need guidance....pursue rebuild or look for alternative?

[patrickshofner]

ok folks, need some help here. I stopped to visit with a local bike mechanic last night. I took my basket case CB77 engine to him to get a preliminary assessment. He wasn't afraid to take on reassembly so we took out my pieces for him to get a closer look. currently, the bottom case is split and the trans/clutch/everything is disassembled. as he turned the crank, we noticed quite the ding in one of the weights.



other than that, the only other crank wear looked like a few small dents along the edges of the weights.

then there's this bent baffle and gash marks in the bottom case-





So it looks like something was in the bottom end wreaking havoc. Who knows where it came from. The guy told me he could disassemble/clean/diagnose the remainder of the engine for $90-120.

Without knowing just how complete the trans/clutch/kickstart mechanism is, would it be wise to spend any money at all on this engine? the odometer reads less than 7k miles. can that crank be repaired/reused? it spins well and there's still compression. my dilemma is spending $600-1k on parts for this engine or spending a few hundred on an engine that may need to be rebuilt in a short while. I'm definitely not giving up on bringing the bike back to life, but I'm not opposed to a heart transplant if its a much more economically sound decision.

[rrietman]

I would be more concerned about the rust on the main bearings. get a different crank assembly, they aren't hard to find.
Randy

[conbs]

I agree with Randy on the crank. They are really expensive to rebuild. No splines on the shafts under the big end. If you could find (and afford) the parts to rebuild it, you would still have to send it out to someone to get it aligned during re-assembly. I tried to tackle just changing one weight. It is not easy. My bearings didn't appear to be rusty, but they almost always are.

There are cranks on ebay all the time. I have gotten a couple of good ones from low miles engines. Even if you buy one that is bad and have to buy a second one, you will still be dollars ahead. You do need to make sure the small ends are good. Honda did sell an over-sized wrist pin which assumes you would ream the small end a small amount. Opinions are divided on whether that will actually work out. I think it must be workable or Honda would not have offered the over-sized pin.

I recently read a post on using sno-bowl to de-rust parts. Milkstone remover. Evaporust. There are several options. You need to get all the rust off of everything in your motor. You can count on it coming off in your oil if you don't. After everything is de-rusted you will have to assess whatever else might need to be replaced.

There are always a few clutch baskets on ebay. Be patient and a cheap one will come along. Look at it closely and "ask a question" and be ready to pounce if you find a complete one from a low-miles bike. make sure it will fit your crank as there are two different depths of splines. If you decide to buy parts that gets a lot more tricky. I think there were six different versions.

Your bike is what it is. Replace everything that is out of limit and you should end up with a very reliable bike. Fudge just a little here and there and you might end up with a bike you can ride a long time without too much trouble - and it might be pretty affordable. There is no real recipe on that front. Ever been to Vegas? Your odds are probably still better and you'll probably spend a lot less money.

I hope that helps.

[patrickshofner]

thanks, guys. thats some good info. i suppose the fact of the matter is that we're looking at ~50 year old machines that may or may not have been appropriately cared for and unfortunately, it's up to us to deal with what's left. everything could be a gamble when you look at it that way.

i'm probably going to go ahead and tear it down further to see what the root issue is. if its something we can deal with i'll probably start a project thread and begin that long, long, long, process. haha

[hondadreamca77]

What's the gash looking mark on left side middle of second pic?

I would definitely de rust the baffles. Bearing shoulders still look good unless you see a through crack..... I would probably go for rebuild after through clean up. dressing nicks, and inspection.

That's just me though...

SC

[patrickshofner]

I was finally able to get together with the mechanic last night. he did a quick tear down to see if we could find the smoking gun. the pistons, cylinders, valves all looked unharmed. he finally found part of a gear floating about in the lower case. also found considerable wear on several of the transmission dogs, and a suspect crank bearing. he was going to put everything through the parts washer, mic everything, and measure to see what is/isn't in spec. as long as nothing crazy pops up, I'm most likely going to try to put her back together.