97' GTX pulling back at WOT

[GGuillot]

Ok, I'm just getting through 2 full tanks on the 97'GTX after rebuild and resto, somewhere around the 8 hour mark. Background, it runs strong, never quits on me, starts everytime no issues. Idles 3k on the trailer, 1.5k in the water. Throttle is always smooth to 3/4, but at times it backs off at WOT, like it wants to shut off, but backing the throttle to 3/4 or lower it's fine and will continue to run. Like I said, speed and power is exceptional, high 50's no problem.

Low's 1 turn, initial high's MAG 0, PTO 1/2. In increments, I've backed the highs out as far as 1 1/2 on both MAG and PTO and still the same at WOT. No matter the settings, it's always the same, after a short burst to WOT it'll back down like it's losing fuel.

The fuel selector is a $17 (replacement OEM) from Bay Area Powersports. On the hose this past weekend I noticed occasional small air bubbles in the line to the carbs. Is this normal sometimes? Or are the cheaper selectors still prone to sucking air? What about an upgrade to larger 5/16 fuel selector?

Next outing I'm going to bypass the fuel selector and see what happens, I'm out of ideas. Though I get great performance, it bothers me it won't sustain WOT for more than a few seconds. Any experience with this issue at WOT would be helpful...

 

[etemplet]

The fuel selector is a $17 (replacement OEM) from Bay Area Powersports. On the hose this past weekend I noticed occasional small air bubbles in the line to the carbs. Is this normal sometimes? Or are the cheaper selectors still prone to sucking air? What about an upgrade to larger 5/16 fuel selector?

The fuel selectors leak at the fittings. I have removed them with needle nose pliers reseated and sealed with Moto Seal and they worked well. I've gotten them from various suppliers and I have vowed to use nothing but OEM fuel selectors. I have also reused the old units if they aren't leaking. I pull a vacuum on selector before I install.... all of the aftermarket units I have purchased... leaked

 

[GGuillot]

The fuel selectors leak at the fittings. I have removed them with needle nose pliers reseated and sealed with Moto Seal and they worked well. I've gotten them from various suppliers and I have vowed to use nothing but OEM fuel selectors. I have also reused the old units if they aren't leaking. I pull a vacuum on selector before I install.... all of the aftermarket units I have purchased... leaked

Pull a vacuum, that's an idea, I have a vacuum pump. Bay Area P claimed the fuel selector I bought was a OEM, or the new replacement OEM. I'm having my doubts. Where'd you get the real deal OEM?

 

[etemplet]

Pull a vacuum, that's an idea, I have a vacuum pump. Bay Area P claimed the fuel selector I bought was a OEM, or the new replacement OEM. I'm having my doubts. Where'd you get the real deal OEM?

I haven't gotten a real OEM yet. I fixed/repaired the last two I got. I use a Mitey-Vac but I also have a pump that will pressure up that I got off Ebay for under $20 I think. I like it because I pressure up the fuel system from the carb entrance line back to the tank. Then I block off certain lines so I know where the leak is located. Pressure is better for the system cuz you can use soap bubbles to identify the exact location. Vacuum is good cuz that is what your pump is pulling. Also clean up your flame arrestor as a precaution. Your ski is way faster than my two. GPS is around 51-52mph. I'm, working on that. Need to get the RPMs up.

 

[GGuillot]

Thanks for the info Gene, I'm gonna to try a few things to figure out what's going on, has to be fuel delivery. I'm not sure why I'm getting a higher mph, maybe higher compression from a new rebuild? At 3/4 throttle and brief sprints to WOT this weekend it hit 58 briefly according to peak mph. I'm going to double check with gps later. From idle when I nail it takes off to 7K and wants to stay there until the brief pull back like it's losing fuel.

I have the older non slotted RAVEs, I m not getting the 5K delay like some experience, but I do get the rough mid range from 3-4.5K. In a very tight left turn I can get it to load up and delay hitting 7K. I think the speed drops off as they get high hours, I bet if you did a new top end the mph would increase.

 

[etemplet]

The 97 Ski has a new top end and compression is 170psi. My cousin and I discussed a fuel flow measurement instrument to address just the problems you are having and we were having initially. May not be fuel flow but that could rule it out pretty quick. Did you test for leaks around your fuel pump gaskets? You have have seen the valve lapping mandrel I made to clean up the seats on the fuel pump. I've been all over these skis. LOL

WE could have interesting conversations. LOL What is your Pop Off setting ? Did you check the carbs for leaks ?

 

[GGuillot]

Pop off is around 36-37, both carbs. Yep, pressure tested with diaphragm in, good there. On the clear fuel lines, just before the carbs, I've been seeing some small air bubbles traveling ever since I got it running, I'm thinking it runs so well so not a big deal. Until now, I didn't want to start tweaking and discovery until through break in period. I only see this with the seat off running it on the trailer and blipping the throttle. Under load at WOT, I'm sure it's pulling a lot of fuel and any introduction of air would cause the intermittent issue of pulling back at times. When I let up is resumes power, never dies. I'm bypassing the fuel selector next outing on the water...hopefully in a couple days...

I've ruled out pistons seizing or ignition kill, I've got the highs way out and it still does the same thing.

 

[mikidymac]

Air bubbles in the fuel lines are always a bad sign and a good way to seize the engine.

Also 58 mph on the stock gauge is a dream. These 3 seaters are a 52-53 mph at best.

Also no way a stock rebuild is 170 psi. If it is your squish is dangerously out of spec.

 

[GGuillot]

Air bubbles in the fuel lines are always a bad sign and a good way to seize the engine.

Also 58 mph on the stock gauge is a dream. These 3 seaters are a 52-53 mph at best.

Also no way a stock rebuild is 170 psi. If it is your squish is dangerously out of spec.

Yeah, not my rebuild, I'm getting 150 each cylinder. I knew you'd doubt the speed, I'm going to verify with GPS or a Candoo GPS. Concur on the air bubbles leaning it out, I'm bypassing the fuel selector....

 

[Marcusknight23]

Pull a vacuum, that's an idea, I have a vacuum pump. Bay Area P claimed the fuel selector I bought was a OEM, or the new replacement OEM. I'm having my doubts. Where'd you get the real deal OEM?

The OEMs I find online for like around 34 dollars and I think they are stamped Taiwan on them. Watch for that.

 

[etemplet]

I like to use the pressure side of my hand pump and pump into the fuel supply hose at the carbs. I use my line clamps to clamp the fuel hose between the fuel valve and the tank. This isolates the fuel valve and fuel filter. I clamp either the ON or the RES line to 5-10psi. I set the selector on the line I have clamped and then cycle the switch to OFF. There should be no change in pressure. Then I swap lines and do it again. Also, I clamp both lines and pressure the system. If there is a leak, I will find it. Muhaahaaha !!!

 

[GGuillot]

Well, it was the stupid fuel selector, a brand new 'OEM replacement', it now runs great at WOT, no more pull back.

 

[etemplet]

Sure is a shame. Gets so you can't trust anything, always need to verify. I have checks I do to every fuel selector before I install them, new or old. If they pass, I use them.

 

[etemplet]

Funny thing or intriguing aspect is that your ski runs OK with the PTO High Speed adjuster open a tad. When I open the one on the 96 GTX 1/4 turn, I lose 100RPM on top. I still say that with a density altitude of 1800'-2000' in my area.... the ski is rich but I'm not rejetting. I'm betting in October my RPM will increase by 200 on each ski. We'll see.