Hello.
I recently had rebuilt my .21 nitro engine and now i am having major problems starting the engine at all. Basically i just tore the engine down and cleaned every part sealed the engine and put it back together. Well i havent started it since then. To start off my glow plug is fine. My igniter is fine. Im using rotostart with a cordless drill. Before i took the engine apart it had good compression all the time. Now the engine has good compresion to start out but after using my rotostart for a few seconds it seems like there is no compression at all. I havent even got it to start for a second. I now have the engine off the truck again and im trying to figure out what could be wrong. Any advice accepted ill tell you if ive done that yet or not. Really wanna get back out there with my nitro car. Its a blast.

Also when using my rotostart the rotation of the piston is in consistent it will be going fast with load pops then randomly slow down and have almost no pop (compression). It goes back and forth never consistent any advice??

How did you clean the piston and sleeve? Did you use any abrasive products? You could have damaged the fitment.

Such as???

One way bearing is slipping. Remove and clean or replace, also check/clean the shaft it runs on.

If you had good compression before the rebuild why did you even rebuild it?

Also you said you sealed the engine so it's quite possible you went overboard on the sealant on the backplate and some foreign matter is messing with the one way bearing?