'97 spx carb tuning question #3

[sportsfreak90]

took my jet ski out to the lake today and had the following issues that I've been trying to resolve:

Starts great when it's cold, won't start very easily once it's hot.
If you go from idle to any throttle under 1/2 throttle, runs fine. if you go from idle to half throttle or more, it bogs for about a second and then takes off.

I have adjusted the low speed needles from 1/2 turn out (lean) to 1&1/2 turns out (rich), none of which helped with the hot starts or the bogging.

I was reading the Carb Adjustments thread and was reading that the High Speed Jet could possibly be my issue? Would I adjust the High Speed needle to fix this problem? The carbs have been 100% blown out and cleaned twice with carb cleaner, removing all the jets and needles and filters with replacing ALL of the fuel lines so I know none of that is my issue.

Thanks! I really appreciate all of the help I have gotten so far on these forums!

 

[Dr Honda]

Does the bogging only happen once, after a restart? If it is OK after that, and runs fine until it sits again... then it's just the fuel draining out of the high circuit. (not a real issue) If it's doing it every time... and you know that carbs are clean... check the compression, and the clearance on the rotary valve. (this problem is a little more common on a reed valve engine, because of leaky reeds)

The hot restart could also be part of the draining issue. If the carb is draining after you shut it off... then the engine will be partly flooded, and the carbs won't have any fuel in them. When you did your rebuild... did you use an OEM diaphragm? (has a red nipple) The aftermarket kits cause the problem you are having.

 

[Bills86e]

Did you use a pop-off tester and do a leak-down test after re-assembly?

When you open the gas cap, do you get a large Expell of Air?
A common cause is a carburetor needle(s) & seat(s) leaking fuel into the cylinders. How can gas get past a needle valve other than what I have talked about? One way is if the fuel tank pressure release check valve in the OUT vent line is not functioning. The fuel pressure in the tank overcomes the spring tension on the needle valve and gas is FORCED past it.

A pressure test consists of two tests. One when assembling the carb, by installing the needle valve, the lever and the spring, then soaking the needle with gas or WD40, then pumping up the pressure and watching for bubbles around the needle valve, then more pressure to measure when it pops off.
The second test comes after full assembly. This is the one that gives you an idea if they leak or not. You pump up at least 10 psi and watch the guage to see if it leaks off. It should hold 10 psi for ten minutes.

What is happening is if the needle valves are leaking after a full assembly, is that the diaphrams that you installed over the lever, is actually holding the levers down enough to allow the otherwise good needle valves to leak. This can be stopped by bending those lever arms down a little bit so the nipples on the diaphram are not resting against the levers that open the needle valves.

 

[sportsfreak90]

I think I just need to take the jet ski to a dealership to have this stuff tested. I'm a college student with very few tools.

The bogging happens everytime, whether i've had it WOT for a while and let it come back down to an idle, or it sits and when it fires up it bogs a little but its only when you give it half throttle or more out of the hole.

I asked for an OEM kit and the dealership got me some aftermarket kit and I need to call them back because when I rebuilt the carbs the first time, I had to put all the other gaskets back in it because all the aftermarket gaskets turned a bit white and dried out. I didn't spray ANYTHING into the carbs until after removing all of the gaskets so I know it wasn't my fault. On top of that, one or two of the rubber gaskets/rings wouldn't even go back in after removing them, they didn't fit the same.

 

[6KJR]

Theres some good places on the net to get rebuild kits for carbs. Avoid the dealer if possible cause you will pay too much for everything.

I think you should cover some of the things the people said above. My 97 SPX STILL doesnt run right and its carb problems. Still working on it. (few minor mods)

Have you done any mods to the engine at all?

 

[sportsfreak90]

engine is stock, only thing aftermarket is the impeller. I don't have the tools to do anything more than what I have done. All I can really do is twist the needles in and out, I don't have any tools to test the pop off pressure and that stuff.

 

[Dr Honda]

I don't have the tools to do anything more than what I have done. All I can really do is twist the needles in and out, I don't have any tools to test the pop off pressure and that stuff.

Then you need to take it to a shop before you roast your engine. If things are running right... the engine will run perfect with the stock needle settings.

 

[sportsfreak90]

Then you need to take it to a shop before you roast your engine. If things are running right... the engine will run perfect with the stock needle settings.

How would I roast the engine? The plugs are the color they should be both at an idle, and after a WOT pass. It's not running lean on the top end. I'm working on getting it in right now but shops are busy..