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Put my 1990 SP in the water today!!!

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mike_dmt

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So a day earlier than I thought I would, I dunked the SP today. Trailer tested it first after dropping in the donor engine, fired off great but had some issues fairly quick.

After about a minute of running, clearly cooling and oiling, it decided it didn't want to idle in the water. No biggie, I don't sit and idle much. But it ran pretty decent at 3/4-2/3rds throttle.

Made a few quick passes off the trailer, seemed O.K., but wouldn't idle, or run at full throttle.


Ended up riding for a couple of hours that way, but I want it to be better.

Here's the symptoms: runs good at partial throttle
wont idle for more than 2-3 seconds
requires choke to re-start even when warm
dies when decelerating, unless choked about 1/4 of the way
stumbles after 10 seconds of full throttle, but if choked a bit, it runs better and faster.




I figure this is leading to a carb rebuild, which is fine with me. The fuel lines are replaced with automotive grade already, all clamps, no zips. Using what I believe to be a factory pulse pump.


So how do I find the carb part# so I know what kit to buy?
 
A few things....


A) DON'T keep running a 2-stroke jet ski if it is not running right. Fuel, is the life blood of a 2-stroke, and you CAN KILL a perfectly good engine by running it lean.

B) Yes, you need to rebuild the carb... but the fuel pump can be a problem too. You will need to verify it's output.

c) If you don't feel like rebuilding your carb... I have a carb, and fuel pump sitting in a box, that is clean, and ready to be bolted on, that I will sell you cheap. ($40 + ship)
 
I did pull the plugs after about 15 minutes of riding. They were dry, and a medium brown color, which I believe is what I want, going off of the carb adjustment sticky. I did mix 2oz. per gallon in the fuel as well just to be safe.
 
The extra oil will help keep you safe... but if you are running lean (The reason it's dieing up top) the combustion will be hot, and can melt the piston crown.


Here's the pic of the carb you asked me for.


 
I actually just discovered that I connected the fuel lines at the carb upside down. I have the supply feeding the top nipple and the return hooked to the bottom nipple... Could that be whats causing my problems?
 
It could since there is a restrictor in the carb. I'm surprised that it ran past the start-up.
 
Yeah, I just switched them around. I didn't want to run it on the trailer for too long so I dont know if it will run any better in the water.

What adjustments are on these carbs, I see the idle set screw, and the adjustment just above it, which only seems to turn about 1/3 turn either way. Is it possible its just dirty? What can I do to clean it up some?
 
On the old carbs... there is only a low needle. it should be set at 1-3/4 turns out.

There is no... "Cleaning it up some." Take the carb off... take it apart... and clean it right. (If it needs to be cleaned) BUT... see how it runs will the feed, and return lines hooked up properly.
 
So, popped the carb off and took it apart. From what I could tell it was really clean. no debris or anything in any of the passages. After looking at it closely though, the idle set screw was adjusted out so far I think that could have been part of the idle problem. Also the low side needle was probably set wrong, and thanks for answering my next question about proper adjustments there.

Now carb is back on, fired right up with good response. What should idle speed be out of the water and in the water?
 
in the water is 1500 rpm. Out of the water is irrelevant. You can set it to 3000 RPM out of the water... but you will just wind up readjusting it when you get to the water.
 
Yeah, I kind of figured that after I posted the question. Thanks for all the help Dr Honda. I might see if i can get to the water today to see if any of the problems are resolved.
 
Good News!!! Made the fuel line correction. Made the adjustments to the carb and it ran like a champ all day. 99% of the issues are resolved.

In reading up on the carb adjustments and from what Dr Honda recommended, my low speed screw is adjusted to 1 3/4 turns out. If I idled for very long it wanted to start to load up and smoke a bit. If i brought it up to about 1/4 throttle it cleared out well enough and had good throttle response.

I am still running a bit of pre-mix as insurance, so I'm thinking that might be the culprit, but I'm not 100%. It does want a bit of throttle to start when warmed up, maybe 1/8th to 1/4 open. Does that indicate a rich or lean setting on the low speed screw, or just a result of extra oiling?


Also, I have a SBN 38 laying here. Are there any performance advantages to it, or just the convenience of the built in pump?
 
You may want to turn the low speed mix screw in about 1/8 of a turn... but if you have some oil in the fuel... don't adjust anything yet.

It's normal to have to give it just a touch of throttle to get it to restart. The reason for that is, the fumes in the bilge build up... and it needs a little help.

Yes... there are a few advantages of the SBN. It will flow more air... and the internal pump is easier to deal with.
 
Dunked the Sp again today. Ran the rest of the premixed insurance out of it. Starts and runs even better, as I imagined it might. I might try that SBN 38 just for fun, if it will make a bit more power, but like the saying goes, "don't fix it unless it's broke"
 
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