Author Topic: The unintentional 71 750K1 build or I am truly a glutton for punishment (Read 1987 times)

Just John · « **on:** February 01, 2020, 02:41:21 PM »

I'm starting this off wondering about my sanity. Last year I started semi restoring a 77 K7. It was not a priority and somewhere along the line I started itching for an earlier bike. A 69-70 would be great but totally out of my financial comfort zone. I stopped all work on the 77 and started looking for an earlier frame. A 73 frame popped up on Craigslist. Done! But I was still wanting something a bit earlier. A derelict 72 was the next Craigslist purchase. It looked much better in pictures. After the seller assured me the motor would turn over I bit. This is when I really started wondering if I should be committed or at least medicated. As luck would have it a friend found a nice 71 frame. Joy oh joy. My first impulse was to put the 77 motor in the 71 frame but I couldn't bring myself to do that. How about the 72 motor? Now I was really wondering about my sanity. This will be a slow going project as I am accumulating parts and pieces. Enjoy!

Just John · « **Reply #1 on:** February 01, 2020, 02:59:34 PM »

The 73 frame that is now going to storage.

MauiK3 · « **Reply #2 on:** February 02, 2020, 09:09:30 AM »

looks like you have some work ahead!

rb550four · « **Reply #3 on:** February 02, 2020, 01:28:38 PM »

Wow! If the pictures make the frame in the 1st three pics look better, take more until they look like something to work with. Holy cow, it looks roached. Is there any metal left in the frame? Could it be straight and not all bent up?
I only ask because I've been known to grab bikes out of junkyards that probably should have been left there, but wow that looks rotted..
You would be a glutton for punishment in my book.
I must ask. why would that nasty looking 72 frame seem like a place to start this project when the 73 frame looks so much better? Don't get me wrong, I would be totally interested in seeing how you handle the 72 frame repairs if it's something you've done before. But I wouldn't enjoy it if it beats you up to the point of giving up on the project .
Just wondering why the 72 frame would make this build any better than the 73 frame? I haven't been a 750 guy and don't know too much about them , is why I wonder why the 72 frame year over the 73 condition is that important to you?

Just John · « **Reply #4 on:** February 02, 2020, 07:36:49 PM »

Well, the original plan was to use the 73 frame with 77 running gear. The 72 roached out bike was found by accident. Most of the front of the 72 frame was entirely gone. The only thing holding the engine was the back motor mounts and rust. The bike had been stored with pool chemicals since 84 and some of the aluminum parts had started "melting". I only bought it because the engine turned over and I thought it needed a second chance. Moments after these pictures were taken I changed the carbs, plugs, coils added oil and battery and it started and ran on starting fluid. So I found the 71 frame and wanted to use it instead of the 73 to build an earlier version bike. The insanity started when I also decided to make an attempt at rebuilding the 72 motor.

rb550four · « **Reply #5 on:** February 03, 2020, 04:27:57 PM »

Excellent! Let me get this straight, a running 77 engine was in your possession first, followed by a 73 frame that looks good but you wanted an older machine, then the 72 pool chemical frame that should be discarded came into play, and 3 seconds after taking a picture of the roached 72 frame with a melting motor that runs on starting fluid that you have decided to rebuild/ install in the 73 frame, but a 71 frame shows up. So now the plan is to rebuild the melting 72 engine and install it in the 71 frame and mothball the 73 frame in good condition... for some reason this is making sense now ...but whatever happened to the 77 engine?
No worries , I'll just stop in every now and then to see your progress on whatever year machine that you might be building that day. I like it ,sounds like great fun.
One last question, did the insanity really start when you decided to rebuild the 72 engine?
Just kidding , go for it man ,whatever it is! It's all fun and games!

Just John · « **Reply #6 on:** February 03, 2020, 09:57:04 PM »

Yep you got it and I think the insanity may be genetic! 72 motor in 71 frame. The 77 is still more or less complete. It was just a motor and untitled rolling chassis when I bought it at an auction.
Regards,
John

Just John · « **Reply #7 on:** February 03, 2020, 10:07:24 PM »

I will admit I was hesitant to tear down the 72 motor. The cam/valve cover had started bowing inward on the left side (over #3 & 4 cylinders). The screws were totally melted into the aluminum cover. I managed to remove all but 6 of the screws using my JIS impact driver. I drilled the tops out of the remaining 6 and all of those screws were then easily removed. The cam will be replaced. Here are the only pictures I'll post of the engine as tear down is very boring.
Regards,
John

rb550four · « **Reply #8 on:** February 04, 2020, 03:51:41 PM »

Excellent!! The project has begun.

Don R · « **Reply #9 on:** February 05, 2020, 11:41:51 AM »

Have fun, I'd enjoy using the best parts more than what came on a particular model. I got my hot rodded 70 running first and over the years as parts present themselves it slowly finds it's way back to original.

Just John · « **Reply #10 on:** March 05, 2020, 02:13:23 PM »

I've been busy gathering parts but no major movement on this project. Actually it is not a priority at the moment as is clearly shown by the lack of updates. I had a small setback with the steering bearings. I bought a tapered bearing kit from an EBay vendor. They were listed as All Balls and had the same type packaging. However, there was no manufacturer labeling just the seller's description. The price was decent so I took a chance. My mistake! The first indication was the races seemed a lot thinner than my previous All Balls races. Apparently trying to convince myself I had not been fooled I marked that up to a change in bearing supplier. Using every trick I know to install bearings/races resulted in the junk going into the trash!

The old 72 motor is still coming apart slowly. We made a trip to Arkansas last week and we are headed to the VJMC/VMA swap meet in Eustis, Florida tomorrow. I may find some 71 parts I need like a rear fender, fork ears and a seat!

Just John · « **Reply #11 on:** March 15, 2020, 12:05:36 PM »

Back from Florida and didn't find a single thing for the 71. However, did buy some bits and bobs for two Harley projects that have suffered from lack of attention. The bearing saga continued when another set of tapered bearings were also crap. So I installed stock races and new ball bearings instead. The bike is on wheels but it is raining again so pictures will have to wait. This is only a mock up to make my friends think I'm actually working on it. One asked "Wouldn't it be easier to just buy one?". Yes, yes it would but where is the fun in that!

ctcycleworx · « **Reply #12 on:** March 17, 2020, 07:43:33 AM »

Don't let it discourage you, it will look great when shes done!

Just John · « **Reply #13 on:** March 18, 2020, 05:03:59 PM »

So I slapped it together as a roller with some parts scrounged from friends, some from EBay and some I found in the garage. I know all the parts are not correct for a 71 and most are only there as place holders until I find the correct parts. I'm not doing much else until I get it titled which with the current world health situation may be a while. I'll continue looking for 71 fork ears, seat and a rear fender/tail light.
Regards,
John

Just John · « **Reply #14 on:** September 24, 2020, 02:08:15 PM »

Update: The 71 project has progressed but slowly. I finally removed the head on the derelict 72 engine but it took a bunch of effort. Kudo's to the power of silicon sealer but it was a pain. I got tired of waiting and bought an engine from a fellow member. So the 71 is sitting on wheels with an engine installed and a seat. But at this point I got tired of waiting on parts. I've had parts on order for 2-3 months and while some have trickled in, some are still waiting shipment. I've pushed the beast into the corner and I am looking at my options. I currently have enough parts in the Garage of Lost Dreams to make this bike a runner. If I choose this path it will look a lot different than a 71. I would say "stay tuned" but I am horrible with updates!
Regards,
John

MauiK3 · « **Reply #15 on:** September 24, 2020, 06:57:15 PM »

A 71 is worth doing right, might want to wait it out.

754 · « **Reply #16 on:** September 24, 2020, 09:33:58 PM »

Should have just gone to Bill Benton, probably would have everything..
Did you get them tappet covers off. They being better alloy , looked better than the cam cover.

SOHC4 Cafe Racer Fan · « **Reply #17 on:** September 24, 2020, 11:32:15 PM »

Quote from: 754 on September 24, 2020, 09:33:58 PM

Should have just gone to Bill Benton, probably would have everything..
Did you get them tappet covers off. They being better alloy , looked better than the cam cover.

Yes. It’s not too late and it will probably be cheaper to get parts from Bill.

Terry in Australia · « **Reply #18 on:** September 25, 2020, 12:41:33 AM »

You can do it mate, I started with this in April last year:

Terry's Swamp Rat CB750 28 Apr 2019 9 by Terry Prendergast, on Flickr

And finished with this in November:

Tuesday Swamp Rat tinkering 5 November 2019 by Terry Prendergast, on Flickr

The good thing with CB750's is that they're still "A dime a dozen" in the US, and parts are plentiful. As long as you've got access to Craigslist/Ebay, you can make it as good as new. Well done so far.

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Author Topic: The unintentional 71 750K1 build or I am truly a glutton for punishment (Read 1987 times)