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Discussion Starter #1
Need some help here please. I have a 2005 King Cat with carbs that quits running on the PTO cylinder when it's gets warm. I've searched the forum, and have tried everything I could find without success. I'm trying not to rebuild the engine, but I think that's next unless someone can think of something I've missed. Here's what I have done so far.
1. New Plugs, same coil. Both plugs have good spark. When I swap the plug wires and plugs, it does not follow. Plug is always wet on the PTO side.
2. Carbs and fuel pump checked and cleaned. All were very clean when disassembled, made sure all jets, screws, and port were cleaned. Both carbs are sync'd, both chokes move freely, and cables are rigged per the SM.
3. New fuel filter and checked the pickup in the tank.
4. Checked compression when cold and warm. Each cylinder is 120 psi both times.
5. Checked reed valves, no damage noted. Swapped them to see what happens, does not follow.
6. Checked the power valves, both valves and cables move freely, servo moves one time after start.
7. Did a pressure check on the coolant system just in case a cylinder may be cracked even though no coolant is being used. Holds 10 psi hot and cold.
8. Used propane all around the outside of the engine to check for air leaks, none found. Engine only sped up when I placed it in front of the carb.
I don't have any tools to do a pressure check of the cylinders, but making some was going to be my next attempt to find out what is wrong.
Thanks for the help,
Jeff
 

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Did the leak down check today, and it was 45 seconds per 1 PSI drop in pressure. I know this is out of limits, but the pulse line for the fuel pump doesn't have a clamp on it at the bottom of the crankcase, so there might be a small leak there. Otherwise, I couldn't find any leaks anywhere else. Will probably pull the motor to check the bottom and clamp that hose. Can anyone think of anything else I may be missing?
 

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Took the engine apart, found the outer bearing inner race on the PTO side was cracked, along with bad inner bearing and connecting rod bearing on the same side. Run out was way out of limits at the crank shop. Had the crank rebuilt. Just waiting on free time to put it all back together.
 

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Depending on calibration (accuracy) of compression tester used, a reading of 120psi will run...

But, that’s way below what those 900’s have when new. An accurate gauge will render 150+ psi per cylinder after no more than 4-5 pulls MAX (with throttle held open for max air intake at those engine speeds)

I’d seriously look at rings gaps in mag cylinder, to see how far out of spec they are, as I’m figuring you have made the decision to AT LEAST re-ring the PTO side (if not just install 2 new piston kits)?

Those 900’s are very hard on piston skirts. They truly need pistons replaced approx every 5k miles to avoid shattering a skirt.
 
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