Freestyle Looking for 62t 760 freestyle specifics 64x Decking Porting

[lamar311]

They are...everything is clean as far as I can tell. I pulled them apart. I am guessing they were rebuilt incorrectly by the previous guy as he could never get them to work either. I will pull them apart again. Originally I thought it was a pop off issue, but obviously that wasn't the case. I might try switching the pump section from a working carb I have and see if that fixes the issue. I wish I had two workiing 38's or 44's I could just slap the fuel pump sections on and call it a day. This thing has been so odd to get back together.

 

[lamar311]

so I finally got her running and on the water yesterday. I had to chase down a few air leaks. Because my cylinder was decked I had to do way more work to get this thing into spec. Funny part is my jetting is actually lean on the low end. I had to turn my screws out 1.75 on the bottom to get her to run decently and my plugs were still very dry and very hot. I think I am going to bump up to 120 lows and start at 1.0 turn out. It won't even start with the 115's until I turn it out 1.5 times.

I am have a pretty severe lean hesitation on the bottom but damn...1/4 throttle this boat is hard to hold onto. Interested to see once I get her jetted in. BTW...my pop off is at 22 psi per group K.

 

[lamar311]

Well I figured I'd add a little more to this thread. I ended up at with the following carb set up for dual 44s.

120 lows
135 main
22 psi pop off

Bottom 1.5 turns out Top 1.75 turns out. I am a tad rich but that is ok...my plugs are a little black but not wet.

I ended up keep my 10/16 hooker but bored out the Raider nozzle I had to 84 mm. I am also running a wet wolf cone.

This ski makes incredible power for the cost. Paying to have the cases decked is SOOO much cheaper than paying for a BB kit on a 61 x set up. I was shocked at the low end punch this ski now has, and from 1/4 throttle on it tires me out quickly.

Great thread here. I think if ppl would take a better look at the 760 motor there would be a great shortage of cylinders available.

 

[jo5hi3]

Well I figured I'd add a little more to this thread. I ended up at with the following carb set up for dual 44s.

120 lows
135 main
22 psi pop off

Bottom 1.5 turns out Top 1.75 turns out. I am a tad rich but that is ok...my plugs are a little black but not wet.

I ended up keep my 10/16 hooker but bored out the Raider nozzle I had to 84 mm. I am also running a wet wolf cone.

This ski makes incredible power for the cost. Paying to have the cases decked is SOOO much cheaper than paying for a BB kit on a 61 x set up. I was shocked at the low end punch this ski now has, and from 1/4 throttle on it tires me out quickly.

Great thread here. I think if ppl would take a better look at the 760 motor there would be a great shortage of cylinders available.

so you decked the cases instead of the cylinder?

 

[mxr181]

Yes...@nucklear prefers to deck top case rather than removing sleeves, decking bottom of cyl, then reinstalling the sleeves. He will do either but decking the cyl is more work and therefore more $$$

 

[Sasquachcrap]

Thanks for the update. @lamar311

 

[lamar311]

so you decked the cases instead of the cylinder?

I thought I should give a better answer to this. Yes, I decked the cases and had to bore them to accept the larger sleeves and add a second pulse nipple as they were a standard set of 62t cases, not the 760 cases. Also, when you do this you have to grind the corners of the bottom of the cylinder sleeves for clearance as you have now dropped everything by .065. Its not a lot...just worth noting.

Decking the cases is super easy for any machinists to do. I had a local guy do it for a case of beer (granted he is a buddy). Also, I bought a used head with really crappy domes off ebay for like $60 shipped. Because I had to have the domes adjusted anyway I bought a 701 set up as they are common and than had the same machinist cut into the domes to adjust for clearance ,proper squish, and larger bore. The domes cleaned up really well due to the amount of material he had to cut out. Saved me a ton of cash over buying a new head and clean domes.

I had the cylinder and pistons from a previous motor set up but here is the cost I had incurred.

1. Used head : $60
2. 62 t cases (I traded parts for these so free but usually $175-$200)
3. Machine work $100 (again I had a buddy do it for a couple cases of beer)
4. Dual 44s, mani and reads $150. (I was able to trade parts for these as well)
5. Gaskets $100

My actual cost was only about $175 but I had a lot of parts to trade/ ect.

All porting was done by another buddy using the sport port template. Again on the cheap (Beer)

For the money I spend I am blown away at the power

 

[jo5hi3]

awesome, i never really thought much about this cause i never had plans to build one of these. But i like the idea of decking the cases instead of the cylinder, much less work. Glad to hears yours runs good.

 

[lamar311]

Its not power valve power mind you, but I would put it next to any resleeved big bore and can gaurantee it pulls as hard and I have WAY less $$ in it. Plus you can get a hold of a 760 waveraider on the cheap which comes with trim and a 155 pump.

 

[yamabro]

Thanks for all the great info. I'm about to do this and wake my 91' square nose UP!!!

 

[lamar311]

Question for the OP. Did you have your carbs run with dual fuel pick ups from the tank? Or were you running the oem set up with 1 fuel line split to each carb? I just switch to a dual feed set up. I haven't had it in the water yet, but I can notice a significant difference in the throttle response with dual fuel pick ups. I am wondering if this is why my jetting needed to be so much larger than yours to get her to run right. Wondering if now I am going to be over jetted.

 

[Half flip95]

I would put it next to any resleeved big bore and can gaurantee it pulls as hard.

doubt it

 

[Quinc]

doubt it

Why's that? Same cc, same port timing, ported?

 

[Sasquachcrap]

I think he spent to much on a big bore and is sour. He's been bashing this idea since I started this thread last winter. But will never give any specific specs or advice as to what makes it better.

 

[Quinc]

@Sasquachcrap, going back through the thread how did you get your carbs this shinny?! Or is it paint?

 

[Half flip95]

"I think he spent to much on a big bore and is sour."

I run an 82mm bore.


"...will never give any specific specs or advice as to what makes it better."

What makes what better than what?


I just don't believe the hype.

"I'm only in it 500.00" - (and 100 hours?)
"I would put it next to any resleeved big bore and can gaurantee it pulls as hard." - (Am I supposed to believe this is the fastest big-bore ever built?)

 

[Harbor]

It might be silver powder coat ?

 

[kevbo]

I think he spent to much on a big bore and is sour. He's been bashing this idea since I started this thread last winter. But will never give any specific specs or advice as to what makes it better.

This sport is completely subjective when it comes to engine performance. The only two meaningful aspects of freestyle propulsion is response and thrust. I have not found, in the past 20 years, another jet ski rider timing throttle response or measuring thrust. Its all based on personal opinion.

 

[lamar311]

"I think he spent to much on a big bore and is sour."

I run an 82mm bore.


"...will never give any specific specs or advice as to what makes it better."

What makes what better than what?


I just don't believe the hype.

"I'm only in it 500.00" - (and 100 hours?)
"I would put it next to any resleeved big bore and can gaurantee it pulls as hard." - (Am I supposed to believe this is the fastest big-bore ever built?)

I was into mine way less $ than that but I had a bunch of parts to sell/trade and a buddy to do the machining. Also, I had about 10 hours into it, from removal, teardown, and port work (I didn't go as deep into the case work as the OP), and reinstall. Keep in mind though I didn't pull the sleeves like the OP. I had the cases decked and than adjusted the bottom of the sleeves for the lower position of the cylinder. I have ridden a bigbore set up done by Kommander Industries here in town. My buddies ski has almost an identical motor set up (regarding bolt ons) and mine pulls as hard and has immediate throttle response just like his does. He is running the same carbs as I am and his flywheel is a little lighter but there is almost zero difference between the two motors.

By all means doubt me..please! It will give others the chance to pick up 760 cylinders for $60 like I did and build one of their own. True cheap power ...if you are willing to put in the time. I don't really see any Hype here. There are only a handful of us that have done this and ALL of us say the same thing. However...please keep spending the cash on the BB cylinder. 760's are hard to find....

 

[lamar311]

I think he spent to much on a big bore and is sour. He's been bashing this idea since I started this thread last winter. But will never give any specific specs or advice as to what makes it better.

Are you running a single fuel in with split to both carbs or are you running dual fuel pickups?