Topic: 1975 CB750K5, the one I've been waiting for.

[iismatthew]

It's been about 4 years since I started riding, it's been a passion of mine since I was a child... dirt bikes, mopeds and now vintage Hondas. I started with a 1979 CM400t a few years back as my first bike..

After that I had a 2003 Bandit 600 for about a year and hated every minute of it, sold it and bought an engagement ring...

And a few weeks ago my wife helped me get the one I've always wanted, a 1975 CB750K5



Took it home made sure it started and immediately took it apart, planning a full rebuild.




The plan here is build a reliable, stock displacement ride with a brat style and removable seat cowl for more spirited solo rides. I want something I can ride across country or through the twisty back roads of VA with or without a passenger. I've been reading over a build on here that has really inspired me

http://forums.sohc4.net/index.php/topic,131917.0.html
Funny thing is he (CognitoMoto) is also from Virginia and also built it to have a ride to share with his wife. Even mentioned a cowl for the seat.

I've already started to tear down the engine and the frame is stripped down and is ready to get a Gordon frame kit, modified since I do not have the removed parts and of course a kicked up rear frame hoop for a proper brat seat.

This is going to be one hell of a journey.

[SOHC4 Cafe Racer Fan]

Devin's bike is a great source of inspiration.  Feel free to ask questions and use the search function in the top left (not the window in the top right) for advice. 

[Stev-o]

Welcome, subscribed. 

[Buckskin Bandit]

Looking forward to watching this build!

[70CB750]

Welcome, neighbor!

I am near Warrenton, where in NOVA are you?

[iismatthew]

Thanks for the comments everyone, now that I know people are paying attention to what I'm doing I'll be more motivated to keep this updated.

Welcome, neighbor!

I am near Warrenton, where in NOVA are you?

I am in fair fax, so not too far from you at all.

[70CB750]

Very good, so some day in the future we will meet on Skyline Drive?   

[iismatthew]

Last night I got the jugs off and took a look at what I was actually getting in to with an engine from 1975 with 40k on the odometer.





As far as I can tell I don't think I'll need to replace the pistons, just use a flex hone on the cylinders and replace with standard size rings (suggestions are welcome) My main purpose of getting in to the engine is to check out the lower end, replace primary and cam chains and hone/replace rings as well as all gaskets and oil seals. I don't plan to do a high out put engine on this, might eventual go to a 836cc kit and a mild cam but that would be further down the line.

Any pointers for what I should be replacing while I"m in here, certianly trying to keep this someone reasonable as far as cost goes, but I don't want to have an engine fail on me in 20k miles either.

I was also thinking of hitting the valves and such with a soda blaster?

And then lapping the seats, they seem to be sealed up pretty well and don't believe they need to be replaced, correct me if I'm wrong.

So far I'm thinking this.

• Primary chains: $100
• Standard Ring Set $60-$90
• Piston Circlips $11
• APE Heavy Duty Cylinder Studs $92
• Cycle X Gasket Set and Oil Seal Combo $81
• Cam Chain Roller (x2) $50

If there is anything I can skip/ or should add I'd certianly be welcome to suggestion as this is my first real engine build.

[iismatthew]

Very good, so some day in the future we will meet on Skyline Drive?   

I grew up in Front Royal and learned to ride out there, spend many a night running around on the skyline drive.

So short answer, yes maybe we can get a small group off here together for a ride. There is a meet up called Bikes and Breakfast that meet in Clifton, not too far from either of us.

[Bigsam302]

Awesome find.  I can't wait to see how it turns out!

[70CB750]

Yeah, I know Clifton.

To your list you could add tappet adjusters, depends how worn they are:

http://www.dynoman.net/bikepages/sohc/oe.html

Also The Book:

http://forums.sohc4.net/index.php/topic,65293.0.html

if you dont have it already.

[iismatthew]

Yeah, I know Clifton.

To your list you could add tappet adjusters, depends how worn they are:

http://www.dynoman.net/bikepages/sohc/oe.html

Also The Book:

http://forums.sohc4.net/index.php/topic,65293.0.html

if you dont have it already.

Thats a great looking book, I currently just have the Honda shop manual i printed off and put in a binder with plastic sleeves for the pages.

[70CB750]

Mark Paris is a local guru (Hondaman).

The book goes over the engine step by step on disassembly, check and assembly - the whole bike actually with power enhacement tips.

 Well worth the money, even it is clear that you have some wrenching experience.

[iismatthew]

Tonight I didn't get much done, I've been looking at this frame thinking of the best way to repair/stiffen it back up



I was looking at the Gordan kit but that's going to be hard to do without the original frame... Ran across this

http://carpyscaferacers.com/shop/honda-cb500-cb550-cb750-parts-upgrades/frame-adapter-1969/
But my frame is cut too short, I emailed Carpy and he said he could send some extra tubing to weld on, sounds like that might be the fix. Any recommendations? I'm a little concerned about stability being 6'3" and 260LBS.

[70CB750]

If it was me, I would weld the frame back together the way it was from Honda - with tubing sleeves were the cuts are.

But there are people who love the Gordon's kit - it is pretty much like motorcycle/car oil discussion 

If the welding is done by good welder, either with the kit or back to "original"  it will hold just fine.

[iismatthew]

If it was me, I would weld the frame back together the way it was from Honda - with tubing sleeves were the cuts are.

But there are people who love the Gordon's kit - it is pretty much like motorcycle/car oil discussion 

If the welding is done by good welder, either with the kit or back to "original"  it will hold just fine.

I too would re-weld the tubing, but if it were me, I'd install a frame kit at the same time. Having the frame kit will make it much easier to service your motor with the engine still in the frame, and if you do plan on a future 836 kit, you won't need to pull the engine, just the head and jugs.

If you get hung up finding a welder, let me know. I'm sure I can get it TIG welded up for you with a welded/wledless frame kit. I'm down the road in Richmond (right next to Devin) and travel back and forth to DC constantly. I grew up in  West Springfield, so Fairfax is very well-known to me.

As for Devin's seat cowl, he hasn't done anything to the bike since he built it. Had a kid, moved his shop, and is going full bore with his business. He does now offer some really great looking metal cowls for projects, but they aren't "brat style" if that is what you seek (www.cognitomoto.com).

Definitely bu Mark Parris' book. You will save yourself money, time and aggravation. Its the most comprehensive collection of 40 years of expertise and service guidance in print.

I definitely want to make it removable after you made that point, it'll save me a lot of effort to be able to do the upgrade in frame, especially since I hopefully wont need to split the lower case for a while after this..

Dose anyone know where I can get the hardware or something similar from the Gordon kit? OR a cheaper place I can get it for under $175. Still shopping around trying to get this done as inexpensive as possible while still getting the rigidity back.

As for a welder the person I bought it from said he could get the welding done for free, we'll see if that comes through if not I will definitely keep you in mind.

Has anyone tried to make the frame more like a DOHC frame where the lower rails come up, or would that interfere with the tank?

[SOHC4 Cafe Racer Fan]

Frank aka 754 has a weld-less frame kit, but I am not sure what the price point is.

[iismatthew]

I machines something very similar for my subframe. Bolts on and off and the slugs are welded into the tubing.

I'd love to see that.

Sent from my m8whl using Tapatalk

[iismatthew]

Check out the last page or two of my 500 build in my signature.

That looks like the ticket, thats pretty awesome work... Might have to recruit you for that.

[iismatthew]

What could be very trick is to use aluminum for the removable section. Since its bolted, it won't matter. The stock I used is .125 wall, 6061 1" OD. Should fit perfectly. Tap the steel lugs to screw into that are then welded to stock frame. Strong, versatile and lighter.

I'm sold, what would the cost in something like this be?

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[iismatthew]

Since I can't really get any parts or get any painting/powder coating for this at the moment (24 year old growing up in NOVA$$) I did manage to get a few things done.


A good friend of mine offered to do some work on the frame, so that's off at his house. In the mean time I managed to get the head studs out with a tip from calj737, heating them up till they are red, tap it with a hammer and they come right out.


Just. One. More.



So now that thats out of the way I'm kind of idle for the time being, hunting down a set of 18" aluminum rims at a good price isn't going anywhere anytime

[Stev-o]

Time to clean clean clean that motor, doesn't cost much money.

[SOHC4 Cafe Racer Fan]

Buchanan's Sun Rims are not an arm and leg. If you want cheap, try to pick up a used GL1000 rear wheel (uses aluminum rims).

[iismatthew]

Time to clean clean clean that motor, doesn't cost much money.

Cleaning is in order, I do have a soda blaster...

Buchanan's Sun Rims are not an arm and leg. If you want cheap, try to pick up a used GL1000 rear wheel (uses aluminum rims).

As for GL1000 rims I am hunting down two rears per calj737's recommendation.

[SOHC4 Cafe Racer Fan]

Actually, the GL1000 may have had 17 rears.  Make sure to check before buying.