Vintage Dirt Bike Q & A

So I pulled up to my buddy's house and saw this little bike sitting by the curb at the neighbors next to a couple trash bags. I knock on the door and ask what's the deal with the bike? The guy says it was in his garage when he moved in. I asked if I could have it and I am now the owner of a 197? Honda Elsinore MR50.

However, how do I know which year model it is? The number on the forks read MR50-1006803. I have also already disassembled the tank, seat and pulled the motor/tranny out. The motor does turn over so I know it's not froze. The carb needs a rebuild but how do I go about knowing if the motor is still good? Pull the head or should I just take it to a shop? Also, the boot and wire that attaches to the plug and then to wherever it goes is missing. Does anybody know how/where to hook these up? I will also have to get a new throttle cable as the one on it is broke.

I know it's a lot of questions but can somebody help me out?

Thanks

It's a 1974 model. I'd pull the head and inspect the piston/cylinder. Also, pull the engine side covers and see if you can move the crankshaft at all. If there is any up/down or backward/forward movement on the crank, you'll need to split the cases and put in new bearings. Good luck, it sounds like a fun project.

What should I look for on the piston/cylinder wall when pulling the head? Obvious deep gouges and scratches but anything else?

Yes, that's what you're partially looking for, but even if the piston and cylinder look good, I'd stick a new set of rings on. If you can't do it now, at least measure the piston ring gap (take rings off, push down into cylinder using top of piston and measure gap). If they are within specs, you can probably get by. The other thing to check while you're there is for clearance on the main rod bearing. Should be NO up and down play. side to side play should be per specs (and I have no idea what that is on the MR50). Also, inspect the top wrist pin and bearing.