Is there hope for a holeshot?

[beachedflunkey]

Okay I got a very good deal on this former "race" ski and just got it running better than "good enough" for my lucky wife's first sj and decent enough to be a backup for me :sneaky:. Is there hope for turning this into more of a holeshot/freestyle ski with a little tuning - read low-budget? I just gave it its first water test yesterday and really have no complaints but if this should be stronger then I might like it to be someday...

I'm mostly thinking the carbs and possibly the port job or compression could be the obstacles. I'm no pro but with the help of derm we got the carbs dialed in well enough to make this a fun ride. I will likely leave well enough alone until curiosity gets the best of me and I get a wild hair to play with it a bit more so if that happens where might I start?

• 760 "race" ported motor (I'm told it's a "light" port w/61x cyls on 62t cases)
• GroupK modified head - 140-150psi w/fresh gasket :question:
• Dual mikuni buckshot 48's (110 main, 115 low, unsure of popoff)
• Unsure of reeds/spacers/stuffers - I didn't have spare gaskets to risk disassembling there
• R&D wet pipe - unsure of restrictors
• "Modified" cdi - I'm told the rev limiter was raised but not eliminated if that is possible...
• Protec reduction nozzle - about 80mm
• Stainless non-swirl prop - unknown pitch and make
• Stock cone
• Worx 201 grate
• Riva Groovy plate
• and a couple other things not related to thrust

*haven't tested extensively yet (ie, for more than 5-10min or WOT for more than a sec or two) - I just gave it a fresh hone and top end prox rebuild but it seems to ride very nice so far.
**Oh and it needed a little hull work too :biggrin:
Before:

After:

 

[douglee25]

I think your problem is with compression. 140psi to 150psi isn't gonna do much for that ski. Bump that up to 175psi or 180psi and I bet your ski will run much better.

Doug

 

[sflsurfrider]

that is a nozzle must be for racing @ 80mm. do you have enough material to bore it to, say, 86mm? thatd help out a ton for thrust and for cheap.

a jetworx flow control valve before the stinger also makes a noticable difference in holeshot...... and for cheap.

raise the compression if the head isnt too "modified" already..... again, cheap.

solas concord impeller. you can find em cheap too.

 

[PancakePete]

Ski looks awesome Mark. We will see you soon ! :biggthumpup:

I would say same thing. Bump compression up a little.

Its killer looking though... that color Rocks. :Banane01:

 

[beachedflunkey]

Wow thanks for the fast responses! Okay now just another question or five :biggrin:

Milling the head is not an option if it leads to downtime. If I were to mill an old 64u stocker I assume I'd have to get it done to match the 84.5 bore? It's a 61x on there now with three water fittings. Pros and cons of using a 64u + tapping for cooling? I should have measured the dome size before I put the head back on :banghead:

sfl, there is not much room to bore out the nozzle except maybe 1mm on each side. I could keep my eye open for a cheap Al stocker or how bout a cone? Would this adversely affect performance w/o switching out the prop?

Switching to 44's is not a priority due to $$ or downtime right now. But if it works out, could I reuse the R&D intake? pic: http://www.wavejunkies.com/gallery/albums/userpics/10040/Jena Build 2006 carbs 001.jpg

Thanks for the compliments guys. I think she glossed out nice. The ski too! Taking the skis to Kerr Lake for the next couple days for "training".

 

[Matt_E]

The compression is likely that low because it's a 760, and it's race ported.
I'd be careful bumping cranking compression up too much - you might get into trouble further up in the RPM range.

 

[douglee25]

The compression is likely that low because it's a 760, and it's race ported.
I'd be careful bumping cranking compression up too much - you might get into trouble further up in the RPM range.

He should be ok with high octane fuel and factory timing with no advance.

Doug

 

[sflsurfrider]

sfl, there is not much room to bore out the nozzle except maybe 1mm on each side. I could keep my eye open for a cheap Al stocker or how bout a cone? Would this adversely affect performance w/o switching out the prop?

a cone would certainly help, but i think youd do better with a stock nozzle and a cone or just a bored stocker.

make sure to measure the inner and out diameters of that protec nozzle. ill bet you can bore it more than 2mm based on the ones that ive seen.

i noticed dramatic changes with just a bored stocker nozzle.

 

[oxnard111]

that is a nozzle must be for racing @ 80mm. do you have enough material to bore it to, say, 86mm? thatd help out a ton for thrust and for cheap.

a jetworx flow control valve before the stinger also makes a noticable difference in holeshot...... and for cheap.

raise the compression if the head isnt too "modified" already..... again, cheap.

solas concord impeller. you can find em cheap too.

I have been looking into control vavles... do you have to change any tunning when installing one? Oh yeah, the wiffy is pretty hot

 

[beachedflunkey]

Okay it is 83-84 ID - my bad. And 90mm OD. Isn't that the same stock? If that is the case, I don't really see the point in this aftermarket nozzle unless the 96's originally had a plastic nozzle :dunno:. It doesn't seem to be extended either. And I'll add "doublecheck timing" to my todo list next time I wrench on it.

Its killer looking though... that color Rocks. :Banane01:

Thanks Pete! She'll have a bit more color to her after getting ridden and baked in the sun all weekend :haha:
edit: I'm sleeping in the dog's tent this weekend for that!

 

[sflsurfrider]

Okay it is 83-84 ID - my bad. And 90mm OD. Isn't that the same stock? If that is the case, I don't really see the point in this aftermarket nozzle unless the 96's originally had a plastic nozzle :dunno:. It doesn't seem to be extended either.

maybe the fact that it doesnt have vanes plays a role in the fact that the opening is that of an OEM. not sure. :dunno: