Topic: My first rebuild/project 1972 Honda CB750

[TheyAllFloat]

Hey everyone, just would like to start things off by saying this is my first time taking a engine apart and rebuilding it. The bike ofcourse is a 1972 Honda CB750, engine is currently not running and the problem seem's to be on the bottom end of the engine.I have not yet messed with the bottom end and I am hoping to start that tonight if work does not keep me here late.  I have limited space to actually work on the bike which sucks but i have the support of all the people who surround me.

Anyways what I hope to end up with is a classy cafe racer, already making a list of a few things I want and things I will need for the entire thing to go smooth. But first I have to get this engine working, I took apart the top end the first day I got it which was this past sunday. Everything looked fine so that's when I said the problem must be in the bottom end but then again I never took a engine apart so I asked a friend of mine who is handy with the wrench to take a look at it. He verified that the top end was fine and the bottom end needed to be checked which I will do like I said hopefuly tonight.

Since I don't know exactly how to tell what is wrong with any part I will take some pics of bits and pieces of the bottom end and post them on the forum to get some help identifying what exactly is the problem(my friend is not easy to get a hold off most of the time). I read a few threads and the people from this forum are very helpfull and know what they are talking about, so I hope you guys can pass some of that knowledge to me!

I took a few pics this morning of just the bike, I was in a hurry so I did not take any engine pics. Will post more pics hopefully tonight and hope to get some good info from everyone thnx!

[TheyAllFloat]

It keeps saying the entity is to large, won't let me post the pics.

[KB02]

The attach function only allows so big a file. You might want to use a photo hosting site like www.Photobucket.com or something. Otherwise, you'll have to resize the pictures.

[TheyAllFloat]

Thnx I will try that.
 
 

[harisuluv]

Nice bike. Just curious how did you know there was something wrong with the bottom end?  Would hate to see you take apart the whole engine if you didn't need to.

[TheyAllFloat]

Thnx Harisuluv...good question, well from what I could tell the top end was fine. My friend took a look at it, he also said it looked fine. I took the clutch apart to see if maybe that was bad but no it was good too, so all that is left is the bottom end. Unless I missed something(noob after all).

I can post pics when I get home of the top end of the engine piece by piece, maybe you guys can spot something I missed? Also the guy who sold it to me thought the bottom end was the problem.

[harisuluv]

Never believe the previous owner, ever.  Also when there is something wrong with the bottom end it can be semi catastrophic.  Without even knowing anything else I'd say it's probably fine in there.  You need a point to go from where you know where to start.  If you already have the top end apart though, you are going to need new gaskets and everything anyways for the top end so you might as well make sure the bottom is ok.  >.<

[Tews19]

Welcome to the site and looks like you got a big project in front of you.. Did you remove the rear wheel and forget to put the cover back on the side of the hub? The tires look interesting, front big as hell and the back looks to be either really skinny or extremely worn. Were you able to get the bike running before taking out the engine? Did you have electrical power?

[TheyAllFloat]

harusuluv maybe you are right but it is to late now lol. Tews19 thnx for the welcome and yes the rear wheel was off when I purchased the bike, he actually gave me another tire as well. The bike has been sitting since 1977 which was the last time it was registered, the engine was not running when I took it out and it did not have power.I really just went by what the person who sold it to me said.

I was goin to start working on the bottom end tonight but that won't happen due to my bro not been home to open the shed we're the motor is 

[ekpent]

Usually I always try and get a motor running on a new project before tearing into it so I personally can make an assessment as to its issues. Might be something simple. As mentioned its hard sometimes to take a PO's word unless they really know these bikes well.  Out of curiousity what did the PO say was wrong with the engine specifically in his opinion ??.

[TheyAllFloat]

The person had a couple of bikes and he was actually just finishing restoring 2 1970 something BMW R75/5, I think that is why I took his word. He did not specify the exact problem just said engine was not turning over and he knew the top end was fine(guess he probably took the top end apart before).

[lucky]

"Anyways what I hope to end up with is a classy cafe racer"

Now repeat after me...."I WILL end up with a classy cafe racer."
Say that every day.

[lucky]

Nice bike. Just curious how did you know there was something wrong with the bottom end?  Would hate to see you take apart the whole engine if you didn't need to.

Yes, I agree unless it has 200,000 mile or ran out of oil.
People say the strangest things about engines, with NO evidence at all.

[lucky]

Thnx Harisuluv...good question, well from what I could tell the top end was fine. My friend took a look at it, he also said it looked fine. I took the clutch apart to see if maybe that was bad but no it was good too, so all that is left is the bottom end. Unless I missed something(noob after all).

I can post pics when I get home of the top end of the engine piece by piece, maybe you guys can spot something I missed? Also the guy who sold it to me thought the bottom end was the problem.

I would not believe any stories. Only facts.
Also if the top end was ok and not scored or burned, then that means it did not run out of oil.

How many miles are on the bike?

[TheyAllFloat]

Lucky the miles on the motor are 186,XXX...so dumb I did not notice the miles on the dash  . The bike still had oil when it was purchased, Lucky got any ideas of what the problem might be? Also is there any special tools I need for the rest of the disassembly? The valves have major carbon build up I know there is a specific tool to remove them care to point me in the direction of where to purchase it at a good price? How would I go about cleaning the valves? Or should they be replaced?

I still have not had time really disassemble the bottom end, hoping it will be soon. Thnx in advance for the help!

[TheyAllFloat]

Please let me know!