Pulling my hair out

[colofiremedic]

Hey all,

Here's the short version. I rebuilt the carbs on my 1993 Seadoo SPX about two weeks ago. Took it to the lake and once it was warm, it seemed to run fine. I did notice a slight hesitation at about the 1/4 throttle position. I parked the machine and went to do some "fine tuning" at the lake. The machine starts right up with no hesitation, and idles well. The hesitation I noticed at the 1/4 throttle position seems to be worse. If I back off the throttle and hold it for 30 seconds or so, it will slowly gain RPM and plane out. Once the RPMs are up, I can do what I want. I get good throttle response and don't seem to have many problems. (unless I park it for 20 min or so) If I shut it down, I have to start the process again. The Low speed needles are set at 1 1/8 turns out. I've tride for the past two hours to tune the carbs and cannot figure out what is going on. Does anyone have any thoughts or ideas? I would sure appriciate the help.

Thanks,
Colofiremedic

 

[6KJR]

Did you use OEM parts in your carbs?

 

[colofiremedic]

Yes, all parts were OEM. Nothing aftermarket on these skis. They are completely stock. I read your post earlier and went outside to check for vent plugs.....none there. I can't seem to get the correct setting for the ski to run properly under load (in the water). It idles fine but has a real dead spot about 1/4 throttle. Any thoughts??

 

[6KJR]

Now Im mad, just typed a pile and its gone. What the ... I cant get rid of my part throttle bog yet, still working on it.

Now its point forum

Fuel tank sending unit should have 4 lines, Vent, Return, and two Feeds, one for RES one for ON.
Rebuild your fuel pump?
Pulse line in good shape?
Does it do the same on the RES setting?
How do your plugs look when it runs rough?
Water injection working?
Do a pop off pressure test upon carb rebuild?

 

[colofiremedic]

There are four lines and they are all in the correct place.
Fuel pump is good
Pulse line is new
I havent checked it on the res setting (will do that tomorrow)
Water injection works fine
and the pop off pressures were set to factory specs when the carbs were rebuilt.

 

[CAVPILOT]

I rebuilt the carbs on my 1993 Seadoo SPX about two weeks ago.

This is what MIKUNI recommends:
<CUT>To achieve an accurate calibration with a Super BN you should adjust the tuneable circuits in the following order:
1. LOW SPEED ADJUSTER - to adjust a smooth idle
2. POP-OFF PRESSURE - just off idle to 1/4 throttle in conjunction with the low speed jet
3. LOW SPEED JET - just off idle to 1/3 throttle
4. HIGH SPEED JET - 1/3 to 3/4 throttle
5. HIGH SPEED ADJUSTER - 3/4 to WOT
The reason for adjusting the circuits in this order is because several circuits contribute to the total fuel delivery of the carb. Changing the low speed jet for example, affects WOT fuel delivery to some degree. The exceptions to the rule are the low speed adjuster and the regulator portion: The low speed adjuster has no effect past 1/3 throttle. The regulator portion has no tuning effect past 1/4 throttle, although it continues to control the fuel supply.<CUT>

 

[colofiremedic]

I Checked compression in both cylinders last night. Both were right at 120psi. I dont think I'm getting enough fuel to the PTO carb. If I pull the choke out about 2/3 the ski will accelerate rapidly and I have GREAT throttle response. The plugs indicate that they are burining lean and I can do Nothing short of pulling on the choke to richen the mixture up. I appriciate the help so far, and I'll try the callibration listed above, but I dont have much faith. Any ideas on other possible problems??

Thanks!

 

[6KJR]

At 120 PSI that engine is getting weak. Try someone elses tester and see what you get.

Pulling the choke will create more vacuum and pull more fuel through. Hows the clearance on the rotary valve? You could crank the lows out a full turn just to see if it makes a big change or not.