more engine troubles.

[broken_line]

the other day i was farting around and loaded the sled onto the trailer ran perfect then, go to another spot take it off let it idle for a little bit. i go to take off and theres nothing there, it only would go about 7mph maby 10 downhill. so far i have cleaned the valves and where they go spotless. got brandnew spark plugs, different coil and nothing has cured it. it almost seems that it runs on one cylinder when i open it up heres a video of the valves with the covers off.

[Macgyver55]

It looks like the valve that is closest to the camera is not moving as much as the other.

Have you done a compression test since this started?

Also check the VES valves for free and complete movement too. If one is stuck open it will run poorly too.

These valves need to be removed and cleaned every 1200 to 1500 miles.

[Dave S]

You beat me to it MacGyver.

[broken_line]

both valves move freely, havent checked the compression.

[Pinusbanksiana]

What you are describing is not a simple dirty power valve problem. I would look at in this order, clutching and jetting.

[broken_line]

im leaning twards something wrong with the carbs. because the pto side cylinder runs at all times the starter side cylinder only seems to run at idle. but when i pull the plugs after a 100 foot ride the pto side is nice and brown, warm and the starter side is like brand new, not as warm and sopping wet. there is a GREAT spark as it jumped a good 2.5" to my hand when checking it.. im leaning twards reeds or some carb work in order..

[311Hemi]

I would check compression first, and then probably look at the clutch if you know you have good spark. You mentioned you have good spark and a wet plug on that other side, so it sounds like you have fuel and spark there.

Did let the engine idle down before shutting it off when you check the plugs? I know when checking your jetting you usually shut the engine down while holding half throttle or full throttle after a short ride so you get the proper reading at those throttle positions.

[Surface Tension]

I hate seeing you have this much trouble.

Everything that is described would have me thinking low compression on the right side. BUT I thought I read you cleaned the carbs. Did you use something to clean the main jet that would have enlarged it?

If so that get another set of jets.

Do the compression test first.

[broken_line]

i dont see anything with the bore scope on the the top end.. everything looks fine.. my compression tester is also.. broke... im going to try switching the carbs around and see if that does it.. i used starting fluid and compressed air, it ran PERFECT till i put it on the trailer and took it off it decided to act up.. both cylinders had 92.5 psi before this happened, with lots of power and a great idle..

[broken_line]

i switched the carbs and the problem followed. not its on the pto side. im guessing its carbs or just my really bad luck. i will disasasmble them tomarrow. this time the pto side was wet and smokey, pull start side was nice and dry and warm. possible stuck float? i also noticed when i opened the throttle that when the needle on the throttle plate lifed fuel seeped out at a pretty good rate.

[Macgyver55]

If the problem followed the carb then thats where you need to go. Pull them off and clean both and check float height. Could be a bad needle and seat or just a piece of debris that got in there. Make sure to get them back on the same side they came off as sometimes they use a bigger jet on the PTO side to compensate for the extra load on that side. Its important to sync them so they are open the same amount at idle, and that they open at precisely the same time when the throttle is squeezed.

I still believe that 92 psi sounds low for that motor (or most any 2 stroke) I'd question the gauge and double check it with another.

[broken_line]

there are 320 jets on both sides. does that sound about right?

[Macgyver55]

Probably are ok.

Not all motors use a bigger jet on the PTO side, only some. Its just something to be aware of in case they do, so you dont mix them up.

[Pinusbanksiana]

jetting is fine for that model. Now I would suspect the bad carb float. Things are expensive though. Not much can go wrong with these carbs, but a faulty float will flood the cylinder and prevent the sled from running. Switch the floats and see if the problem follows.

[broken_line]

well the 4 hour diagnose started on the wrong side of the motor and it turned out to be my fault for not tightening this little bugger enough.. can i use blue loctite on it?

i wonder what the jet size was with this sitting at the bottom of the bowl? haha, thanks for the help!

[broken_line]

also rigged a compression tester off of a air compressor gauge.. got 115 psi dead even both cylinders

[hydro]

Well, that would sure do it, and its an easy fix! We all do stuff like that now and then and finding those little problems helps us to be better at doing it the next time. Swapping the carbs to see if the problem followed was very good troubleshooting logic, and it is good to see that you found the problem.

By the end of the season you will know enough about the intricacies of that Polaris engine to be an expert on this forum!

[Surface Tension]

"im leaning twards something wrong with the carbs. because the pto side cylinder runs at all times the starter side cylinder only seems to run at idle."

Then contrary to your statement, the right cylinder was never firing. If the float drop is incorrect, or the inlet valve isn't shutting of the fuel the cylinder would flood immediately and not fire at idle.

Good: Then that would lead me to think the inlet valve acquired a piece of dirt and its stuck there and letting gas run continuously raising the fuel level in the bowl.

Not good: That could be the float drop is incorrect, leaking inlet valve, or enlarged jet.

Edit: I was going to ask if your main jet fell out. Just snug it up.

[Macgyver55]

also rigged a compression tester off of a air compressor gauge.. got 115 psi dead even both cylinders

Ahh, that sounds much better! Not many will run well if at all below 100psi.

Glad to hear it was an easy no cost (other than time) fix in the end.

Dont use locktite or any thing on the threads. Too much chance of getting into the jet itself and causing a real problem. Just make sure they are tight.