780 overfueling - Snowmobile Forum: Your #1 Snowmobile Forum

Bud · 03-09-2008, 11:26 PM

I have a 96 mach z 780 and it has run great all season until now. Suddenly it seems to be overfueling and basically has very little power. Pulled the plugs and they are soaked ( washed with gas). changed plugs and still have problem. choke seams to release ok. compression is at 110 psi in each cylinder. it had 125psi at the start of the season. the last time I had it out I went on a 10 hour ride and hit a max speed of 175km/h a couple of times on the lakes. Did this damage something? it was -18C at the time. I am wondering if I damaged a float or something more serious. Any help, would be greatly appreciated. Thanks,

**smallengineguy** · 03-10-2008, 07:50 AM

Could be a weak spark. The Z's were famous for stators going bad. Although 110psi is right at the limit compressionwise. Those had around 130-140 factory.

Bud · 03-10-2008, 09:53 AM

Would a spark tester be able to tell me if it is weak? I've never seen one , so that is why I ask. Also, is there a way to check a stator?

**smallengineguy** · 03-10-2008, 10:08 AM

Ignition generator coil

1) White and Red 24-36 ohms
2) White and Blk/Red 3-6 ohms
3) Black and Red O.L.
3) Black and engine 0-.5 ohms

White and Red should make 30.0-50.0 VAC and White and Black/Red should make 4-10 VAC, average of 3 pulls.

Trigger coil
White/Yellow and Black/Yellow 190-270 ohms, output should be .200-.350 VAC, again average of 3 pulls

Bud · 03-10-2008, 06:30 PM

Thanks alot! I am away this week, but I will check this on Friday and report back. Is the stator pressed on? Any tips on changing it? Should the drum be changed as well?

**smallengineguy** · 03-11-2008, 07:41 AM

You remove the flywheel (drum?) then 3 screws hold the stator on. MARK the stator/mounting area so your timing stays correct when you put the new one on.

Bud · 03-11-2008, 10:46 AM

Is there a certain type of puller that needs to be used for the flywheel?

Bud · 03-15-2008, 12:28 PM

Ok. Started up sled today and it runs great again. Warmed it up and it still did not have a problem. Did testing anyway and here are the numbers.
white & red = 63 ohms and 30 VAC
white & blk/red = 4.2 ohms and 5 VAC
there is no black wire for the 3rd and 4th tests

For the trigger coil test I have only a single blk/yellow wire. So I could not test.

The 1st test is 27 ohms over the spec. Could this be a problem? Remembering that it seems to run pretty good at the moment. I noticed a brown wire that is grounded to the recoil housing has been rubbed through quite a bit. Maybe this is an issue? Any help on this is greatly appreciated. I have 3 - 4 feet of snow and it is driving me crazy! Thanks,

**smallengineguy** · 03-17-2008, 07:18 AM

I don't think that rubbed wire is the problem, since it's a ground anyway. Unless it's almost broken. You need a harmonic balancer puller to get the flywheel off. I'd take a look at the stator/trigger to be sure it's OK.