# 2 Stroke Yamaha 50 Rebuild Myself?



## jmrodandgun (Sep 20, 2013)

If you have pieces of broken piston or ring, you're probably going to need a machine shop. The machine work is not terribly expensive, it's the tear down and assembly that kills you. It's a good motor and worth rebuilding. Pulling the power head isn't too bad, the machine shop will do the cylinder work and fit it with the correct pistons and rings. Bring it home, put it back together, hit the go button. Easy peasy. 

As for replacing just the one bad piston, it's a bad idea. If it's not balanced it will rip the whole rotating assembly apart. I mean, you could balance it, but why risk it?


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## JMZ400 (Aug 30, 2015)

Thanks for your reply. I was figuring I'd just be dropping off the cylinders to be honed/bored etc. Then assembling it myself. Are you saying most will assemble it if I provide the correct parts?


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## Creek Runner (Sep 1, 2011)

$1800 bucks for a brand new power head from Yamaha, piston and rings alone are going to run you $400+, if you got a bad rod your going to have to buy an whole crank assy, which is probably $800+. Save a little more money and just buy the new power head. Either way make sure those carbs 100% correct or you will be doing it all over again. 

I assume this is a C motor.


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## JMZ400 (Aug 30, 2015)

Yes it is a C motor. What is the reason for needing an entire crank if I have a bad rod, other than the obvious that if a rings is bad then the crank could be bent to. Are the rods not removable? I'm guessing they're pressed on. Where does find a new Yamaha powerhead for 1800? Thanks


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## RunningOnEmpty (Jun 20, 2015)

The crank is pressed together unfortunately. You can get the crank rebuilt for about half the price of new. Creek Runner is 100% correct on the carbs. It doesn't take long for a lean cylinder to burn up.


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## DuckNut (Apr 3, 2009)

Powerheadexchange has complete rebuild kits for $395, $1300 for a rebuilt one.

$1,800 sounds cheap for anything from Yamaha.


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## RunningOnEmpty (Jun 20, 2015)

Is this a complete motor or just the block? http://www.boats.net/parts/detail/yamaha/Y-63D-W0090-20-4D.html


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## DuckNut (Apr 3, 2009)

It is just the block. You will need to use some of your existing parts.

Wait for cut runner to chime in or chase him down, he know Yamaha.


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## Creek Runner (Sep 1, 2011)

That is a complete crank case assembly, it will include the Block, all internals, Intake, head. You will use your firing systems, carbs, flywheel, starter, etc. I was off by $29.88 not bad for an off the top of my head ball park. 

That is the route I would go, but if you want to save a few bucks than tear her down and rebuild her. But your going to have somewhere around $800 in parts and machine shop labor if all your replacing is the piston and rings if you bore her .20 over. If the cylinders are good you'll save a little money, but if you bore one you have to bore all 3. If a sleeve is bad that figure will go up from there. 

How do you know a crank rod bearing doesn't have a heat or flat spot in it if it ran lean? You would have to have a machine shop break it down and inspect it.

That's why I feel it's worth the $1800 to just buy a brand new power head from Yamaha, a couple carb kits, new water pump, and thermostat. Once I had all the parts I could have it off and swapped out, carbs rebuilt, water pump changed, in under 4 hours and headed to the water. 

btw- Duck I'm a Certified Master Yamaha mechanic and have been since 1997, I know a little something about Yamaha's to. Not that Cut's opinion isn't warranted or appreciated, but he don't work on no stinking 2 strokes anymore, all he does is work on 300hp and 350hp Yammies now! 

Running on empty those kits aren't OEM parts, some people like them some people don't! I only use Wiseco or OEM pistons for stock motors, just my opinion.


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## JMZ400 (Aug 30, 2015)

Thanks for all of your input guys. I guess the next step is to at least open her up and find out. 

Creek Runner- you make a real strong argument for a new powerhead.


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## RunningOnEmpty (Jun 20, 2015)

Creek Runner, Is it safe to run rebuilt cranks? I know someone that's into boat racing and he runs them without any problems. The guys at Carson Marine suggest against it? It wasn't me that suggested no name kits LOL


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## Creek Runner (Sep 1, 2011)

RunningOnEmpty said:


> Creek Runner, Is it safe to run rebuilt cranks? I know someone that's into boat racing and he runs them without any problems. The guys at Carson Marine suggest against it? It wasn't me that suggested no name kits LOL


Running aw yeah sorry, (Duck those kits aren't OEM parts)lol!

I run rebuilt cranks someitmes on race motors as most of them are modified anyways.


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## DuckNut (Apr 3, 2009)

Creek...I know you are a Yamaha tech and in my post I never said they were OEM parts, just giving the man options with a very reputable business.

I would never imagined the head could be had at that price. Definitely a strong case.


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