I've posted a few threads on this ski but I thought I'd start a new one for this new problem. I've had this ski, 1997 XP 787, for about a month now and have done lots of work to it but it's still not quite right. Top end is good now after cleaning and replacing the RAVE valve bellows. I saw an indicated 57mph (stock speedo, not GPS) which is the highest it's ever hit. I can hold it WFO all the way across the lake and it runs great, never misses a beat and will now outrun my 2000 GS with the 720. I'm still having problems on the low speed end of things. Very weak at anything below half throttle. I've done some testing on the trailer in the water and here is what I am seeing. I can run the ski on just the rear cylinder by grounding the front plug wire. This would be similar to a fouled plug in the front cylinder. The ski will start easily and I can slowly increase the throttle all the way to WFO with no issues....no power but no bog or rough running. Same test on the front cylinder with the rear plug wire grounded and the ski will die at about 1/3 throttle. I'm doing this test with the flame arrester off and I can partially cover the front carb and the ski will easily go past the dead spot and from 1/2 to WFO there are no issues. I have rebuilt the carbs with genuine Mikuni kits and new needles and seats. I checked the pop off before I replaced the needles and seats and it was at 55psi. I changed springs and have it right at 32psi now. I've pulled the carbs since the rebuild and confirmed that both transfer ports are open and passing a full stream of carb cleaner sprayed into the low speed jet. Jets are the OEM size, 65 on the low and 142.5 on the front high and 147.5 on the rear high (I may have the specs off....I know they match the specs).
It seems to me that the front carb is lean on the transfer ports but I don't know why. I replaced the check valve on the metering block and I've confirmed that the jets are clean and appear to be the correct size. The transfer ports are open to the low speed jet. I don't have any fuel delivery problems as it will run WFO as long as I am willing to hold it there. At this point I'm down to swapping parts between the front and rear carbs to see if I can isolate the problem. Anyone have any other suggestions? The low speed/transfer circuit seems to be pretty simple, am I missing something?
It seems to me that the front carb is lean on the transfer ports but I don't know why. I replaced the check valve on the metering block and I've confirmed that the jets are clean and appear to be the correct size. The transfer ports are open to the low speed jet. I don't have any fuel delivery problems as it will run WFO as long as I am willing to hold it there. At this point I'm down to swapping parts between the front and rear carbs to see if I can isolate the problem. Anyone have any other suggestions? The low speed/transfer circuit seems to be pretty simple, am I missing something?
