to replace them. If you find the problem before you install the new seals, then you will have them if you ever need them. I would test your igniton components ie; stator, pickup, cdi, coil, spark plug and make sure you have a good connection between the coil wire and the plug boot. You may have spark, but it may not be strong enough. Do you have a manual? It would have info needed to do the tests on your ignition components. If you can get it to run, check the timing. Maybe even try adjusting the timing a little just to see if it helpls get it started.

[handyhiker]

Just asking, did you try a new spark plug?

[ATVmechanic]

Just asking, did you try a new spark plug?

Yes, it sounds like ignition to me. Maybe as simple as a new plug, wire, or coil.

[hawlinbass]

Thanks guys for all the responses. I haven't been able to get back to working on the bike. My new seals came in on Friday. I plan on working on it Tuesday. I will try the seals as I have already pulled old seals. If that doesn't work I will try the other things you all have suggested.

Thank you!

[DirtDemon]

Good luck man, let us know how it goes.

[hawlinbass]

Ok, The wheeler is running like a top. Once I removed the clutch, I found the crank seal blown out. I bought a bottom end seal and gasket set and replaced all. Now the bad news, while doing so I broke the temp sensor on the head. Does anyone know where I can get one of these and is this the sensor that turns on the fan for the radiator? I ran the engine for about 5 minutes but the fan never turned on so I shut it off. I do not want to burn the engine up after all the work I have done. What is the temp the engine should run at when the fan turns on?

[Stoopidbot1]

If that's the only thing the sensor does you could bypass it and just hard wire the fan so it run as long as the atv is on

[hawlinbass]

I thought about that but would like to find out if that is the sensor for the over temp light or fan or both first. Thanks

[handyhiker]

The one in the radiator should be for the fan. Unplug and jump the wires and see if the fan comes on. This way you will know for sure.

[hawlinbass]

Thanks to all, my machine is up and running. I have had it out several times in the last few days. Cant wait to burn through the tank of double oil and its broke in. So far the thing runs flawlessly.

[DirtDemon]

Great, now all you need to do is ride the hell out of that thing, it helps to pretend you stole it!! After it is properly broken in ofcourse.