97 GTX another surge problem

[cmartin248]

Okay, I have a matching pair of 97 GTX's and one of them is giving me a fit. The engine runs fairly well at mid rpm's, but coming out of the hole or WOT, it is very weak and surges. Sometimes it feels great for a few seconds and then dies back to 40 mph at WOT.
I have; changed the fuel lines, cleaned the carbs and filters several times, and the small carb filters, cleaned the RAVE's, tried the red wire from the rectifier, 130 psig on each cylinder, checked the pump and bearings, good stream of fuel to the carbs, makes it run worse if you slightly pull the choke, new plugs, and new plugs again, slow needle at 1.25 and high at 0.0.
Help,, thought I was a mechanic....
Thanks for any advice......

 

[robin savell lloyd]

Okay, I have a matching pair of 97 GTX's and one of them is giving me a fit. The engine runs fairly well at mid rpm's, but coming out of the hole or WOT, it is very weak and surges. Sometimes it feels great for a few seconds and then dies back to 40 mph at WOT.
I have; changed the fuel lines, cleaned the carbs and filters several times, and the small carb filters, cleaned the RAVE's, tried the red wire from the rectifier, 130 psig on each cylinder, checked the pump and bearings, good stream of fuel to the carbs, makes it run worse if you slightly pull the choke, new plugs, and new plugs again, slow needle at 1.25 and high at 0.0.
Help,, thought I was a mechanic....
Thanks for any advice......

Carbs may be out of wack inlet neadle pop off preasure. or water regulator adjustment. :cheers:

 

[cmartin248]

I presently have the carbs off will check the pop off and clean the water regulator AGAIN... thanks

 

[cmartin248]

Okay,,, I went back through the carbs, and didn't have the setup to do the 4 psig pop-off test, but everything looks fine. Did a plug read and it doesn't seem to be a lean or rich problem. The plugs are a pretty chocolate, so the problem doesn't seem to be fuel. Spark seems fine also. Took the water valve completely apart and checked the diaphragm. The top was a little out of shape due to long term spring pressure, so I adjusted the spring tensioner a little, with no effect. Adjusted both RAVE's in both directions with no change.
If the throttle is held full open... the ski accelerates sluggess until about 5000 rpm and then it powers on normal until about 6200 rpm and then it drops back to 5500 rpm or so, back up to 6000-6200. I feels normal for a few seconds sometimes and then back to the surge.
This thing is driving me crazy... short trip... ANYBODY?????

 

[timmyboy76]

Okay,,, I went back through the carbs, and didn't have the setup to do the 4 psig pop-off test, but everything looks fine. Did a plug read and it doesn't seem to be a lean or rich problem. The plugs are a pretty chocolate, so the problem doesn't seem to be fuel. Spark seems fine also. Took the water valve completely apart and checked the diaphragm. The top was a little out of shape due to long term spring pressure, so I adjusted the spring tensioner a little, with no effect. Adjusted both RAVE's in both directions with no change.
If the throttle is held full open... the ski accelerates sluggess until about 5000 rpm and then it powers on normal until about 6200 rpm and then it drops back to 5500 rpm or so, back up to 6000-6200. I feels normal for a few seconds sometimes and then back to the surge.
This thing is driving me crazy... short trip... ANYBODY?????

The 4psi, is for carb leakdown, you need to do pop-off on n/s(needle and seat assy). Did you, when rebuilt carb/s, replace the spring in n/s assy??

 

[cmartin248]

I understand how the pop-off works, but I'll have to make a rig to test it. Been building these types carbs since Walbro made the first all position carb for the old Homelite XL12's. I did not replace the needle and seat w/springs when I reworked the carbs. The probability of the springs changing enough tension to affect the pop-off, seems very very slim. Just to make sure, I will take the carbs back off (wish they snapped on) and give it a try. Thanks for the advice.. hope it works