Author Topic: My CB755 Project - COMPLETED!!!! (Read 34497 times)

mwvachon · « **on:** June 15, 2012, 10:01:07 AM »

Just about to start yet another major restoration project. Found this diamond-in-the-rough a couple months ago. It has not been on the road since the early '90's. Previous owner revealed that he'd had an accident with it - which explains the missing chunk of the front fender, a broken stop on the lower triple tree and a couple dents in the tank. The bike is a later K1 model, but it has '341' series exhaust on it[? ? ?] Not sure if these are the originals or not. Doesn't matter, I'm fitting proper '300' units (already bought) when the time comes. Odometer shows over 30K miles, but it's mostly complete and hasn't been molested/hacked, so it's a great starting point.
I'm calling this the '755' project because I already have a 750 Four (K1 also) and I need to keep the two separate (in my mind at least). This time out, I'm hoping to shoot a series of short videos to document the process that I use to do most of this work.

Greggo · « **Reply #1 on:** June 15, 2012, 10:04:39 AM »

Sweet, I like the Root Beer Brown bikes

harisuluv · « **Reply #2 on:** June 15, 2012, 10:47:01 PM »

King and Queen seat spotting! *everyone takes a drink*

Nice bike!

Gurp · « **Reply #3 on:** June 16, 2012, 01:39:39 AM »

i love that seat it looks so comfy.

mwvachon · « **Reply #4 on:** October 02, 2012, 01:19:27 PM »

OK, I've been neglecting this thread - My bad...
To date, I've purchased a complete new '300' exhaust set for this. I did open all the funky shaped boxes and drooled all over the chromed goodies before boxing them back up into a manageable bundle and tucking them away for now. I purchased a POR-15 tank kit to undo the ravages of almost 30 years worth of sitting with degrading fuel in the tank (luckily, no weak spots!) I also bought some NOS fork covers - one is the Candy Ruby Red and the other is the hideous Valley Green. I got the right side from CMSNL (I understand there are a few of these left) and the left-side unit came from JF Marks in NY (always a pleasure to deal with). Seems a shame to sand blast these, but this project will be repainted in Polynesian Blue Metallic. Hope to begin actual dis-assembly this weekend. Also got a pair of repro side covers from Z1. Nice units. Original covers are intact, but are showing cracks. I neglected to replace them on the Family Heirloom and am now sorry I didn't as those are cracking again, despite being reinforced when I had them painted.

mwvachon · « **Reply #5 on:** October 18, 2012, 06:40:47 PM »

Ok, enough slacking off! Finally got to it in the past week or so and have some progress to post! In the tear-down process now and found more weirdness with this bike. In addition to having 300 series mufflers on the #2 & #3 cyl and 341's on #1 & #4, I found some decidedly non-stock bolts holding the oil tank on. Fortunately, the original 6 mm thread holes are intact - whoever mucked with this just used smaller bolts with additional nuts on the back. Also noted the broken cover over the front sprocket - not typical damage. The air box was food & home for some very ravenous critters, too! Engine tear-down went well - except for the part where I over-looked the four hidden 10 mm bolts under the rubber plugs that are under the cam holders. Also had bad luck with the #2 spark plug. The plug broke off just below the hex surface - leaving the threaded sleeve in the head! Hopefully I can just run a close tap into it and drive a bolt into it from the inside to push it out.

mwvachon · « **Reply #6 on:** October 18, 2012, 06:42:28 PM »

The Engine shots:
Once I get the gasket kit, it's off to the machine shop for the head and cylinders... Stay tuned!

mwvachon · « **Reply #7 on:** November 01, 2012, 03:18:03 PM »

OK, major tear-down completed and off the lift. I always wanted to take a picture of one of these all apart, but I just didn't have the time/room to lay out EVERYTHING!

mark52 · « **Reply #8 on:** November 02, 2012, 08:29:31 AM »

Hey mwvachon, got luck on your project. I am also in the process of restoring a 75 750k. If you are not in need of the 2 341 pipes and would like to get rid of them, please let me know. I thought that I would get some of the reproduction pipes after I saved up the money but it now looks like everyone that was selling them are out of stock. Who knows if any will show up again. Anyway, if you do not need them send me a PM. Thanks.

mwvachon · « **Reply #9 on:** November 24, 2012, 07:59:21 PM »

Slowly making progress. Recently got the engine gasket kit, so now the head & cylinders can go off to the machine shop. Just finished the POR-15 inside the gas tank. Also did some sandblasting on the bigger parts this weekend.

mwvachon · « **Reply #10 on:** December 01, 2012, 03:45:04 PM »

After dropping the head & cylinders off at the machine shop yesterday; today I decided to turn my attention to the bottom-end of the engine. The initial plan was to do a general clean-up and pull the clutch. I stopped cold in my tracks when I started to clean the area around the sprocket [see image]. I've heard and read about these kind of repairs, but this is the first one I've seen on a 750. I went through a range of emotions in a short period of time; totally pissed that the previous owner saw fit not to mention such a major repair; pissed at myself for not discovering this sooner; to relief that I have not one, but three spare motors as alternatives. I'm now breaking down the rest of this unit completely and will mark and store all of the individual components for possible future use. I can't believe someone would do such a hack repair line this on one of these, but then again, this particular example was also unceremoniously tucked away in a not-all-that-weatherproof garage for the last 20 years.

mwvachon · « **Reply #11 on:** December 02, 2012, 05:22:32 AM »

I was able to split the cases (the welded repair patch was of pretty soft material). As I suspected, I found a few good sized chunks of metal (more than likely from the initial case damage) inside the oil pan. Most of the internals looked to be in good condition.

Dream750 · « **Reply #12 on:** December 02, 2012, 06:16:25 AM »

Subscribed and great project thread!

I’m also a fan of the Polynesian Blue Metallic color as it’s rarely seen and a nice choice.

Click on image for best view:

nitsua93 · « **Reply #13 on:** December 02, 2012, 06:30:57 AM »

Quote from: mwvachon on December 01, 2012, 03:45:04 PM

After dropping the head & cylinders off at the machine shop yesterday; today I decided to turn my attention to the bottom-end of the engine. The initial plan was to do a general clean-up and pull the clutch. I stopped cold in my tracks when I started to clean the area around the sprocket [see image]. I've heard and read about these kind of repairs, but this is the first one I've seen on a 750. I went through a range of emotions in a short period of time; totally pissed that the previous owner saw fit not to mention such a major repair; pissed at myself for not discovering this sooner; to relief that I have not one, but three spare motors as alternatives. I'm now breaking down the rest of this unit completely and will mark and store all of the individual components for possible future use. I can't believe someone would do such a hack repair line this on one of these, but then again, this particular example was also unceremoniously tucked away in a not-all-that-weatherproof garage for the last 20 years.

This is exactly how mine was. I was heart broken. I bought another case online and used a saline torch to cut that part open. No metal chunks in the engine though.

Sent from my HTC One X using Tapatalk 2

mwvachon · « **Reply #14 on:** December 11, 2012, 09:54:14 AM »

Crap! The back-up K1 engine has the same patch!!! It's an epidemic, I tell ya! Fortunately, the salvage K2 motor cases look fine. I know it's no big deal, but I'm kinda bummed about not having a correct serial# engine going into this project... I guess I'll get over it - and most folks would care less...

Tews19 · « **Reply #15 on:** December 11, 2012, 01:10:57 PM »

Damn two cases like that. I had found my points cover was cracked on my K1. Owner hid it and forgot to mention this when I was looking at it.. The sheet metal prefectly covered it... Subscribed and I like the project. Do you have the unicorn triple to go with it?

mwvachon · « **Reply #16 on:** December 13, 2012, 04:43:09 PM »

So, I completed the tear-down of the original K1 engine. Found a couple more chunks of metal in the bottom end (half the size of a corn flake?). Looks like the initial damage also impacted the 2nd/3rd gear set. The smaller gear had half of it's teeth flattened a bit. Gear set feels like it would have still shifted ok, but no way to know how it would've behaved under load. I took some more shots of the damage inside the case and a shot of the 2nd K1 engine crap-tacular patch job.

mwvachon · « **Reply #17 on:** December 13, 2012, 04:48:00 PM »

I just got two brand new DID rims (OEM sizes) from Z1-Enterprizes. I've been shopping for new rims as the originals have just too much surface rust and scratches/gouges to be suitable for this build. While Z1-Ent sells CB750 stuff, the rims are not listed there. You have to go under the Z-900 listings to find them. Got both for just a bit over $200 (including shipping). I was seeing just rear rims in the neighborhood of $180! So I've added the old rims to the growing scrap pile...

mwvachon · « **Reply #18 on:** December 13, 2012, 04:53:57 PM »

Despite all the problems with the lower end of the engine, the top end is moving along ahead of schedule. Local machine shop, KJE, does their magic once again. Cylinders honed out perfectly, despite 20+ years of sitting. Head had to be planed slightly (perhaps because of my head removal difficulties?), but valves were perfect and broken spark plug removed without issue.

Prospect · « **Reply #19 on:** December 13, 2012, 05:09:40 PM »

Quote from: mwvachon on December 13, 2012, 04:48:00 PM

I just got two brand new DID rims (OEM sizes) from Z1-Enterprizes. I've been shopping for new rims as the originals have just too much surface rust and scratches/gouges to be suitable for this build. While Z1-Ent sells CB750 stuff, the rims are not listed there. You have to go under the Z-900 listings to find them. Got both for just a bit over $200 (including shipping). I was seeing just rear rims in the neighborhood of $180! So I've added the old rims to the growing scrap pile...

Thanks for the heads up. I'll remember for my next build.

lucky · « **Reply #20 on:** December 16, 2012, 09:53:36 AM »

Get rid of that #630 chain before it causes more damage in the future.
Go to the #530 chain and sprockets.

The engine case can be repaired. Have it TIG welded by someone that knows what they are doing. Cut a piece of 6061 or 5052 aluminum that fits EXACTLY into the empty space to keep down any warpage. Use a thick piece to soak up the heat.
Use copper back up bars too and that will help keep down any warpage. Then check the fit of the cases bolted together.

mwvachon · « **Reply #21 on:** December 16, 2012, 04:26:10 PM »

Thanks for the input, Lucky. A couple other folks have said I should get this repaired (as opposed to scrapping), but because the original repair was done so badly, I think I'd be just wasting my time. I'm not even going to bother with the other salvage K1 cases (repair is even worse on that one). I have a perfectly good K2 motor that just has some broken cooling fins on the head. Since the original K1 head and cyl have already been done up by the machine shop, I'll go with those. The tear-down on the K2 engine is progressing well (pulled the cyl studs out today).
I do need to do some research on chains. I'm getting confused by all the varying recommendations in some of the posts I've read. I'm not a fan of the O-ring chain press-on link. I've always run a regular roller chain (can't remember which #, it's whatever is specified in the shop manual) on our Family Heirloom (the '71 K1 my Dad bought new back in the day). I'm always careful about the locking clip on the master link. Dad & I were talking about it just the other day and I was telling him how fortunate he was that he never had the broken case issue. He did recall that initially he was going through chains quickly (apparently he was religious about checking that before riding) and he struggled with the auto-oiler settings. I told him the REAL answer was to just plug that and use REAL chain oil.

mwvachon · « **Reply #22 on:** January 01, 2013, 05:33:52 AM »

Even though I had time off during the holidays, I didn't get out to the shop nearly as much as I would have liked. Still crawling along with the alternate K2 engine. Hoping to complete the dis-assembly today. I've been taking my time because of all the various worn or damaged parts I've come across when I tore down the other two K1 engines. As on this engine, I found a broken tab on the outer clutch basket retaining plate. No obvious reason why it would have broken. It doesn't really do anything. On the trans cover for this K2, I noted that someone had replaced all the Phillips screws with socket caps - it's the only place on the engine that they did so - weird. Also, those socket caps had 3/16" hex cuts - not metric??? What the...

On the outside screw for the shift drum, I noted the screw head was chewed up. The outside cam on the shift drum looks pretty worn as well. It seems that part of doing these rebuilds is like forensics - trying to decipher just why something is not normal. Alarm bells always go off when I detect something has been previously disassembled... hoping the main internals are good...

mwvachon · « **Reply #23 on:** January 01, 2013, 05:47:21 PM »

OK! Moving right along... Managed to complete the K2 engine tear-down without any more unwanted discoveries. I did find a couple fasteners that weren't very tight (neutral switch holder bolt, One of the oil pan bolts). The cases split apart almost effortlessly. A couple taps here & there and I only had to gently pry in one spot. All of the gears seemed in very good condition as were the shaft bearings for the transmission shafts. I did note one lower crank bearing had a bit of scoring on it, but all the other solid bearings and the crank itself looked perfect. Next task will be to clean up the cases and begin checking clearances. I'm not going to bother refinishing the cases until just before they are ready to be reassembled.

mwvachon · « **Reply #24 on:** January 04, 2013, 06:04:21 PM »

Shifting to inspection mode! Finally got the cases all cleaned up. I started to panic again when I found this broken mounting boss on the back side of the lower case, near the final drive shaft opening. I checked my other two salvage engines and they are exactly the same! I'm guessing this is unimportant?? Doing crankshaft clearance checks this weekend.

*******Update!*******
I'm thinking this is for the lower screw on the sprocket cover (broken boss). Now I'm wondering if JB-Weld would be strong enough to fix this or would I need someone to TIG a slug of metal there that I can drill & tap?
Thoughts anyone???

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Author Topic: My CB755 Project - COMPLETED!!!! (Read 34497 times)