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  1. #1
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    225 promax failure diagnosis

    Hi scream and fly,

    Hoping someone can help give some insight into why this motor failed. Background it’s a 1999 225 promax OG817411. Motor is stock apart from 35.5cc heads, ccms reeds, light blending of exhaust chest and some port matching. 25:1 oil during break in. Injectors recently cleaned and vst tank cleaned.

    Motor was just rebuilt and would like to get to the bottom of it before rebuilding again. During first break in run engine had poppet issues and overheat alarm went off at 3500rpm. Motor was brought back to idle and alarm went off but was running warm on temp gauge. Second break in period poppet valve issue was fixed and engine had been running 3500-4800 up and down every few minutes for about 1.5hrs. 3.5hrs total run time since break rebuild. Started to increase engine rpm and at approx 5200-5300rpm felt a miss and backed off straight away and turned the motor off, noticed metal flakes on the spark plug on number 6. Temp gauge was only on 1/4 temp when this happened.

    piston skirt appears to be damaged and lost compression on number 6 approx 50psi. All other cylinders appear fine. Was oil/fuel in the bore when the heads were pulled and no signs of overheating on the plug that I could see.

    cheers
    Attached Thumbnails Attached Thumbnails 79E7F2DC-ADD9-4300-8A97-92E1A9FABFD8.jpg   448A28F8-6CAC-4EBA-B2EC-A62F70DFB8A1.jpg   6604EE35-A512-4A66-A68F-A673F822D09F.jpg   CCA1EEB2-9BF0-4B3B-8F8E-CEA8FB8EF0DB.jpg   80A453FE-C2B8-4CAD-995B-D86624CDEF95.jpg  

    AD089361-15AF-4B81-92F6-B0000A41C071.jpg  

  2. #2
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    what was tha cause tha first time?.. that looks like heat and/or tolerance issue.. ta me anyway.. a plug may/may not show over heat.

  3. #3
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    Quote Originally Posted by tlwjkw View Post
    what was tha cause tha first time?.. that looks like heat and/or tolerance issue.. ta me anyway.. a plug may/may not show over heat.
    I only just brought this motor and it’s been a nightmare. When I first got it had only recently been rebuilt. Couldn’t get it to rev over 5k and really down on power eventually pulled the heads and it was rebuilt with the pistons in the wrong banks. So to answer the question I don’t know why it was initially rebuilt, but last time it burnt number one.

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    sounds like ya need ta start back at square one with complete motor.. if it wasn't done right tha first time then no tellin' whats happenin' inside tha thing..... ie: machine work, parts (all of 'em) and such... sorry but jmo.

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  6. #5
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    Ya. You need get the block to a well known machinist and have him measure EVERYTHING I'm with tlw looks like when it started to build heat she stuck from not enuff clearance maybe? Could had been electronics also tho , u said fuel system was cleaned so I didnt mention that

    What did that plug look like. Look lean? Cause piston dont look lean
    Last edited by Merc 2.5; 04-15-2020 at 05:32 AM.

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    Quote Originally Posted by Merc 2.5 View Post
    Ya. You need get the block to a well known machinist and have him measure EVERYTHING I'm with tlw looks like when it started to build she stuck from not enuff clearance maybe? Could had been electronics also tho , u said fuel system was cleaned so I didnt mention that

    What did that plug look like. Look lean? Cause piston dont look lean
    Thats what had me stumped plug looked paper bag brown, nose of the insulator wasn’t melted etc looked normal. Piston wash on that cylinder didn’t look lean, and piston top was still wet with fuel/oil in the bore when I pulled the heads. Timing set at 23.5 degrees.

    if the pulse pump or vst ran out of volume/failed and it ran out of fuel would you expect to see damage on the piston top?

  8. #7
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    Wat is the number on your ecu? A17 SUCKS!
    there is a service bulletin about you also need to set the max advance to 23 dgr
    Best to install pyrometers and an adjustable fuel pressure regulator

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    I no if u run a 2 stoke out of gas it's not good , but I have ran out gas in all kinds 2 strokes and never had a failure like that. Dosent look like a fuel issue to me. I'm thinkin clearances

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  11. #9
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    No telling what "rebuilt" involves. Many sellers claim "rebuilt" but dont meen squat if they dont know exactly what's been done to it.

  12. #10
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    Measure the bore, looks like it was just abit too tight, temp wasn't up piston got warm and tried to stick , ports dont look chamfered to much either.

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  14. #11
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    I agree, looks like a clearance issue. Is that cylinder standard or oversized? Probably need to clean off the piston top to read the stampings...

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    If the pistons were installed incorrectly by the "rebuilder" the 1st time. Dont let him touch the mota for any reason again.

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    Quote Originally Posted by roadkill636 View Post
    If the pistons were installed incorrectly by the "rebuilder" the 1st time. Dont let him touch the mota for any reason again.
    the time it was rebuilt with pistons in the wrong banks was with the previous owner, but I just got it done again by someone familiar with these motors. Whole motor is 0.20 now, will take it back to engine builder. Just seeking some other opinions first

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    Thanks Panronnie new to these motors. I’ve read the A17 is a learner curve than the a32, anything else wrong with him? Going Bosch pump and adjustable fuel reg before I even start it this time

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    .020 normally equals wiseco's (what they look like) that usually equals sticky if not done exactly right with clearance's and temp break-in with tha v6 merc... jmo

    think a lot of tha a17's (mighta been tha a12 though?) were recalled and fixed/replaced but not all...
    Last edited by tlwjkw; 04-15-2020 at 04:10 PM.

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