Other mag pump or prop or what? help needed

[gedskee]

I recently swapped over my running gear (+ some new gear) from 06 sj to fr2.

My ski FR-2, 760cc (stock bore) non-ported, ada head, 46mm SBN Carbs, Boyesen Manifold w/ reeds, Bpipe mod with porting, Flame total loss, skat-trak (12 vein) mag pump with skat track 12/17 swirl and bored exit nozzle (85mm)...

Im a bit unsure why the ski doesn't perform like a mad man in the surf it seems to have the power but possibly not enough drive I'm thinking it could be the pump setup... off the water the ski revs up beautifully and sounds awesome. the ski was setup with no corners cut and with professional help, it has no Cavitation, the curve is 32 degrees (i think, specially from atp) and run on other skis very similar to mine (and they ripp)

will a hooker 9/15 prop benefit me in more accelaration and more pop of the waves ?

Or is the motor not powerful enough to run this mag pump?

Does the cylinder need porting for all this to perform as one?

im lost for ideas : (

any suggestions would be greatly appreciated.

Thanks,

Ged

 

[OCD Solutions]

Have you ever run this motor before? The 760's have different porting than a 701 and are quite doggy in stock form. Ported correctly they perform quite well but porting will be crucial in making it perform as you wish and I would not trust just anyone to do this.

The rest of your parts look good.

 

[gedskee]

yes i ran that setup in my sj without the 46mm carbs, boyesen manifold and total loss and she went well!! now it seems to only go marginally better than before....

I'm thinking the prop needs to be more bottom end and/or porting of the cylinder to make everything gel/rip together.

the current setup is putting out 6900-7100 rpm

thanks OCD, is there any more suggestions out there?

 

[OCD Solutions]

The pump may be slightly too much load which could make it harder to tune the new carbs. If your jetting was borderline then it could cause it to fall on its face. Pitching down the prop would be a good start and make jetting a little more forgiving.

I run a ported 760 and found the 9/15 was too small in an oem pump. The mag will definately add some load and change the equation but that 12/17 should still be spot on.

How much time have you spent on jetting the new carbs?

 

[JetManiac]

Have you ever run this motor before? The 760's have different porting than a 701 and are quite doggy in stock form. Ported correctly they perform quite well but porting will be crucial in making it perform as you wish and I would not trust just anyone to do this.

The rest of your parts look good.

Ged, OCD has run 760 cylinders quite a bit so his guidance so be good. The 62t 701 or 760 cylinders have a higher exhaust port timing so they tend to be weak on the bottom as compared to a 61x.

The pump may be slightly too much load which could make it harder to tune the new carbs. If your jetting was borderline then it could cause it to fall on its face. Pitching down the prop would be a good start and make jetting a little more forgiving.

I run a ported 760 and found the 9/15 was too small in an oem pump. The mag will definately add some load and change the equation but that 12/17 should still be spot on.

How much time have you spent on jetting the new carbs?

When you change multiple things at once it can be hard to pinpoint the issue. Did you start with a proven carb jetting and popoff/N&S setup?

If you think that the 12 prop may be a little too tall on the bottom, then you can try adding a prop washer or 2 behind it to loosen up the bottom. If it is better then you can repitch or replace your impeller. I would make sure carbs are setup well before too much pump work though.

 

[gedskee]

thanks guys

i have an experienced fellow who jetted and setup the carbs for me. i know the n&s were 2.3 but jets i'd have to find out.

I'm pretty confident that the carbs are setup well, so its whether i change the prop to lower pitch so i can run my current setup or get the cylinder ported to produce the power to push my current prop. what do you think?

is it possible that a ported header pipe and ported exhaust manifold on a non-ported motor would make it lose bottom end??

also i forgot i to mention i changed from a LTD Bpipe Setup to a MOD Bpipe Setup could this be a factor???

 

[JetManiac]

thanks guys

i have an experienced fellow who jetted and setup the carbs for me. i know the n&s were 2.3 but jets i'd have to find out.

I'm pretty confident that the carbs are setup well, so its whether i change the prop to lower pitch so i can run my current setup or get the cylinder ported to produce the power to push my current prop. what do you think?

is it possible that a ported header pipe and ported exhaust manifold on a non-ported motor would make it lose bottom end??

also i forgot i to mention i changed from a LTD Bpipe Setup to a MOD Bpipe Setup could this be a factor???

Yes, the mod pipe is known to have less lower end, but some would disagree about that. Porting your pipe won't hurt bottom end.

I would get a 61x cylinder and start from there instead of messing with the 760 cylinder.