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  1. #1

    I keep destroying my number one cylinder.

    So here is the short version of my problems. About a year ago on my single pipe gp1200r i blew the motor up. I lost a bearing on the center rod and it did a lot of damage. Fast forward over the winter i took my time rebuilding the entire engine with oem parts and replaced the shredded middle cylinder. I ran the boat as a single piper for about ten hours before i decided to install the triple pipes i had laying around for the last few years. I put them in and yes i have all the nessecary mods (cdi, rejetted carbs, jet in the fuel line to build up pressure, pop off pressures altered etc..) The boat still ran great for about 3 hours till the vibration destroyed my servo for the power valaves which i knew would happed so i got a set of gas valves from phillip gpr. He gave me a set in great shape. I installed the valves per riva and greenhulk member instructions. Took the boat out and it ran good for about ten minutes then I lost the front cylinder. I always take a plug wrench on the water cause i am a plug chop nazi. Pulled the plug on number one cylinder and no compression. Got the boat on land and pulled the cylinder and did a compression check. While i was doing the check (this is all probably horrible luck) but the starter solenoid locked in and the motor wouldnt stop turning over so i ripped the fuses out and to my suprise not only had i lost a cylinder and a starter solenoid now. I also saw smoke pouring out of the cdi box. I opened it up and the cdi had melted a ton of wiring and the resistors inside it pushed themselves out. The cdi was a r&d by the way. I got the cylinder on my bench and it appeared that the gas valve had clipped the top piston ring and done some terrible things to the piston and cylinder. So i took all the valves to a buddy who is a kawasaki and yamaha dealer and he concurred with what had happened so he was gracious enough to mill all the valves down so i wouldnt have this issue again. It took about 3 months but the nicest guy on earth oside bill located and sold me a advent cdi so i could get my boat back in the water. I got another cylinder and piston kit and put the boat all back together. I put it in the water yesterday for the first time and just took it east trying to break in the new number one and it ran great so i flushed it waxed it and put it away happy as could be. I took it out today and as soon as i got on it to do a plug chop i felt a sudden loss in power and the boat cut off. I lost the number one cylinder again. And this time the piston struck the spark plug. I would say i am mad but i was the one who couldnt leave the thing stock. Any thoughts would help cause i would appreciate not making it a fourth time is a charm scenario.

  2. #2
    I didn't see anything about oil mixture, pre-mix?. maybe no water going through the cyl. And I have a mint cond electrical box, if you need. Frank.

  3. #3
    PolarisNut's Avatar
    Join Date
    Dec 2006
    Lower Michigan
    Well, if the piston hit the spark plug, you more than likely have a crank issue...My guess is that the bearing is bad on that rod. Lets see some pics of the piston, cylinder, head, and rod bearing thrust washers.

  4. #4
    when you rebuilt it if the front piston #1 hit spark plug ,you missed seeing damage in the rod big end bearing!unless your ski is converted to premix with the oil pump removed its possible that if the oil pump is still in use that it has an air lock,or one of the small check valves in oil line is thing for a modded ski,remove oil pump so you can premix exact ratio you want,JMHO>Marvin

  5. #5
    Ot is a premix.

  6. #6
    Its mixed 32 to 1

  7. #7
    i know water is going through everything. I am anal and I ran 6 pissers. Three up front that correspond to the heads and cylinders ans three coming off the transom for the pipes. I will post some pics of the piston and cylinder tomorrow.

  8. #8
    Here are the pictures of the cylinder. She got hot.

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