09-01-2011, 09:18 PM #1
All sorts of problems with slx 780
Heres the story. I bought an 95 slx 780 with a melted PTO piston. The previous owner said that he bought the ski with a siezed jet pump. He rebuilt the pump and after riding for a while, the PTO piston melted. So I buy it and rebuilt the top end (SBT exchange program), rebuilt the carbs, set pop-off, checked entire fuel system. I put about 5 hours on the engine breaking it in and then I noticed there was a pretty good vibration in the driveline. Also, once the engine was warm, I had to crank it for a about 10 seconds while playing with the throttle before it would finally start. With the ski on the trailer, the driveline vibration started just off idle and got worse as rpms increased. I can see the thru hull seal carrier shaking pretty bad. I thought maybe previous owner rebuilt the pump wrong, so I rebuilt another stator I had laying around and swapped it in. I bought a pump alignment tool and aligned it the best I could. I also made sure the pump housing was installed properly and flush against hull. Still have vibration issue. I gave up for a while (2 months) and did some research. Heres where I'm at as of today:
Compression: PTO=120psi Center=140psi MAG=140psi
Crank Index (using vernier caliper) Center piston at TDC, MAG and PTO show an average .030 difference after a few tries.
Plugs on all 3 pistons are always wet and black colored. (possibly bad reeds?)
Im not sure how to check for driveshaft runout without v blocks. The splines on the shaft seem fine. It has a solid metal coupler too; splines seem fine inside as well. I havent done a leak down test either. With the pump and drive shaft removed, Ill start the engine and coupler seems to be spinning slightly out of round, but I cant tell if it's just the engine vibrating on the mounts.
So Im thinking I have a few problems here. Crank out of phase, engine alignment slightly off, and bad reeds. And possibly a bent drive shaft. If I remember correctly the previous owner said that the pumped siezed up while the guy was riding it at speed. So maybe it threw the crank out of phase and possibly bent the drive shaft. What do you guys think? I tried describing everything best I could. Any help would be greatly appreciated. Ohh and my avatar picture is with a different slx (in case abuse was on your guys minds)
I have a SBT crank,bearings,inner seals and outer end seal kit sitting here on standby too.
09-06-2011, 04:00 PM #2
09-06-2011, 11:14 PM #3
- Join Date
- Oct 2006
- Cleveland OH
Did you check your motor mounts?
Is the engine secured to the engine plate? (bolts rattle out if you/PO don't use Loctite)
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