Author Topic: 1972 CB750 Basketcase find - ENGINE NOW TURNING (Read 9253 times)

Rio_CB750 · « **on:** July 16, 2011, 09:59:48 AM »

Hey all! I'd figure I would post my build here. This is my second CB750, the other is a stock briar brown. I found this latest basketcase, and it is, on Craigslist. I figured I would take the bike for the parts and see what I could come up with to salvage. I got the bike for about a 1/4 of what the guy was asking for, he sounded tired showing people the bike only to have them not show up with a trailer or wanting a running bike for nothing. When I pulled up with my trailer and cash, the deal was done.

Here it is... did I say it was a basket case?

What's NOT wrong with it... not much good here.
Major issues: Engine is locked up and the PO said that he pulled the plugs to try to unlock it. After I got it home, I found out he only pulled 1 and 4, probably because he didn't have the Honda magic tool for 2 and 3! You won't get an engine unlocked with only two cylinders open... I had to free my other bike, so I know it's possible...
Points side case is cracked, see below.

Those are the two biggies. If I can get the engine free, then I'll try to start her, if I cant.. it's the junk heap after I strip what I can, lots of problems here...

bluesmoke69 · « **Reply #1 on:** July 16, 2011, 11:17:20 AM »

Best of luck with the motor.

Beergineer · « **Reply #2 on:** July 16, 2011, 04:26:11 PM »

Looks like my bike did...lots of time on the wire wheel. Enjoy the resto!

Rio_CB750 · « **Reply #3 on:** July 16, 2011, 07:40:39 PM »

Thanks so much guys, I put a chalk mark on the crank side today and I think, I think, I actually got some movement before I got to tired of rocking the bike. Tomorrow, it's more Marvel Mystery Oil.

Rio_CB750 · « **Reply #4 on:** August 01, 2011, 08:41:54 PM »

Well, after a month of sitting (a bit less) of PB Blaster and MMo in the cylinders, my son has decided it's time for more drastic measures. He wants to pull the engine and see what's inside.

Amazingly, for the hulk of rust that it is, the threads of most of the bolts are coming out fine. Those that done get hit with a drill and/or easy outs and out they come. My son even took a shot at drilling out a phillips head screw and it came out like butter (carb boot clamp).

We have pulled the airbox, carbs and oil pan. The PO took off the battery case (I have it) and the tank and chrome (have it also). He had no idea what he had, he was selling parts that were worthless and about to scrap the triple tree!!! Ha, my gain! I got the whole bike for just $40 bucks, but I showed up with a trailer and cleaned out his garage...

Anyway, the inside of the airbox is like new, as are the carb slides, weird. The outside looks like it landed on the moon, but the inside is just perfect, gives me hope for the engine.

For the engine I tried to put it in gear and rock it, nothing. I even marked the crank with chalk. I even hit the other side with an impact wrench, back and forth, nothing... wish me luck.

My son wrenching

Inside of the carbs

SUELZER · « **Reply #5 on:** August 04, 2011, 06:58:18 PM »

Love it John! $40 for a garage of parts and something for you and your son to mess around with

best of luck

Quote from: John D on August 01, 2011, 08:41:54 PM

Amazingly, for the hulk of rust that it is, the threads of most of the bolts are coming out fine. Those that done get hit with a drill and/or easy outs and out they come. My son even took a shot at drilling out a phillips head screw and it came out like butter (carb boot clamp).

We have pulled the airbox, carbs and oil pan. The PO took off the battery case (I have it) and the tank and chrome (have it also). He had no idea what he had, he was selling parts that were worthless and about to scrap the triple tree!!! Ha, my gain! I got the whole bike for just $40 bucks, but I showed up with a trailer and cleaned out his garage...

xedge4lifex · « **Reply #6 on:** August 04, 2011, 09:14:16 PM »

Quote from: bluesmoke69 on July 16, 2011, 11:17:20 AM

Best of luck with the motor.

HAHAHAHAHAHAHAHAHAHAHAHA

Rio_CB750 · « **Reply #7 on:** August 09, 2011, 08:05:40 AM »

I'll post some pics tonight, but the motor is almost out. Again, with all the rust, all the threads are clean, even the tack cable insides look great, outside like the bottom of the ocean. I think there is hope. Even the back wheel got loose.

This weekend, I'm buying a soda/particle blaster from harbor freight and making my own sandblasting box out of a rubbermaid container. My son loves the electrolysis, so I know he'll absolutely love sand blasting!

Rio_CB750 · « **Reply #8 on:** August 09, 2011, 06:11:45 PM »

Well, I feel like I gave birth! Here she is, with the engine out. Lesson learned, take off the rear wheel and damn near everything else on the bike. We had a hell of a time getting that thing out, but we did it! The bike still amazes me, most of the threads just come undone. After this, it's frame stripping time and a trip to the chinese store for some soda blasting equipment!

The frame and engine in it's glory!

The engine, she's getting a custom made 2X4 engine trolley soon!

Just what's left, and a bucket of parts

Rio_CB750 · « **Reply #9 on:** August 09, 2011, 06:16:24 PM »

Thanks Suelzer! Looking forward to Cleveland Mods v Rockers!

Prospect · « **Reply #10 on:** August 12, 2011, 07:23:13 PM »

very cool. It'll take a lot of work and money but crusing with a big grin on a bike that was destined for the scrap yard is priceless.

mrbreeze · « **Reply #11 on:** August 12, 2011, 08:29:24 PM »

Reminds me of the 71' I just sold to Terry in Austrailia right down to the extended forks and locked motor!! I got $200 for mine though so you got a great deal!! That unicorn top triple is worth what he paid me for the whole bike and you got one too for only $40.....awesome!!! Don't lose the washers in the triple tree on the clamps. If they are already missing.....get some and make sure they are the right thickness. If it were me I think I would have left the engine in the frame,use the atf/acetone magic sauce, and put it up on centerstand.With the drive chain connected and the sparkplugs out.....put it in gear and turn the back wheel back and forth. Too late now though!!! Heres some pics of mine...............er.... I mean Terry's!!

Rio_CB750 · « **Reply #12 on:** August 13, 2011, 08:25:17 AM »

Very nice Mr, I sent some old exhausts that I had to a chap in Poland! Thanks Prospect, my other 72 took many hours, I get a small group of guys at each bike night looking at it, I'm sure you do also! I'm enjoying working on the bike with my son, so if it amounts to a pile of scrap, we'll have had fun. We tried the rocking of the bike, but we got impatient and with the clock ticking on warm days in beautiful sunny Cleveland, OH, we figured do it now while it was nice and warm.

Last night we got the last of the valve cover screws out with a combo of a chisel and easy-outs, but they are all out now. I'm using an old trick from my high school days, cardboard in the same pattern, my son pokes them through, to keep track of the screws, but we'll need new ones. A good friend down the street loaned me some snap-on tools for the cam chain bolts, they were tight and my craftsman tools were looking like they were about to strip them, we got them out.

On Steal-bay, I did manage to source the two "missing" parts, the chain guard and a set of front shocks with boots in all, they are being shipped. That'll make it at least look like a 72 again! I'll definitely need controls, if anybody has some laying around PM and we can hopefully work a deal. Cables are being shipped also, got those as well.

We pulled off the right side rocker arms and am working on the left side, with luck, the top end will be off later today, stay tuned for pics of the cylinders!

Rio_CB750 · « **Reply #13 on:** August 13, 2011, 04:49:54 PM »

Well, we pulled the head today and got the engine free. This was after about 2 hours of pb blaster (again) and hitting (gently of course) the pistons with a piece of wood and a rubber mallet. Yes, I accidentally broke one of the fins...

I found an interesting problem, the number 1 exhaust valve is frozen open... Cylinder number 1 was heavily carbonated and after smacking it with some wood and rotating the crank at the stator side, success! I promise to build an engine stand for her tomorrow!

I'll have a host of questions, but basically: Do I need to (must) replace the gaskets? Best way to free the valve?

And the video:
MVI 0402

mrbreeze · « **Reply #14 on:** August 13, 2011, 11:42:02 PM »

Good job man but sucks that you broke a fin. I have heard of them being repaired but don't really know much about how its done. Don't throw that piece away!!!!! HELL...........don't EVER throw anything away till you are totally sure you won't need it anymore.

Rio_CB750 · « **Reply #15 on:** August 15, 2011, 05:36:38 PM »

Thanks man, you can see the damage a bit on the video, just to the right front of number 1... missed a rubber mallet blow on a piece of oak, WTF! I was tired! I saw your sale on the for sale site, I need an old points plate with all the nuts and bolts, happen to have one laying around MR?

Is this a 750 cc powered lawn mower? Nope, just the motor, in process of getting cleaned and a poor man's top end rebuild on our home made engine dolly thingy.

Rio_CB750 · « **Reply #16 on:** August 21, 2011, 06:44:38 PM »

Some additional fun

My son and I took on the front end today to get the frame onto a rolling 2X4 stand by the fall. We took off the headlight, turn signals, spedo and tach and buzzer. Oh, by the way, after 40 years, the buzzer still works! It was cool to hear that thing that hadn't buzzed since at least 1989. So far no surprises. I did manage to break off the headlight screws, two of them, trying to get them out. I didn't think that was going to happen. I'll work on those, but we did get the headlight apart and the trim off.

A good friend of mine who works at a powder coat plant offered to powder coat anything and everything that I could get to him, he'll media blast it for me and powdercoat any and all parts. I'm so happy. My son and I will slowly box up the parts and he offered us a weekend at the plant blasting and powdercoating. He mentioned that he's confident he spills more powder in an hour than that bike will use to coat the whole thing.

If folks are reading this, what do you all think about powder coating things like the rims "silver" rather than rechroming them (I wont do that) or black. From 10 feet away, I'm not sure I could tell between that and dull sanded chrome!

Here are some pics

Pulling apart the headlight

Since we got the engine free, I decided to get some "new to me" and new parts, got the missing chain guard, front forks, boots and ring (a nice find at $50), cables and an old points plate on the way.

The bike, no more chopper forks!

And a slew of pics so we know where everything goes...

SUELZER · « **Reply #17 on:** August 22, 2011, 07:47:35 AM »

glad to see you're still moving forward on your project!
i think doing the rims pc should be alright...not sure what the chip factor would be on the spokes?
lucky dog to have a avenue for paint, i should really figure that out someday

Rio_CB750 · « **Reply #18 on:** August 22, 2011, 06:59:30 PM »

Hey Suelzer! Thanks man, we are making progress, and we're happy to, a little bit each week and month. I'm trying to get some missing parts now, the crank shaft thing and a spark advancer, I'm getting closer. For the parts, as I figure out when we'll make that trip, I'll make sure to let you know and you can drop off whatever you want. We're planning on being there a full day and my son loves to media blast, he could do it all day long, so hopefully we can get you covered on a least a few parts powder coated when we take our trip to powder coat heaven!

Quote from: SUELZER on August 22, 2011, 07:47:35 AM

glad to see you're still moving forward on your project!
i think doing the rims pc should be alright...not sure what the chip factor would be on the spokes?
lucky dog to have a avenue for paint, i should really figure that out someday

SUELZER · « **Reply #19 on:** August 23, 2011, 06:20:31 PM »

thanks john, that'd be great

lucky · « **Reply #20 on:** August 23, 2011, 09:37:42 PM »

Do you know how many miles were on the engine?

Rio_CB750 · « **Reply #21 on:** August 24, 2011, 04:40:59 PM »

Hey Lucky, There are 16628 miles on the engine. The outside is crap, lots of dirt and flaking, but the bolt threads and insides all look good so far. Once I get all the parts that I need, we'll be putting it back in the frame and trying to start it.

The kill switch works, but the starter switch is toast, completely corroded, so I'll use most likely a momentary contact switch and wire that into somewhere.

We're still going through the electrical, I think I found how to hotwire the key switch, so the quest continues! I'm targeting fall sometime to have it started, then we'll pull it back out of the frame and the real work begins!

CycleRanger · « **Reply #22 on:** August 24, 2011, 04:56:19 PM »

What is your plan to repair the broken case?
Enquiring minds want to know.

lucky · « **Reply #23 on:** August 24, 2011, 05:00:45 PM »

Thanks for telling me the mileage.

You will have to install new piston rings and ball hone the cylinders.
New gaskets too. Minimum.
You cannot just put the pistons and old rings back together without honing the cylinders. It will just smoke and burn a lot of oil.

Did you get that valve out that was stuck?

If you have the broken parts to the engine case for the points area it could be TIG welded but that would require complete tear down of the engine.
Depends how much of that points case is damaged.

16,000 miles is not that much for that size engine.
Did you remove the oil pan and look at the screen?

Like Cycleranger said, "Lots of questions."
After cleaning any aluminum part spray it with WD40 right away.

Rio_CB750 · « **Reply #24 on:** August 25, 2011, 09:52:04 AM »

Hey guys, for the engine, I'm still not decided. There are two of three points plate mounting locations still there and I think I can get a third by drilling a small hole (carefully) and inserting some thread and JB welding it in place. After that, I'm not sure. I've shown it to a few folks in the know and the feelings are mixed. One even said, just don't ride in the rain...

For the engine, agreed that it needs new rings, or could and also all new top end gaskets. But, things being things, I'm going to put it back together with just a new head gasket just to try to start it. If I can get it to turn over, then I'll tear the top end apart again. My fear is that a bearing is bad or something worse, so I don't want to put a lot of $ into the top end of this, also considering the damage, until I hear it run. It sucks I had to pull it to get it free, but after I did, it was good that I found that stuck valve - still stuck. I work on it a little every day.

I removed the oilpan recently, looks great. Amazingly, the engine is clean inside, at least what I can see.

My Theory: This bike was bought and quickly laid down on the right side. Evidence: Cracked case, mangled points plate, bent and damaged (but still OK) turn signals, scraped right foot peg, damaged right grip, and a minor dent in the tank. That was a bike killer, so it was rolled next to a garage and traded, and swapped and who knows what. Knowing that, I think it's fixable! I'm optimistic if nothing else!

News:

Author Topic: 1972 CB750 Basketcase find - ENGINE NOW TURNING (Read 9253 times)