[V12NOS]

Hi
i just got my sleds running 4 the year. i took my 1995 ext 580 efi out this afternoon and it ran great but i was taking it easy to make sure everything was ok. on my final run across my lake to my house, i opened it up to full throttle. i got to about 80 mph at like 8000 RPMs and it immediately boged down and stalled while i was going 80. it started right up once i pulled it and it ran fine all the way back to my house, up a steep hill and then idled fine for a minute. i checked everything out and when i went to start it only kicked over and ran slow for about 10 seconds at a time and did little backfires like every second or so and then shut off. now it wont even start at all. one plug looked kinda gray and charred so i changed both for fresh ones and no change. please help. thanks. Ben

 

[UECAR]

Sounds like you need to do a compression check first and go from there. Gray is a bad color.

 

[94ZR580]

Did you look down the plug hole of the gray plug? Gray is usually melted aluminum, so like what was said above, you need to do a compression test to help tell you if that piston melted.

 

[bigrdg]

I have a 1996 ZR 580 EFI basically the same motor and the same thing happened to me last week. I was cruising across the lake doing about 90 and the thing shut off. It started back up and I limped it to the truck. I pulled the plugs and like you said one of yours was a greyish color, mine was too. I tested the compression in both cyliners and the right had 120 and the left only 90. I still havent taken it apart but I think it may be another melted piston. There was only 600 miles on it since the last rebuild, so I will have to try to find what caused it to melt down like it did. Goodluck

 

[94ZR580]

You're going to want to look to the rubber flange that connects the throttle body to the cylinder. They tend to develop cracks under the clamp and that leads to an air leak, which results in a lean condition and a melted piston. That is one of the more common causes of lean burn downs on the EFI machines. A pressure test will tell you if the cranks seals are in good shape.