bad luck

[ryansteely@yahoo.com]

well I just finished doing a top end rebuild along with a couple of other things like free flow exhaust kit and I milled .020 off the head this friday. I hooked it up to water on the traile and let it run for 4 hours everything seemed to run right. I pulled the spark plugs and they looked great. I launched the damn thing got up for a couple of seconds and the damn thing died. pulled the center plug and it was smashed but the other two were fine. I checked for compression and I wasn't getting much out of center cylinder.I guess the spark plug knocked a hole in the damn piston.So after I get It back together and fixed this time I guess I will have to find shorter shank spark plugs or put a washer on the plug. Did anyone else have to do this when they milled their head

[beerdart]

What type of ski?? It is not possible for the piston the hit the plug. Something else happened. Take some pics for us to view.

[philip_gpr]

maybe a cranksahft problem?

[ryansteely@yahoo.com]

the ski is a 01 gp1200r. the piston had to of hit the spark plug that is the only way the plug would have been smashed like it was. apparently I needed a shorter shank plug after milling the head or There is too much play in the crankshaft bearing causing the piston to move more than normal. I am hauling it back to my machine shop tommorow and will post what I find if anyone is interested.

[shooter98xpl]

sounds like your middle rod is going to need to be replaced. Do you have individual heads or one piece head? Reason I ask is maybe they messed up and milled the middle one much more than what you had asked. If thats not the case, crank needs to be sent off. Check dead top center on each cylinder to see if you get different readings. Measure distance from top of piston to the tip of the spark plug hole.
SHOOTER

[WFO]

What type of ski?? It is not possible for the piston the hit the plug. Something else happened. Take some pics for us to view.

+1

the plus threads would have to be 2" long to hit

[ryansteely@yahoo.com]

I did the mill work on the stock head myself. I know there is no way that the middle is shorter than the rest because I set it up and had it zeroed out with my lastword mike. after I was done I miked the thickness of the head and was pretty even from one end to another only off by about a thou. hopefully I have time tomorrow to take it apart and check out the crank and rod. But I just can't figure why I lost compression. I pulled the plug and looked for a hole in the piston and could not find anything. I sure am not looking forward to dumping more money into this damn thing

[OsideBill]

You may want to read up on proper break in methods, letting a newly rebuilt top end run for 4 hours on the trailer is not advisable.

[sleeplessnMS]

h2o

[RDH]

what plugs are you using?

i had some plugs do that before, and the only reason why was the PV dropped and took a chunk out of the piston off, and those fragments were coming up and hitting the spark plug gap closed..

you should break it in under load....