M1000 goes down?

[specialk6r]

Got my first good ride on my CPC stage 3 08' M1000. It ran perfect at 5.5 lbs (running 91 w/ 2 gal. 111 race fuel) for 1/2 hour, then as I was cruising through a field at around 6,000 rpm I feel like I lose one cylinder and have the dreaded metallic clatter sound.

We towed it out and got it home and plugs are all a uniform light brown and the pistons look fine except for a small score mark on the exhaust side of the PTO piston. How about some guesses?

 

[Vertical-Extreme]

how long were you holding it at 6000??? might have been lean in the midrange, and if you don't vary your throttle position it could get warm, just a thought

 

[diggerdown]

A score at the exhaust port is usually lean, add some fuel to mid range.

 

[Tonysnoo]

Got my first good ride on my CPC stage 3 08' M1000. It ran perfect at 5.5 lbs (running 91 w/ 2 gal. 111 race fuel) for 1/2 hour, then as I was cruising through a field at around 6,000 rpm I feel like I lose one cylinder and have the dreaded metallic clatter sound.

We towed it out and got it home and plugs are all a uniform light brown and the pistons look fine except for a small score mark on the exhaust side of the PTO piston. How about some guesses?

It's hard for me to imagine a light score mark causing a metallic clatter. I wonder if you had something else come loose/break? How are you looking at the piston...y pipe off or looking through the APV slots? Is it possible that you had deto break the area of piston between the rings? I actually broke a ring once, it made a clatter in the turbo....$$$$$$$$$$$$$$$$$$$. Hope that isn't the case.

I agree with the others...richen up mid/lower.

Good luck

 

[specialk6r]

I'm checking the pistons through the exhaust ports. It still has good compression, but sounds terrible at idle and only runs on one cylinder. I'm guessing the PTO crank bearing is toast. I'm probably due for a top end anyway, so I'll just get a crate motor for $2000, then part the old one.

 

[428PONY]

timing at 6000rpm goes to a fix at 24deg. If using egts you can watch egts climb beyond limits. at 4900rpm will never be an issue but steady at 5-6400 you will burn down. Call dale at cutler he will verify this.

 

[RACINSTATION]

Yes, midrange is very tough on modded Cats. Powervalve opening (which is load based) varies from 5500-6500 rpms and the timing is advanced a bunch in this range. You have to feather it in and out to keep it lubed and if you add enough midrange to keep it cool it will be groggy in the middle.

 

[specialk6r]

Unless my thumb is against the bar, I always feather the throttle. Do you fellas think that my crank failure could be caused by a lean condition? The score on the piston is just one single gouge, like one piece of debris made it's way to the top end.