[Tfin70]

Sigh.......Talk about throwing money away![!] Warning....long post ahead.

Ok, here goes: I rebuilt my 97 XLT SP at the begining of the the season, because it had 6000 miles on it, and I figured it would be a good idea to do it then, then wait for a melt down some time during the winter. Never checked compression after the rebuild, so I don't know the starting compression.

I got about 450 mile on the rebuild and ended up frying my pto side piston due to a faulty (cracked) base gasket. Had it rebuilt (again) at a shop. They honed that cylinder, replaced the bad piston and rings, along with a new base and head gasket. The sled never ran well after that rebuild (only 140 miles since then). Was constantly fouling plugs.

Now I can't even get the damn thing to start. It sputters like it wants to go, but won't. Here's the deal. I've cleand and synced all the carbs idles, throttle and choke cables. Made sure they're all working correctly and to spec. Needle n seats are new viton tipped ones. I stress again, carbs are clean! Plugs are wet, and all are getting good spark.

Compression: pto: 115 center: 115 mag: 100

I know 100 psi is low, but is this low enough, and enough of a difference compared to the pto and center cylinders, for the sled to not even start?

If I can't get the thing started, how would I know if the crank seals are bad? If they were bad, would they cause my no start problem?

If the cylinders are losing this much compression this soon after a rebuild, am I looking at having to bore the cylinders and go with over size pistons, in order to maintain compression?

 

[canadianguy]

One stupid question is it timed right? Because all you need is spark (ok) fuel(ok) and compression(ok) maybe something as silly as timing?? just a thought. I have found that when you look too hard and look for something out of the ordinary, try something easy. Good Luck

 

[Tfin70]

Well, when I rebuilt it, I was never able to get the flywheel off, so I never touched the stator (timing), and it ran fine after I initially rebuilt it. This fouling and no starting problem only showed itself after that second rebuild, but it was only a top end rebuild, so he wouldn't of touched the stator either. I suppose the screws that hold the stator on could of loosend a little which may of allowed it to turn?

ttt

 

[UltraGN]

You probably spun the crank out of phase.

 

[blewbyyou]

after 6000 miles the biggest reason for refresh build would be for the benifet of having new crank and rod bearings with new seals. you might as well do that now and the crank will be in phase for sure when you get it back. double check pistons,reeds,etc when your puting her back together and she should do ya proud[B)]

 

[ACEXLT]

You don't have to worry about checking the reeds-there are none, its a piston port motor.

 

[Tfin70]

Yeah, I am concerned about the crank, if it is spun, that would put it out of time, which would make the piston be in the wrong place when the plug fires......correct?

I'm going to have the cylinders measured to make sure they're within spec. Just concerned about the mag piston only having 100 psi while the pto and center are at 115 psi.

Anyone have any idea how much it would cost to have the crank rebuilt, and/or "trued" if necessary? I'd bring the crank into the shop myself.