Hi,
Rebuilt a 2002 Polaris 800XCSP model S02Np8CSA engine (broken crank). It was a basket case so I didn't have the opportunity to take it apart. Has new crank (180 deg twin). Replaced a few other wear items. Turns over well (manual) with plugs out. With plugs in it acts like it is hydro locking but cylinders are clear. This is with no exhaust, exhaust valves removed, no anti-freeze, no gas, no ignition.
Stuck; am a 4 cycle guy, limited 2 cycle knowledge. Could reed valves, carbs be part of problem? Thanks:

No Oil? When you reassemble a 2 stroke, you should use a liberal amount of 2 stroke oil on the crank,rod,wrist pin bearings and the both cylinder walls, at least I do. That said, it does take quite of a pull to turn over a 800 twin. Question 2, why are you cranking it over without carbs, valves, exhaust, etc., but with plugs in? No, reeds and carbs would have nothing to do with it.

Hi,
Used liberal amount of oil during assembly. Turned engine over on bench with recoil starter, no plugs spins fine. Installed plugs, turns about half a turn and the recoil rope stops dead. Had someone else pull the rope incase I was wimpy, same thing, can't get by about half a turn.

Hi,
Make sure when you try to test turn over a twin 800 that you have all the parts installed. Took the drive clutch off to do some work on it. Without the drive clutch (flywheel effect), the twin will stop on the first compression stroke. The belt cover hid the fact that it was missing. Works much better now.