Topic: CB750K2... Ol' Sarge project

[RAFster122s]

The leaking gaskets on the Subaru motor sre often indicative of blocked Crankcase Breathers...excess crankcase pressures blowing out the gaskets. If the flame trap/crankcase breather is not maintained that is what happens on many motor designs.
Look into it...

Thanks! I ordered a new PCV valve for it when pulled the engine out, and will be replacing the heat/radiator hoses when I put it back in as well. I'm not familiar with a flame trap, so I'll google that and replace parts as needed. the order for the Yamabond 4 marine was canceled as out of stock, so I ended up ordering Permatex optimum grey, and hope that will be good enough.

Flame trap is what another manufacturer called the PCV system. They had an oil separator system with a reservoir box the PCV valve fit to. If not serviced the box which was a baffled design would clog up and cause the blown seals. So, ensure the orifices for the PCV valve and its passages are clear.

[onepieceatatime]

Flame trap is what another manufacturer called the PCV system. They had an oil separator system with a reservoir box the PCV valve fit to. If not serviced the box which was a baffled design would clog up and cause the blown seals. So, ensure the orifices for the PCV valve and its passages are clear.

I see. Thanks for the info. I'll be sure that is on the checklist. I would hate for all this work to be for nothing, because it blew the new gaskets out.

[70CB750]

Following

[onepieceatatime]

Some of the Subaru parts showed up in the mail, so I had to work on it a bit today. Waiting on some more parts before I can finish, so I spent some time on Ol' Sarge.

Some Motorcycle parts showed up today too. 
Henry Abe breadbox filter

Gaskets and cam chain... still waiting on tensioner

NOS S&S turn out slip on mufflers

and some 25mm steel tube (no picture).


I measured and cut some tube to reinforce the frame section that I had cut. I drilled some 3/8" holes in the original frame tube to be able to weld my reinforcement tube in place.

I am getting a section of 3/4" steel rod to go inside that tube, which I will bend and weld in, and that will be the mounting point for my yet to be designed and built sissy bar.
I also welded in the frame section that I had cut out of the K5 frame.

and then I cut it back out.

Really just the triangle brace, as I had welded in my old frame kit. I drilled it for the flat frame kit pieces before cutting it, so now the frame is all set up with a frame kit.
I cut more of the 25mm tube for where the seat will be, and tacked it in place. I need to do a bit more adjustment to the pieces, but wanted to make sure positioning would be right.

Around that time, the low battery indicator on my welding helmet started flashing, so I stopped welding for the night/morning. I'll buy new batteries when I wake up this afternoon.

[onepieceatatime]

Today I finished the angles and bevels on the new tubes for the seat area of the frame. I leveled the frame then leveled the tubes and welded them in. I forgot to take a picture. I modified the a couple of clutch baskets in accordance to HondaMan's instructions in his book. I spent a while honing the cylinders for the K5 engine, and took anther look at the K2 engine. It looks like someone did some work on the intake part of the head. That will warrant some follow up investigation. Most of the engine cover bolts are missing, so I will have to source new ones.

I pulled the points cover and found this:

and the shifter cover to find this:


It looks like some kind of hard epoxy was used to hold the cover on at some point, but it separated without issue.
Inside the clutch cover looks equally delightful, and black RTV on that cover.

And the cases are split.



I pulled the transmission out of the lower case and spent quite a while scrubbing the old hardened oily grime off the case, and the black sludge out of it.
Hopefully I can get the oil filter bung welded back on and bring this engine back to life.

[onepieceatatime]

I took a picture of the frame, since I forgot to previously. When I weld in the steel rod, I will put in a few gussets as well.


I also added American style grease zerks to the swingarm bolt to replace the Japanese ones. Then I sorted through my parts and rebuild kits to figure what I still need for both the K5 and K2 engine, this bike, and my K7 build.
I thought I had 2 tapered steering stem bearing kits, but only found one, I need the engine oil seals for all three, and a few other miscellaneous parts. I also need to figure out how I will mount the front lights, what kind of mounting brackets to make for the ammo cans (I have a couple of ideas for that one), how I am going to assemble the fuel tank, what to make the oil tank out of (or which kit to buy), and where to mount the battery and electronics. Plus I still have to buy correct color and gauge of wire for the custom wiring harness, and build the sissybar including cross braces for the rear frame section.
Even with all those things left to do, and many more, It is beginning to look like what I have had in my head for quite some time.
I was thinking about my fender mock-up and realized that I probably had not left enough room for the tire with the suspension fully compressed, so I adjusted accordingly.


I also cleaned up the old liner from the CB650 tank tunnel that I will be re-using to mount the tank to. I trimmed off a bunch of extra metal, removed 5/8" from the length and adjusted the angle of the rear mount tab.

Then I held one of the tanks up to it, to check positioning and full range of steering. The picture doesn't clearly show it, but I have room, and the tank ends at the rear mount tab of the tank tunnel.


After that, I noted that I can trim a but more off the tunnel.

[RAFster122s]

You want to be generous with the gap between the bars and the tank as the handlebar will flex some before bending if the bike goes down on that side.

[onepieceatatime]

You want to be generous with the gap between the bars and the tank as the handlebar will flex some before bending if the bike goes down on that side.

Good thought!
I'll measure the gap on some of my other bikes, and use that info to pinpoint placement for approximately the same gap.

[onepieceatatime]

I didn't do anything too exciting last night. I took apart, cleaned, and rebuilt the front caliper and master cylinder for both this bike and the K7. Then I searched through my bolt bins for some fender and caliper mounting bolts that were missing. I messed around with a couple other little things in the garage, and did a little work on the K7.

[onepieceatatime]

I finally got my cylinders back from the machine shop, bored for my second over pistons. It would be a good story for the pissed off thread in the open forums.

I dropped the cylinder block and 1st over pistons off November 12, after no word from the shop, I went in on November 25th to find out a status.
They told me that they had farmed it out to another shop, and it would be only a couple of days turnaround.
With holidays, work, and everything else going on, I didn't make it back until January 6th. "Oops, we forgot. We'll get it".
January 16th... "We got your parts and took them to another shop. The pitting is too deep for the 1st over pistons, can you bring in a set of second over"?
January 29th, "My dad and brother are out. I don't know where your parts are".  (turns out they were out with COVID-19)
February 4th I was able to pick up both sets of pistons, and the cylinder block. The shop they farmed it out to, the second time (I should have asked who they were), did a beautiful bore and hone job. 0.0006" piston to bore clearance.

Now I have to set ring gaps and reassemble the engine.
My FSM shows a service limit of 0.7mm, but I did not see a minimum ring gap. Any one know the specs?
What's the best way to trim the rings? Just careful file work? There is currently no gap when the rings are inserted in the cylinder, and I know that isn't good.

One of the rings in the top cylinder.


In the time I wasn't working on this, I drained the old gas and cleaned the carb on my generator, as I had let it sit for a few years without running it.
I started repair on my fiancé's dad's generator. It has not been stored well. There was a lot of rust in the tank, plugged carb and fuel filter, and the rope broke on the third pull. 

I also did some mock up of the parts and pieces for my gas tank for this bike, figuring out exactly how I am going to put it all together.
And I went to a retirement sale for a local-ish Honda dealer. I bought a few shop made specialty tools, their wheel balancer (only 9 years old, with all the adaptors to do car and bike wheels, and a bunch of weights), a NOS hitch for my GL1500 (only $25), several HM branded wrenches, a pair of '78 Hawk side covers for a friend, and a large Honda Riders Club patch.

I also had a spare tank painted to match my (Dad's) '74 CB450 and installed a new cap, latch, and petcock on it. I am waiting on the badge retainer clips to arrive so I can put the badges on correctly.

[onepieceatatime]

Now I have to set ring gaps and reassemble the engine.
My FSM shows a service limit of 0.7mm, but I did not see a minimum ring gap. Any one know the specs?
What's the best way to trim the rings? Just careful file work? There is currently no gap when the rings are inserted in the cylinder, and I know that isn't good.

I found the specs in Hondaman's book, but still wondering the best way to trim the rings, to open the gap.


I think this is about how the tanks will sit. Slightly askew in the picture, because it is hard to hold everything in place and take a picture at the same time.
I still have to drill the filler bung hole, the holes for the connecting tubes, and the petcock bung hole, then tack weld it all into place and braze it for a nice seal.
The ratchet straps will then go away, but I may keep the stainless clamps, positioned differently than in the picture, for aesthetics.
I'll probably add a strip of flat bar between the tanks also, once I have the rest of it assembled.

[onepieceatatime]

I got the new rings end gaps set, the rings installed on the pistons, the pistons on the connecting rods, and the cylinders installed on the engine. Assembly lube on the wrist pins, and the rings and cylinder walls oiled.

I probably should have pulled the valve springs before, to inspect everything and replace seals, but didn't until tonight. Unfortunately it is not up to par...



Hondaman has the head for my K7 already. It looks like he might be getting this K5 head sent to him too.