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Discussion Starter #1
I dunnoFrustrated!

I have a 73 panther with the kawasaki 440 motor in it. I rebuilt the motor with all seals and gaskets. The only thig stock is the piston and rings but the compression in each cylinder is great. I reasently retimed the motor to the correct spects. (again) I also just converted the carb to a mikuni. this is the third carb on this sled. The cooling fan and belt are fine. It seems no matter what I do I continue to have the same issue. After about 10 minutes of riding at 40 MPH it starts to break up so I turn off to cool. The plugs are super hot but the rest of the motor seems normal. If I stick new plugs in it she starts right back up and we start the process all over again. Im kind of at the end of my rope with this one. Any help would be awsome.
 

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Sounds like it is running lean. What is your main jet size? Do you have any air leaks between the carb and the motor?
 

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Discussion Starter #3
I am running a 280 main with a 35 pilot. Strange thing is the plugs look great when I take them out. I forgot to mention I am running 40:1 with 91 octain non ethanol fuel. I also cut the exhaust apart to check for blockage.
 

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I would check the carb mounts, boots, and gaskets carefully. It wouldn't hurt to go up to a 300 main and see if it improves.
 

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Discussion Starter #5
I will check the carb mount and gaskets. I was thinking somthing with ignition. I did start with a 330 main and am down to a 280 because it was breaking up once I started to pull the needle. I was even thinking of going down to a 260 wich was in the carb I took off a 76 cheeta 5000. It ran great with the tilotson but still overheated. Same thing with the wolboro.
 

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Discussion Starter #7
Not yet but I can give it a try. Would you know if a 76 cheeta Suzuki motor would fit in my 73 chassy? With minimal Fab?
 

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Anything is possible. The problems would be motor mounts and pipe connections (at the least). Making sure the clutches are lined up can be a challenge!
 

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another common mistake, did you torque the cylinders before the intake? you need to snug up the intake bolts to align the cylinders so they dont leak aorund the manifold.
 

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Discussion Starter #11
Thanks for the replies , No mouse house here. I did snug the intake 1st by the book. Some of these motors have plastic blocks that go between the intake manifold and jugs. I installed them to help with the heating issue with no resolve. Should I keep the or pitch them? How do you feel about retarding the ignition?
 

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The plastic spacers should be OK if not cracked. When you say the plugs look good when the engine is hot do they look white or brownish?
 

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Discussion Starter #13
The plugs are brownish. After running on a lake for a few miles I turned the motor off to let cool. It was about 10 degrees with a 25MPH wind. After a few minutes I could grab the exhaust manifold with my fingers. The plugs would still melt the flesh from your bones.
 

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OK, perhaps you have plugs that have the wrong heat range. Have you tried a set of "cooler" plugs?
 

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Discussion Starter #15
Im running the B9ES. I did try the B10ES last year with no help. Is there somthing cooler out their or am I just masking a deeper problem. At this point I am just trying to gather information. I think I might just rebuild another motor. I have a 340 motor from the same year. I will try your sugestions soon but the sled is in another location so I only see it on the weekends. I just want to ride! Thanks for your imput.
 
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