Mike Sher
Ontario Canada
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I've just rebuilt my engine it blew the rear cylinder piston and the bottom end bearing. a lot of people have told me to remove the oil injector pump and go to premix gas. Two questions; what mix should I use? Why / what causes the issue with the pump and it seems most people have issues with the rear cylinder letting go! I've blocked off the mounting hole with a machined plate and am ready to put the engine back in with all new parts; crank, pistons, bearings, etc.
Look forward to hearing your comments
Mike S.
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Moabmonkey
Utah
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Joined: 04/30/2007
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Unless you're using very expensive oil like Amsoil Dominator on a modded ski use a 32:1 mix including the break in period of the rebuilt cylinder.
Few other things in case you were unaware: Make sure to zip tie the floats on your oil sender or your ski will give you alarms. And remember that any time that you premix you are leaning out the ski, so make sure to compensate by opening up your carb adjustors or add more fuel thru the EFI controller. I would also keep extra plugs with you because if you spend long times idling on a premix you can foul the plugs because oil injection varies your ratio at different RPMs and now you'll be at a constant 32:1.
Not sure if there's anything specific that causes what happens - could be a line coming off, could be a manufacturing defect, could be inferior oil...
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Mike Sher
Ontario Canada
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Thanks for the tips I didn't know to tie up the floats and the mix ratio is around what I was thinking. On another site when I asked what was the most likely cause of the bottom end going and the sieze they almost all replied with the comment " are you running with the OEM pump" USE PREMIX!
I used to race two strokes and had always used premix back then and had very few issues with bottom end failures. Most siezes came from running to week, trying for that extra bit of power!
Again thanks for the input.
Mike S.
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Mike Sher
Ontario Canada
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Forgot to ask,how do I make the required changes to the carb adjustors and the EFI controller. Do I need to get a dealer to do it or can I?
Thanks, Mike S.
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Moabmonkey
Utah
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I only had it on good authority to make the carb or EFI change from people who have done it before, but I suspect those people may have either had modded crafts or were just meticulous in their switch from injection to premix. I guess it's possible that you may not need to do it, and that it would just mean a few more fouled plugs a season but I'm not 100% sure. It was more of a better safe than sorry remark. If you haven't heard of it, check out greenhulk.net and post that question there in the 2 stroke section of the Yamaha forums, you'll be sure to get a fully informed reply.
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Mike Sher
Ontario Canada
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Thanks for the info, I'll post later in the year and let you know how it goes
Mike S.
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HDYMER
austin
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Joined: 06/20/2008
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what year is the boat?
if its a 2000 you have carbs not EFI....the oil lines have a tendency to slip off the carb nippple.... when switching to premix you dont need to run larger jets,,,,,its ok to run non yamalube oil as long as you have a d-plate instead of the cat-con...i use quiksilver in mine....
is the boat totally stock? do you plan on modding it more?
00 GP12R...triple piper...everything but an rxp pump/05 pump/propski mod
03 GP13R...stock...... conversion candidate
00 GP13R...bigbore
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Mike Sher
Ontario Canada
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You're right the unit has carbs and not Fuel Injection, wasn't thinking when I read the first response. The ski is a 2001 and is as you say a carburated, from what you say I don't need to change the jetting just block off the pump unit. That iv've dune I made up an allum plate and installed it. What is a "D-plate or "Cat-con" ? Not used to the modern acrinims for probably what is common for you PWC guys.
Thanks for the input, with your help and the other postings on the site I hope to get the unit going by next week end. I'm going to get the coupling alignment done tomorrow it went in easy once I got the engine onto the mounts, just slid right in so I don't think it'll take more than one shim to get it right.
Mike S.
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HDYMER
austin
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Mike Sher wrote:You're right the unit has carbs and not Fuel Injection, wasn't thinking when I read the first response. The ski is a 2001 and is as you say a carburated, from what you say I don't need to change the jetting just block off the pump unit. That iv've dune I made up an allum plate and installed it. What is a "D-plate or "Cat-con" ? Not used to the modern acrinims for probably what is common for you PWC guys.
Thanks for the input, with your help and the other postings on the site I hope to get the unit going by next week end. I'm going to get the coupling alignment done tomorrow it went in easy once I got the engine onto the mounts, just slid right in so I don't think it'll take more than one shim to get it right.
Mike S.
cat-con is catalytic converter,, and d-plate is the piece you replace the cat-con with,,,, the cat's have a tendency to go bad after 50+ hours and need to be replaced
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Mike Sher
Ontario Canada
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Thanks for the info, were would I get a "D" plate from?
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