no bottom end power!

[bored&stroked]

So previous owner got it in trade and knows nothing, and you know nothing. Its a factory single carb intake. You sure its not a 650 engine in there?

 

[Kyle c]

So would a good way to go be trying to find a 62t bottom etc and swap it out?

 

[Spyder]

I'd pull the head and see what bore the cylinders are at. If the top end is 650 as well, then no point in bottom end swap. Can't remember what 650 bore is but 701 bore would be 81mm and if it's truly a 760 the it should be something like 84mm

 

[Kyle c]

Okay I’ll try that tonight, thanks for all the advice guys

 

[maxboost]

Okay I’ll try that tonight, thanks for all the advice guys

when you get the head off measure from the deck surface to when the exhaust port opens with a micrometer, with that you can figure out exh duration and that will give you an idea of when your power is going to come on

 

[maxboost]

http://www.x-h2o.com/index.php?threads/port-timing-duration-specifications.21863/
this has the port timings for some Yamaha jetski motors, should give you an idea where your at

T=R+L+C-E​

• R is stroke divided by 2
• L is the connecting rod length
• C is the distance of the crown of the piston to the top of the cylinder in TDC (Deckheight)
• E is the distance between the port and the top edge of the cylinder

You can use this to get your degrees duration from your measurements

 

[Kyle c]

I’ll have to look alittle more into that thanks

 

[Kyle c]

Update, head was pulled and cylinders are bored to 84mm and Can anyone tell if there was any porting?

 

[iQRTurbo]

Is the motor a turd and has no power or is the pump slipping like your original post indicated? If it’s slipping the wheel then adding more power is only going to make the problem worse.

 

[Kyle c]

More so slipping, it’s a slow take off, the motor seems pretty snappy by ear, just no thrust

 

[CARBONX2]

Update, head was pulled and cylinders are bored to 84mm and Can anyone tell if there was any porting?

Definitely ported. The problem is in your pump if you are describing slipping. Pull pump to check impeller condition/clearance. What cone is in and what size is the exit nozzle?

 

[schicks]

Might be way off, but i just got done chasing my tail on an issue where my ski wouldnt rev out correctly, seemed to bog almost. The low end torque was terrible, but i could pin it across the lake and it would go. ended up being a bad stator. My check order was swap cdi, coil, went through carbs, then swapped stator and that ended up fixing it. Stator looked brand new, but somthing wasnt right with it.

 

[Kyle c]

Update I took the pump unit out, it has a solas 13/17 prop in mint condition, it is a 144 pump unlike the guy said, (I’m assuming stock superjet pump) the exit nozzle is 94mm

 

[Kyle c]

.015 clearance between the wear ring

 

[CARBONX2]

Update I took the pump unit out, it has a solas 13/17 prop in mint condition, it is a 144 pump unlike the guy said, (I’m assuming stock superjet pump) the exit nozzle is 94mm

You mean 84mm on the reduction nozzle?
Clearance is good
What cone?
You can cut the impeller for setback (and/or take washer out), will help hookup
Leading edges of pump vanes look damaged, need a better pic

 

[Kyle c]

Sorry yes i meant 84mm and it had a stock superjet cone, and the vanes have some pitting on them but there is no major chunks or anything taken out of them
Is the 13/17 with the 144 pump a good setup for what I’m looking for?

 

[Quinc]

Might be way off, but i just got done chasing my tail on an issue where my ski wouldnt rev out correctly, seemed to bog almost. The low end torque was terrible, but i could pin it across the lake and it would go. ended up being a bad stator. My check order was swap cdi, coil, went through carbs, then swapped stator and that ended up fixing it. Stator looked brand new, but somthing wasnt right with it.

Buddy just had this same issue with a wsm stator.

 

[SuperJet-Dave]

More so slipping, it’s a slow take off, the motor seems pretty snappy by ear, just no thrust

Have you looked at the spline on the shaft, where it mates with the mid shaft? I had a similar issue where the spline was worn down and causing slippage. Good luck.

 

[newbee]

Really think the pro would me a good start. Jetmaniac or impros could get you the prop for your setup. Being a 760 with bolt ons I would think you would be better with a 10/16

 

[Kyle c]

The spline looks good, and okay thanks for all the advice guys, I’m gonna look into it a bit more, maybe get a 62t bottom so I can have the bigger reed cages an duel carb and maybe invest in a lightened flywheel and impeller