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Thread: Lamey meltdown

  1. #1
    cfgp927's Avatar
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    Lamey meltdown

    Went to the water early this morning to test and tune my son's (Corey) boat. It's my old GP800 with a 927cc Dan Lamey motor in it. It's a pretty stout boat. Factory Pipe twin pipes, Novi modded I-bodies (44mm), Pro-tec CDI, Cut valves, Skat pump/prop, Riva trim, etc.....

    Warmed it up on the trailer for 2-3minutes, then unloaded it for some more warm-up time. After about 5minutes of no more than 1/3 throttle bursts, it was time to put the "hammer" down. The boat literally wanted to jump out of the water from a rolling start, it pulled really hard up to 7180rpms then died. I always carry some tools with me so I pulled the plugs.....lost an electrode on the front plug. Had my son who was riding his mom's xl800 tow me back to the ramp for a new plug. I replaced the plug and headed back to the water.....The boat ran really strong for about 5 minutes and then died after a short full throttle burst. Decided to call it a morning and we limped back in and loaded the boats.

    Tonight I got home and decided to do a compression check....checked the rear cylinder first 125psi.....just what it's supposed to be. I breathed a short sigh of relief and then checked the front cylinder..... 26psi....my heart dropped into my stomach. I decided to check it again.....26psi again. Pulled the head and sure enough the motor appeared to go lean during that last full throttle blast and scored the cylinder slightly. I might be able to get away with just honing the cylinder and re-ringing the piston but I won't know until I complete the teardown in the morning.

    Right now I need a beer and a shot of 101 Wild Turkey.
    Mike

    Hopefully I can get it up and running for the next weekend.....we'd planned a weekend of nothing but riding waverunners instead of boating/tubing/skiing.


  2. #2
    Flying Scotsman's Avatar
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    Good luck on the hone I take it you have piston and rings on hand.

  3. #3
    cfgp927's Avatar
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    Yes, I always try to keep at least two pistons and ring sets available for back-up.....I just wish I knew what caused it to go lean.....guess I'll find out tomorrow.

  4. #4
    Hydrotoys's Avatar
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    Pressure test the pipes.

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    cfgp927's Avatar
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    That's one of the things I was planning on doing before going to the water with the new top end.....I'll probably go through the carbs again as well. Not quite how I planned on spending tomorrow.
    Mike

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    800AMSOIL4U's Avatar
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    Quote Originally Posted by cfgp927 View Post
    That's one of the things I was planning on doing before going to the water with the new top end.....I'll probably go through the carbs again as well. Not quite how I planned on spending tomorrow.
    Mike
    Seen plenty go lean due to garbage in the carbs or the lines. Do you have fuel filters on it?

  7. #7
    cfgp927's Avatar
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    Yes, I have fuel filters on it, they aren't that old (changed late last season), but I'll probably change them as well. I may replace all the fuel lines again and the pulse lines. I cooked one other motor due to a pin hole in front cylinder pulse line. Other than that, it'll be a quick hone on the cylinder and new piston/rings/circlips. I'll also reseal all mating surfaces in the intake area with new gaskets or 1211. Carbs will also get looked at again.
    Mike

  8. #8
    ....back from the dead.... J-ME's Avatar
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    Man, that sucks. I hope you get to the bottom of it.

    Please post some pics, maybe we can help you remotely diagnose it.

  9. #9
    cfgp927's Avatar
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    Digital camera is at the wife's office, I may pick it up after I go to the gym....gotta work off some frustration.

  10. #10
    cfgp927's Avatar
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    Well, I didn't pick up the camera, but I did pull the motor and tear it down. The rear cylinder is fine, almost appears that it was running way rich, no wash on the top of the piston. The front cylinder on the other hand shows the black wash that comes from running lean. Upon removal of the engine I pulled the cylinder and sure enough the piston shows signs of a 4-corner seizure. It almost appears that the fuel circuits on the front carb are way off.

    I checked the jetting in the carbs and have the following : 1.5n/s and silver spring (f & r), 172main (r) 175main (f), 142pilot (r) 145pilot (f), lows out at 1-1/4, and highs out 1 (r) 3/4 (f). This is the jetting that came from Lamey.

    I pressure tested both pipes and they are fine. I will completely rebuild both carbs again with Mikuni kits and replace all fuel lines and pulse lines as well. Right now I don't have a clue as to why the motor melted down unless I had an air leak after installing a reed spacer plate that Dan @ Powderlites made for the stock reeds on the 66E motor.

    I did notice that one of the cylinder head bolts didn't break free like all the others did upon disassembly. I'll be checking all threaded holes to make sure some aren't stripped allowing for an air leak due to improper torquing of the head bolts. I'm running a modified stock head, but may have Lamey's crew cut me some domes for some Riva BB heads I have laying around. I like the idea of the cylinders being girdled....especially if I up the compression to say 140-150psi. I promise to post pics soon. I need some help diagnosing this engine failure.
    Mike

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