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      Moving Site   11/22/2017

      If you want to keep this site up I need your help total cost to move this site to Godaddy will be $300.00 this will also include 2 years hosting then the total a year is less than $100.00 verses $937.00 a year come on guys to keep this site going whats it worth to you Carr has transferred the Domain name to me so it will be our site I can swing $100.00 a year can you swing helping with the transfer cost? if not I will close this site at the end of dec But we need to act by the end of this month 8 days to raise $300.00 Your call but don't come bitching to me cause we are shutting down Paypal  thechopperunderground@cox.net WhiteWolf
Crazy Cats

Another cb750

211 posts in this topic

I started this build about a year and a half ago. Due to some health issues and the demands of my job I have spent very little time on it since the beginning of last summer. I have a build thread for it on another site, but there is possibly some info that may be helpful so I'm going to copy most of my progress here too. I finally have a day that I don't have to give up my weekend for work and there is too much snow to get to the shop so I'll finally take the time to get this thread started.


It is a cycle one frame. I have no idea who made the girder. If you know, please post. These wheels are not the ones going on the bike. They still need to be powdercoated and relaced. The tank as you can see is started, but I still have to finish the sides and mounts, as well as the plumbing.


I have most of the parts to finish this one, I just need the time. I have to move some stuff out of the garage right now so that I can have some structural work done on it, so I decided to start working on the motor. The motor in the bike is just there for mock up. The engine that is going in the bike is one that I picked up a few months ago from an old retired drag racer. I got it in about 6 boxes. lol. He started the rebuiling process. The machine work is done. It just needs to be finished. I haven't split the cases yet, but will be doing so soon. I can see a set of golen rods coming up outta there for sure. Not sure what else I will find when I open it up. Displacement on this one is 1080cc. I decided to start with the head because it was on the top of the pile of boxes.


It's already been ported photo3-7.jpg

Came with stainless Manly valves. Aquired loonynum keepers and APE springs.


Cleaned it up and painted it all black. Decied to try my hand at cutting the fins.


Came out pretty good.photo3-5.jpgphoto5.jpgphoto-6.jpg

Masking is all pulled and I am currently cutting the valve seats an lapping the valves.

More to come

Edited by Crazy Cats

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I've run into two little snags. First, one of the guides has a hairline crack in it. Not sure how it happened, maybe during installation? They sure don't appear to have ever been run. New guide is ordered though. The second problem is that the two center bolt holes on each of the cam towers are bad. The motor saw some hard running back in the day and the holes were repaired with helicoils. The coils were not seated all of the way into the head, so I cleaned up the top of the threads with a dremel. As I was messing around with them, the helicoils started coming loose. I pulled the first one out and there were barely any threads holding it in. It looked as though it had been repaired before, pulled loose, and a new helicoil had been put in place in the old hole. Pics are to follow as well as of the repair.


This is a shot of the failed repair. There are four of these. They are the two center bolt holes on each of the two cam towers. You can see the remanants of the helicoil threads where they were pulled out.


I found some oversized inserts that are actualoly made to repair this very kind of thing. I had to order them though. More on that when they come in.

While waiting, the next piece to be addressed is the cylinders. New sleeves have already been pressed in and bored to size. I just need to put a good crosshatch in them before assembly. The outside needs to be cleaned up though. I've started with the Dremel and a wire brush. I am about half way done. I need to get everything cleaned before painting. One of the fins has a rough spot on one of the corners which needs to be filed smooth also. I'll shoot some more as work progresses.




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I was finally able to get some work done on the head today. These valve guides look as though they have never been run, not a spot of carbon on them. I can't figure out how this one got damaged. They must have done something wrong when driving it in.

cracked valve guide:



Here is the new one driven in and reamed


On to repairing the holes. I was planning on using some oversize inserts from Time-sert. While trying to order them, I was on the phone with Terry from TAS and he said that he had just the thing I needed. Cleaned the holes out with a drill.





new inserts treaded in


I re-lapped the valve on which I replaced the seat and tested it for leaks. All is well. I just ran out of time in putting it together. Ought to be able to get that done tomorrow.


Finished the valvetrain today. Not really a big deal, but it's together.


Cylinders are painted. Waiting for everything to dry all of the way so I can start cutting the fins.


That's tomorrow's project.

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the lines on that bike are fookin ace!!!

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The bottom end on this motor was halfway through a rebuild when the guy quit and abandonded the project. The machine work was done to the top case to fit the bigger sleeves. The crank is stuck. Not really stuck but gummed up good. I can see the hardened assembly grease between the rods and the crank lobes. I have to assume that the main bearings are the same. It's been sitting for at least 10 years open to the air with no oil in it. I am splitting the cases to clean up what I can and replace what I cannot. Here's what I am starting with. I removed the one piston to make it easier to measure for rings. It had all of the studs when I started. Had to stop when I remembered the camera.





This really pissed me off. I took a whole set of heavy duty studs out. THe were never torqed. Never ran. They just spun right out. But theya re all rusted to hell from exposure to the air.


The rotor was a bitch to get off. wasted a couple of hours dicking around with it. Finally got it with the bigger air compressor coupled with the bigger impact gun. There are pics in the album on my photobucket of the clutch disassembly if anyone is interested. The cases came apart pretty easily. This is what she looks like inside. There was some gunk laying in the bottom of the pan. You can see some here on the oil screen. It's just laying there from being flipped over.





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11/23/09 cont.

I finished breaking the motor down today. There is a little rust on a couple of the gears and shafts from sitting so long. I'm not sure yet if I am going to bead blast them, or if I'll just replace them. I have a stock motor that I picked up from Java last summer. I'm kinda thinking of stealing the kicker, output sprocket and shift forks from it. I still have to make sure that everything lines up.

empty case


some of the goodies


rusty ass kicker shaft


shift forks


This is the stocker. It's lookin pretty good.



The motor already had a lightened rotor in it. Here it is side by side with the stock unit.



The top of the case had to be machined to accept the larger diameter sleeves. There are also some spots inside the case clearanced for the rods. I don't know if this is necessary or if he was just being cautious.


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I have just been cleaning parts and cases the last couple of days. This is worth noting though: This is a replacement case. If you look at the top of the top case, there is no number, and the serial number plate is off to the side from the normal configuration. What I think is kind of cool is that the opening for final drive has two locating grooves to accomodate both lengths of final drive shafts.



Well the cases are cleaned up and ready to be repaired. The bottom case has one bolt hole that has a small piece cracked out of it. It doesn't really do anything except give the case bolt a surface to bear against. Here it is before repair.


I have the cracked piece, so JB weld it is. I'll post another pic once the good dries and I get it cleaned up.

You can see in this pic


where the top left side motor mount is broken off. It was kind of jagged and actually angled into the case area. I considered welding a chunk of loonynum on there and drilling and shaping it. I didn't have a lot of faith in welding to that cast loonynum, so I tried something different. I started making my repair before I remembered to take pics so I apologise for the pics starting in the middle. I cut the jagged ends of the mount off of the case. The holes in the case were drilled out and a piece af 1/2 od steel tubing has been pressed in place. A hunk of spacer was pressed onto the tube, then welded in place. The motor mounts will actually be bearing on the steel tubing, instead of the loonynum. I'll fill the gaps and file it down to look pretty.

Here is a look at what I did in progress



This is what it looks like pressed all of the way in


Hopefully I will have some shots of the filled areas tomorrow.

While that stuff is drying, I went on to start going through the transmission. There are several bad spots on the trans that was in the motor. I had thought about getting one of the cycle X setups, but I have some what appear to brand new pieces from a motor that I got from Java last summer. Here is the original Kicker gear and shaft.




This here are the ones from the other motor


This one will be going in the motor. This is the middle shift fork. The old one is looking kinda chewed up


The one on the bottom is hard to see, but is looking a little bit chewed up. This pic is the two of the same gears from two different motors. The top one came out of the big motor. look at the wear on the edges of the dogs. They are not even round anymore.


The same shaft also had a few areas that looked like this.


I disassembled, cleaned and reassembled the back up shaft.


It's ready to go as soon as the case is ready for it.

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...I have no idea who made the girder. If you know, please post...

Just a guess, based on the shape of the spring, but I'd venture it might be a Durfee girder.

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Thanks Maxx, that gives me a direction in which to look. I'd really like to have one with a shock instead of just a spring. I kind of think that this particular one goes too well with the frame to change the actual girder, so I may have to make new mounts when I get to doing the front end.

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Due to the arctic temperature, I have given the filler extra days to dry. This is the finished repair of the lower case:


The top case is also done. It doesn't look stock, but who cares? I think that once there is some paint on it, no one will notice the repair at all.



The case is all washed out again and currently drying. I'm hoping to start putting her back together tomorrow. Also going to have to finally take the time to make an adapter for the engine stand.


I have finally had a chance to get some work done on this. Over the last couple of weeks I have cleaned all the little innards. Replaced most of the transmission. I've also cleaned and repaired both of the cases. Time to start putting things back together. I started with assembling the pistons and rods. The circlips came from wiseco and the wrist pins are heavy duty units from APE.


Here is #1 all put together. Along side it is my handy dandy fancy schmancy circlip installer.


All kidding aside though, if you ever have a chance to get ahold of an actual circlip installer tool, it really is awesome. I just haven't been able to justify the cost to myself. Here they are all finished.


Next, I moved on to the bottom case.


First to go in was the primary chain tensioner.



Don't forget the locktite. The bottom transmission shaft is next. But first the bearing has to go in.




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1/05/10 cont.

To get the shaft in place, it is easiest to remove the very outside slider gear, put the shaft in and seat it in the bearing, then slide the final gear in through the bearing hole on the side of the case.


After the trans shaft is in place, the shift drum can be slid into place. Remember that the neutral switch actually holds it in place. I forgot to take a pic of this. Next is the shift forks and the shaft that they slide on. Mahe sure that the drum is in neutral. This is important for later on when the cases are put together.


The kickstart mechanism follows




Make sure tha the spring is preloaded and the ratchet thingy is in the right position.

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1/05/10 cont.

The top case is next. I started with the final drve shaft.


The bearings are greased and the case is ready for the crank.


New cam and primary chains. The case is open to do all of the other work, so I just couldn't put the old chains back in.


The crank gets dropped in place with the new chains


The top transmission shaft is next. Make sure that the primary chains are offset by half a link.


Rod/piston assemblies finish it off.


I wasn't sure how to torque the rods, so Mike from Steel Dragon Performance dug this out. It is an original golden rod installation sheet. Cool stuff.


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Well, I forgot to take my camera out with me last time. It's too fricken cold to and I'm too lazy to run back in the house to get it, so I don't have pics of the cases actually going together. Here is a shot of it done though.


I reused the old bolts for now. It is all torqued down to let the yamabond seal properly. Once I paint it, the bolts will all be replaced. I'm inside warming up a little. Heading back out to start checking the oil pump. After that, it will need to be reassembled and installed followed by the clutch and shift linkages. Hopefully I will remember to take my camera this time.


Made it out there for a bit this afternoon. Got the cases put back together again and got it in the engine stand. I forgot the camera this time when I went out, so unfortunately no pics this time. Disassembled and cleaned the oil pump. Checked the rotor to make sure it still was in spec and reassembled. I put the old oil pan back on it temporarily to keep some of the dirt out of it. I picked up a chrome one a while back so it will be going on after transluscent red powder. Probably do the shift linkage next. I still have to cut the fins on the cylinders, so I will probably stay and do it after hours at work. I'll do the honing at home. I don't want all of the loonynum chips flying around with an open motor in the shop.

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Well, got to work on the motor for a little while today. Got very little actually done and came up with some questions to find the answers to. Started out putting the shift linkage side together. The first step is the bearing retainer.


Screwed up here and just getting started. I forgot to get the new screws to hold it in. These are the old ones.


Going to have to go back in the next day or two and put those in. As far as the actual shift mechanism, I think that I can put everything else together as planned and just go back and slip the bearing cover screws in past everything else so onward we go. I start with the end of the shift drum. Put the pins in place.


Next is the big flat washer thing with the spacer.


The outside piece is last.


Followed by the screw.


Don't forget the locktight. The gear shift positive stopper assembly is next. This is the order that it goes on.


The drum stopper assembly follows. This little piece goes in first to give the springs something to anchor against.


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The pivot shaft threads in and holds that in place.


The larger of the two rollers goes first with the spring in place behind it.


Then there is a thick washer/spacer.


The shouldered bearing is next. The shouldered side goes out for the other roller arm to ride on.


The spring drops into place


followed by the outer arm.


Everything looks to be out of alignment until the washer


lock washer


and nut is in place


Tighten the nut down slowly pulling the arms back against the spring tension and letting them fall in the correct positions. Make sure that both of the arms are resting on the shouldered bearing surfaces and are not pinched in between spacers. The shift arm drops into place easily like so.


I still have to go back and replace those 4 screws in the next day or so, but other than that, this side is done.

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thanks for the excellent thread , pics , and explanations .

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thanks for the excellent thread , pics , and explanations .

No sweat. I figure that there are enough newer guys out there with these motors. Hope it helps someone.

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So I flip the motor over on the stand so that the clutch basket is up in ther air and I prepare to put it all together. I picked up some Barnett plates, steels, and springs. I think that I am going to use the clutch center and pressure plate from the 76F parts motor that I am using. I read the barnett instructions and the manual and things are not matching up. I have the parts that I am supposed to have from Barnett. Howver it looks like a pre75 clutch pack that came out of the 76 motor. 76 is the first year that had the one different friction disk. These ones are all the same though. There is also no outer ring in sight. So I look at the one that came out of this motor. It is way out there. There are 9 disks instead of 7. They are also thinner. The overall thickness of the assembly is wider though. Here they are side by side.


The one on the left came out of the race motor and the one on the right is out of the 76F. Both of the outer baskets are obviously cut for the wider seventh friction disk.


I got to looking at the two clutch packs and the race motor actually had a different clutch center in it. It uses the same springs, but is deeper to accomodate the extra plates. Here are the two centers side by side. You can see that the left one is taller.


I would think about running it but the center is pretty gouged up. The steels look flat, but I haven't put them on a stone yet to see and I don't have a service limit for the aftermarket friction plates. Looks like I'm going with the Barnett setup as planned.


Started cutting the fins on the cylinders today. I have to watch the amount of noise that I make in the evenings, so I thought it best to get started since I was able to work in the afternoon today. This is just the bottom.


Have to turn it over and do the top edge of the fins next. I'm in the house warming up now. Probably won't get back to this for a couple of days. Going to have to work on some quieter stuff until then.

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nothing better than a complete cb eng rebuild. i did one about 3 or 4 years ago now. it was my first complete eng rebuild, either these motors are very forgiving or i did it right because it still runs like a bat out of hell. great work man :thumbsup:

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So I finally finished getting the clutch together. I started out by prepping the steels. I took them out of the wrappers, and this is what you have.DSCF1282.jpg

This pic shows opposite sides of the steels. They are stamped in a die out of a sheet of steel, and they get a sharper edge on one side from the process. The edges on the bottom disk are rounded and smooth. The edges of the top disk are much sharper. You can actually feel a little bit of a lip where the metal is deformed a bit. They can be run this way, but I like to take the edge off. It helps decrease grabbing and helps the clutch engage and disengage more smoothly. I lay the disk, sharp side down on a full sheet of 600 grit paper.


Just move it around a bit. Don't have to overdo it, just want to smooth the edge. this is what you end up with.



Next is to soak the friction disks. I use an old dog bowl.


They fit in there just about perfectly.


Use the same oil that is going in the motor.


I have always soaked them for about a half hour. This Barnett pack though said 5-10 minutes is enough. Any longer would not be a benefit. I gave it a little longer anyhow because I am resistant to change and old habits die hard. This splined washer is the first piece that goes into the outer basket.


I didn't take pics of the assembly of the clutch pack because My hands were covered in oil. This is what I ended up with.


It dropped into the outer basket like this.


there is a spring washer that goes next.


Followed by the lock washer and nut. You have to remember to bend the tabs up to lock the washer in place.


Springs are next.


The lifter plate finishes it once the four bolts are in place. Make sure to stagger them and tighten each a little at a time. Try to keep them as even as possible going in.


I changed the seal in the inner cover and put it in place with a fresh gasket, and forgot to take pics of that. I reused old bolts for now, until the engine is painted, then I will go back through and replace them one at a time.

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The lifter plate finishes it once the four bolts are in place. Make sure to stagger them and tighten each a little at a time. Try to keep them as even as possible going in.


How tight did you tighten the four bolts?

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It has been a while, but It should have been 8 ft-lb. I always use a dab of locktite on all internal fasteners too.

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I finally had a chance to get a little work done on it. Finished cutting the fins on the cylinders yesterday. Came out pretty well.


Going to pull the masking and hone the cylinders next. I also am getting ready to start trimming the covers for the left side of the motor. This is the before pic.


I started out by trimming all of the extra stuff off of around the gasket area.





Then I roughly smoothed the edges and rounded the top edge just a bit.



I started smoothing the tops. I used a 40 grit flap wheel on a 4 1/2" grinder to rough it in.



Followed that with 120 grit DA sander to take the big scratches out



Had to stop here for now.

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I haven't finished polishing the covers yet. Instead they are taped up and on the motor to act as masks, so that I can paint the cases. You can see the hole in the case here, between the two covers. This is where I am going to run the wires


I also still have to trim the case where the wire passages were, behind the areas that I already removed from the covers.


Trimmed up the case today. Before:




I also got the cases painted today, although I forgot to take a pic when it was done.

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Got to work on the motor for a little while today. Put a fresh cross hatch in the cylinders.


Got the studs in and rings on the pistons.


pieces and parts of the cam chain tensioner.


The open end slips over the chain.


There is a little slot to locate the center of the wheel.


the axle slides through and the rubber piece fits into place.


The rubber end pieces drop into the slots in the top of the case.


Didn't have enough time to get the jugs on today. Maybe tomorrow.

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