Super Jet My 1st Superjet

[Vumad]

I have an ada head with a coffmans pipe single cooling and I have a slight sizzle.

Off the head and head pipe? or just the chamber? Sizzle off the chamber is right, but I don't think I should be rolling steam off my head...

 

[Vumad]

I had Xscream tap my manifold for dual cooling as well as my pump. They charged $75, very steep imo, but they always do good work. It also bought some time talking to chuckie. Chuckie said my ski was over heating because I was running single cooling with 2 lines off the head. This was cutting the cooling to the pipe in half. This seems like a very reasonable explanation, and since no one else can offer any other explanation, I am forced to accept it. (I should have Y or T the lines off the head and fed the pipe with both lines)

I didn't get to talk to chuckie until after the work was done, so I went ahead and set it up for dual cooling anyway to get back on the water. I may go back to single cooling at a later date so I can have my stock bilge back. Anyway... Xscream sells some nice Y fittings for only $2 that I am now running instead of T fittings. Traditional dual cooling on my ski. 2 lines from pump to manifold. One line from head to stinger/pisser. Second line from head to pipe, then to the second pisser.

I can't tune my pipe. It's actually an A-pipe that is damaged. The top screw has been removed and the middle is blocked. The bottom is wide open for now, but I will try to tune it some later. The one picture shows how water flows through it on the hose. It's a 1/16" hole wide open. I have a blue jetworks valve running wide open, well, one turn in from wide open. I will try to tune the pipe next if I can, then the jetworks valve.



My carbs are working perfectly atm. Pop-off is stock at 53 with no leaking from the needle or seat right up to the pop. I am running a 135 main with a 75 pilot. My low screws are about 1.25 turns out. I am running a hardline tach with a smooth idle about 1200 RPM. My top screws are at about 1.25 front and 2.0 rear, although I would have to count again to know exactly.

I have good smooth linear power (like stock curve) throughout the RPM range. I was able to avoid having a strong uneven power band which is something I do not like. I like smooth predictable power throughout the range. There is a noticable increase in power at 5000 RPM, but I have good power everywhere, no 2-stroke light switch that I hate. I peak RPM about 7100 RPM with a 10/18 skat trak prop at 48mph. I am sure that if I can get some response out of my one working pipe screw and dry out my pipe that I will get more power on the top. I'll probably need a new prop in the near future.

I was going to post a video but I forgot my go-pro at home.

Left: Rear, Right: Front

 

[Vumad]

Copied from the other thread. It didn't get any replies. Just going to stick it here with the rest of the stuff about my ski. I haven't had time to figure this out because it only happened a few days ago. I'm going to look for obvious problems, but if I can't find any, I might consider doing 2 fuel pumps. Also looking at dropping my popoff from 53 to 20 or 30. Any insight would save me hassle and time.

Trying to get my ski set up as a full limited but like stock reliable rec boat. Lots of bolt on mods. Trying to get it to work perfect, like stock, just a lot more power everywhere.

Stock motor, Ada girlded head 180 psi, fpp manifold kawi fpp head a-pipe head pipe sj limited chamber, stock water box, dual 38 with reed stuffer carbon dual reeds, #0 lighten flywheel, msd ignition, 10/18 prop, aggressive scoop intake, works dominator ride plate, hard line tach.

Carb set up is dual 38mm stocker rear fuel pump front slave. Stock pop at 53, jetting 135/75, back top screw out about 1 turn more than front.
Pipe is damaged so bottom screw is wide open, middle and top are completely closed, lots of water in the pipe. Jetworks blue valve one turn in.
Dual cooling to manifold, no restrictors.

Ski runs real good. Will hesitate if I cruise around at 1/4 throttle for a while but I think it's just loading up with water. Good throttle response everywhere unless like I said I let it load up but were talking about 20-30 seconds and a lot of water goes into the pipe. I tried 137.5/75 jetting and the ski ran like .

My big problem ATM is that the ski dies on my after 20-30 seconds wot. Just plain shuts off, start right back up with great throttle. Pretty sure it's not my petcock, lines or vent.

A number of people say my setup should be perfect and others disagree. One person claims my ski won't run right with 53 popoff, drop it to about 20, but can't give me jetting specs. Others say 53 should be fine.
Some say fuel pump is fine, others say I need to run fuel pumps on both carbs. Can I just get the one missing plate and add it to my front carb?

I don't want to damage my motor. Carbs testing out right. Anyway, I would just like some more opinions because I have only gotten a hand full. I'm not tweaking this thing out for full race craziness. Just a powerful surf/race/flatwater boat.

Oh, pretty smooth idle at 1200 rpm, peak rpm is 7100rpm give or take and rev limiter set to 8000. The dying issues happens around 7000-7100.

I think the hesitation at 3000 is because of too much water in the pipe, clears out immediately and doesn't come back. Now I'm just rambling. Ill see if I have a decent video to post up tomorrow.

For lower popoff, I could do stock N&S (1.5) with 65grm spring for 32 psi, or 2.3 N&S with stock spring (115grm) for 20 psi. 2.3 N&S with 95 grm spring would give me 18 psi. I'm guessing the low speed jet with that set up would be 70 or 72.5...

 

[Vumad]

Well, I couldn't tune the issue out. Seemed lean in the back. I didn't have time or the proper tools to continue with a leak down test. I dropped it off with Jesse. He did a leak down test. Leak from the rear base gasket and rear crank seal. Also had a minor seize, hone and piston will make it like new. Hope to have it at 100% in another week or 3.

Edit: The lesson to be learned here is that no matter how good a stock ski runs, leak down test it before upgrading it to a limited. What ran perfect at 6000rpm became a huge problem at 7000rpm.