oldmxrider

Find what You changed a slight error was made. Hope You have not run it for a long time since this started happening.

Did it pop out of gear before You worked on it ?

Maintenance times on motocross race bikes We use easy to install hour meters. They are cheap and work great !

I have been rebuilding motocross crankshafts for 19 years. I have a 35 ton press and a jig for assembly.. A 20 ton press was not enough to get them apart.

Been a while since I repaired this one. Best I can recall is someone had played with the shift adjustment and it started jumping out of gear but they kept pounding on the unit and I replaced some gears that were worn. The machine also needed a few sensors and a initial setting done to make everything work as it should. The machine was treated VERY bad and lived in water and mud.

Will it move at all when in the forward gears ? Might be a sub transmission problem ! I only played with one hondamatic it barley tried to move lots of grinding noise. The repair was just the simple sub transmission used parts were bought from eBay and it worked like a new one when done.. I did not pull the engine for the repair pulled the swingarm and rear end was able to do the repair with the engine in the frame.

Does the machine move in reverse normal with no noise or clattering?

I think the old engine is a four stroke and crank seals will not be involved.

I would also check for air leaks. s

The bolts coming loose might not be very common but I have seen it more than once!

What did You end up doing with it?

www.jetsrus.com

Looks like You have some gouges and worn nikasil on the exhaust port and some aluminum stuck to the nikasil on the intake side. Does not look pretty. What does the piston look like ? Muriatic acid removes aluminum from nikasil plating.

I was just going to ask for an update! Hope it goes well!

Is the crankshaft centered in the case ? I take a feeler gauge to both sides and center them. I do have a press. Though as to deep said are You sure the main bearings were completely seated ?