1996 GSX 787 slow cranking

[1993XP657]

Update: Donated another 5 hrs to it after work a few nights this week. Rebuilt the starter again tonight with an OSD kit as it burned up the brushes again, with similar results.

Jet pump is off and wear ring was slowing engine down for sure. Verified 150 psi in both cylinders today with my Snapon compression tester. Jumped starter switch and also went thru fuel system, bypassing fuel selector switch and strainer and added fresh gas after siphoning out all of the old fuel and a clear fuel filter like my other skis.
I have strong spark and have swapped a known good cdi box from a 96 xp I'm working on for a customer. Carbs have been rebuilt with OSD kits as well. Won't start on starting fluid either or mixed gas poured into carbs. I pulled rotary cover and double checked the rotary valve timing with my wheel and it's at 145*.

Still no start. Will act like it's gonna start and then the motor slows down and starter will disengage. This is getting out of hand. I'm out of ideas.

If the flywheel keyway was sheared, wouldn't it backfire?

 

[artr]

Since you tried swapping a good CDI box from a 96 XP, why not also try swapping the holder relay also from the 96 XP. If that relay is intermittent or the contacts are dirty where it losses some of the voltage that it supplies to the CDI box, the ski will crank but lose spark and not start. If you don't have access to the 96 XP anymore, you can look at a schematic, but if it is the same as the 96 XP and GTX, just short the red/blue stripe wire to the red/purple stripe wire from the holder relay for test purposes. Make sure your battery is charged and good and don't leave it shorted together for a long time because the battery will drain without the ski running.

 

[1993XP657]

Since you tried swapping a good CDI box from a 96 XP, why not also try swapping the holder relay also from the 96 XP. If that relay is intermittent or the contacts are dirty where it losses some of the voltage that it supplies to the CDI box, the ski will crank but lose spark and not start. If you don't have access to the 96 XP anymore, you can look at a schematic, but if it is the same as the 96 XP and GTX, just short the red/blue stripe wire to the red/purple stripe wire from the holder relay for test purposes. Make sure your battery is charged and good and don't leave it shorted together for a long time because the battery will drain without the ski running.

I will try that tomorrow. I'm used to 717 and 657 skis where they don't have that. There has to be an underlying issue here.

My 587 gts has been sitting 3 months, fires right up with a little choke.

This thing wont hit a lick. Lol

 

[1993XP657]

FIXED: Ended up pulling the stator cover and found a bunch of metal on the magneto, put it back together and same thing. I remembered flywheel had been off and realized the magneto cup had been transferred. It was 2 bolt holes off and about 90* retarded timing. Clocked magnets correct, runs and starts good. I think the fuel was firing so late that it was causing it to fight the starter.

After warming up, engine acts like it has a rev limiter at 3000 rpms. Unplugged red wire on rectifier and it revs to 7000. Pretty clear rectifier failed too.

 

[1993XP657]

This was solved by correcting the magneto cup position on the flywheel. Previous owner had it 2 holes off and timing was 90* out.