Piston Wash, Superjet 62T w/B-pipe

[jetskidude1113]

I was reading up on checking piston wash also with plugs reading. I just drop in a 62T/62T raider motor w/ limited B-pipe setting: top close, mid close, bottom 3/4 out, R&D head, and F/As into my 91 SN with jetting spec: 75 pilot, 135 main, 1.5 n/s, 95g spring. both adj about 1 turn. I'm about 195lb the ski got excellent bottom end but top speed I am only getting GPS 48mph which I expected to be a little bit higher like 49-50mph. I also have a 08 OEM Superjet prop and JetDynamic deep loader and plate combo. The plugs looks good and this is what my piston wash looks like. I feel it's a little rich, what do you guys think? Throttle from 3/4 to full the power/speed feels the same. I am thinking about dropping the main to 130 and turn the hi speed up a tad.
Thanks and advance,

 

[Vortex]

While you're in there clean all that carbon off the top of the pistons. You can actually get detonation from bits of carbon in the combustion chamber that get hot and cause the fuel to ignite at the wrong time. Yamaha shows this in their 2 stroke service video

 

[Quinc]

Swap the 75 pilot jet to a 70 or 72.5 for improved bottom end. Get a tach and see if turning the high screw out a hair helps or hurts you before swapping to a 130 or 140. Boring your manifold and headpipe I would start at 46mm bore and test it. TnT has a post on one of the bpipe threads talking about not going over 48mm.

 

[jetskidude1113]

Thanks for all the constructive inputs. truly appreciated. I definitely need a tach, iPhone'GPS zip-tie onto the cross bar pad just ain't cutting it for true tuning. lol
Anything better then a TinyTach these days that won't break the bank? I had one or two of them back in the mid 2000's tuning my SXR with a wet pipe and the thing keeps freezing up.

 

[jetskidude1113]

Pipe adjs are: top close, mid close, bottom 3/4 open. Chamber temp strip indicator 1" down from coupler is about 158F highest chasing buoys at our local spot. I kind of like to keep it cooler to preserve the life of the coupler, what a PITA to have to replace it. lol

Sounds about right for top end speed for that Package. You could close the Head Pipe Bottom Screw to 1/2 turn open. Do the water sizzle test on the Chamber for ideal temperature setting.

Show a photo of your Cooling Hose set-up and routing.

What rpm's are you turning? You might be able to squeak a little more speed by fine tuning the Carbs with a good Tachometer.

The deep scoop Intake will scrub some speed but gives better hook-up. Adding Front Sponsons will increase buoyancy which will decrease drag and help top speed.

Some Riders will sand and true the Hull Bottom to decrease drag and improve tracking. Another has actually coated the hull bottom with truck bed liner for a 1 mph gain.

A Pump Gas Cylinder Port job will make your SJ more responsive and faster. Yamanube sells a proven DIY Porting Template.

You could bore match the Exhaust Manifold and Head Pipe to 50mm diameter for more top end. Buy a 50mm Gasket and use it as a Template.

pipe water routing are: Single cooling, 3/8" pump to exhaust manifold, 3/8" rear cylinder head top out to headpipe bottom, 3/8" headpipe top out to Tee side, 3/8" Tee side out to 3mm restrictor to stinger, 1/4" Tee middle out to Kawasaki 1/4" pisser. 1/4" front cylinder head out to Kawasaki 1/4" pisser

 

[Vortex]

Swap the 75 pilot jet to a 70 or 72.5 for improved bottom end. Get a tach and see if turning the high screw out a hair helps or hurts you before swapping to a 130 or 140. Boring your manifold and headpipe I would start at 46mm bore and test it. TnT has a post on one of the bpipe threads talking about not going over 48mm.

Group k just bored one for me from 42 to 52mm. We'll see how I does lol. And I thought they were 'conservative' with their builds.

The older b pipes with 42mm id were detonation city

 

[jetskidude1113]

The older b pipes with 42mm id were detonation city[/QUOTE]
really... that's not good, but good to know.. mine is an old I would say mid 90's 62T manifold and headpipe. came out of a 94 62T/62T Raider motor. Sold the Raider/Blaster Mod chamber and bought a limited B chamber.

 

[MTRHEAD]

Group k just bored one for me from 42 to 52mm. We'll see how I does lol. And I thought they were 'conservative' with their builds.

The older b pipes with 42mm id were detonation city

Interested in hearing what you found. I tested a few different sizes on different combinations. I will comment I found a loss of throttle response as you get real big on stock stroke 81-84mm bores.