Correct way to rebuild bottom end...

[DeePa]

I have a bottom end of a 350x motor that will stop when i turn it over by the flywheel. I would like to fix this motor up nice and then throw an aftermarket piston and maybe a cam/valves in to to make a little more power.

What could cause the flywheel to suddenly stop when i try to rotate it over? It doesnt complete one full stroke.

Also, what should be rebuilt/replaced when redoing the bottom end? I have never split cases before, but it seems really fun to try, and itll be worth it when finished.

So if you guys who have had experience doing this before could please let me know what parts I would probably need so I can order some of the stuff before i dig in.

I have the honda service manual but i dont know how much of a help that would be.

Thanks,
Mike

[Blown 331]

I would guess you might have a stuck valve causing the motor not to turn over and in my opinion I wouldn't split the bottom end if there is nothing wrong with it.

[chris200x]

Your not going to know exactly whats wrong until you open it up. If your going to do this yourself and have never done it before be sure to have a manual and a camera to take shots as you disassemble the cases. I would look behind the flywheel for a broken key or anything else external before I dive in. It is no fun by anymeans if you don't know what your doing.

[DeePa]

there is no cylinder head / cover on the motor, just a cylinder/piston so it cant be the valves.

I thought the cam chain fell into the bottom of the case but i looked and looked and theres nothing there...any more ideas?

[MTS]

Chunk of piston in bottem of the crank case's perhaps? Anyways, if your rebuilding the bottem end, depending on what the crank bearings look like, i would replace them, also 350x's are known for weak connecting rods so i would replace that with a heavy duty one.

[Dirtcrasher]

Could be anything at all, unknown until you dive in. 4 stroke bottom ends are real real tough and unless they ran real low on oil usually do not require alot of attention. Of course the clutch etc. wear out and if abused bad enough, the gear train could have some problems. Truly, I don't think I have ever even changed the main bearings in a four stroke, they are in constant contact with the oil and never seem to wear out. If they have been beat that bad or ran out of oil they are not worth repairing and better used for parts. You could have a simple easy problem but won't know until you split it, which by the way is usually when people tend to ruin alot of good parts from inexperience and some screwdrivers in the wrong places...