Topic: CB750K2 '72 Resto

[Vidgameking]

So here we go, yet another restoration. Picked this bike up in 2008 for $800. It had about 400 less mile on it then. I got it from my old boss who got it from the original owner.  The original owner is the one who put all the miles on it and kept a log of miles and maintenance. I don't know how common it is to find a bike of this age with less than 10K miles on it but when I tell most people the say the odo must have rolled...

I got it working, and rode it a bit but then it started leaking fuel and oil, and then the fuel got into the oil so I let it sit. It sat almost 9-years in a storage unit until I figured it was time to start working on it. When I got it out I noticed the upper triple was cracked on both forks, I guess it was tightened too much and it gave way while in storage. The engine isn't frozen and actually it doesn't really have much more rust on it than when I picked it up. It's just there is lots of little things to fix up. I took a bunch of photos for my before reference I'm not sure what people want to see on these forums for before pics.

The plan is to make it look really really close to stock. When I first picked it up I was thinking about making a cafe racer but I'm older now and I kinda like the classic look of the stock bike. Especially since retro is in again (brother just picked up a brand new triumph that looks dang near close to this bike!)

What would you all say is a accurate budget for a build like this? Reusing as much of the original bike as possible and only replacing the broken/have-to replace parts.

[Davez134]

Welcome, and very nice bike! I just finished a K2. Like you, I started off with intentions of a more modified bike, but went mostly stock. As far as budget, it can be all over the map. Does motor have good compression, how bad are oil leaks? Where is oil leaking from? A full carb clean/rebuild is in order, as well as probablly petcock, new battery. Correct K2 triple trees I've seen for over $100. Yours broke because you do not have correct spacer/D-washer in the top clamp. Are you doing labor yourself? All goes into figuring realistic budget. Lots of knowledge from folks here. Check FAQ section often and post lots of pics along the way!

[Johnie]

Welcome to the board. You have a great start on a stock bike. If those pipes are as good as they look you are in really good shape. It is hard to find decent OEM exhaust and those pipes really bring the looks of the 70's. If you decide to chrome stuff it is costly. Try some 0000 steel wool together with WD40 on the rust spots. To bad someone did not put that upper "D" shaped washer back on the top triple clamps. That is the cause for the failure there. That washer keeps you from clamping the top tree to the breaking point. You can source parts on this board in the wanted section, David Silver Spares, Z1 Enterprises, Yamiya, etc. There is info on this board of places to source parts. I imagine the gas got into the oil from the floats being stuck. Carb cleaning and rebuilding is not as difficult as you may think. Most of these bikes do have a slight oil weep from the head gasket. Not a big deal and the general rule is to leave it unless it gets real bad. You will probably want to rebuild the caliper and master cylinder. The guys here are more than willing to help out and this board is full of great info. I would suggest getting Hondamans CB750 book. He is a member here. Excellent guiding you through the bike repairs. We do like pics here so keep them coming. Good luck and keep us informed of your progress.

[Vidgameking]

Here are some close ups of the pipes, let me know if you think they are in a restoreable condition.

I'll be doing the work myself. As far as the leaks, the fuel and oil were completely drained in a couple of months. But I suspect it was a leak from oil filter or drain plug. It's been such a long time I'm not as familiar with it as I was.

When I got the bike it actually had a full front fairing on it, like a police bike or the such. But I was young then and wanted a cafe racer so I threw them away... I'm not sure if it was a valuable piece that I should have kept...

[madmtnmotors]

You will be able to better assess its condition by making it drivable first. That would likely include:

>Rebuild carbs
>Clean fuel tank if necessary. Inspect/clean fuel filter screen. New fuel line(s) if necessary.
>Rebuild front caliper and master cylinder. Braided stainless flex hose is cheap insurance. Your old rubber hose is just that, very old...
>Brake pads are cheap insurance. Replace brake pads front and rear
>New tires and tubes
>Check cables for smooth operation. Might as well lube and adjust the cables (this is a maintenance item anyway)
>Full 3000 mile tune up. New plugs and filters would be cheap insurance
>New battery

Drive it some to get a feel for overall performance and condition. Then start working on the cosmetic items if you feel the bike is worth it.

[Vidgameking]

Alright here is a list of the MINIMUM things needed to get this bike rolling:

• Rebuild carbs (including new rubber hoses)
• Replace upper triple tree
• Fix oil leak (suspect drain plug and oil filter area)
• Secure tail light ( there's a bolt missing)
• Need battery
• Fix Throttle Control (new cables and sleeve)
• Un-freeze front disc brake. (It was frozen when I got it before... Copious amounts of brake cleaner)

I get that done and the bike will be where it was 9-years ago when I got it and was riding it.
Later it'll be a mater of cleaning and polishing...

[madmtnmotors]

I get that done and the bike will be where it was 9-years ago when I got it and was riding it.

Except that your tires will be nine years older now. I suggest you do not go very far or very fast on those old tires. I can see waiting to make sure it will run well...

just don't wait too long.

[Vidgameking]

They were new nine years ago, and the bike was in a storage unit. The tires "look" good, do you think they would need to be replaced still?

[madmtnmotors]

They were new nine years ago, and the bike was in a storage unit. The tires "look" good, do you think they would need to be replaced still?

That's a personal decision. Many threads on tire age and whether they have an "expiration". I would suggest checking the date code and verify that they were indeed "new" when you bought them. Those "new" tires you bought nine years ago could have been four years old (or older) at the time you bought them. For tires made after 2000 there will be a four digit number on the sidewall somewhere. The first two digits are the week of manufacture, the last two digits are the year. So a four digit code of 4502 would be the 45th week of 2002, a four digit code of 2708 would be the 27th week of 2008, and so on.

[ekpent]

You will need a little more than brake cleaner to fix the front brake up well. The caliper will need to be split, the piston and o-ring removed and groove cleaned out well, pads derusted and dressed up if reusung etc. Pretty easy job actually.
   As for the carbs clean well what you have in there already and don't go for carb rebuild kits.

[madmtnmotors]

You will need a little more than brake cleaner to fix the front brake up well. The caliper will need to be split, the piston and o-ring removed and groove cleaned out well, pads derusted and dressed up if reusung etc. Pretty easy job actually.
   

+1. Remove the caliper, but leave the brake line connected. Use the master cylinder to pump the caliper piston out. Then remove the brake line, clean the caliper and piston thoroughly, replace the piston seal, reassemble, reinstall, bleed the system.

EZPZ

[Vidgameking]

   As for the carbs clean well what you have in there already and don't go for carb rebuild kits.

That's promising! I was looking at $300 for parts to rebuild the carbs... I was going to get four new rebuild kits and four new floats and other parts.

I'm just going to have to take the carbs apart and see what I need to replace. I figured if you take the carb apart you have to replace all the seals and gaskets.

[Tews19]

Hey I have a brand new HondaMan 750 book if interested. I bought it thinking I borrowed it to someone and they never returned it. Well after spring cleaning I found mine. PM if interested. Subscribed as well!

[Johnie]

Just make sure you put all the parts you take from carb 1, 2, 3, 4 and put them back in the same carb bodies. Use like 4 plastic containers marked for reference. And if you want to save yourself future problems, separate the carbs from the stay plate so you can replace the o-rings on the fuel T between carb 1&2 and carb 3&4. I get those o-rings at Napa and they are part number 727-2605 and you will need 8 of them.

[ekpent]

I have done many many 750 carbs and the only parts I have ever replaced was one bowl gasket, few fuel pipe orings and some junk aftermarket jets somebody put in once.Found a couple bad floats on a K1 but those were brass that year. New o-rings on the fuel pipes may save some grief so everything is just a one shot deal. Be sure to heat the old rubber carb manifolds well with a heat gun and the carbs will come off and on much more easily.

[SOHC4 Cafe Racer Fan]

There are threads discussing the effects of time alone (not including environmental factors) on tires.  I guess you can be the judge, but the safe bet is to replace old tires if you want the best performance out of them. 

[Vidgameking]

So.... This is a big project in general. I need to break up tasks to 1 to 2 hour tasks. I was thinking about pulling and polishing the covers, and maybe work on one muffler at a time. How much time is it to remove the carbs? how much time is it to clean a carb? I also need to clean the control switches and levers, Would it be better for me to buy new generic controls and a generic master cylinder off ebay? Motogadget? How much work is it to rebuild the control pods?

[madmtnmotors]

So.... This is a big project in general. I need to break up tasks to 1 to 2 hour tasks. I was thinking about pulling and polishing the covers, and maybe work on one muffler at a time. How much time is it to remove the carbs? how much time is it to clean a carb? I also need to clean the control switches and levers, Would it be better for me to buy new generic controls and a generic master cylinder off ebay? Motogadget? How much work is it to rebuild the control pods?

1 to 2 hour tasks? Aren't to many of those unless you are well practiced at them. Member harisuluv rebuilds carbs. Send him your carbs and they come back working like new. The master cylinder and caliper are easy to rebuild.

Why do the control switches need "cleaned"? Are there electrical problems? I would keep the low-mileage originals and shoot some electrical contact cleaner through them and be done as long as there are no known electrical issues.

For such low miles, I would be inclined to reuse as many of the original parts as possible. The only hard parts I would even consider replacing would be any part that had corroded or was damaged beyond repair. No need to throw money at things that aren't necessary. There will be plenty of things that will be necessary to throw money at!

[SOHC4 Cafe Racer Fan]

Unless you're a pro and experienced with CB's, you may have difficulty completing the rebuilding of systems/projects within 2 hours.

I recommend that you get Hondaman's book and go through your bike system by system.  Allow yourself more time.

[Vidgameking]

I am totally going to be getting hondaman's book! I guess I want to take this one part at a time, in small bits of time and devote weekends to larger parts that would require more time. Like removing one cover, cleaning and polishing it. Then another part. Breaking up the whole massive project into smaller tasks that can be done after work but before dinner. That's the thought. With that being said, where is a good starting point?

[madmtnmotors]

Forget the cosmetics for now. Get it running first. That is the highest reward for effort. If you spend all your time and energy making it look purty and then can't get it running? That is like a kick in the nads...

Make it run. You only need two things:

>Correctly metered fuel
>Correctly timed spark

So drain the oil, clean the carbs (or have them cleaned or rebuilt), do the 3000 mile service described in the manual, and fire it up!

Then work on the cosmetics.

[Vidgameking]

got it.

BTW, controls have to be cleaned because brake fluid leaked and got into right-hand control pod. Possible down the throttle cables as well. throttle doesn't open smooth and at that only a mm or two at the carbs...

[madmtnmotors]

got it.

BTW, controls have to be cleaned because brake fluid leaked and got into right-hand control pod. Possible down the throttle cables as well. throttle doesn't open smooth and at that only a mm or two at the carbs...

Ahhhh.... yeah you'll want to at least remove the controls and hose out the switches with electrical contact cleaner. Go ahead and pull the throttle cables off completely (take some pictures of the cable routing!) and check the cables for smooth operation. At this point you can try operating the carb linkage by hand to determine whether the cables are hanging up or whether it's the carbs hanging up. If you can't free up the cable(s) then replacement cables are pretty reasonable.

[Johnie]

Keep in mind you can not get the valve cover off unless you remove the motor. No room with the frame in the way. Like the guys say...cosmetics is not important. Get it running first then play with the shine.

[Vidgameking]

Yeah I saw that I have to take the engine out. I was reading elsewhere on the forum there is a kit that I can put in where I cut the frame up there and I can do top end work w/o having to remove the engine.

I agree I'll get it running first, then I'll pull it all apart and do a top to bottom cleanup/rebuild as needed.