Author Topic: CB750K3 (Read 9826 times)

SSK · « **on:** June 12, 2011, 12:07:46 am »

Hello,

Just purchased a bike that was my childhood dream to own and after owning a few other brands and styles of bikes and more or less putting riding away (after I had a few heart attacks I thought it is not safe for the others who I share the road with) my 19 year old son asked to build a cafe racer together and it made me think of the CB750 again I started looking on EBay and Craigslist for CB750s and came across a few that were over our budget and some that were "dead long ago" until a few days ago I spotted this one and I remembered in 1977 my friend who was a few years older than me at the time had a 1972 CB750 and got me interested in pursuing this one and the kid who owned it and was going to travel out of country wanted $1,750 for the bike and bunch of parts, 2 helmets and some clothings and finally after a couple of back and forth we made a deal for $1,250 and so finally I have the bike in the garage and my son and I are going to do a complete "frame up" rebuild! The only minor issue is that the last time I rebuilt a bike was in 1975 - 76 when I was a teenager and the bike was a Yamaha 80 (mini).

We need all the help we can get , we will be posting images and videos of the process and I am sure enjoy some father and son time while doing this. Hopefully, it will run again some day! According to the kid who owned it, it has not ran since he changed the wiring harness late 2010 and he did it because various light and indicators had stopped working and after he changed the harness they all worked but no sparks on any of the plugs, and there was winter and now he was traveling and etc...

Now there are so many different styles and designs out there and my son is most inspired by the one from Race Katz and we ere hoping anyone who knows anything about how that bike was made to help us with info like stock swingarm or not, what kind of shocks, wheels, and any other useful info. I also found an email for Mark who build that bike and send him an email but haven't heard anything so far.

Sorry for the long story, I am sure it will get shorter and to the point as we go forward.

Thank you for reading.

immortal · « **Reply #1 on:** June 12, 2011, 12:22:26 pm »

Welcome to the forum and am looking forward to you posting some pics to see what you have there. You have come to the right place for your project. This forum will get you through it. There are lots of great people here doing every imaginable variation of your CB750. Good luck!

SSK · « **Reply #2 on:** June 12, 2011, 07:33:06 pm »

Thanks immortal.

We had a busy day today, we disassembled:

Tank
Seat
Wiring harness
Battery
Rear fender
Front fender
Handle bar
Rear shocks
Exhaust we took out the eight nuts on the head one the bolt came off with nut on it. But both right side pipes are stuck, I brushed some brake fluid on them and see. The left side ones are loose but it seems they are coming out flange and all so there just be hole in there, where as the picture I look at inthe books shows the header has an in h or so of pipe sticking out after the exhaust is removed.

SSK · « **Reply #3 on:** June 13, 2011, 08:59:03 am »

here are some pics from yesterdays work.

SSK · « **Reply #4 on:** June 13, 2011, 09:00:25 am »

left side

SSK · « **Reply #5 on:** June 13, 2011, 09:02:09 am »

front

SSK · « **Reply #6 on:** June 13, 2011, 09:03:35 am »

left rear

SSK · « **Reply #7 on:** June 13, 2011, 09:05:21 am »

Frame number - 1973 -k3 , correct?

SSK · « **Reply #8 on:** June 13, 2011, 09:07:22 am »

engine number

immortal · « **Reply #9 on:** June 13, 2011, 09:12:08 am »

Looks like you got yourself a nice bike there. If your going to strip the whole bike down. I recomend getting yourself a can of PB Blaster for those rusted or stubborn nuts and bolts. In my case I degreased then pressure washed my bike and engine then hit every nut and bolt I could find on the bike with PB Blaster. As soon as I removed my motor I did it again on all the nuts and bolts on the motor. My bike looked like it came from the bottom of the ocean when I got it, in fact it had been rotting outside for 25 years.....but I did not lose a single nut or bolt by using PB blaster, great stuff. You bike is way cleaner than mine was but I would still do the same to make life easier.

Panotaker · « **Reply #10 on:** June 13, 2011, 09:53:30 am »

I think you have a K3, not a K2. The K2 serial numbers started with 20 and K3 started with 22. Someone correct me if I am wrong. I have a K2 and my instruments mount different, and my wiring harness only has one fuse instead of 3.

SSK · « **Reply #11 on:** June 13, 2011, 12:01:48 pm »

You are correct it is a K3, it is late production 1972 but a k3. I think what came out of factory after september 1972 was a k3 and yet still a 1972. Tha is what i hear.

SSK · « **Reply #12 on:** June 13, 2011, 01:45:31 pm »

How do I get this exhaust off the header. 7 nuts and 1 entire bolt and not. The two left side pipes are loose but the rigth side feels like like it is ccoked in there!!!

Help please.....

SSK · « **Reply #13 on:** June 14, 2011, 05:41:49 pm »

Got the exhaust out but one there is just 4 holes in the head. All the picture I see on the books show 1 inch or so of pipe coming out of the head after the exhaust is removed.

What is going on?

JJONES450 · « **Reply #14 on:** June 14, 2011, 05:53:20 pm »

I think there is a bolt for each head pipe at the head. Look by the round air fins right where the exhaust starts at the head. A dead blow hammer and patience should get them off.

hyde7278 · « **Reply #15 on:** June 14, 2011, 06:09:11 pm »

SSK

It could be an aftermarket exhaust post some pics and someone will let you know if things look right. Good luck with the build

SSK · « **Reply #16 on:** June 17, 2011, 09:46:08 am »

I got the exhaust off and it is a 4x1(think kerker) and we dont like it at all so itt is not going back on the bike. We like the 4x4 setup and the OEM is about $1200. We did some reserach and have some ideas but have no clue if it is doable or not, ready? here it the crazy idea:

Cycle x make a raw 4x4 drag pipes that is supposed to be bolt on:
http://www.cyclexchange.net/index%20pics/Cycle%20X%20Wrap%20Pipes%203.JPG

Lowbrow Customs have these slip-ons:
http://www.lowbrowcustoms.com/index.php?l=product_detail&p=889

The million dollar question is: Can we somehow bend the drag pipes and connect the slip ons and somehoe manage to support exactly the same way the original pipes are supported on passenger footpeg?

If this is doable it could be a nice looking setup, especially since we plan to powder coat the exhaust so if there are some welding, etc... it wont show as much.

MCRider · « **Reply #17 on:** June 17, 2011, 09:51:28 am »

Quote from: SSK on June 14, 2011, 05:41:49 pm

Got the exhaust out but one there is just 4 holes in the head. All the picture I see on the books show 1 inch or so of pipe coming out of the head after the exhaust is removed.

What is going on?

The original setup had 4 spigots in the head, which would result in the 1 inch of pipe you see. The stock exhaust was swaged to fit over these spigots and clamped into place. The spigots were held in be 2 oval head screws each.

The spigots are often removed when an aftermarket pipe is used. Then there is the option to use bolts or studs and nuts to draw the aftermarket header into the hole in the head/exhaust port where the spigots and the spigot screws used to be.

MCRider · « **Reply #18 on:** June 17, 2011, 09:53:59 am »

Spigots like these:

look like this installed:

SSK · « **Reply #19 on:** June 17, 2011, 10:42:06 am »

Thank you MCRider,

The pipes i Pulled out were 4 into 1 (kerker I beleive) and the spigots were in but not as neatly as your picture shows and they didnt have a philips screw in them either there were two long studs/bolts (thread on both side and no thread on the middle) that were held in place by a not on the spigot so naturraly I tried with undoing the nut and 7 of the 8 nuts came off easily by one of them was stock in place and so the entire bolt came out of the engine header. So whe I pulled the ppipes out the spigots were stock to the pipe and the came off also. So I need to talke out these ugly long threaded studs, any suggestions on the tool to use?

MCRider · « **Reply #20 on:** June 17, 2011, 10:51:02 am »

You can double nut it, and hopefully it will turn out.
How to remove a stud
"anti-clockwise", tee hee. worth it just for that.

If you have room, i always prefer my stud instal/destall tool.

Harbor freight
http://www.harborfreight.com/catalogsearch/result?q=stud+remover

Or this
http://www.google.com/products/catalog?q=stud+extractor&rls=com.microsoft:en-us&oe=UTF-8&startIndex=&startPage=1&um=1&ie=UTF-8&tbm=shop&cid=12327328650882586890&sa=X&ei=CpX7TY7AD-j30gHtzpisAw&ved=0CGIQ8wIwAA#

Although this one looks intersting
http://www.srtmanufacturing.com/?gclid=CKuH29i_vakCFRFoKgod0AzBhw

SSK · « **Reply #21 on:** June 17, 2011, 07:01:49 pm »

Thank you real old timer, you are great!

I am sorry, I realize my terminology is not correct, while I can speak, read and write fairly well in English, I don't know the names of parts and tools. So I explain'em instead and that may take some time.

I will have some pictures later of the engine head and the exhaust. By the way do you know what the original exhaust bracket looks like the one that attaches the exhaust muffler to the passenger foot peg?

SSK · « **Reply #22 on:** June 18, 2011, 11:18:14 am »

Here are some photos of the head and exhaust. By the way I want to sell the exhaust and want to go 4 into 4. I really want to know if i can do what mentioned above with Cycle x long drags and reverse cone dunstall style mufflers. Any suggestions and information will help. My goal is to get as close to the original 4 into 4 hm 341 and secure it to passenger foot peg the same way or close to it. Not having done anything like this before I appriciate any feedback.

thanks again

SSK · « **Reply #23 on:** June 18, 2011, 11:27:40 am »

Saam on the bike before disassembly

SSK · « **Reply #24 on:** June 18, 2011, 11:28:42 am »

Exhaust I think it is Kerker

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Author Topic: CB750K3 (Read 9826 times)