Topic: Spiider's '73 CB750 - "The Baby Elephant"

[Spiider]

Hey everyone!

I just picked up this project bike last night, very excited to have a sohc4!



Lot's of work here, the seat is ill fitting, the Dunstall tank needs relining.
I also need to rejet and resync the carbs, already ordered the Morgan tool and will be picking up some bigger jets thru the week when get near the local shop. A compression test will be first on the list though before I get into the carbs.

Anyone have an idea where to start with jetting this old girl? The last owner has put pod filters on the carbs, and it looks like the 4into1 has been on there a while.  I've been reading a bit and the general number is 125 then move up or down if needed. Would a wideband O2 gauge help with setting the jets?

Thanks,
-Jeff aka Spiider

[Stev-o]

Wow - that bike looks sweet...Congrats!

What running cond is it in now? You get a good deal??

[Spiider]

I had it running today. Tried to take it easy as I don't really know the condition of the engine.
I gave it some throttle and started it and held it around 2krpms just to warm it up.

It wouldn't run off throttle and wouldn't run at all with the choke open too much air would be my guess.

At 2-4k it was smooth and had a great sound, I didn't dare go any higher until I get a compression check. Actually it was irresponsible to blip it up that high until I knew more but I was soooo stoked that it was running (and it seemed to love it).

I did a quick look at the plugs before and after and took a peek in the valve inspection holes and it looked good so I put some gas in her. The plugs had a good color and dry after warming up, prior to running they were a tad oily for my taste but I think someone fogged the cylinders.

The tank is weeping a bit so I'll have to seal it with some epoxy or something to seal it good. I know fibreglass tanks are prone to this so no biggie.

I got it for $2500 cdn, which is a bargain as far as I'm concerned.
He said there is $1500 in NOS parts put on her before he ran out of money and decided to part with her.
I would guess he's not exaggerating, considering brand new tires (Bridgestone Spitfires) and the rims are rear NOS and front from eBay. He had them re-laced and trued. New throttle and clutch controls, new cables all around. Also, all the nice finned engine covers....I know it adds up quickly.

Brakes feel good, I had to bleed the fronts today to clear out some old fluid that was amber. It looks like the front master is weeping at the lever so I can probably get away with a rebuild kit.

Shocks feel good but the forks are saggy and lack good rebound. I may need to do new springs and fork oil.
Maybe some progressives? Any opinions on springs or fluid?

I ordered some stuff from Carpy, bar end mirrors and a manual.

I'd love to do rear sets, but the most important for me right now is to get the engine running like a swiss watch.
I also need to affix the seat a little better as it is loose and wobbly.

I'd like ideally to have a shorter tank but given its a classic tank I'll likely leave it there and make it work until I decide on something else.

Anyway....I'm excited and rambling, lol.

-Jeff

[Stev-o]

All sounds good, you have good reason to be excited!

Since you don't know all history, it may be a good idea to give it a full "3000 mile" tuneup and clean/sort the carbs.

Does it have electronic ignition? If not, you may want to consider an upgrade.

Good Luck.

[Spiider]

Yes definitely, an electronic upgrade is one of the items on my shopping list.

Is the "Dyna S" the most popular? or what else is recommended?

[MasterChief750]

hondaman sold here on the forum has some great reviews and there is a new electronic one on the market but not much has been said of it because its so new. its in/was theforsale forum

[Spiider]

Awesome! I'll take a look.

[Stev-o]

I bought the Dyna S before I knew about Hondaman's, and have been happy w/it.

Here is the link to Hondaman...

http://forums.sohc4.net/index.php?topic=67543.0

[Old75_ratafe]

I have the dyna S as well and love it.  Although I didn't know about the hondaman either

[Spiider]

So, you can go Hondaman and keep your points? or Dyna S and lose them?
I think I'd prefer to lose them, out of a maintenance perspective only.

Does the Dyna S have the same type of transistor based switching within the sensor housing?

And I guess the best thing is to keep the Honda coils as well from what Hondaman is saying about spark duration.


And today I got the seat and tank off to take a peek and see what the poor mounting issues were with both and they look like they will be easy to work out. It helps that I work with the biggest machine tool distributor in Canada so I can cut pretty much anything I need to for a project like this. Maybe some nice 5 axis cnc tank and seat mounts in my future!

The frame is pretty decent condition wise, it will need to be powder coated so maybe I'll get it all torn down over the winter and get the frame and swingarm out for painting.

Looks like some of the wiring is a bit ratty too, not hacked just getting old. I may get a NOS wiring harness for her if I can find one. When I rebuild after paint I will toss that in instead of the old.

I can't find a decent compression tester anywhere either, most of the ones at the automotive shops are...well...for cars. The hose is huge so I don't think the readings will be very accurate. I read that was the main issue with compression testing on bikes.

-Jeff

[Old75_ratafe]

On my S its a all contained in the "points" plate.  No brain box or anything just a direct bolt in replacement.  I do however have the green 3ohm dyna coils I've heard rumors of them having issues overheat but have never had a problem.  I do like that the plug wires are easy to replace on them.

[Stev-o]

I have the Dyna S w/stock Honda coils, no issues.

[bluezboy]

I have the Dyna S w/stock Honda coils, no issues.

 Count yourself damn lucky, because the Dyna i my bike fried the coils! So  my mech replaced them with better non Honda coils,  and ouch that hurt my wallet!

[Old75_ratafe]

I have the Dyna S w/stock Honda coils, no issues.

 Count yourself damn lucky, because the Dyna i my bike fried the coils! So  my mech replaced them with better non Honda coils,  and ouch that hurt my wallet!

Not sure how the dyna could have fried your coils... it does exactly the same thing as your points....  and non honda coils should have been cheaper.  What did he replace them with?

[Spiider]

I'm looking at some parts shops online...old bike barn, partsnmore, etc.

But, I don't want to get jerked around by these guys I've read bad reviews of old bike barn....any online parts shops worth going to? Which ones to avoid?

partsnmore has complete wiring harnesses, my wiring isn't bad just old. I thought it would be good to throw in a new harness to clean things up.  

What about all in one rectifier/voltage regulator combos like the Oregon Motorcycle units?  
Or am I better to stick with OEM replacement parts.

This is going to be strictly a cafe style, not a period perfect restoration so I can go aftermarket without going against my conscience.

[unitedguitar]

I got my wiring harness from parts n more and it works fine. I've seen a lot of people use the all in one rectifier/regulator but some people have said that it sucks when one part of it goes out and you have to replace the whole thing.

Most of the parts for mine came from either partsnmore.com, cb750supply.com, bikebandit.com, slingshot-cycles.com, outwestmotorcycles.com, motionpro.com, cyclexchange.net, customdynamics.com, amazon.com, z1enterprises.com and maybe a few more that I can't remember. Didn't have any problems with any of them and some even offer free shipping.

[Old75_ratafe]

I'm looking at some parts shops online...old bike barn, partsnmore, etc.

But, I don't want to get jerked around by these guys I've read bad reviews of old bike barn....any online parts shops worth going to? Which ones to avoid?

Yea stay away from bike barn.... See my thread they sent me wrong parts and refused to do anything but store credit for the difference.

[Spiider]

Great info! I can see how its easy for Newbies like me to get sucked in by places like the old bike barn.
I was about to hit the button to place a large order before I decided to google them and ask here. Thank goodness I didn't.

Since I have a good list of vendors now I'll dig more. I also like to support the vendors that support forums like this one.
I'll try to spend money there first if I can.

So far I'm getting a long but surprisingly not that expensive shopping list together for my bike!
Lots of jobs to do over this winter, hopefully I can have it ready to ride for next summer.

Thanks,
-Jeff

[Spiider]

Ok, this gets interesting....I just was looking at carb kits and realized my bike has a 222xxxx serial number and the engine has a 3xxxxxx serial number so the engine is a 78 sohc4!

The profile of the carb bowl definitely matches the pictures of the 78. It is a Keihin 28mm carb but the bowl has that distinctive shape I see in the pictures.

It must have had an engine swap at some point. Is that bad?

Anything I should be careful of when buying parts?

I guess I need to stick to '78 engine parts, and '73 chassis parts.

[Spiider]

Ok, this is supposed to be a "project" thread....so where is the project progress, right?

I spent a few days carefully considering my next step, should I gut her down to the frame or fix what's wrong and enjoy riding her?

I decided to tear her down to the frame for a bead blast, magnaflux, a bit of frame smoothing and finally some nice new powdercoat. (Likely gloss black but I haven't decided.)

With that decision made I moved forward today with the teardown. I had a few hours this afternoon to really get into it and this is the result so far.


^Getting started, tank, seat, sidecovers and headlight pulled.

How am I going to remember where all this goes when I go to put it back together in a few months?


^Pipes off


^Drained oil, drained front brake and pulled caliper off. Signals removed and boxed up.


^Wire harness yanked, clutch, throttle lines removed. Battery box removed along with the rectifier, regulator, safe start module, solenoid, and turn relay pulled as well.

Starting to look clean, and getting down to more large mechanical parts now.

Next up, wheels, forks misc other components...hopefully my next update will be down to the frame and swing arm.

I have to buy a solid workbench for tearing into the motor. I'm going to do the top end, replace what should be and adjust what can be.

[Spiider]

More updates...an hours worth of work per day, finally getting somewhere.




^Here we are from the front, wheels, chain, oil tank, rear fender liner, fork tubes, carbs etc. all removed.



^Rear view of same.

Finally down to essentially the frame and engine...a friend may come over on the weekend to help me lift the engine out of the cradle and hopefully I can get a bench in there to put it on for now.

Good thing I tore it down, the head bearings feel lumpy and crappy. I guess one of the first upgrades will be a taper bearing kit for the headset.

I put a couple rubber gloves over the intakes, there was a lot of varnish inside the intake tubes..ugly.

It has me thinking that while I've got the frame out for bead blasting, powder coat etc., I may tear down the top end. It will give me a good chance to clean things up there intake and exhaust wise anyway and replace and adjust everything in there. In the meantime I'll order enough stuff to get it back into "roller" condition at least.

I may go for some of the parts from Joker Machine, gorgeous stuff there.

[Spiider]

Something else to look at...after a half hour of near constant swearing and bloody knuckles I finally got the engine out.

I used a cherry picker type engine hoist with a few ratchet straps to manipulate the engine attitude.
I then got it up about waist high and walked it out of the frame by holding up th frame and moving it around with the engine hanging static in front of me.

It was a lot easier with the cam breather and oil pan removed.
I don't know how anyone could get the engine out without those items off at least.

The three pieces are ready to head out for bead blast and powder paint.
I may do a few covers while I'm at it but thats for later once I get into the engine.




I've already knocked out the head bearing races, that was easy enough with a brass drift and tapping...north, south, north, south...evenly until they popped out.

I may get my own bead blaster, I think it could come in handy with this project.

[Spiider]

Oh, if anyone is interested I am going to sell the Dunstall tank and seat combo and go a different direction.

Still keeping her cafe-resto-mod but with a smaller leaner tank and a two up seat similar to "The Natural" if you know that bike.

Actually I love everything about that bike!
http://thetarantulas.net/post/459558445/the-natural-seat

[Spiider]

Got the valve cover off, I had to drill out practically every other screw...but regardless of that PITA very pleased with the condition under here, just like a new bike. I want to clean up the valve cover and either paint or polish it up anyway so it was a worthwhile effort. I'll put new screws in there and a small amount of anti-seize as well to stop corrosion.

I don't think I'm into a total tear down that's a given, what  a relief.
Maybe some intake and exhaust port cleanup, adjust the tappets and cam adjuster and see how it goes. 

I bought a small hand held sand blaster and some glass beads....didn't work out as well as I'd hoped. It is still going to be useful for small parts but there is no way to do the entire frame with such a small unit. Plus, you'd go through $100 in glass when it would cost less than that to get it done commercially.

[brandEn]

I love reading project threads. It looks like yours is off to a good start. Keep up the good work! Looking forward to more pictures and updates.