engine stucks at TDC

[truq]

have a savagex with Nosram 30Monster (=LRP spec2) Last weekend i went to a new place to race with my friends, flat fast track... during the day suddenly the engine begun to idle crappy and was impossible to tune perfect... cleaned the carb but noticed also the rotostart hardly turned it over... however i made the racing day with not-so-perfect idle, off-idle and power.

today i tore the engine apart, no visible cracks, leaks etc.. but at TDC, without cyl-head, the engine is very tight... actually the piston has a dead spot at tdc where it is stuck and i can turn the flywheel many degrees without any movement on piston... what is this situation? was i running too lean long periods of WOT and ruined the piston-cyl... the engine has seen only some 1/2 gallons of 25% quality blend, and worked and tuned perfect this far.

help and ideas are greatly appreciated, since i need to outrun my buddies next weekend thanks.

 

[Snook Man]

Being able to turn the flywheel in either direction a few degrees when the piston is in the pinch zone at TDC is fairly normal with tight pinch. Any more than a few degrees could indicate a problem with the piston wrist pin saddle, wrist pin or connecting rod. With the rod attached to the piston is there much slop between them? Slop at the rod and crankshaft?

 

[truq]

thanks for reply, is there a trick to remove the rod/piston from the engine... back-plate and cyl-sleeve are out but there seems not to be enough space to slide the rod off crank.

 

[Snook Man]

If the sleeve is out, the rod should slde off the crank with the the piston at TDC or BDC depening on the engine design.