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Discussion Starter #1
I work for a very small ski hill and am a diesel mechanic by trade, so I'm not great with small engines. I primarily don't operate the sleds, so getting told what happened when things occur is slim at best.

This started last week when the sled fouled a set of plugs out on the trail. The operator swapped plugs and said the machine ran fine coming back. These sleds tow a 600 drag groomer and are typically ran in the low end. Saturday the sled was taken and brought back for no power. Here begins my adventure. I test rode and noticed it was very slow to rev in neutral and in gear, could barely get the sled to do 15mph and would stall at idle. Pulled in the shop and checked the plugs, both fouled. Did compression test while plugs were out 130psi/135psi pto/mag. New plugs installed, idled better but still slow to rev and no top end. Noticed oil leaking from exhaust after this test run. Checked choke plungers, both moved freely and pulled out smoothly. Checked oil pump and it is right on the mark. Pulled bolt from bottom of crankcase and drained a lot fluid, wasn't able to collect to measure quantity. Removed carb bowls to check needle, cleaned and reassembled. New plugs, test run mile and a half, ran better, won't do above 30mph. Plugs were dry this time, slightest of brown, almost no smoke when idling after run.

I have an identical machine I swapped the carbs off of it this morning. Machine #2 is perfect runner, and still runs great with the sick sleds carbs on it. #1 is still slow to rev but this time I noticed it had a fuel mist coming out from the silencer side of the carb when the throttle is applied. These engines don't have reed valves, and when I spin it over by the recoil, I can watch the piston and connecting rods unobstructed. Pistons feel tight, tops are very black but dry. Just for grins I swapped coils, no change in performance either machine.

I'm at a loss on where to go next. I've ran down the entire shop manual troubleshooting and I'm out of options. I have little experience with these types of engines and the dealership is 80 miles away, so the company doesn't want me to waste most of the day dragging it down there.
 

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Does the machine have a fuel filter on it?

This really sounds like the diaphragm in the fuel pump has ruptured. Pull the pulse line off (hose going from the crankcase to the fuel pump) and check for fluids. It should be dry. It is wet, take the fuel pump off and either replace or rebuild. I'd take it apart first, specially if there is no fuel filter. Little bit of debris can cause a headache in the fuel pump.

Other than that, maybe check that the choke plunger is getting all the way to the bottom and plugging the hole. Choke is an enricher and just allows additional fuel through. If it is slightly open, it will bog and not have power.

Might also check the screen on the end of the fuel line inside the tank. Make sure it didn't fall off or get plugged. You can usually fish it out with a coat hanger, so you don't have to drain the tank and pull it apart.
 

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Discussion Starter #3 (Edited)
There is an inline fuel filter, it was checked and found clean. I will pull the impulse line when I get out to my shop. I have the chokes adjusted so the gauge goes all the way in per the tech manual. The choke on our good running sled I can't get the gauge to go under the choke plunger, but that machine runs too well to justify messing with it. I'll adjust the plungers back down if the impulse line is dry. Thanks for the help, I can't tell you how much it's appreciated.

Edit: Pulled impulse line and it's soaked, ordering repair kit now. Will update once it arrives and is installed. Thanks again!
 

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My method for adjusting the chokes is a bit different. I adjust them so, with the choke off, the plunger hits bottom just as the threads match up. I found that this seems to work perfectly every time.
 

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Discussion Starter #5 (Edited)
Dennis Kirk didn't have the correct rebuild kit so a brand new fuel pump is installed, still not running great but definitely better. Still slow rev until about 3k rpm, higher than that it runs great. Did a 2 mile test run, just a couple drops fluid came out when I pulled the drain plugs. No more oil on the exhaust manifold either. Still getting a fine mist of fuel out of the carbs when the throttle is cracked in lower rpm's.

I am sure the fuel pump was a problem, but just one of the problems. I still have the carbs from my good running sled on this one so I'm hesitant to mess with them. Smokes like hell at lower rpm when it's acting like it's loading up. Get above 3k and the smoke clears up, plenty of power and snappy.

Could this be getting too much oil injected at lower rpm? Smokes like hell with engine hot or cold. I'm lost what to look at next.
 

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Compression?

I just rebuilt a motor and bone-headed after honing the cylinders I forgot to re-bevel the ports. One of the rings caught on an edge and busted. Frustrating...
 

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Discussion Starter #7
130psi PTO, 135psi MAG
 

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Discussion Starter #8
I'm really starting to hate this sled. Had a chance to work on it again this morning. Adjusted secondary clutch so belt rides at very top, isn't as boggy as before but will barely do 25mph on flat ground. When I fired it up and noticed fuel drip onto the exhaust manifold from under the shroud. Drip had stopped when I checked immediately after run, but started after idling for about a minute. Checked compression and had 120psi - pto and 115psi - mag. Engine was still hot and I didn't put any oil in the cylinders this time.

Just ordered a top end kit and will hopefully have time to tear it down next week.
 

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Swt has high/low gearing. Are you sure you’re not on low?
 

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Discussion Starter #10
We've ran the sleds in both gears. The good one easily does 30mph in 1st, the sick one won't do above 20mph.
 
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