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Building an engine from the crankcase up?

McNinja

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Hey guys,

New guy here. What's up?

I have access to a CB750K crankcase. Completely bare. I want to learn more about engine building and figured this would be a great project that could really be neat.

How available are parts for this bike? Obviously I will need stuff like the transmission, oil pump, clutch, pistons, etc. Where are the best places to source these? My biggest concern is the oil pump and transmission assembly because I cant do anything without those. Assuming everything works okay, what about a frame, swing arm, etc?

Thanks guys!
 
Can be done but you are going to spend far more piecing a bike together then if you bought one that needs work. Bought your only source will be ebay. I would find a cheap used motor that has most of the major hard parts that are still usable.
 
Can be done but you are going to spend far more piecing a bike together then if you bought one that needs work. Bought your only source will be ebay. I would find a cheap used motor that has most of the major hard parts that are still usable.


I think you have a great idea there. Do you know the best place to source motors for these besides ebay? I've dug around ebay and they seem to go for $500-600 with $250-300 freight. $900 for an engine that will probably need at the very least some top-end love seems a little pricey doesn't it? I'm not sure if anyone here in in Vegas, but it seems like no one ever has a CB750 or engines available locally. Any tips for scoring one for a decent price?

Thanks again!
 
Sorry if I missed it, but what year?

I've since abandoned the idea of building it from the crankcase up. I'm now looking at an engine from a 1975 cb750 (not sure what trim) that will probably need a top-end rebuild.

What price should I be aiming for on these engines?
 
I have a stuck '74 engine that would probably need a top end rebuild, although I've read of some that just get their engine unstuck and it runs fine... crapshoot I guess. Also have a non-stuck '75 that may or may not need a top end rebuild... I've never started it, although I tried briefly before I started taking the bike apart. I also have a '75 that I've started, although never had in a bike that I've ridden. I've listed the engines on Craigslist and got no takers... prices were too high or just happened to post them when no one was interested. Prices were, engine w/o carbs:

$100 Stuck engine
150 non-stuck engine
200 "running" engine

Just yesterday I saw on Craigslist near here a '72 titled frame with stuck engine for $175.
 
I have a stuck '74 engine that would probably need a top end rebuild, although I've read of some that just get their engine unstuck and it runs fine... crapshoot I guess. Also have a non-stuck '75 that may or may not need a top end rebuild... I've never started it, although I tried briefly before I started taking the bike apart. I also have a '75 that I've started, although never had in a bike that I've ridden. I've listed the engines on Craigslist and got no takers... prices were too high or just happened to post them when no one was interested. Prices were, engine w/o carbs:

$100 Stuck engine
150 non-stuck engine
200 "running" engine

Just yesterday I saw on Craigslist near here a '72 titled frame with stuck engine for $175.


$100 for the stuck engine is super reasonable. $175 for a titled frame and stuck engine is even better. Where can I find these? Haha. Ebay seems to be hitting around $500 for a decent running engine, $300 for a stuck engine that will need to be completely rebored and everything.
 
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