Topic: Total Rebuild Thread

[bunghole]

So here's the deal:  I'm just going to start a new thread for my rebuild.  It's been done before and it was an extreme motivator for me to do my own.  As I start tearing down my '77 750k, I keep finding little things that I have questions about.  These might be no-brainers for some of the experts on this board, but to me, I have no idea.  This is the first major rebuild I have ever attempted.  I've never torn apart an engine in my life.  I have done tune-ups and other minor mechanical work.  I've invested in many tools (I LOVE TOOLS) over the years.

Here is the bike I'm starting with:

[bunghole]

The plan is to convert it into a cafe racer a la Carpy.  I love the stuff he does and I'm going to go for the same look.  In a perfect world, it will be something like this:



I want to do as much as possible on my own, but when it requires ridiculously expensive equipment, I will defer to people with the goods.

[kghost]

Get to it. 

[bunghole]

Get to it. 

Ohhhh....I'm in it, but I'm just getting y'all up to speed.

[bunghole]

In hindsight, I probably would have focused on getting an earlier 750K.  I've found that the '77 and '78 bikes are oddballs as far as carbs.  It's a bit trickier to find rebuild kits, etc.  But I've got a '77 now and I'm going to do it up.

[bunghole]

My first goal was to make sure that I could replace the tank with an earlier version.  I personally don't like the '77 and '78 (let's refer to them as the Disco years) tanks with the gas doors.  I found out that the earlier tanks will fit, but they are shorter than the Disco tanks.  However, since I am planning on doing a cafe style seat, I will just find one (or make one) that is longer to fill the gap (mind the gap).

Huzzah!

[bunghole]

I bought a tank that was advertised on "super crappy ripoff bunch of dimwits-bay" as a '73.  The seller advertised it as having no dents...guess what...dents!  Wheee!  They also stopped communicating once I called them on it.  It is possible that it happened in transit, but it was packed pretty well.

Here it is:



For whatever reason, it looks like a PO maybe altered the petcock mount and now I have a tank with a male threaded 3/4" spigot that seems to be non-standard.  Let me know if I'm wrong.



Anyhow, I like the tank and filler cap, so I'm going to go with it.  I really like "knee indents" in tanks, so I had a few beers in me and decided to take a mallet to the tank.

Here is how it turned out.  It will need bondo, but I think that's inevitable.

[bunghole]

Next step was to pull the engine and begin the engine rebuild.  I disconnected the relevant parts and laid the bike on its side:



I forgot to remove the drive chain before laying the bike on its side.  Since the chain will be replaced anyway, I just cut it off with a cutoff tool.

I got the engine out and then realized that it was too heavy to lift by myself as I have a herniated disk.  So I went to Harbor Freight and bought a chain hoist for $50.  Here's a pic:



I should also mention that I bought an engine stand from Harbor Freight as well and modified it to hold a motorcycle engine:



Here is the engine in the stand waiting for teardown:

[bunghole]

The bike had a bunch of broken and or chipped fins, so I found a head and cylinder set on Ebay that was advertised as '77 vintage.  I have questions about that I will ask in a later post.  Meantime, I had the "new" head and fins dipped and sandblasted and decked and now they are mostly ready for re-installation.  It came with the pistons as well, but no rings.  In searching for rings, I found that the '77s cost about $160 a set from Honda, so this was my motive to just buy an 836 displacement kit from www.cyclexchange.net.  The Wiseco pistons, rings, and pins are $399 through them.

Mmmmmkaaaay.  It is getting late, so I will follow up with the beginning of the engine teardown tomorrow if I have time at work.

Good night!

[bunghole]

Random picture...shifter mechanism:

[altf4]

Great job so far, and thanks for keeping us up to date. Looks like you've got a nice place to do a rebuild!

[bunghole]

So the next step was the engine teardown:

I pulled the valve cover.  Here are some pics:




I think I mentioned in another post that I picked up a head and cylinder on Ebay that was advertised as a '77 750K.  I bought it since I had some pretty nasty chips in the fins on the bike.  When I pulled the cover, I noticed there were some differences between the new and old heads:

On bike:



On Ebay head:



Also, look at the difference in these casting marks:

On bike:



On Ebay head:



What do you all make of that?

[bunghole]

Next, I pulled the cam...comments please...

Look at the pitting on this lobe:

[bunghole]

So then I pulled the cylinder off:

[bunghole]

Next was the shifter mechanism.  Here I ran into a little trouble and have a question:

This screw gave me a bit of trouble, so I had to cut some slots and get a bit medieval using an impact driver.  I got it off, but it will need to be replaced:





Even before I went to town, I noticed that this spacer was bent/warped:



Is that normal?

[Jerry Rxman Griffin aka MuthaF'er]

The -392 head was basically the first performance improvement Honda made on the head. It first appeared on the 75 750F then the 76 750F1, 77 750K7 and 78 750K8. Turn it over and compare the chambers. You'll notice more of a hemi design on the -392. This head is the reason or part of the reason for the compression bump to 9.2 to 1. There were 2 piston dome designs for all 750s (not including the 77/78 750Fs) that I once thought accounted for the CR bump but I've seen both designs in the later model 9.2 to 1 engines so maybe the -392 head accounts for the increase itself.     

Your "spacer" is normal. I'd replace that screw if it were me.

[bunghole]

So does that mean my bike had the head swapped out at some point in its history since it isn't 392?

Thanks for the answers!

[cleveland]

RxmanGriff, I like your signature.  I told mine the same thing about my guns. 

bunghole,  Looks like you have you work cut out for you.  I'd replace the cam while your already in there.  You should be able to get one pretty cheap from one of the guys here on the forum. 

I look forward to seeing your progress!

[bunghole]

Cleveland,

I'm going to an 836 displacement, so I think I will get a different cam as part of that process.

So many parts....so many dollars....so much time.  I'm loving this project!

[cleveland]

So many parts....so many dollars....so much time.  I'm loving this project!

No kids.......obviously. 

[bzr]

Damn, you either work lightning speed or you've been holding these pictures from us. 

How's that engine stand working out for you? I've been thinking of getting one myself. How did you modify it to fit a 750 engine?

[bunghole]

So many parts....so many dollars....so much time.  I'm loving this project!

No kids.......obviously. 

AND my wife is travelling for work.  It has been nothing but garage / music / beer for the last week.

[bunghole]

Damn, you either work lightning speed or you've been holding these pictures from us. 

How's that engine stand working out for you? I've been thinking of getting one myself. How did you modify it to fit a 750 engine?

I've been putting in about 3 hours a night on it, but I started the thread quite a while after the initial pictures were taken.  The thread is now real time and will slow down quite a bit.  If I took pictures of everything I was doing, there would be a lot of me with a beer in my hand staring at some part of the bike trying to figure out what the hell I'm looking at.  And then there would be pictures of me looking at the manual.  Very little of it would actually show me with a tool in my hand

The stand is great.  I got the modification idea from this other rebuild thread:

http://forums.sohc4.net/index.php?topic=29364.msg309143#msg309143

I was a little worried about my weld job, but I've had no problems with it.  Hopefully there will be no new posts from me that start with "I crushed my toes today".

[martino1972]

with the camshaft in that shape,you want to check the rocker arms as well,would be a waste if your newly found cam would be eaten by a rocker arm thats worn out ...they are in conctact with each other so i can picture it being in the same shap....
not sure if you can have the rocker arms machined or not,and what that would cost,but i'm sure someone here could give you a detailed answer on that...

[Jerry Rxman Griffin aka MuthaF'er]

Bung,

Are we sure it's actually a '77 engine? Whats the engine's serial number? May be from another year. Are the combustion chambers different in the 2 heads? That's the tell tale sign.

Thats a good point about the rocker arm. It probably has some excessive wear due to it's contact with the pit in the cam lobe. Last time mine went back together I discovered a small chunk off the side of one lobe. Considering it is a Yoshimura Daytona cam it went back in. I'd hoped it wouldn't spit off another chunk and it hasn't. If your engine isn't a 75/76F, 77/78K or a 69/70/71 then that cam is pretty mild anyway.