Reasons for middle cylinder burndown....


First thing I thought of was a cracked carb boot or oil delivery problem in the center cyl. What if you run pre-mix in the sled instead of running with the injection system?
Is this possible?
Get the crank checked like said before.
Get the jetting checked and clean those carbs.
Check pv's and adjust them correctly. Maybe stretched cables or broken cable could be the rpm problem.
Is your tors disconnected?
 
Ensure that you have good compression in all 3 and clean fuel supply to all 3 and from all 3. Once you get to that point, the only issue is plugs and power valves.
 
By reading this post, I think I would simply remove the carb rack and clean all the fuel circuits and air bleeds out very well, make sure you can see thru the jets while holding them up to a light and can send carb cleaner thru the passages in the carbs. The fact that it doesnt go above 8000rpm and is still burning down the center cylinder tells me the clutching is probally just out to lunch as most aftermarket "kits" are anyways, so I think correcting the lean condition in the center cylinder would yeild more positive results then fooling with clutching at the moment, do the carbs first then look for airleak problesm around the reed blocks if all is well and correct in the carbs.
 
check the power valve the cable wears through the valve and the exhaust cant get out because the valve doesnt open, make sure the power valve motor is plugged in too,
 
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duhr8m said:
check the power valve the cable wears through the valve and the exhaust cant get out because the valve doesnt open, make sure the power valve motor is plugged in too,
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you're power valves will not stop the exhaust from exiting you're motor. you're sled will run fine even if you unhooked all 3 valves, you would just lack in performance.
 
Update......

Tore into it, the middle cylinder was so bad it chewed the piston down to where the ring came up and out of place. The piston showed signs of cold seize. I went into the carbs, the pto was 152.5, and the others where 150. The sled has vforce reeds and a gutted airbox which I just realized. I checked the outer cylinders and they were perfect.

It's jetted up, the boots are fine. I'm going to clean the carbs, but I'm nervous that the same thing will happen. The one weird thing was that the coolant consisted of green and red. WTF?

I also read on here that the 98-99's had the mag fatter, and the 2000-02 had the pto fatter. My outer cylinders are fine, but the middle is the problem.

Clean the carbs and hope for the best? I'm stumped, maybe it's the red/green coolant?
 
If the coolent is a mixture of green and red, I would suspect someone added the newer long-life coolent [orange]to the original green coolent but that's just a guess without actually seeing it.
 
Equalizer said:
If the coolent is a mixture of green and red, I would suspect someone added the newer long-life coolent [orange]to the original green coolent but that's just a guess without actually seeing it.
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I thought you weren't supposed to mix the 2?
 
blue missile said:
what color is the oil you're burning. could be the oil somwhow getting into the coolant.
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Not sure how to tell?

The 2 outer pistons look fine. I'll try and get some pics up. I figured I find something obvious like a torn boot, plugged jet.......
 
triple said:
I thought you weren't supposed to mix the 2?
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Your not, the organic acids in orange types will cause separation of silicates in the green type, which greatly reduces corrosion protection. But it's possible the previous owner was not aware of this.
 
Equalizer said:
Your not, the organic acids in orange types will cause separation of silicates in the green type, which greatly reduces corrosion protection. But it's possible the previous owner was not aware of this.
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Would this cause a lack of cooling? Especially on my middle cylinder that keeps blowing?

My PTO is 152.5, and the other 2 are 150. Would it make sense to jet the middle up to 152.5?

How do you adjust the needle on the center? It seems like the outer carbs have a screw up top, but nothing on the middle. I have jetting expereience with my old YF450, the needle setting was easy. Just remove the top of the carb, remove the allen bolt, pull the needle out and move the clip. I'm a little confused on how to adjust these Mikunis. I guess I'll jet up the center's main and richen up the needle. 2 seizures in 400 miles has me worried it's gonna happen again!!!!!

It seems the previous owner just sold me his reaccuring mess. #$%&*
 
triple said:
Would this cause a lack of cooling? Especially on my middle cylinder that keeps blowing?

My PTO is 152.5, and the other 2 are 150. Would it make sense to jet the middle up to 152.5?

How do you adjust the needle on the center? It seems like the outer carbs have a screw up top, but nothing on the middle. I have jetting expereience with my old YF450, the needle setting was easy. Just remove the top of the carb, remove the allen bolt, pull the needle out and move the clip. I'm a little confused on how to adjust these Mikunis. I guess I'll jet up the center's main and richen up the needle. 2 seizures in 400 miles has me worried it's gonna happen again!!!!!

It seems the previous owner just sold me his reaccuring mess. #$%&*
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No I don't think the mixing of the coolent would be the cause, it might jel when it gets really cold but it would still keep the engine cool. I'm sure someone on here can help you out with the carbs and jetting but if it were me, I think I'd find another airbox [that's not gutted] and jet everything back to stock.
 
Those pics in that post are not over heating pistons, they are lean burn down pics. There is a post in the tech section on how to adjust the needles. Maxdlx
 
maxdlx said:
Those pics in that post are not over heating pistons, they are lean burn down pics. There is a post in the tech section on how to adjust the needles. Maxdlx
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OK thanks.
 
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