Hello all. Hoping to get some help and advice before I totally give up. Due to a completely burned/low compression MAG side piston, just completed a top end rebuild including new jugs, pistons, etc. Ran better than new first time out for a couple hours. Zero issues. Took it out today and after about half hour of running great, engine stalled. Tried to start and engine turned over a few times. Second attempt, engine felt like it looked up. After trailering, I pulled plugs and engine turned fine. I installed PTO side plug and engine ran on that cylinder. I replaced CAM plug and engine turned without starting. Basically, the same scenario which prompted the top end rebuild prior. Just a side note. Before top end rebuild, I did have the carbs rebuilt by a very reputable shop. The first time I took it out after carb rebuild, engine acted similar to today. Low compression/burned CAM piston discovered after removing head. I have been checking compression almost daily since I completed rebuild. Solid 150psi both sides. Unfortunately, after problem today, 130psi MAG side/150psi PTO side. There is obviously an issue with the MAG side. I may be overthinking again. Could that side be running too lean? Possibly lack of oil to cylinder? May be a dumb question. Is there a way to confirm oil travel to cylinder? I have attached before and after pics. The low compression MAG side does not look too burnt and it appears the PTO side piston has a bit more oil barely visible on top. Also, engine turns fine with head off. The GTX is like new cosmetically. Hate to give up on it. Any help or ideas greatly appreciated.
1994 Sea-Doo issue after top end rebuild
- Thread starter bevmale
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JC-SUPERJET
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Was the Bottom End opened, cleaned and inspected? Were new Crank Seals installed?
Was an Air Leak-Down Test (8 psi x 10 min) done on the re-assembled Engine prior to installation?
Thinking that Metal Debris or a Leaking MAG Crank Seal in the Crankcase is damaging that MAG Piston.
Seems like Seadoo Cranks need to be rebuilt/replaced with every new Top End.
At the very least cleaned and carefully inspected.
Was an Air Leak-Down Test (8 psi x 10 min) done on the re-assembled Engine prior to installation?
Thinking that Metal Debris or a Leaking MAG Crank Seal in the Crankcase is damaging that MAG Piston.
Seems like Seadoo Cranks need to be rebuilt/replaced with every new Top End.
At the very least cleaned and carefully inspected.
Hello all,
Thank you for the replies. Just a follow up regarding compression. I checked again today. Compression on both cylinders at 140psi. Previously, engine was a bit hot and I did not have throttle wide open as I was checking. Next step, carb rebuilds again. May have been issues with initial rebuilds. Waiting for reply from tech. If I have no luck, are there any reputable on line carb rebuild sources?
Thanks
Thank you for the replies. Just a follow up regarding compression. I checked again today. Compression on both cylinders at 140psi. Previously, engine was a bit hot and I did not have throttle wide open as I was checking. Next step, carb rebuilds again. May have been issues with initial rebuilds. Waiting for reply from tech. If I have no luck, are there any reputable on line carb rebuild sources?
Thanks
Thank you mikidymac,
I just discovered both high speed settings were open. MAG side bit more than PTO side. According to what I have read, should be 0 turns/high speed, 1 1/4 turns low speed. Please correct me if I am wrong. Attached is pic prior to adjusting down to zero. First start, it idled a bit high, after a couple starts, seems like normal idle. I also plan to replace old grey fuel lines soon.
I just discovered both high speed settings were open. MAG side bit more than PTO side. According to what I have read, should be 0 turns/high speed, 1 1/4 turns low speed. Please correct me if I am wrong. Attached is pic prior to adjusting down to zero. First start, it idled a bit high, after a couple starts, seems like normal idle. I also plan to replace old grey fuel lines soon.
A theory on why the pto piston goes is that there is a twist in the crank since it it closer to the drive shaft and stress…and fails due to heat/metal fatigue,,,and or the timing advance becomes out of norm,,,that’s all I know,,,for that very treason engine builders,,(racing) and some OEM manufacturers on stock skis ,,,,increase the main and or pilot jet sizes,,,usually 2.5.
Or like Yamaha on the 760’s they actually tried changing the timing and lowering the compression on the rear cylinder. Crank twist.
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