Engine Rebuild Question??
 

It wont move once you tighten the clutch nut

I did tighten the nut, should I crank on it harder?

I did notice when I was checking the inside bearing, not the front bearing, that it had a tiny bit of play. Not up and down but in and out. I'm guessing that's the issue.

The crankshaft is locked by the front bearing and should slid a tiny bit in the main bearing because expansion of the crank case. There is allway a tiny bit axial play as long it is not sideways.

Also important to pull out the crankshaft as much as you can and at the same time push the cone against the front bearing.

Thanks! thats what I did. Still a tiny bit of axial play. I've never checked that before maybe it was always like that. Just don't have another to compare it to.

You can have some tiny axial play as long as there is no radial play.

Thanks everyone, ran it and had no issues. Took it apart again and the play is because of the main bearing, seems as if there is a little (~1mm) axial movement. Seems normal.

Normally the main-bearing does not determine the axial play, the front-bearing does. Also 1mm seems like a lot to me.
What is the engine you are talking about?

Nova Rossi Flash .21 PT, 2 gallons through it.
I have no play at all in the front bearing.

Ran it a couple weeks ago (2 Qualifiers and a 20min main) no issues. Took it apart and everything looks good.

If you have no play in the front-bearing then it is impossible that you have play on the flywheel once you have mounted the flywheel and tightened the nut.
So if you have play on the main-bearing(you state ~1mm) how does the bearing feel when you rotate the inner ring?

The main bearing feels smooth when i rotate it, no grit or unusual feel. It does however have slight axial play.

I'm rebuilding it tonight again, and I'm going to make sure the flywheel is up against the cone. Also have to make sure the cone is all the way up against the front bearing.
I know what you mean, doesn't quite make sense. Maybe I need to crank down on the flywheel some more.

So the main-bearing seems good to me.

When you mount the cone, make sure you pull the crankshaft when you mount the cone(open the cone with a small screwdriver if needed), push the cone firmly to the ball-bearing. then mount the flywheel and tighten the nut.
When this is done you should have almost no play.

Anyway, if you engine is working without any problems, then I should not worry too much.:)

As mentioned, the crankshaft must slide through the main bearing and must have some axial play/space so it can deal with the expansion of the crank case. If the crankshaft has a tight fit betwean the bearings then the crankshaft will be locked when the crank case is heating up.

Just wanted to follow up on this thread. Engine ran fine, took it apart again after the race and no damage or signs of wear on the pin or connecting rod. Thanks for the help fellas.

I am missing something like "now it runs lie crap" ?

By taking it apart and put it back together you have to be sure the sleeve is located in the right way. Sometimes the center pin is lost or what I have seen with non listed Novarossi products they have put 2 slots for the center pin into the sleeve. Also be sure the piston/rod is placed in the right way.

And if you did remove the main bearing putting it backwards in you also will face some binding issues.

Yes made sure the cylinder was placed correctly, only goes in one way really. Same goes for piston, I identified the exhaust port side and installed it as such. I did not remove the bearings as I do not have the proper tools to press them back in.

Check the head shims? A lost shimm can cause issues.

Maybe remount the head in small turns of the screws in a cross-side way (sometimes people tighten the 1st screw that hard so the burnroom is not straight)

Sorry to hijack this thread but what does everyone do to clean the engine and how often?

I only use a clean cloth and wipe the internals, nothing else. If I have a bare block in my hands (for example, when I change the bearings) I'll flush the block with brake cleaner and again clean with a fresh cloth. That's all there is to it, and make sure to lube it very well when assembling.

I never clean it, If I open the motor it is only to check the color of the piston and to replace the rod. When replacing the rod I sometimes clean the top of the piston and the burnroom but it is not needed.

I think we have a mis-communication here lol, the engine runs great! I was just letting everyone know that a little play in the bearing is ok.

I use nitro fuel to clean it. Shouldn't be too dirty though. Mainly I clean the piston top and the area around the carb. I also polish the crank when I have time. Be careful with the silicone on the crank though. And also lube it with after run oil lightly when rebuilding. I do that after every race weekend and have never had an issue.