Anybody a small engines guru?

MinnesotaMulisha

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I recently bought a 1985 Arctic Cat Panther with a two cylinder, fan cooled engine.

It starts rather easily, usually 2 or 3 pulls. But, when under throttle, whether wide open or halh cocked, she sputters a lot.

I've went through and cleaned the carbs, twice. Once after removing the gas tank and cleaning the crap out of it. I adjusted the choke so that there's just a slight amount of slop before you pull the lever.

The pick up line and check Valve are in good shape. Looks like they were replaced not too long ago.

I've put a new coil, plug wires, caps and plugs on it.

The fuel filter is new.

I've measured compression at wide open throttle, and measured 75 psi. I know that's on the low side, but I don't think that's the cause. I could be wrong.

Not sure where to go from here.

Any ideas?

Thanks.
 

MotorOilMcCall

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I'm with Hilton... these engines are notorious for air leaks. Take a can of brake cleaner or starting fluid and spray it around each of the carb boots (away from the air cleaner). If the engine suddenly rev's up, you found your leak.

Could be base gaskets too.
 

dang472

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When you cleaned the carb, did you pull the emulsion tubes out? The brass tube the main jet screws into. Also a bad stator will cause sputtering under load.
 

Waorani

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Never had much luck cleaning/rebuilding small engine carbs. Most can be had for cheap and easier to just replace. May not be the case for a 35yr old snow machine though.
 

Sieg

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With the crap ethanol fuel now days, I'd make sure the carb bleed circuits, pilot, and main jets are unrestricted. The small orifices in pilot jets are easily clogged by ethanol fuel that's sat. In modern 4-strokes due to really small orifices it's sometimes easier to just replace them.
 

MinnesotaMulisha

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crank seals dry out and crack sucking air past them. an old 340 arctic cat that I had did the same thing.
I'm leaning this way. Clutch side cylinder spark plug is pretty damned clean. Looks new.

Other side is running rich.

I tried spraying some starter fluid near the crank seal and it seemed to idle just a bit higher.
 

MinnesotaMulisha

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I'm about ready to pull the engine, out new crank seals and pistons in both side and just be done with it.

So much for a $400 sled lol
 
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knuckleballz

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Things I would look at, make sure float height is correct because that will effect fuel pressure, put a level on the carburetor body to make sure it is level. That can screw with float. Could there be crap in the fuel tank obstructing fuel deliver? I've taken a gas tank off a good running motorcycle or generator to test a problem engine. Numbered drill bits work great for idle and main jet cleaning. Torch tip cleaners can work also but be careful, they will remove brass if you get aggressive. Air obstruction feeding carburetors?
 

knuckleballz

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If it has the oil injection pump make sure that is adjusted correctly. Could be to lean or to rich. The cable adjuster can loosen up from vibration and someone might have changed the adjustment.
 

knuckleballz

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I have had problems with new champion spark plugs in sleds and low compression engines that would cause the same problem you are having. I would use NGK plugs.
 
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Spowell0217

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I recently bought a 1985 Arctic Cat Panther with a two cylinder, fan cooled engine.

It starts rather easily, usually 2 or 3 pulls. But, when under throttle, whether wide open or halh cocked, she sputters a lot.

I've went through and cleaned the carbs, twice. Once after removing the gas tank and cleaning the crap out of it. I adjusted the choke so that there's just a slight amount of slop before you pull the lever.

The pick up line and check Valve are in good shape. Looks like they were replaced not too long ago.

I've put a new coil, plug wires, caps and plugs on it.

The fuel filter is new.

I've measured compression at wide open throttle, and measured 75 psi. I know that's on the low side, but I don't think that's the cause. I could be wrong.

Not sure where to go from here.

Any ideas?

Thanks.
Those mikuni carbs are particularly sensitive to ethanol. When they were made, ethanol was not used in gas, which breaks down the diaphragm and gaskets overtime. Don't get me wrong, those carbs are great!! But for a lot of years, the rebuild kits were were OEM material, which would just cause the same problem all over again. Rebuild the carbs.
 
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MinnesotaMulisha

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Those mikuni carbs are particularly sensitive to ethanol. When they were made, ethanol was not used in gas, which breaks down the diaphragm and gaskets overtime. Don't get me wrong, those carbs are great!! But for a lot of years, the rebuild kits were were OEM material, which would just cause the same problem all over again. Rebuild the carbs.
The carb doesn't have a diaphragm, but I have rebuilt the carb twice. Gaskets are in good shape. The needle and seat is good and the jet looks like it's free of debris. I don't have a # drill bit set to check the size.
 
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Cy Rosenlund

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Sounds like something you would find at Hay Days! Another thing that hasnt been mentioned, is your needle getting worn out?
 

MinnesotaMulisha

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Sounds like something you would find at Hay Days! Another thing that hasnt been mentioned, is your needle getting worn out?
It is, but at half the price! 😂😂

Needle seems to be good. I out a new top end in it and crank shaft seals, and still runs like garbage.

Tried a bunch of different settings as far as moving the c clip on the needle and lost the throttle plate in the process.

Service manual showed up yesterday, but now I'm on the road until the 10th so now she sits again.
 
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Cy Rosenlund

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One time we had a sled in that would idle fine and then plug up after you hit the throtle. The carbs got cleaned and adjusted several times before I realised the pipe was shifted and most of the exhaust was coming back into the engine bay. The intake would then grab the dirty air and starve of oxygen. Im not saying this is the case with yours, but you run into some wierd stuff ever once in a while!