Should I rebuild the top-end of my 657?

[jagilbert]

Hi,
I gotta 95 Speedster - twin 657 Rotax. The port engine PTO cylinder is not firing.
Compression: 135psi Mag side, 25psi PTO side. :-(
I pulled the head and found that the mag side cylinder and head are wet/oily & the cyl wall is shiny and pretty smooth. The pto side is dry and moderately scored. I can noticeably "rock" both pistons from above with my fingers. Last time I ran it, I noticed the port engine maybe wasn't smoking as much as it shoulda.

My Plan:
1. Convert both engines to premix
2. Get a top-end rebuild like this one:

http://www.ebay.com/itm/321378427161?_trksid=p2055119.m1438.l2649&ssPageName=STRK:MEBIDX:IT
SEADOO 650 657 Top end rebuild Kit Piston Cylinder BLOCK Bored engine 150$ Core
289.99$ plus core....a new top end rebuild kit for a SEADOO 650/657x twin. It will include 2 new pistons, rings, clips, top end rod bearings, and all gaskets needed for the top end. Brand new and ready to install. Cylinders have been bored to match the new pistons.

My Question:
What do ya think?
In general, is this a good plan.
Specifically, do I need to do more diagnosis to determine if the bottom end is worthy of a rebuilt top end?

Cheers,
Jeff

 

[howie099]

most people will say go for the whole engine if you don't the hours on it. if you have like 250+ hours on the crank will be the week part. It might get you buy this season or the next but you will need an engine soon.

 

[jhjesse]

Hi,
I gotta 95 Speedster - twin 657 Rotax. The port engine PTO cylinder is not firing.
Compression: 135psi Mag side, 25psi PTO side. :-(
I pulled the head and found that the mag side cylinder and head are wet/oily & the cyl wall is shiny and pretty smooth. The pto side is dry and moderately scored. I can noticeably "rock" both pistons from above with my fingers. Last time I ran it, I noticed the port engine maybe wasn't smoking as much as it shoulda.

My Plan:
1. Convert both engines to premix
2. Get a top-end rebuild like this one:


My Question:
What do ya think?
In general, is this a good plan.
Specifically, do I need to do more diagnosis to determine if the bottom end is worthy of a rebuilt top end?

Cheers,
Jeff

Do the whole engine. It will be money well spent. That engine will give you years of service in return. The 657 in my opinion is one of the best engines Sea Doo ever built. They are practically bullet proof.

 

[Bonmotwang]

Do the whole engine. It will be money well spent. That engine will give you years of service in return. The 657 in my opinion is one of the best engines Sea Doo ever built. They are practically bullet proof.

I thought 947 is "one of" them too. LOL


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