Author Topic: Salt Racer CB 750 OZ style (Read 168540 times)

Old Scrambler · « **Reply #75 on:** October 30, 2012, 07:35:33 PM »

I would be suspect of that case.......looks like 'crushed' metal supporting the bearing race. I saw similar cases with a bent crank after the bike hit a curb. Too bad your across the big pond.....I have several sets of cases......not all are perfect.....and seven spare motors on my 'junk' bench. Also, a friend in the salvage business has about a dozen motors stored indoors because they all turn over. A few more are 'frozen' in the weather. I am having thoughts of using the F2 cases with the deeper fins on the sump.

johno · « **Reply #76 on:** October 31, 2012, 05:19:38 AM »

Thanks for your comments Den,

good thinking I'll check the crank for runout just in case although I will be using the crank from the other engine ( chain damaged eng cos its looking better. )
Dennis, its been a difficult two weeks, first both the cases turn out to be duds then I bought a 750 fuel tank off ebay and I now realise its a 450 honda and doesnt fit the 750 frame, I had my RC webber manifold welded up ( after I broke it ) now have to machine it. Hit the wall a bit on the big cam operation, I started on the frame this week and set it up on a bench to rake the front a bit and while measuring up have found the swingarm to be not good enough, its not bent as the square tube section is spot on but where the axle holders are welded in they werent set up right at the factory and are 3mm different height. Boys had too much Saki for lunch at the factory. Kind of looking at the time frame now and thinking hmmm, anyway was feeling a bit ordinary about it all today so I machined up a couple of different shape guides for something to do and will chill out for a couple of days and have a play on the flow bench till I get over it.

Parts for Hondas in this country are very difficult to find, or are so for me. Living in the middle of nowhere is not easy getting used parts but its also noone around to chew the fat with, lucky for me this forum works as a therapy. sohcitis is a bad disease.

If you know of a used parts supplier who could be trusted I would quickly purchase a set of good clean cases, If you do PM me and Ill jump to it as would only take a couple of weeks.

cheers Johno

johno · « **Reply #77 on:** October 31, 2012, 05:24:48 AM »

My poor manifold is in hospital receiving some therapy at the moment, decided to run with the original 1 to 2 cable set up. If it was for the street I would use linkage but as its only flat out the weight thingo won me over. Ciao Johno

johno · « **Reply #78 on:** October 31, 2012, 05:28:52 AM »

One of the manifold ports was slightly bigger in a small area so I bit the bullet and had it filled in so I can reclaim it to where I want.

while its getting its treatment.
ciao

johno · « **Reply #79 on:** October 31, 2012, 05:44:57 AM »

If anyone has some thoughts re the gearing in the engine.
My gearbox is an early one K3 and I have undercut the gears etc but it has got me thinking.
Looking at the torque and HP curves it goes flat from around 8,500 to 9,500 then gets going briefly.
Since this graph I have had a play and by reducing the port diam and the exhaust pipe diam etc the curve has smoothed out and picked up a couple of points on the torque curve and the HP curve, so Im happy, its still slightly over cammed for the 750 displacement but pretty damned close.

What I'm thinking about is the 4th gear ratio. which has two options 31 T early or 30 T later I am thinking that the closer the ratio between 4 th and 5th the better as at that kind of speed in top it will be loaded up, like uphill , a very steep hill. If thats the case I was evan thinking of running in 4th and using the sprockets to get the final ratio. In car scene I never had any luck with overdrives and performance , it was kind of like one gear too many and a gear that didnt like load. I guess if I plan for it and take enough sprockets to try both ? any thoughts

that HP dip at 8,500 worries me a bit

ciao Johno

Tintop · « **Reply #80 on:** October 31, 2012, 05:58:30 AM »

On the sidecar I went the other way and put in a 5th with one tooth less (closer to 4th), and therefore less OD. Then used one tooth less rear sprocket than the other guys to get the top end back. Also changed 1st to get a better standing start with the rear sprocket.

754 · « **Reply #81 on:** October 31, 2012, 07:31:22 AM »

The 450 tanks look good on the 750,s, need a bit of tweaking though..

johno · « **Reply #82 on:** November 02, 2012, 04:24:58 AM »

This the final engine plan, the previous graph was when I was comparing the Meg cam to the RC cam and settled on less duration with the meg. Then Doc D beat me up on the untidy graph curves so this is the result.
I made the inlet port a mm smaller and the exhaust pipe diam smaller and both the torque and hp curve smoothed out and gained slightly from the previous graph.
Itll be something to hope for anyway

I will post two other charts to show the technical details like cam stuff, headflow stuff, exhaust stuff etc

The head numbers are based on some generic flow numbers from around the traps max 70 cfm at 10inchs

Cheers

johno · « **Reply #83 on:** November 02, 2012, 04:26:54 AM »

engine details, hope you can enlarge !

johno · « **Reply #84 on:** November 02, 2012, 04:30:15 AM »

Some of the results technical data, some things to notice, the port air speed mach number plus

other stuff
ciao johno

Doctor_D · « **Reply #85 on:** November 02, 2012, 07:26:37 AM »

Johno:

I don't recall beating you up, just tried to contribute to your success. Because, if you break the record -- we all win.

Happy to hear that my input was helpful.

johno · « **Reply #86 on:** November 02, 2012, 02:33:17 PM »

D ..... Dont get the wrong idea but You Beat me up in the best possible way

Normally thats my wifes role LOL johno

Old Scrambler · « **Reply #87 on:** November 02, 2012, 04:32:23 PM »

Very nice info on the charts.......for the small part that I understand

How would the numbers look with 110 octane fuel?

+1 with TinTop on the lowering of 5th and use sprockets for the final ratio. I use a close-ratio box of gears on my T20 Cub. That would also help you get through the flat-spot on the dyno graph.....it may be cured with a minor change to the intake length.....or a minor change to the cam grind / timing. I actually think that flat-spot will be worse on the course, especially with any wind to consider. My motor builder used a 2-stroke emulsifier tube on a 29mm Mikuni to place the fuel mixture in the middle of the air-stream feeding my 201cc single.

johno · « **Reply #88 on:** November 02, 2012, 06:06:52 PM »

Dennis, very observant grasshopper

yes the charts show the octane is ordinary and if you look at the ignition advance you will see the cosequence with the low advance in mid range, the bad RPM have an asteris along side showing low advance to avoid the detonation then things get better near the top end with 31 degree. two things, As I will be running in fuel class at this stage not running methanol but some of that top line racing poison petrol concoctionI am expecting to be able to avoid that detonation and retarded advance in mid range. I am planning to use the cycle X 4 seperate coil ignition with programmable curves. I dont know how good they are yet as I havent heard any feedback from the forum about them but I hope they do the job. I am a bit of a fan on the individual spark and I agonised over wether to run a good old fashioned maggy or the new fangled electronic stuff. I chose the new fangled stuff based on it was more aerodynamic than the ol ARD mag

I also agree with you blokes about reducing 5th and using the sprockets to get what you need but with the Honda 750 I'm not aware of any 5th gear changes available only 4th hence I have been thinking just get 4th how I want and run in 4th only and use the sprockets to get what I want like you blokes

I'm in unknown territory with this type of top end action but I have found any overdrive to offer poor or no accelleration and evan though the impression is that salt lake racing you just hold it flat

I still feel the key is the ability to accellerate and I am approaching it like it is the WORLDS LONGEST DRAGSTRIP

cheers Johno

Old Scrambler · « **Reply #89 on:** November 02, 2012, 06:43:19 PM »

If the run is long enough.......the acceleration is mild to eliminate wheel spin. The goal is to get into top-gear and have time to allow the motor to get up to speed and get into your best tuck.

Tintop · « **Reply #90 on:** November 02, 2012, 07:42:57 PM »

Agreed johno, OD sucks for performance, it's designed for fuel economy and lower revs at cruising speeds. Contact / PM bwaller, or Sam750 about gears, they know a guy in the UK who can make just about anything you'd want. BW got one or more made for the 360 six speed he put in his 550 racer to make it a close ratio. You would only need one gear to close up the 4th / 5th spacing. Stock CB750 4th is about 1.1-1 & 5th is .94-1, a Nova 4th is 1.06-1, 5th is .97-1. I run a .98-1 5th in the sidecar, with stock 4th (XS engine).

Quote from: Old Scrambler on November 02, 2012, 06:43:19 PM

If the run is long enough.......the acceleration is mild to eliminate wheel spin. The goal is to get into top-gear and have time to allow the motor to get up to speed and get into your best tuck.

From what I understand about land speed, that's the key.

754 · « **Reply #91 on:** November 02, 2012, 09:11:13 PM »

Late 750s have different gears to the sprocket shaft, may or may not help..
My thoughts..pick a gear you WANT to go thru the traps in, then sprocket accordingly..p

Old Scrambler · « **Reply #92 on:** November 03, 2012, 07:39:51 AM »

More than one GEAR-HEAD on this site will know which crank to clutch ratio (they changed) and tranny gear selection is available.............Frank is right about getting the most powerful motor rpm to match the desired speed just before you enter the trap. At Bonneville the trap is 1 mile long.........if you can get up to FULL speed JUST BEFORE you enter... and HOLD that speed to the next post............you will have accomplished something. Your timing-slip will show the results.

This calculator has helped...... http://www.rbracing-rsr.com/gearspeed.html

If the flat-spot in the power-band is just below the motor rpms as you engage top gear.........great.........if its higher, I don't think gearing will help to pull through it unless you are willing to settle for a lower overall top speed.

bear · « **Reply #93 on:** November 03, 2012, 08:34:50 PM »

Tracked down cases if your still looking mate.
Give me a ring.

Cheers,
Brian

bear · « **Reply #94 on:** November 29, 2012, 08:38:17 PM »

How is the Salty going Johno?
Any luck with the cases?

Cheers,
Brian

johno · « **Reply #95 on:** December 02, 2012, 03:31:45 AM »

Hi Bear,
Been feeling a bit like you lately, havent been able to walk for a couple of months, just starting to hobble around this week. Nothing as spectacular as a bike prang, was looking for a shipping container to set up as a base during race week and was on top of the container checking it out and decided the ladder was too slow to get down , the ground looked soft so I jumped. Wham bam ! two torn fascia plantis ( I think thats how its spelt) Moral of the story " old fat men shouldnt jump off containers"

Got a taste of feeling like an old man, it sucks. Screwed my head up a bit and got lazy, it has cheered me up getting into the shed this weekend though, the ol schedules looking a bit dodgy, I'll know more by xmas,
If there a few blokes going from the forum I will throw something together, got to have an excuse to go ! a few weeks ago I thought about getting an electric gopher and putting a bigger KW motor in. LOL

I am going to run with the cases with one ignition mount missing and I have managed to get another complete engine which I will save for the big motor next year.

Should be able to start working in the shed now so will keep the thread updated.
ciao Johno

Bill/BentON Racing · « **Reply #96 on:** December 02, 2012, 08:37:27 AM »

Need a tank,have plenty,let me know.Bill

Flying J · « **Reply #97 on:** December 02, 2012, 11:57:38 AM »

Subscribed,

sohc boy · « **Reply #98 on:** December 02, 2012, 02:31:51 PM »

Johno , what were you thinking jumping off a container ? shouldv'e had your "ACME "old bloke jumping off container automatic deploying safety parachute fitted ,as you know talked to Bear about using his big mota in a bike , so if you dont have yours done we may have somthing to run , if not we just go anyway , have some time off, watch racing,drink beer ,tell stories ,more beer ......

pete

bear · « **Reply #99 on:** December 02, 2012, 06:22:19 PM »

Quote from: sohc boy on December 02, 2012, 02:31:51 PM

Johno , what were you thinking jumping off a container ? shouldv'e had your "ACME "old bloke jumping off container automatic deploying safety parachute fitted ,as you know talked to Bear about using his big mota in a bike , so if you dont have yours done we may have somthing to run , if not we just go anyway , have some time off, watch racing,drink beer ,tell stories ,more beer ...... pete

I'm definitely up for that.

Have we got dates at this stage?
Johno jumping off a container? You idiot

I have a good set of cases I've been hording, that I haven't converted yet, if your up for replacing them later their yours.
Anything else I can help with? Give me a buzz.

Cheers,
Brian

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Author Topic: Salt Racer CB 750 OZ style (Read 168540 times)