Rebuild Struggles

[Mayor118]

What I meant was 36cc is 36cc..........won't matter on the brand, or even the squish band for that matter. If it's 36cc on a 701, it should only make around 175psi. So that's sort of wierd.

I had to have the cylinders machine for a one over. The rear piston started to mark the walls and get hot. The believed root cause was the rear crank seal.

It’s interesting this ski never had a rebuilt and the original owner owns a Yamaha dealer where I purchased it.

I guess the overall question is changing out the pistons x1 and having the engine machined for those could change my compression values to push me into race fuel?

 

[Myself]

I've seen the Pro-x pistons raise compression. I've also seen the Wiseco 'Pro-Lite' series pistons raise compression. I personally have NOT seen that with any other brand. Just going oversize on the bore doesn't affect compression too much to even matter........unless it's a 'big bore' setup.......then EVERYTHING changes!

 

[Mayor118]

Ran a tank of avgas through for break in. Boat seems solid with some small carb adjustments.

However I’m getting some vibrations when at low idle (no wake zone) that seem much different then before. You can also feel it slightly in the bars on plane. It’s been all winter since I have been on it but it doesn’t feel right.

The boat has new motor mounts which I used the original shim locations along with a new mid shaft which I also used the factory shim locations. When changing alignment as per the manual everything seems to be aligned. I pulled the plugs and checked different points throughout as I rotated. It’s hard to get anything in there but confident it’s good.

Then pulled the ride plate and went through the bolts on the pump. Again all seems correct. Just doesn’t feel right in my gut and I have seen skis misaligned shake themselves apart.

 

[Mayor118]

I've seen the Pro-x pistons raise compression. I've also seen the Wiseco 'Pro-Lite' series pistons raise compression. I personally have NOT seen that with any other brand. Just going oversize on the bore doesn't affect compression too much to even matter........unless it's a 'big bore' setup.......then EVERYTHING changes!

These are Pro-x pistons on the fresh build. Will check the compression again after the tank I ran. Avgas was not as much as I thought so if it’s still high I might just run it all season.