89 X2 with a 750 small pin, Sudco blue 42mm Help?

[lovewinz]

I have a 89 X2 with a 750 small pin, Dual Sudco blue 42mm (, Low screw 1 1/8, high screw 1 1/2), factory pipe (2 screw version) SX chamber, Westcoast water box, ADA head 26cc domes (180psi +/-2), Boysen reeds, MSD Enhancer 4251, Taylor Cable 8mm Spiro-Pro wires, Jet Dynamics intake grate, Jet Dynamics 2" set-back pump, Mariner reactor swirl prop (pitch unknown), Ocean Pro ocean D nozzle,

Now the problem, I cant seem to get these carbs tuned right.

Took it out yesterday and set the idel to 1300 but when I hit the throttle for a pratice start it died. I adjusted the low screw to the point where the idel came up to about 1500 and hit the throttle and it plowed the water for 10seconds and then jumped out of the water like a rocket. I then found that it I helped if i held the throttle at 18000-2000 rpm and hit it it would take off on a start like it should. When riding on the water it was fine could launch over waves fine throttle response was good. Just not sure why it would plow then take off.

I keep being told those blue carbs are garbage and just to get rid of them.

 

[fastgtfairlane]

Sounds like you need to either change your low speed jetting and or adjust your popoff or possibly you have a dirty carb. Either way I'd take it off and take it apart to see what you're working with and go from there.

The keihins are good carbs, the downside is finding parts and jets to tune them. Mikuni sbn parts are very easy to find so that's a big reason why people don't use keihin carbs.

 

[WFO Speedracer]

Sounds like a lean bog, first off how many turns out is the low speed screw ?

You cannot adjust for highest idle , that will almost always be too lean, you need to set the low speed where uit is slightly over rich then adjust the idle back up with the idle screw , if you have to go more than two turns out on the low speed screw you need a bigger low speed jet.i

 

[lovewinz]

180psi +/-2, Low screw 1 1/8, high 1 1/2, I ordered a pop off gauge to check that and plan on getting a rebuild kit.

 

[Vumad]

180psi +/-2, Low screw 1 1/8, high 1 1/2, I ordered a pop off gauge to check that and plan on getting a rebuild kit.

Buy genuine carb parts. I bought SBT rebuild kits and couldn't get them to seal. I put the old parts back in and got the tests correct. I then bought genuine mikuni kits and had great results. I also had more issues with leaking needles with generics that I didn't have with genuine mikuni parts. I was not happy with WSM or SBT carb parts. Not sure the case with keihen parts. I can probably get you some specs on a 44mm mikuni. Never tuned a keihen.

Prop is not likely the issue but can be. My ski struggled at low RPM but it was over propped. It wasn't a lean / rich reaction, sounded clean, just wouldn't pull until it got onto pipe. No one else with my setup has the prop I do so I'm sure that's the issue.

 

[kevbo]

Your bottom adjusters are for idle only and you have them too lean. If it responds well from 1/4 throttle then the pilots are okay. Make sure the top screws are opened so that the RPM ends up a little below max or just wherever the ski accelerates the hardest. The impeller could be causing much of the problem if it overloads the engine, this was extremely common. Those keihins are very good carbs, anyone that cant make them run has no credibility.

 

[lovewinz]

I ordered rebuild kits from Sudco. If I open the the bottom any more than it is the ski just dies.

 

[lovewinz]

I got my rebuild kits in. The pop off was blowing at 25psi. They started blowing bubbles at 20. I put the kits in and set pop off to 15-16psi. High speed jet is 115, Low speed jet is 90, needle seat is 1.5. Will water test for Fathers day weekend.

 

[JC-SuperJet]

Should pop clean. No bubbling or fizzing. Means the Needle Valve is leaking. Maybe it's the Valve Body O-Ring. Or maybe its the Needle Tip with a wear groove.

 

[kevbo]

A 90 pilot is probably too big for a dual carb arrangement. And a 115 main is on the small side. Try it but make sure you can open the top adjusters enough to reduce power at full throttle.

 

[lovewinz]

Carbs have been rebuilt, pop-off changed from 25 to 15-16. Still runs the same. Once the bottom screw is adjusted the top end falls flat like its running out of fuel. and will scream then die at full throttle. I tried that idle drop test but as long the the motor will idle it is pushing more water that you can put your hand behind. I had a clamp break and blew the coupler off the pipe, the sting line melted so after a half day out riding and tuning I am still in the same spot I was plus more repairs. I guess it could all be building on top of its self.

Previous owner was jetted for 4250' I never go higher than 1300' and most riding is less than 1000'. I never changed any jetting just tried using the screws.

 

[fastgtfairlane]

If keep the popoff at 25psi and go up in pilot jet. Have you also verified good compression on both cylinders and done a good leak down test to verify no air leaks?

 

[JC-SuperJet]

Kawasaki 781cc small pin w 650 West Coast Pipe ​

42MM TAPER BORE SUDCO BLUE RACING CARB A/M Flame Arrester & Pipe​

*No Inner Venturi & Smooth Finish for more Air Flow​

Keihin Pilot #105 Low and Main #165 High jet​

 

[lovewinz]

If keep the popoff at 25psi and go up in pilot jet. Have you also verified good compression on both cylinders and done a good leak down test to verify no air leaks?

180psi both, no change after 30 seconds

 

[lovewinz]

Kawasaki 781cc small pin w 650 West Coast Pipe ​

42MM TAPER BORE SUDCO BLUE RACING CARB A/M Flame Arrester & Pipe​

*No Inner Venturi & Smooth Finish for more Air Flow​

Keihin Pilot #105 Low and Main #165 High jet​

Do yo know what pop-off you are running? Turns out on the fuel the screws? 781 is a little bigger than my stock bore but give me something to compare to.

 

[JC-SuperJet]

781cc is only 15ccs more per Cylinder than a 750. The Jetting should be almost identical.

The Point is that your Main Jet is way too small and you are sticking your Pistons every time you do a WOT run and the Engine shuts down.

You should be able to adjust the Low Speed Screw to match your current Pop-Off Pressure.

But your main issue is at 3/4 to WOT which involves the Main Jet and Main Jet Adjustment Screw.

You need to learn how to tune using a good Tachometer.

Follow the Keihin Carb Tuning Method. It's the easiest way to tune PWC Carbs as a good Tachometer does not lie. No screwing around with Spark Plug Color, Exhaust Sound Pitch or tying the Ski to the Dock. No guessing here.

So leave the Ski strapped to the Trailer, back it into the Water, start and warm up the Engine, USING A TACHOMETER set the Idle to about 1500 rpm. Then find the highest Idle rpm reading by tweaking the Low Speed Adjusters, not the Idle Set Screw. When you find this maximum, be aware that this will be TOO LEAN to ride with and will hesitate or "fall on its face" when you open the throttle because the Engine needs more fuel underway with the Rider Weight and Water Drag on the Hull. So now, OPEN THE LOW SPEED ADJUSTERS 1/4 TURN MORE to get the right amount of fuel into the Low Speed Circuit (Idle to Half Throttle). This will be close to perfect. To test, idle out into the water while on your Knees, then snap the Throttle open, if it jumps out of the Water and snaps your Head back, then it's spot on. If a delay in response, it's Lean, If it sputters, sounds rough and gurgles, it's rich. Adjust the Low Speed Screws accordingly. But the Tachometer On-the-Trailer Idle Max + 1/4 Turn should be almost perfect, if the Engine has no Air Leaks. Now reset the Idle back to about 1500 rpm using the Idle Set Screw only.

Next, assuming you have the right size Main Jet, with the Tachometer velcro'd to your Dash, make a couple of WOT flat water passes no longer than 100 ft each. Note the highest rpm reading, then try opening the High Speed Screws by +1/4 Turn and test again. If the rpms go up, then open another 1/4 turn and repeat until the rpms go down. Go back to where the highest rpms were reached. Then fine tune with 1/8 turns. You have three turns out maximum available on the Screws.

If the rpms go down when the high speed screws are opened, then it's too rich, so turn the Screws in 1/4 turn at a time and retest. Pete and Repete till the best rpm is reached.

On another note, did you ACTUALLY rebuild the Carb FUEL PUMP(S)? Because the standard Keihin Kits don't come with the Pump Rebuild Parts, It's a separate Kit. If the Pump is old and tired, then won't have enough Fuel at WOT.

 

[lovewinz]

I have pump parts but did not rebuild that portion. Everything looked like it was perfect I guess I should do that anyway. I bought the kits from Sudco who has given me jetting for the dual 38mm carb setup. They say they dont have any information on the 42mm. My main's are small for the 38mm.

Should I be able to open the high screw three turns out and that should help??

"The starting specs for the dual 38 CDK II would be 70 slows, 132 mains,
1 turn out on low speed screws and 1.5 turns out on high speed screws"

 

[WFO Speedracer]

I have pump parts but did not rebuild that portion. Everything looked like it was perfect I guess I should do that anyway. I bought the kits from Sudco who has given me jetting for the dual 38mm carb setup. They say they dont have any information on the 42mm. My main's are small for the 38mm.

Should I be able to open the high screw three turns out and that should help??

"The starting specs for the dual 38 CDK II would be 70 slows, 132 mains,
1 turn out on low speed screws and 1.5 turns out on high speed screws"

Yep and it doesn't apply to 42's because you have much less carb signal or vacuum, which is why you need the bigger jets to compensate, follow JC's jetting specs they will at least get you very close, you should be able to tune it from there.

 

[lovewinz]

I had a primer tube brake. When I clipped the end it broke again. I decided to replace all the fuel lines including the primer lines. and thats when I found this. Fuel filter tucked behind the brace and bilge line. I guess Its time to start over since it might be getting fuel now.

 

[WFO Speedracer]

I shouldn't say this and you can call me a a-hole for saying it but , no problem I have been called that before, among other things. Don't feel bad though we had some idiot over at PWCT trying to diagnose an ignition issue without ever changing out the spark plugs, I mean duh -huh.

This is the kind of stuff you really should have already looked at and repaired before starting three different threads on two different websites.

Fuel pumps are still pumps , that includes the primer pump, if they can pump air instead of fuel they will do so and any kind of air leak in the fuel lines, primer pump or fuel filter is a major issue that no amount of jetting will resolve.