- Location
- Cumming, Georgia
I know this isn't a stand up, but I'm nearly out of troubleshooting options here. I've been trying to fix a 92 XP 587 twin carb for a buddy. The ski last ran a couple years ago and started having issues. He replaced the carbs with a used set that was allegedly already rebuilt. It ran very poorly and it sat since then. At this point the gas was bad and I went through the entire fuel system.
Compression: 150 psi even
Carbs: The mag carb was missing 2 diaphragms in the fuel pump and had some black film in it that I haven't seen in a carb before. I cleaned them thoroughly and rebuilt with authentic Mikuni rebuild kits. New 2.0 needle and seats, I used the longer spring in the kit (115 gram I believe) and measured the popoff at 32psi on each carb. New Tygon oil lines and I couldn't find any OEM gaskets / o-rings so I used an SBT intake kit. I try to stay away from SBT, but I couldn't find much else. The carb base gaskets matched fine, but there wasn't a matching rotary valve O-ring in the kit. I used the largest one in the kit that was flat and probably 3mm wide. It could have spaced the rotary valve cover out slightly, but it appears flush. That's the only thing I did that I'm not 100% confident in.
Pilot jets: 60
Main jets: 125
High speed screw: closed
Low speed screw: 1.5 turns
All old gas drained and replaced with new. Put in 40:1 premix for while the oil pump primes the lines.
New spark plugs NGK BR8ES
Checked gas tank vent check valves. It has 2 and they're in opposite directions, which seems strange but looks OEM. I always thought you wanted one to keep pressure in the tank / allow air in.
All new fuel lines, filter cleaned
At this point I got it all back together and it ran great. I set the idle on land to about where it should be. It idles great and revs great, all seems fine. It restarts without the choke or any throttle after being warmed up shortly. I start it at the boat ramp out of the water and it also runs great. I back it into the water and it has a hard time starting. It will finally start using the choke, but has very little power and bogs like it's starving for gas. After it bogged and died, I pulled it from the water and it was hard to restart, but once again ran great after it was started. I repeated this several times with the same result. I even backed it in while running good and it once again started bogging and died.
I then tried backing it in just enough to where the pump intake is submerged. Sure enough, it started right up! It ran great and the jet pump had plenty of thrust. If I didn't have it tied down, it would've ran up into my truck. The jet pump was definitely loading up as it should, producing thrust and running water through the engine and out the pisser. I set the idle (2 turns above what seemed right on land) and it idled great for 10 minutes. I go to back it in the water 2 more feet (still not enough to get it off the trailer) and it dies before I can get out of the truck. I repeated this several times with the same result. But whenever it bogs and dies, it's always hard to restart, even on land. After adjusting the in water idle, the out of water idle is way too high and the engine redlines.
I did initially install a KN mini inline fuel filter just before the carbs. I noticed that it somewhat emptied out while running. I removed the line and blew into the vent line to pressurize the tank. I got good flow through both the factory filter and the KN. The flow was the same without the KN, but I still removed it as a variable.
I also tried filling a bottle with premix and running it directly to the carbs with a short section of hose (no filter) and got the same results.
Sorry for the long write up, but I tried to show all that I've gone through diagnosing this. I'm not sure what the problem could be at this point and I don't want to keep chasing my tail. Any input is appreciated. Thanks!!!
Compression: 150 psi even
Carbs: The mag carb was missing 2 diaphragms in the fuel pump and had some black film in it that I haven't seen in a carb before. I cleaned them thoroughly and rebuilt with authentic Mikuni rebuild kits. New 2.0 needle and seats, I used the longer spring in the kit (115 gram I believe) and measured the popoff at 32psi on each carb. New Tygon oil lines and I couldn't find any OEM gaskets / o-rings so I used an SBT intake kit. I try to stay away from SBT, but I couldn't find much else. The carb base gaskets matched fine, but there wasn't a matching rotary valve O-ring in the kit. I used the largest one in the kit that was flat and probably 3mm wide. It could have spaced the rotary valve cover out slightly, but it appears flush. That's the only thing I did that I'm not 100% confident in.
Pilot jets: 60
Main jets: 125
High speed screw: closed
Low speed screw: 1.5 turns
All old gas drained and replaced with new. Put in 40:1 premix for while the oil pump primes the lines.
New spark plugs NGK BR8ES
Checked gas tank vent check valves. It has 2 and they're in opposite directions, which seems strange but looks OEM. I always thought you wanted one to keep pressure in the tank / allow air in.
All new fuel lines, filter cleaned
At this point I got it all back together and it ran great. I set the idle on land to about where it should be. It idles great and revs great, all seems fine. It restarts without the choke or any throttle after being warmed up shortly. I start it at the boat ramp out of the water and it also runs great. I back it into the water and it has a hard time starting. It will finally start using the choke, but has very little power and bogs like it's starving for gas. After it bogged and died, I pulled it from the water and it was hard to restart, but once again ran great after it was started. I repeated this several times with the same result. I even backed it in while running good and it once again started bogging and died.
I then tried backing it in just enough to where the pump intake is submerged. Sure enough, it started right up! It ran great and the jet pump had plenty of thrust. If I didn't have it tied down, it would've ran up into my truck. The jet pump was definitely loading up as it should, producing thrust and running water through the engine and out the pisser. I set the idle (2 turns above what seemed right on land) and it idled great for 10 minutes. I go to back it in the water 2 more feet (still not enough to get it off the trailer) and it dies before I can get out of the truck. I repeated this several times with the same result. But whenever it bogs and dies, it's always hard to restart, even on land. After adjusting the in water idle, the out of water idle is way too high and the engine redlines.
I did initially install a KN mini inline fuel filter just before the carbs. I noticed that it somewhat emptied out while running. I removed the line and blew into the vent line to pressurize the tank. I got good flow through both the factory filter and the KN. The flow was the same without the KN, but I still removed it as a variable.
I also tried filling a bottle with premix and running it directly to the carbs with a short section of hose (no filter) and got the same results.
Sorry for the long write up, but I tried to show all that I've gone through diagnosing this. I'm not sure what the problem could be at this point and I don't want to keep chasing my tail. Any input is appreciated. Thanks!!!
. Idk what he was using to machine it, but shouldn't of took but maybe 5-10 min to cut that groove once it was chucked up.