Topic: Spirit of '76 CB750 El Cheap-O build

[vorhese]

SOHC here is my CB750 build thread.  These first few posts are over the last couple weeks on my forum www.bayareavintageriders.com. I'd like to share here as well.

I finally got motivated to start working on this thing again. It's pretty much just been sitting for 3 years disassembled.  I originally bought it so that I could ride 2-up with my wife easily and for long distances. This was probably my worst value purchase I've made. I bought it running for $800, and it was an ugly snot monster.

Video:

I figured I could just clean it up a little and she'd be good to go.  When I started working on the forks, there was no oil, just stagnant water, and I swear to god, old leaves IN THE FORK TUBES.  The engine ran good, but sounded like it was gargling beebees.

I started tearing the chassis apart, cleaned up and painted the exhaust, and got a few things in primer, then I moved about 5 times and never got back to it.





Until today.

Today I got the frame all cleaned up and free of grease.



I also spent 2 hours cleaning the engine up before I started disassembling the head. The plan is to just rebuild the head, I think the bottom end is pretty good.  She was a dirty #$%*. It looks like it blew a head gasket, the right side was pretty oily.











So here's one of those things you discover under layers of grease. It looks like the chain snapped at some point and busted through the case. It's been repaired (welded).  I haven't noticed any bad juju from it, so I think it's ok. The sprocket is also very sloppy... I'm not too sure that's the way it should be???



I'm debating if I want to paint the frame or just pony up the money for powder-coating. Painting will be cheaper, but it's a lot of work to make it look decent.  Plus I want something with some chip resistance.

[vorhese]

I dove into the engine.









Bigger wheel looked pretty good, smaller wheel seemed pretty worn.





So everything was going pretty good til the end. I was removing the exhaust manifolds with the impact driver. All every pretty easy until the last one. it just would not budge. It destroyed my driver tip. Luckily I had a spare.

And then I tried to remove the intake manifolds. OK, maybe I won't remove the manifolds. Anyone got a spare???


So I'm pretty much stuck. I cannot get the jug to seperate. I can't find any bolts or screws or anything holding them together. Ideas?

[vorhese]

I FINALLY got the jugs and head to separate! I spent probably an hour working the jug and nothing. I even baked it in the over for 20 minutes tonight.  Then I found this thread on SOHC

http://forums.sohc4.net/index.php?topic=15650.0

The end of the jugs/head has a small notch to get a screw driver in. They came apart like nothing.

Woo hoo

[vorhese]

So I guess I'll do the cam chain, I'm replacing the whole cam chain roller assembly. To replace the cam chain without splitting the cases I need to get a breaker tool, a rivet tool, and a couple softlinks. I have to first break the cam chain that's in there, clip on the new one, and rotate it around and remove the old one. Then I need to rivet the new one together. Eesh.


Paint?
Frame paint will be Rustoleum Appliance paint, black


I'll be painting the jugs with engine enamel

And tins will be spray bomb of some sort, I'm thinking something similar to the Honda green. Pretty basic. Nothin fancy.

I don't have any money so I'm doing all the free stuff I can right now.

Bars?  I don't know yet. Not clip ons. Not clubmans. Not stock bars. Not drag bars.

[vorhese]

This cold afternoon is a Jasco afternoon. I wish I had a neighbor with a big sandblaster.

[vorhese]

Spent all day cleaning and scrapin and grinding. It's pretty amazing how much welding slag and welding rod was stuck to the frame. I ground down a bunch of the worst stuff, just to make myself happy.  Then I got a coat of the appliance epoxy on before it got dark.  Damn there are a lot of surfaces, my finger is still sore. Painting the frame is going to be a multi-week process.  You can't apply another coat until after a week of curing. So next weekend I'll paint the bottom, then another 2 weeks for a second coat. I'm very happy with this stuff.  No need for primer.

Maybe tomorrow I can get a little time in cleaning the cylinders and head, and pop the valves off.



Wipe down with mineral spirits

[mystic_1]

Coming along nicely!


BTW regarding the leakiness, most of the grime on the engine seems to be above the actual head gasket, this sort of leak is most usually due to the heat bolt sealing pucks, the six little black rubber discs, three of which are visible in this pic:



Some people daub the edges of the new ones with a bit of Hondabond or Threebond when installing, this helps prevent leaks in the future.


Looking forward to the rest of your build.

mystic_1

[vorhese]

BTW regarding the leakiness, most of the grime on the engine seems to be above the actual head gasket, this sort of leak is most usually due to the heat bolt sealing pucks, the six little black rubber discs.
Some people daub the edges of the new ones with a bit of Hondabond or Threebond when installing, this helps prevent leaks in the future.

Thanks!
Here's what it looked like originally


I decided to put off any engine work until after the new year due to funds. I'm going to concentrate on the chassis. I got all the parts out, painted a couple pieces, and cleaned the wheels up. They were pretty rusted, they look better now, but still far from perfect. But I'm ok with that. I spent about an hour on each with 0000 steel wool and WD-40.









The hub rubbers broke removing them. Are these salvageable/reuseable?

[bucky katt]

buy new cush drive rubbers, not worth trying to use the old ones IMHO

[vorhese]

My thriftiness tells me I need to be able to repair these things as they're at least $10 each.

[mystic_1]

There's no effective way to repair those, buy some used ones of eBay maybe.

mystic_1

[vorhese]

I had a minor frame paint emergency. I started to paint the bottom side, and wasn't sure if I should wipe down with mineral spirits so I did a test spot. Nothing seemed bad so I wiped down the whole bottom section and painted. 10 minutes later it was bubbling up everywhere. Poop.  I waited til today when it was dried (not cured) and sanded it down and repainted. It says to recoat after 1/2 hour or 1 week, but it looks good.


I got my K4 swing arm bolt so my swing arm is headed for Hondaman soon.

I found some replacement tank and side cover badges.

I found some replacement cush drive dampers.

I may have found a replacement alum intake.

Nothing too exciting.  Painted the oil bag, fork shrouds, gauge bracket, lower trees, kickstand, and all foot pegs.  I also cleaned up the shocks and both foot levers as best I could. Not perfect but good enough for the chicks I roll with.

[vorhese]

Last weekend my buddy gave me some forks he thought might be for a CB750, as they were mismarked for a CB350.  They weren't the right ones, but I thought the internals might swap. I finally got them apart for a comparison.

The stock tubes/components are on the left side of the pictures, unknowns on right.
Big differences are the tubes are the same diameter, but ends have different sized holes. The unknowns have a different damper. The lowers and springs are longer on the unknown.


The fork dampers are different. The unknown does not have the rod across the diameter which allowed you to make a tool to hold it while tightening it. Which stinks if you don't have an impact gun / hex head attachment.


And they are shorter and slimmer.


So the ends of the tubes are different.


But luckily all the internals are a direct swap for the Cb750 lowers.  When assembled they sit the same height.


Guesses are they are 77-78 CB750K or CB750A forks.  I'll be taking these tubes to get shortened once I have everything together.

I also got the headlight shell, sprocket, rotor, and sprocket guard painted. Frame is done.



I bought new wheel bearings and got the old ones out. The bearing in the cush drive was original, and no one had ever attempted to take it out, so it was easy to remove.  I just drilled out the 4 stake marks and made my own pin tool to remove it.


Unfortunately the wheel retainers were so f'd up from previous attempts. I had to drill in at least 8 spaces on each. Both are ruined. $20 each. The more I dig in the more my low buck is becoming high buck.  I'm debating just getting rid of the 16" and buying an 18" rear wheel on ebay for $50 than buying a new retainer for the rear.

[vorhese]

Got a little work in.  I cleaned up the rear wheel's cush drive hub and brake plate. And I also polished up the fork tubes, bar clamp, and top trees.



Action shot


So I am a complete dumbass. I really want to shoot myself.  So it started with putting the new bearings in the wheels. I forgot to put the axle collar in between the two bearing on the rear wheel, so I had to carefully knock one out. I inspected it and it looks like it was fine, absolutely no damage. Phew.

But then, and I have no idea why I made this mistake, I started to try to get the oil seal out of the rear bearing retainer that I have a replacement coming. And it was stuck. So I carefully carved it out. It's a $12 seal and I was so proud of myself for rescuing it! So proud!


30 minutes later it hit me. I #$%*ing just destroyed the GOOD cush drive retainer. I confused #3 with #4.



THESE were the two bad ones.


There goes another $20 + SH plus another week. I really can't believe I was that stupid.  So far this rear wheel is costing me $55 in parts, and I could BUY a wheel on ebay for LESS that. Actually that's what I did. i got myself an 18" rear wheel on ebay that I will eventually put on. In the meantime I'll swap out the cush drive hubs.

Got the front wheel together and forks together. I have them set at 2" lowered. They're just temporarily assembled. Once the bike is fully together I'll know how much to cut the tubes. This will be my last update until next year when I get the swing arm back from Hondaman.

[my78k]

I saw El Cheapo in the title and I thought Tom was back on the board!!!! You old timers would remember Mr. Congeniality right???   

I wonder whatever happened to him?

But I digress.....

Oh and interesting stuff so far. I will have to keep an eye on here and see how you make out!

Dennis

[mcpuffett]

I remember Tom he was a colourful chap  , your making good progress with your bike  look forward to the next installment  cheers Mick.

[bikerbart]

I am doing just about the same thing,hows it going?havent heard from ya,would like to see more.

[traveler]

Good stuff.  First I have seen of this build.....

~Joe

[MJL]

Keep a running total, I'd like to see just how cheap this really is.

[HedNut]

Everybody messes up sometimes...don't be so hard on yourself.  This is ONE DANG GREAT looking build you got going on! And I can't wait to see it progress.  I'm also trying to to an El-Thrifty build....We'll see where that ends up...ahah

Cheers!

[Thor's Hammer!]

Been watching this....wondering how it's going and if you had an update?

[traveler]

Status?

[cb544]

Impressive! Looks like you've a lot of work planned. The wheels & frame look like they cleaned up nicely!