Topic: 1973 CB750 Four K3 -- Project "Terry's Fault" -- BUILD RESUMED

[edwardmorris]

I blame this one suqarely on Terry  !

Why?

http://forums.sohc4.net/index.php?topic=126735.msg1486843#msg1486843

Scroll up a bit once you land there.

[edwardmorris]

So the story is simple, last year when I started with the K2, I had a nice clean stock look in mind and went with it. Then Terry just casually showed off his nice new K2 engine he finished for his bud one day and that was it, I just had to have a bike with an engine that looked that nice. So I decided to keep the K2 stock and eventually look for another K2 next winter. I had narrowed it down to a K2 (3hrs from me) a K6 (45mins from me) and this K3 (3.5hrs from me). The K2 guy wouldn't budge on the price, the K6 guy was plain greedy and desperate, not someone you'd want to deal with. So I went for the K3. Nice friendly folks from Wisconsin, made a good deal, worked things out and now it patiently waits in my garage.

This will be a pro-stock-cafe ish build. 836 with a custom exhaust is what I'm visualizing. The custom exhaust is probably where most of the custom work is going to go. Ages ago there was very nice looking matte black moto guzzi that looked amazing, very stealthy. I wan't to mimic that style for the rest of it. No chopping the frame, just a cafe style seat (like the one on Tige's K1 GT). Any suggestions, I'm all for it, lets build something fun this time nothing stock, all stainless hardware etc. etc.


Looks like its mostly there, has a nice kerker exhaust, carbs look alright on the outside but won't know until I remove the tank. The surface rust under the seat is pretty bad, that'll be the first thing I'd wanna address as I begin tearing it down. No idea what those gauges are.

[edwardmorris]

More

Weird looking brake rod lever..

[edwardmorris]

Looks like a custom footpeg, early year tail light??

[edwardmorris]

Definitely fell on both sides, and duct taped gas tank cap

[DH]

More

Weird looking brake rod lever..

Ed, are those carbs stuck? something in the pic i noticed..I'd think the throttle rods would be down at idle if they were stuck, but....IF they are,, DO NOT FORCE THEM TO OPEN FARTHER THAN THEY ARE NOW WITH THE THROTTLE GRIP. UNSTICK them BEFORE you twist the throttle, because forcing them open (when they're froze) with the throttle grip will cause the needle plates to bend. Carbs with bent needle plates are impossible to sync correctly, and until you correct it, you'll be scratching your head as to what is causing the weird running problems.
Just throwin that out there. I've seen those plates unmercifully bent by someone forcing the throttle open on stuck carbs before..looks like  a fun bike..

[edwardmorris]

I didn't mess with them yet, the throttle grip is hanging loose off the handlebars, will check it out today. Its all coming apart anyway so I didn't do a close inspection of things yet, but good catch, thanks!

[seanbarney41]

Ed, why would you want to have two full rebuilds going on at once.  Just do the minimum work to get that on the road safely and ride until project Ice Cream is done.  Then you can ride project Ice Cream while building this one.

[edwardmorris]

Ed, why would you want to have two full rebuilds going on at once.  Just do the minimum work to get that on the road safely and ride until project Ice Cream is done.  Then you can ride project Ice Cream while building this one.

Sean,

   Save for buffing up the dyno cover, Project Ice Cream will be officially done reconditioning wise and all that remains is assembly. I've decided to do that in spring, close to when I can actually ride and break it in. As much as I'd love to have it put back together, it would just bug me all winter that its just standing still in the garage

    This one, is going to be a vrey laid back build. I had to save this one before it ended up being parted out  I drove all the way to Cedar Grove, Wisconsin to get it. This will be an 836 build, which I have absolutely no idea or experience with, so heads up for some rage inducing noob questions everyone 

     I need to know what kinda jetting, what kinda exhaust type etc. etc. to first finish the design concept. THEN, probably next summer when PIC is done and running, I will have this to tinker with. But the winter, since I have nothing left to do with PIC, tearing this one down will be a good way to pass the time. Would love to get the engine blasted clean so I can see what I'm working with, then maybe even send the head out to JMR, swingarm to Mark etc. etc., standard stuff basically

[Terry in Australia]

G'Day Rafi, well done mate, you can't have too many projects, I reckon. I'll be interested to see what's inside that engine, who knows? It could be an Alladin's cave of hot up parts from the era? Regardless, you've got some good bits from your K2 build to use in this one, so with your attention to detail, I'm sure you'll build something really cool.

I'm working away from home for the next month so I won't be on here much, but when I get a chance I'll look in on your build, it's always good to see quality work. Cheers, Terry.

[edwardmorris]

G'Day Rafi, well done mate, you can't have too many projects, I reckon. I'll be interested to see what's inside that engine, who knows? It could be an Alladin's cave of hot up parts from the era? Regardless, you've got some good bits from your K2 build to use in this one, so with your attention to detail, I'm sure you'll build something really cool.

I'm working away from home for the next month so I won't be on here much, but when I get a chance I'll look in on your build, it's always good to see quality work. Cheers, Terry.

Terry!! I'm kinda wanting to dive in there myself. From the looks of the horridly uneven wear on the hyper wiiiiiide and 16/17" rear wheel, the pods, the kerker, there's a good chance that this thing was abused pretty bad. I'm no drag racer but looking at the rear tire, I can tell someone did some nasty burnouts on it.

As for the bits left from the K2, I hope that web cam 41-a and HD springs will suffice for 836cc. Not entirely sure what the benefits of the 41-a are over the 63-a and such. Doing my due diligence and searching right now

What I'd like to figure out early on is the breathing:

• How much porting to do
• What jets to use
• Keep or ditch pods
• Baffled or straight through pipes

[Bill/BentON Racing]

Rafi, cool. 836 is going to get your attention. MR head etc, you have lots of options. I'm in, Bill

[oldhatt45]

Edward,

Boy you sure do like to jump into things with both feet. 

When I saw your new project thread and read the description, I thought about a thread I've been watching recently.

http://forums.sohc4.net/index.php?topic=27159.0

It's authored by FunJimmy.  Titled the Gentlemen's Roadster. 
If I were going to build something along the lines of what you are describing, I'd definitely think seriously about doing something along the lines of what FunJimmy has done. 

I generally don't like the "café" style, but what he has done is absolutely amazing. 

Take a look (although I'm sure you probably already have) and see what you think. 
And I know his is a 550, but a 750 version would be Very Cool.

Good Luck,

Charlie

[edwardmorris]

@Bill! Glad your subscribed, will be needing a lot of your racing expertise.....and maybe a few visits to the bat cave too 

@Charlie: I work a lot, all the time, so when the wife mandated no work Sunday arrives, I'm bored outta my mind, especially in the winters where we can't go out much on a whim. So something fun to keep busy is nice to have I looked at the FunJimmy build, although great work, its not quite what I'm going for. I have two very specific things in mind about the look, color scheme and exhaust. Its going to be a stealthy matte black all across, with limited chrome accents. I feel like all the bling in PIC needs a bike to counter it 

[edwardmorris]

Lets get the exhaust out of the way first, shall we? So after some initial searching, it looks like pods can stay or go with a 836 as some people have stuck with their stock air box, just went up on the jet sizes and used a K&N. I'll get to the pods debate later. The other end of the breathing side is what I haven't quite figured it out. I'm guessing that the old style full open HM300s work better for the 836. Below is my terribly poor attempt at "shopping" an image. Pic courtesy of Tige (Thanks man!), I had him take this particular angle when he was nearly done with his GT

http://forums.sohc4.net/index.php?topic=131724.msg1509047#msg1509047

(so you see I've had this in the background forever, and I STILL blame Terry  )

I'm thinking of slip on extensions to the stock headers with a simple cylindrical end pipe (never really liked cone anything) with either a HM300 baffle at the end, or a glass pack set up with an inner pipe with a bazillion holes.

Thoughts? Feasible? Which is better?

[SOHC4 Cafe Racer Fan]

I'd run the muffler higher to give you better ground clearance (not just for the muffler, but the path of the pipe below).

[edwardmorris]

I'd run the muffler higher to give you better ground clearance (not just for the muffler, but the path of the pipe below).

The rear foot peg mount is missing in the pic above, if you look closely, I just drew a black line as a guesstimate. I was planning to mount the muffler ends similar to how the stock ones are mounted by the foot pegs. The OD for the pipes will be same or slightly less than the OE pipes, so hopefully the clearance should be sufficient......right??

[BPellerine]

if I remember right your org head had some damage maybe from the big springs in it don't think I would use them,new ones from cycle x are a lot smaller and work.bill

[edwardmorris]

if I remember right your org head had some damage maybe from the big springs in it don't think I would use them,new ones from cycle x are a lot smaller and work.bill

Yep, one of the cam tower bolts was stripped, but all others were fine. Hard to tell if it was the springs or the PO on that one. They will eventually end up with JMR when I get the head work funded and ready, so if they fail his inspection, I won't use them.

[edwardmorris]

Just a little clarification on that exhaust after some feedback via PMs, it is going to be a 4-4 not 4-2. The crappy foto-chopped image up a few posts is the basic blueprint of the final design I have in in mind...

[edwardmorris]

Found a better pic here, not sure whose 750 (gold dude?), but had the right angle shot to try and "foto-chaap". Looks like the bends aren't so severe but won't know for sure until actual bending/mocking up starts. There are other pix of the pipes from the under the chassis too in case you guys need to review and offer insight.


Think this is what I want to go with

Black/Red Perforated tubing = Same size as stock header = 1 1/4" OD with flared ends for slipping on
Outer/Black tubing = Approx stock size = 2 3/4" OD with tapered cone end caps
Blue spots = fiberglass packing

Will have to decide on lengths when I physically have the tubing mocked up/mounted on the bike. What do you guys think? Should I order up some mild steel?

[calj737]

I've never been taken with the look of straight pipes on street bikes. Makes them look like drag pipes to me. A mild up-tick at the end always looked better to me, and it does provide better clearance when riding. (You do intend to ride this thing like a cheap Prostitute, don't you?)

If you're in search of a "cleaner" look at the end, I'd recommend 2:1/4:2 into modern slip-on styled silencers. Tinker a bit with the length and shape (conical, round, triangular) until it fits your eye.

My $0.08 (devalued currency exchange rate applied).

[edwardmorris]

I'm kinda partial to retaining the 4-4 aspect of the bike Cal, never really liked the look of 4-2s, can live with 4-1s if they didn't kill the center stand.

Ground clearance is all I got feedback on, and I'm not even worried about that (although I should be ). Ordered the material through my local auto shop, they have the larger dia pipes already, just need the 1-1/4 inner to arrive. Will also be borrowing their tubing bender when everything gets here.

Next I need some help from the skilled fabricators out here, need to figure out end caps. I will post up a mock drawing soon, but need advice on what kind of sheet metal to use for this?. Simple cone ends with cylindrical slide, held in place by a screw, much like the HM341 end tips.

Also, the PO had welded on metal tabs to install custom pillion foot pegs, how do I get rid of these without hurting the frame?

[edwardmorris]

Endcap proto

[calj737]

Mill the end caps from aluminum on a lathe. Remove the square peg with a cut-off wheel very carefully.

Regarding your pipe material, mild steel tolerates the heat cycles of exhaust tubing work better than stainless, but stainless has better corrosion resistance. Both metals benefit greatly from ceramic coating inside the pipe and out. It also provides better performance for your motor. A screw to hold your end cap works well.

You can weld small mounting bungs on the back side of the pipe to aide in hangar bracket locations.