jetting question for 760

[jetski9010]

My buddy just bought a superjet 760. This is one of ross champions old skis. The ski has a bad flat spot in it so we took the carbs apart and cleaned them. It seemed to run a little better as the carbs were full of crap but still had a dead spot and seemed to be running lean. when we pulled the ski out and looked over it we found the plugs looked really lean and the one spark plug bridge was broke off! The jets that are in it are a 125 main and a 70 pilot. I know in my 760 that is all dialed in I have a 135 main and a 75 pilot. He has a bunch of different bolt ons on his ski then mine starting with a pro tec pipe. Does anyone eles think that the jetting for this ski sounds really low? When we bought the ski we were told it was in working condition so I am just guessing that who ever built this ski had it set up this way for a reason. Any help?

 

[jetski9010]

we got the broken plug figured out just need to know about the jetting.

 

[Sospikey]

What size carbs? What mods do you have? Porting?
All important info if you want someone to step up and give advice!

This might be helpful:
http://x-h2o.com/showthread.php?t=19403&highlight=jetting+list

 

[jetski9010]

they are stock 38 carbs, pro tec pipe, .050 squish, 200 psi compression, not sure on porting specs put I belive home porting done so nothing too aggressive. blowsion air filters.

 

[jetski9010]

oh yea it has 62T cases and 62T cylinders too.

 

[OCD Solutions]

Taken from my buddies email, his skis all run exceptionally well as he spends countless hours tweaking his jetting.

At that point I upped my jetting to 77.5 pilots, 137.5 mains, 2.0 needle, 31 psi pop off (stock flame arrestors), 1 turn out on the low speed screws and 1-1/4 out on the highs. It runs good and colors the plugs turkey turd tan. You can run your pop off around 24 psi with the Proks flame arrestors. I think you can run 1.5 needle & seat with the 38's as long as your pop off is close. If you use this jetting, you will be in the ball park. I searched every thread and this is what works.

The motor I have that I'm running the 38's on is bored to 83mm, if I could (sleeve's too thin) bore it to 84, it would be a 760. I setup the jetting when it was a 701 When I bored it, the jetting stayed the same

I run my Ported 62T/62T 760 with Taper bored 38's on a stock intake with 77.5 pilots and 135 mains, 2.0 N&S, 115g spring. Plugs chops are always right on and my ski runs great bottom to top with very crisp response and no dead spots.

There are so many other factors that come into play as well as jetting so be ready to keep messing once you start. It is best to take a baseline and record your current jetting and all adjustments so you can always come back to it.

 

[jetski9010]

Taken from my buddies email, his skis all run exceptionally well as he spends countless hours tweaking his jetting.





I run my Ported 62T/62T 760 with Taper bored 38's on a stock intake with 77.5 pilots and 135 mains, 2.0 N&S, 115g spring. Plugs chops are always right on and my ski runs great bottom to top with very crisp response and no dead spots.

There are so many other factors that come into play as well as jetting so be ready to keep messing once you start. It is best to take a baseline and record your current jetting and all adjustments so you can always come back to it.

Thanks that helps a lot. My carbs are not taper bored yet but jetting should be right around the same. I know I will be messing with the jetting somewhat but I just wanted to know what jets I should put in there to start with when I take it out the first time. Thanks again.

 

[OCD Solutions]

I just had another set of stock 38's cleaned and clearanced for my other ski and they were sent back with 75 Pilots and 135 Mains with the choke plates removed. Previously I had added a primer kit but left the choke plates in and ran with 70 Pilot and 130 mains.

I once heard that OEM 38's are hard to jet if you pull the choke plates. Can't remember the specifics of the conversation but a dead spot rings a bell.

Start big and work your way down. 75 pilot and 135 main should be a fairly safe starting point.

 

[Mark44]

Purchase a tach from Watcon he has the best price on them and tune it properly it is really easy to do if you use a tach, works much better than the feel method and will save your motor in the long run when tuned properly.

Mark44