Ponda

Geezus...this JS550 is giving me fits. $50 paypal'd to the person who gets this thing running.

SYMPTOMS:

-Will not start under load. I can get it to fire up and idle out of water fine but I can't get it to start in water.
-Smoke seems to be coming up out of the carb after attempting to start the ski in water. Is this normal? Seems odd to me. What would cause this?

TROUBLESHOOTING - here's what I've done so far:

-Leak down test. Bottom end holds pressure fine.
-Compression test. ~140psi in each cylinder.
-Spark is good.

NOTES:

-The ski will not start out of water on stock carb settings. I richened the carb up quite a bit and got it to start easily. From what I've been told - the ski should be starting on stock settings even with the higher compression.
-The carb is freshly rebuilt. Popoff pressure has not been tested, though.

Somebody please save this ski! A few more days and I may give it a viking funeral.

Arctic

The reeds are FUBAR'd and without the exhaust underwater it has enough draw do get enough of a air/fuel charge into the motor to run. When you add the resistance of the water it's blowing back through the carbs.

I guess your ski might be old enough that whatever is the functioning "intake valve" is fuct.

http://www.animatedengines.com/twostroke.shtml

Ponda

^ JS550's don't have reeds.

Arctic

I edited it. Something has to function as the "intake valve" and I'm guessing that it's not working? What else could it possibly be? It's not like you have a metal chassis that is getting an electrical short when you put it in the water. Somehow either the exhaust is getting completely plugged or the intake valve is not operating properly.

Ponda

Hopefully this makes sense...

The ski is trying to start while it's in water - seems like it's going to start but won't quite get there. After that I would pull the plugs and hit the start button to make sure I wasn't flooded. I think the excess exhaust was just creeping through the intake since the exhaust was blocked by water.

If it were a timing issue - it shouldn't run at all. Even on land.

no fear here

just for kicks, pull the flywheel. sometimes the wodruff key will shear and the flywheel will move slightly.

Ran into this on more than one occasion.

__________________
"Riding an '89' is a Splash from the past
PJS Exhaust & Waterbox
Mariner Head - Decked at 185lbs compression
38mm Keihin
Ported & Flow Matched Stock Intake
R&D Reeds, Cages & Stuffers
Skat 15
R&D Toploader Scoopgrate
Ocean Pro rideplate
Pump drilled for dual cooling
500gph rule

Ponda

B triple D. Been der, done dat. Key is in place and solid as a rock.

p10sdad

91 and newer. If it is a JS then no (pre 90) People still call them the JS even though 90 and newer is the SX, and then 91 and newer have the reed engine. Do you have a hose hook up on that? I'll run through a few things here I'm sure you have already done, but need to see anyway. All the exhaust hoses are clean inside? Water flows through the water box just fine, no clogs? The jet pump isn't clogged? The one way valve at the fuel tank works, and is pointed in the right direction? The vent hose from the fuel tank isn't clogged? fuel lines aren't clogged? Fuel filter is clean? Are you getting gas to the motor? Do you have a choke or primer kit? Have you replaced the stator? What state do you live in? Let me know about these things I have a couple ideas.

Ponda

I live in East TN.

The engine is getting fuel. I inspected all of the fuel lines / valve / filter and everything is good. All exhaust lines appear to be clear. Nice stream of water comes from the pisser when it's hooked up to a hose.

I have a primer kit.

I haven't really inspected the jet pump yet. What's a good way of testing that?

p10sdad

Well if your getting water out of the side your jet pump is clean anyway. When you prime it, it starts right? So it runs, just not on the water under a load, is that right? When its been on the hose it has been running right?