Topic: Salt Racer CB 750 OZ style

[Old Scrambler]

We are at the same (but you have an actual cash budget) dilemma.  I have yet to purchase the cam but am leaning toward the KH-F. My thoughts are that it is NEXT to the most aggressive so it should be easier to get the carbs and ignition tuned while on-the-salt.  You won't have a nice clean bench with every possible tool at your fingertips when your on the salt. A jet change with a wind-blown grain of salt makes for real precise tuning. Its even worse when you open the case-cover to check the ignition. We always roll the bike into the trailer for those exercises.

Your challenge is somewhat below sea-level..........I have to be ready for 4,000 or more feet up the hill.

We are in the same RPM range but if all is spot-on, I think a few more Rs can be expected.......especially with the best A/F mixture. Your 10% wheel slippage is not likely.....and then only if you have more horsepower than needed.  After listening to dozens of comments about slippage, its usually the BIG HP or TORQUE guys that have trouble getting the power to the ground.  When you are running at or near max speed AND power, you are likely to have the best traction.........assuming your tire contact-patch is steady.  Getting up to speed may be the SLIPPERY part..........especially if you grab sudden power

Let me know if you want to part with that KH cam.............I am hesitant to buy used without knowing the source. New units are available.

[cbornotcb]

Stay with safe Johno, there's always next year 
Or, be like me (twice) dnf, no time 
Get your head into the gearing calculator and make sure you don't drop below a "usable" amount of ponies when you change up, take a few gearing options, you can always change that mate.
         The seasoned non performer
Tiny

[bear]

I know sweet FA about this salt caper mate, but I'm with Tiny.
Our motors don't like a lot of duration.
Go for the high cylinder pressures, they like that.

Cheers,
Brian

[scottly]

I'm with bear and Tiny. A cam acts different on different size motors. A cam that works well on a 1000cc motor may suffer with a 750cc motor. Any chance you can get the bike on a dyno? It would provide valuable information regarding gearing.

[johno]

Hmmm, Well sounds like a consensus here, Megacycle 125/75 it will be, it will be the first time and I dont want Pete snake arsin all over the salt and dnf. Although I am sure he would love a good tank slapper just to get his adrenalin rush.    I think just getting there and I would like several runs to sort the gearing out etc , tyres , weight balance etc.

Well I phoned my main competitor today Finny the suzy man had a really good chat and he is most helpfull for a green horn like me. ( feeling a bit guilty about trying to beat him now  )    I'm sure he is feeling confident having a reasonable HP jump on me and so was real helpfull. It was nice to talk with someone with a 70's 750 same class.
Finny has run several times, has had a lot of gremilins to sort every trip but pulled it off last year with the record.

Regarding wheel slip he said he purchased two cheapo cycle speedo's and put on front and back, on his best run at 150mph the front was at 149 and the rear was 153, so not much.  He was carrying 30kg ( 60lbs ) of lead ballast on his swing arm.

His first time on the salt he had stock 19 inch front , forks stiffened, not raked and swing arm extended 160mm.
Handling was periods of weird vibration through the bars.

Second time on the salt stock 19 inch front , replaced stock forks with suzy dirt bike for more trail, stiffened them up heaps, same swingarm, Handling was big weaving action

Third time on the salt he run same set up but with smaller 17 inch front to reduce the trail by half and he said it ran straight and true at 150mph.

His max RPM was 8,100 with 18 inch rear conti,  17 front sprocket and 43 rear sprocket, took smaller rear sprockets but didnt need them, run AVGAS which I think may be part of his relibility problem, had foam aircleaners but not oiled and had no salt dusting in the carby / port.

So what do I take out of this chat ? stick to my plans with the exception I'll make up another big momma heavy swing arm out of 6mm RHS filled with lead, it will look real ugly but everyone seems to do it.  I am surprised at his RPM, I thought he would be doing more to get 110 hp.
So there are nice people in the world

[Powderman]

I'm with bear and Tiny. A cam acts different on different size motors. A cam that works well on a 1000cc motor may suffer with a 750cc motor. Any chance you can get the bike on a dyno? It would provide valuable information regarding gearing.

I don't know of any other way to accurately figure what gear to run unless you have dyno'ed and know where you are making peak power. Once you have that you can figure exactly what speeds you should be running at any given RPM. Then you just need to try and figure in the Aero factor.

[Retro Rocket]

Third time on the salt he run same set up but with smaller 17 inch front to reduce the trail by half and he said it ran straight and true at 150mph.

Just a word of caution Johno, the 750/4 has a low trail figure to start with, its under 4 inches which is quite a small number by todays standards, reducing trail will make for a more twitchy,  nervous front end, something I wouldn't want at 150MPH.  Just as an example , My old GSXR1100 had a trail measurement of just OVER 4 inches, nice and stable at 150..
Most straight line bikes like drag bikes have trail well over 4 inches for straight line stability, thats the sane reason choppers like the highway....

[cbornotcb]

When we designed the
V8" bike, we went for 37 degrees, and 10mm of trail, it want like an arrow @ 150 mph (mind you, it was 6 mtrs long !
Tiny

[Retro Rocket]

When we designed the
V8" bike, we went for 37 degrees, and 10mm of trail, it want like an arrow @ 150 mph (mind you, it was 6 mtrs long !
Tiny

I'm not too sure where you are measuring your trail but 10mm is dangerous , especially at high speed, also the fact that when you brake you also reduce trail, the less trail the less straight line stability and bump steer becomes a major factor which is highly dangerous at high speed , sure it wasn't 100mm...?  This is of course using conventional forks...
I just did a quick google and it seems most LSR guys use trail between 4 and 7 inches {100mm to 180mm} to reduce bump steer and aid straight line stability
Here's a couple of links explaining it..

http://www.seegercycle.com/Rake-and-Trail.aspx

http://www.stripbike.com/rake.html

[Tintop]

I only run about 6mm trail on the sidecar RR; but it uses Earl's type forks, and is setup for quick turn-in.

[bwaller]

My case is an example of what RR mentions. To help it turn in I decreased rake from 26 to 24 degrees which reduced trail from 105mm to just under 89mm....big mistake. Eventually it led to a lock to lock tankslapper and a huge crash that didn't end well. I'm not sure why it would be different in a straight line on the salt.

[Tintop]

I was speaking with Denis today Brent, stock 550 rake & trail was what he was trying to establish.  See you at the AGM.

[Retro Rocket]

I only run about 6mm trail on the sidecar RR; but it uses Earl's type forks, and is setup for quick turn-in.

Hi Brian, totally different animal mate....

[Old Scrambler]

Johno..........Always open to better ideas............as of now I plan to use a stock CB triple-tree with CB550 tubes in F2 legs with a 19-inch wheel........no brakes.  The shorter tubes may be topping the upper-tree by a half-inch or so. The internal dampener-rod will be shortened an inch or more.  The 110/90 tire also lowers the stance. All of this should lower the overall neck-height by 2 or more inches and will have a negative affect on trail.

To effectively increase the trail to stock or better, the rear of the frame as measured at the swing-arm pivot will be lowered by 2.5 or more inches.  Changes to the shock-angle, a 4-inch swing-arm extension with an angular weld-attachment, shorter shocks, and a low-profile tire all contribute to the lower bike. We are limited by exhaust clearance but NO CORNER clearance is required.

BTW...........The water-bottle rider will be fortunate to stay in the race with that front-end combo

Basic handling and suspension tells us to reduce un-sprung weight in an effort to keep the tire in contact with the earth. I know you plan on having a somewhat light-weight rider, but I would concentrate on a front/rear balance with the rider in the crouch position.  The rider can shift weight to the rear by applying foot-pressure to the pegs.  More than one Bonneville rider found traction and speed by standing on the pegs with his/her head on the tank

[bear]

I only run about 6mm trail on the sidecar RR; but it uses Earl's type forks, and is setup for quick turn-in.

Hi Brian, totally different animal mate....

Yep................your right there.

Cheers,
Brian

[cbornotcb]

When we designed the
V8" bike, we went for 37 degrees, and 10mm of trail, it want like an arrow @ 150 mph (mind you, it was 6 mtrs long !
Tiny

I'm not too sure where you are measuring your trail but 10mm is dangerous , especially at high speed, also the fact that when you brake you also reduce trail, the less trail the less straight line stability and bump steer becomes a major factor which is highly dangerous at high speed , sure it wasn't 100mm...?  This is of course using conventional forks...
I just did a quick google and it seems most LSR guys use trail between 4 and 7 inches {100mm to 180mm} to reduce bump steer and aid straight line stability
Here's a couple of links explaining it..

http://www.seegercycle.com/Rake-and-Trail.aspx

http://www.stripbike.com/rake.html

OOPS minor typo,,,100 mm , that sounds better.

"when you brake you also reduce trail"
Not in the V8 bike case,,rigid front, and ass end

[Retro Rocket]

When we designed the
V8" bike, we went for 37 degrees, and 10mm of trail, it want like an arrow @ 150 mph (mind you, it was 6 mtrs long !
Tiny

I'm not too sure where you are measuring your trail but 10mm is dangerous , especially at high speed, also the fact that when you brake you also reduce trail, the less trail the less straight line stability and bump steer becomes a major factor which is highly dangerous at high speed , sure it wasn't 100mm...?  This is of course using conventional forks...
I just did a quick google and it seems most LSR guys use trail between 4 and 7 inches {100mm to 180mm} to reduce bump steer and aid straight line stability
Here's a couple of links explaining it..

http://www.seegercycle.com/Rake-and-Trail.aspx

http://www.stripbike.com/rake.html

OOPS minor typo,,,100 mm , that sounds better

Thank f%#K for that, you had me worried there for a bit....

[MRieck]

Johno should have the head in his hands in 7 to 10 days.

[cbornotcb]

Johno should have the head in his hands in 7 to 10 days.

That usually happens just after a massive engine failure ?
Tiny

[Tintop]

Johno should have the head in his hands in 7 to 10 days.

That usually happens just after a massive engine failure ?
Tiny

Is that 7 to 10 days to stop the crying & clean up all the oil??

[MRieck]

No jinxing guys

[Tintop]

No jinxing guys

All ladders safely stored, and the black cat has a new home.

[johno]

Some pics of lightening the crank, dam bald patch gets shiny under the light
just copied what everyone else does, Ape , cycle X etc.
I done two, one std just angle machine the counterweights,   the other I have copied cycle x flying chop milled wedge shape counterweights,   I'll toss a coin to see which one goes in.

[johno]

cross feed is manual so lots of winding, went in at 10 deg , about 4 to 5mm on edge of counterweight removed,
used a 20mm boring bar one way then turned the boring bar upside down and reversed the lathe to do the otherside.

Been  while for me on a lathe so started .010 cuts , then .020 cuts the , stuff it too slow then .040 (1mm) cuts ...ah thats better.
johno

[johno]

I had the cases aqua bead blasted, outside looks awesome but one thing........this will be the last time I ever do it.
the galleries were just full of the glass #$%*, no matter how much detergant I used and pressure cleaners etc it didnt float the #$%* out.........I kept thinking of H2 Eric result.

Notice the plug the glass build up.
Simply if there is a dead end gallery you will not get it all out,   I got 2 out of 3 plugs out so far so I will drillt he last plug out cos I wont risk the beads.