Topic: Salt Racer CB 750 OZ style

[johno]

So today I fixed up a mistake I made with last rebuild on Mellow Yellow.
When I installed the new rubbers in the hub somehow apiece of swarf found its way into the roller bearing and when I stitched up the bottom cases it sounded like a gear tooth was broken or binding and I had just changed 5th gear to tighten up the ratios so I reopened the case to find the hub bearing was making the noise.
I tried to punch out the rollers but they just broke up. I checked NTN bearing web site they saids done use a notch as the outer races are extremely brittle ( as I found out)

[johno]

so next I bought a adjustable inner bearing tool to press out the bearings, puuuurrrrfect

[johno]

pressed out OK , jobs done.

[johno]

painted the cases on the rat Honda, possibly use for circuit if someone is up to not.

[johno]

Both engines to tidy up now.
Mellow yellow to replace the primary drive hub I just renewed the bearings, new piston etc.
The Yellow rat circuit bike, budget big bore.

Covid therapy

[johno]

So this is the yellow rat circuit bike, likely will be a budget big bore with lightened crank, rod bolts, cam chain and slider guides, average head job ( like my sex life) cam etc

The frame has been braced in a couple of places , double thickness stainless engine mounts, wheels etc

My signature yellow paint 

[MRieck]

Looking good johno....keep on it.

[Sam Green Racing]

So this is the yellow rat circuit bike, likely will be a budget big bore with lightened crank, rod bolts, cam chain and slider guides, average head job ( like my sex life) cam etc

The frame has been braced in a couple of places , double thickness stainless engine mounts, wheels etc

My signature yellow paint 

Johno,Your sex life will improve with a proper head job.

CALLING M RIECK. hahaha.

[bear]

So this is the yellow rat circuit bike, likely will be a budget big bore with lightened crank, rod bolts, cam chain and slider guides, average head job ( like my sex life) cam etc

The frame has been braced in a couple of places , double thickness stainless engine mounts, wheels etc

My signature yellow paint 

Let me know what your chasing for the road racer mate.
I have a container of #$%* doing bugger all at the moment.
Fancy a Bill White crank? I have a couple that need a home.
Hy-Vo maybe?

[bear]

Have you caught up with the latest news?

https://www.dlra.org.au/newsletter/dlranews69.pdf

[johno]

Cheers Bear, Yeh u would think even at my snails pace 6 months prep time should be enough.
This year turned to #$%*e on two accounts, first the week before the meeting it poured and flooded the track and the same day Covid restrictions smashed the meet , so either way it wasn't a happening thing.

I felt sorry for the east coasters and US folks who had planned to race, everything cancelled etc.

They delayed the meeting until end of March as the previous 3 years were first week of Feb but the 45 c deg heat is just unbearable so they rolled the dice to late march which is often thunderstorm month and sure enough it was.

The positive thing is the 2020 merchandise shop is discounting 

cheers Johno

[johno]

weather is a bit how ya going so I thought I would put all my racing build notes and info together in one book with an index. Im not sure why but my manual has ended up 4 times thicker than the original bible 

[johno]

spent the last couple of days putting the front end on, new tapered bearings, kit in forks and seals etc, will run with original twin brakes for nostalgia sake and I'm not riding so won't matter  .  If rider complains about brakes Ill just say get thicker soles on ya boots mate.

[johno]

Ive just got back from taking a break from weather and covid etc, I went prospecting out in the desert for 3 weeks, didn't really know what I was doing but an old digger took pity on me and showed me a thing or two.
I found it hard work wandering around the bush all day like some zombi, BUT I had bit of luck and found these few nuggets, about $2,000. worth for 3 weeks work.  That will do nicely in the racing kitty thank but the real bonus is cos I wasn't snacking all day I lost 5kg or 10 lbs 

[Old Scrambler]

Life is usually more interesting when you get off the sofa...........did you stake a claim? So tell me what you think would happen if one were to drill the CB750 rockers at the pins, insert a lump of brass, and drill a new hole 1mm closer to the cam-pads. I'm thinking it would increase the valve-lift (how much?) but would require over-sized lash-caps with final adjustment left to either shimming or skimming the bottom of the cam-towers.

[Jerry Rxman Griffin aka MuthaF'er]

Johno, don't let him be a bad influence on you!! 

[johno]

HI DENNIS,
I thought you were on holiday ? I suppose race bikes are like pets, they drive you nuts when your working on them all day but when their not around you miss them.

Im not sure what the thread was but there was a thread on cams that I latched onto with some trials, experiments etc on, cam design, geometry etc and no matter what happens the valve angle makes things ugly.
 To achieve more than what's offered in the market today No matter which way you go in cam design, symmetrical, asymmetrical, polodyne etc the valves hit, and the geometry of both the rocker pad and adjustment end ensures cam grinders are at the limit with the design, The only way forward is to make new cam mounts,  open valve angle up etc
Ive got an experimental head and a cam with several grinds on same cam that I played with, was fun but went nowhere unless I committed to valve changes, cam mount and roller rockers.
Its a long journey Dennis, 

[Old Scrambler]

Holiday..........almost everyday........but race-day

So while I have the time for 'free-thinking' about a few things..........I put some light-weight springs on some valves and hand-cranked a motor to 'watch' the valve-train in action. By moving the pivot-point closer to the cam, the valve would open significantly more but the cam would have to be re-timed to get best opening/closing points. My valves get close to each other on the overlap, but near mid-point of movement. Slightly retarding the cam would help, not enough to be 'safe' with 35 & 31 mm valves......possibly reducing exhaust to 29 would be best in a K-head versus my current F2 head.......and a corresponding cam versus my current special grind.

[Jerry Rxman Griffin aka MuthaF'er]

Just so happens I have a set of Kibblewhite 28.5 exhausts to go along with the 33.5 intakes just sitting on the shelf

[johno]

Well Den I spent nearly an hour selecting and download some pics to show the journey I went on for a good SOHC top end BUT when I hit the submit button all went pear shape and nothing came through so after a cup of coffee Ill just briefly type what I done and you'll get the drift.

I selected 4 cam profiles based on a valve spring pressure of 100lbs seated 200 or so on nose.
Had a cam grinder weld and grind all 4 profiles on the same cam.
I then on a lathe dialled up all 4 cam profiles for a lift curve in lift per degree of rotation to check the profiles style and characteristics.
To fit the cam in I had to mill away the cam bearing and mill out the head top until fresh air under the cam.
Got the cam in and of course the valves hit badly in overlap as the included angle is too great ,  need to open the valve angle to avoid valve interference.
I took pics of the geometry profile ie the rocker cam pad was too short and was edging on the lobe, with extra lift the adjusters were edging badly on top of the valve very badly, tried an adjuster from a Yammy I had that had a more ball tip rather than the flattish curve of Honda looked better but not suitable for 10,000 to 12,000 RPM.
Had a good look overall at geometry and got my son to draw it up in CAD then on computer opened up the valve angle, raised the cam, changed the cam support bearing to allow an automotive roller rocker with different ratio that would allow any cam lobe acceleration rate suitable for what ever spring tension can be installed.     Easy peasy, made a plan, I bought the aluminium billets for the cam support bearings but lost interest , mainly as I can do lathe work but not that good on the mill and It was hard for me to access a lathe & mill.  I wish I was a retired machinist with all the gear in the shed, with my son a wiz in CAD and 3D the world would be my oyster, After I realised what could be done to improve the SOHC I realised that in fact some people had done this all in the late 70,s, Evan Ken @ cycle X has done the valve guide relocation etc so it all became a bit boring.

[johno]

PS Den
Forgot to say my initial goal was to take advantage of Mikes very special head, with a high flow at .500" lift and Evan more exceptional flow at .100" to .200 " I needed a profile and rocker ratio for .500" lift and a very rapid lobe accelleration rate to capitalise on the big flow rate at low lifts.
Might be best for me not to discuss it Dennis or Ill get all fired up again, especially with this covid crap boring the hell out of me 

[Old Scrambler]

Thanks, Johno.............................Whenever we stop for a few weeks at our daughter's home, I keep busy trying to finish a Honda 305 Scrambler restoration, as well as taking day-trips on the local gravel roads with my new Royal Enfield Himalayan. The cam-thoughts are directed toward a potential 'big-bore' motor, so plenty of valve-room in a modified chamber........may include a degree or two of valve-guide movement and sure to have a proper 'squish-band'. One advantage I found is to use wide lobe-centers. Its somewhat rewarding to listen and learn...then do your own thing and see if works   Several respected CB750 voices told me my CBR motor would not flow......now there is a shortage of RS34s

I am not looking for more than 0.450" of lift.......duration and very steep valve-edges tend to maximize cylinder-fill when no restrictions exist for air-intake at the carbs......Don't get too excited ..........I'm just playing for now

[johno]

Today is painting day, doing the covers, good etch primer and good epoxy YELLOW. 
Thought I would leave the clutch cover chrome cover off , paint the outer of cover yellow, paint the centre black and the lever arm yellow for some contrast.

[scottly]

Thought I would leave the clutch cover chrome cover off

The chrome clutch cover is dead weight, IMHO.

[johno]

Thats the best photo Ive seen your bike Scottly, Nice