Topic: 76 CB750 K

[Markcb750]

This is my 750 when I brought it home in May.

the last shot is of the motor area after a few hours of clean up...

[Markcb750]

This is Now.

The problem was the second photo, rusted out pipes making it hard to set carburetors, and it just was too loud.


There is something about that last photo, an "attaboy" for pointing the problem...

[Markcb750]

I have been cleaning and clear coating the bottom of fenders and brackets, anywhere the chrome is lightly applied due to the plating process.

Two of the exhaust flange mounting screws stripped when I hit them with impact driver!!!

Drilled out screw heads, but I now need ez-outs, off to the parts store!

Interesting thing, when I removed the rear wheel the swingarm was very stiff, I was concerned about looseness due to Hondaman's warnings, but found zero play, in fact I could barely move it up and down...Will assemble to manual directions.

Grease fitting did not look like it had ever been used, just old grease in there.   who knows?

My stainless steel screw collection, kits are helpful, but still need 5mm screws for tach & spedo drive, still need screws for exhaust flanges and fender mounting brackets. off to McMaster Carr land.

[Markcb750]

Wheels Down!  My '76 has landed on its wheels again!





My latest distraction from completing the 750...a 1500 classic.

[Markcb750]

This is the engine now:

Painted cases

Brushed engine fins, (sorry cocooned larvae find a new home)
Polished valve cover and cases
Electroless Nickel finned exhaust clamps and mounting flange
SS hex key mounting screws
Re-chromed pipes.


Putting in the Dyna solid state ignition today.

[Markcb750]

Set timing & started it today!

Interesting batch of carbon dust blew out of the muffler drain holes!

Runs & sounds great, slight problem with leak at gas line connection at "T" between each pair of carburetors, will need different type of hose clamp I guess.

Air box and rubber carb isolators where one of the most difficult things to re-connect. 



I put 15W 30 in lieu of 10w 30 in the forks? seems OK.

Anyone have any experience with using one of the specialty fork oils?

Will ride this week if sun comes out!

Thanks to all who answered my questions.

[Really?]

Looking perty clean there.  Can't help with the fork oil question.  Waiting to find out how the 15wt feels in mine.  Couldn't find 20wt anywhere around me.

[Markcb750]

Have had my first decent rides the last few days!

The All Balls tapered roller bearing set seems to have cured any hint of a woble in the front end, Great!

Motor starts great cold or hot, still very cold blooded but much smoother.

Need to work on the idle, best around 1200, think it should be ok a little lower.

I had a guy in a minivan honk his horn next to me at a stoplight, ask me what year, told me he had a '74, and my bike looked great! No one does that on the Kawasaki 1500 classic!


The CB sure is a great ride around the town! 

I took it to a painter, 400 to 500 to match original paint as close as he can, seems reasonable.

[Really?]

Nice!

[tonycb650]

There are 5 pipes in that picture!?

[Markcb750]

Tony gets the prize!

The fifth pipe is from a used set I bought out of South Dakota, rusted through where the battery spillage impacted the pipe.

I found a new single LH inner pipe to replace that one in the set I had re-chromed.

Did not cut them off to sell as "drag pipes" on evil bay. 

Sent them to the scrap pile.

[Markcb750]

Took the CB to Iron Horse for NC inspection this afternoon, nice the North Carolina no longer requires a sticker, big brother can watch us with his PC's.

Had a guy in an '89 911 shout out 'nice bike" on the way..

[Markcb750]

Just a few pictures to show off...

[Speed King]

Damn- that thing looks nice.

[andy750]

Great job on the bike - looking good!

Enjoy the ride!

cheers
Andy

[Markcb750]

Thanks guys, it has been fun.

#3 quit firing and started pouring gas from the exhaust pipe drain. 


After fiddling with spark plug wires for a few minutes, took off the Carburetors, I must not have tightened the low speed jet, it was just hanging there.

While at it I took apart the low speed circuits and re-cleaned all the ports & holes. 

On reassembly I got a little aggressive with the jet and broke it off!

1) Drill and clean, clean, clean.

2) Travel to Iron Horse and order new jet for $5.50

Here today!

All my plugs very black, debating decision to try one of the high performance plugs or to just go one hotter because I just don't run the 750 very hard. 

I changed to a 17 tooth front sprocket which has increased the RPM a few hundred at 60mph, but this is not enough to keep the plugs clean.

On reading here I also added a few mm to the height of each float. I believe this will make the idle circuit run leaner. Without doing the clear tubing trick I have seen here it is difficult to know for sure but I think I have each float shut off at about 28mm below the rim of each float bowl.  Tried buying a float gauge at Iron horse but they can't provide.

[Markcb750]

Thanks to help and advice available on this forum while I had the carburetors apart I cleaned the the high speed aeration circuit again with better understanding of how the carburetors work.  The carburetor manual available on the SOHC website is particular informative as to what happens as air is drawn through the carburetors. 

Still unable to get it to idle well below 1200rpm, Carburetor Balance?  More tools





Worst part of Honda's design is the airbox!  What a pain in the ass to assemble in place. Keeping the gasket in place  I found I must put the airbox top and velocity stacks on then assemble the remaining airbox parts after I have airbox top and stacks as well aligned as I can.

Best part of my minor modifications is the change to allen screws every where I could.  This sure makes removing and reinstalling the clamps on the carb isolators and velocity stacks more positive.

[Markcb750]

The Temperature was in the low forties here yesterday so I just took it for a 20 mile ride, burrr.

It sure is faster and smoother, the 750 would now dust my Kawasaki 1500!


Comments on some of the improvements.

Repairing swing arm bushing and replacing head bearings with AllBalz tapered roller set...Fantastic, no hint of a wobble at any speed, the front end feels solid.

New sprockets; down one tooth in the front(18 to 17t), hardened and plated rear 48t, and a new Diamond "O"ring, nickel plated chain.  Smooth, easy to adjust. Z1 for the sprockets, ordered chain from local industrial supply house.

New chromed pipes and baffles; It just sounds right to me, particularly after second attempt to  set cam chain tensioner.  No backfiring, I cruise into the neighborhood unnoticed.



Bad idea, I put F model shocks on rear, keeps the chain cover from mounting properly, and it just does not look correct. I would like a set of stock length or shortened rear shocks in equal shape:  anyone interested in a trade?   


 

[Markcb750]

Have switched to NGK D7EA plugs, seems to running smother for the last 300 miles, WTFK?


Had the Carbs balanced by a young mechanic in Indian Trail NC, Nice guy, Motion pro equipment, seems smoother, Idles 1000 to 1100 now.


One of the things he recommended is a "manual" cam chain tensioner, anyone here know if this a good thing to do?  My objective is to quiet the chain noise in at idle.

[Markcb750]

The D7EA's seam to have helped a lot, smoothest operation yet.

Cold blooded it remains but once it is warmed up, sweet. 


The point of my post:

On my Saturday ride I spotted a local classic car group gathered at a local drive in, so I stopped to look. 

I started talking to a guy with a 66 Corvette, He is doing a great job and one of the things he had set up was an O₂ sensor to monitor carburetor jetting! 

He had changed jets several times in an attempt to optimize his Holley four barrel.  It was interesting to hear him describe the same things I have read here several times, all the advice from millions of small block Chevy owners and still no definitive answer! 

He sure has gone scientific to solve this classic carburetor problem on his 327! 

[andy750]

Very informative posts Mark! Thanks! Now go out and enjoy the bike!

cheers
Andy

[Markcb750]

I have driven the 750 almost 2500 miles since my rebuild.  It runs much better in 75 degree temps then 45 degree air.


I have had to retighten the head bearing set once, surprised at the 1/4 turn "easy".  I want to remove the head and really give it a check up ASAP.


O ring chain runs great, minimal lube, and minimal rear wheel cleaning.

I don't want an oil thread but i have started using a 20w50 Casteroil product with this oil change, mostly to see if it quiets the valve train a little.  Still bits of sludge in the strainer that I assume come from putting in 4 to 5 oz of Sea Foam last ride before I change the oil.

The change to D7 NGK's still seems correct.  Over 2000 miles on this set, no loss of a cylinder. Less smoke. Although still an occasional backfire. (carburetors! )

This winters project is to do a complete rebuild of the carburetors.

The drilled front rotor results in a very slight stutter when I break lightly. Perhaps the spiral pattern would help. At 120 bucks this will wait a while to try.

Mark

[Markcb750]

I have continued to enjoy my CB, many interesting conversations with people when I stop.

I have been battling a tachometer seal leak just installed the thicker seal from a DOHC...Time will tell.

The system I installed to vent the valve cover back trough te airbox and through the combustion path has worked reasonably well, I get a drip of oil from the bottom of the air box after long rides.

Trailered the 750 & my 1500 classic to the Adirondacks for 6 days of day trips. Great roads in upstate NY. the CB performed flawlessly even at speeds over 100.  

I have aquired a 76 750F basket case.  I need to haul it here to tear down and decide how to make it road worthy again.  Frozen engine...not a good sign.

I am looking for a restorable (sp?) 750 K tank; if anyone here has one for sale, particularly within driving distance of Matthews, please PM me.

[andy750]

Great update Mark and glad to see you are still enjoying the 750. I was in the Adirondacks a few years back on my K4 and agree there are some great roads there - when I was there in late June they were empty!

All the best
Andy

[Markcb750]

found a tank, from a older bike, petcock on the RH side, two nipples.

I am going to try one of the rust removal techniques discussed on the forum, will let everyone know.

The DOHC tach seal seems to work, photo below.

Also a few shots of my toy collection including my 97 M Edition Miata I just completed a clean & repair job on.  New timing belt, changed all fluids, new Koni struts/shocks, new front calipers and performance Pads, cleaned and repainted engine components. All new speakers and radio, the USB connection which allows me to attach a thumb drive with 8 gigabits of music is great!