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Old 13 August 2008, 11:01   #1
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Yamaha 8 hp engine problem

Hello folks

My neighbour Charlie, is trying to repair a Yamaha 8 hp 2 stroke cylinder outboard engine. The big end bearing on one of the piston rods needs replacing. We can't see anyway of pulling the crank apart. Is there a special tool for this? Is it a dealer only repair? Please see attached image with the 'offending bearing' marked.

Any help would be appreciated.

Keith Hart
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Old 13 August 2008, 11:53   #2
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Quote:
Originally Posted by Keith Hart View Post
Hello folks

My neighbour Charlie, is trying to repair a Yamaha 8 hp 2 stroke cylinder outboard engine. The big end bearing on one of the piston rods needs replacing. We can't see anyway of pulling the crank apart. Is there a special tool for this? Is it a dealer only repair? Please see attached image with the 'offending bearing' marked.

Any help would be appreciated.

Keith Hart
Hola

The pic it's not very clear in details, some engines uses 2 parts connecting rod secured one to the other with 2 screws at the lower end of the connecting rod assy. Seems in your case it's a one piece connecting rod passed through a internal crank pin with a middle needle bearing that holds together in place crankshhat A to crankshaft B. Your engine has 4 crankshafts. In that case will need a special tool for taking apart crankshafts, when jobs done will need a press to put crankshafts back together. Better do it in a specialized place.

To have a better idea of the crankshaft complete assy. See tech pic. Good luck!

Happy Boating
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Old 13 August 2008, 12:50   #3
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as Locozodiac says its pressed together around the bearings.

This is common practice, particularly on 2-stroke engines for outboards, motorcycles etc, but unfortunatly means you need a serious press to take it apart and put it back together again. Of course it needs to be put back together in a jig to get all the angles etc correct.

It can be done, I once did an RD350YPVS Yamaha twin myself when I had access to a 5tn press, but I'd not recommend it.
The guys who do it all the time don't take too long as the jigs etc make the job easy, so the labour charge isn't too steep.

Nasher.
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Old 16 August 2008, 02:58   #4
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Thanks for the info and diagram chaps. I've passed this on to Charlie and he's going to take it into an engineering workshop in Inverness to get it done.

Keith Hart
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Old 16 August 2008, 05:54   #5
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Tell Charlie not to let on it's for a boat, or they'll charge him double
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Old 18 August 2008, 10:49   #6
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"double" !!

You'd be lucky, more like quadruple! I'll pass the advice on.

Cheers

Keith Hart
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