Featured Land Speed Racing 2023

th eway a relative air density meter works is that it saves you having to call a weather station for the local uncorrected barometric pressure and then using that and temperature to calculate air density.

your carburetters meter fuel based on the velocity of the air that passes the through the venturi, whether its at the two little ports under the slide edge or at the top of the needle jet where the mixture from the bowl emerges. your carburetters measure fluid velocity, not density of the fluid. so the pressure drop across the top of the needle jet where it protrudes into the venuri is what meters th efuel. theres different shapes and heights of this very interesting part of the carburetter which are important because as the slide lifts, th eposition of maximum intake vacuum lifts as well. the shape of this machined part of the needle jet interacts with the lifting of that minimum pressure point, so it can be high, low, or cut at an angle.
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anyway, th epoint is that the jets in the carb see fluid velocity, not denisty, so if th ethrottle position is the same but density is less (like if you go up a mountain) then th emixture will become rich. ditto if you do the same but go to a lower elevation thatn what your machine was tuned for.

so you can use the RAD meter to display the actual air density, which is what you need to use to jet the carburetter and set the timing. th emeter has a little aneroid bellows in it like an old timey radiator thermostat, so it combines the effects of pressure and temperature.

my unit is arbitrarily set to read 100 percent at ordinary standard temperature and pressure, STP. when i go up a mountain, it might drop to 95 or 90 percent. when i go the beach on a cold day, it might read101.

when a high pressure system blows over the race course in the cool morning, i have seen the meter rise to 108 percent. when that happens, you jet rich like croesus, and hound the organizers to start the running before the day warms and the density falls. the denser the mixture, the faster you can go, if you tune for it.

if you ignore air density and just leave the jets the same, you will be slower than you could have been.

the fastest times are the ones with the highest RADs, all other things being equal.

what i do is watch the merter over the course of the day. i dont need to do anything until i see a change of around 5 percent, but when i do see it, i jet accordingly.

modern machines dont care about measuring RAD, because the fuel injection systems have engine mapping technologies that take the manifold air pressure and intake temperature into account and change the timing and t he injector pulse width automatically. but if you are running with the dinosaurs, the only ECM you have is the one between your ears, and you need to do the thinking for yourself.

 

loading up. the one accompanying offspring is not riding, but we need a pit bike. he wanted to bring tbe death trap, the little 1971 honda cl100 with original worn out fish oil suspension. got it running after he left the petcock on and filled the crankcase with gasoline. he took it out and came back horrified at its idiosynchracies. luckily hes had the 250 ninja to compare it to. the ninja itself is 16 years old, buts its still 36 years newer than the honda.

so the next candidate came out with fresh fuel and a charged battery



this 1969 BSA thunderbolt runs well and just needs somebody riding it to work out the kinks. i bought it almost 10 years ago non-running, rewired it comletely last fall with stock components from british wiring, and then installed a boyer i had from somewhere. still awkward to start because i have nt run it enough to know what it likes, but when you get it right it fires up immediately and idles smoothly.

its a stock 69 except for the silencers and a later tach. i was going to replace them, but then said, who am i kidding ? 1969 is long gone, and the 70s silencers and tach are working just fine.

so the boy took it out and came back alive with an approval. its a go.

right now im filling up the tool chests to make sure i bring what i need.

i paint the essential oddball tools blue so i dont leave them behind. with the weird junk that i run, i need metric, whitworth, and SAE spanners, and even then unusual sizes.

this is just one tool box,. i carry three, and then three bath tubs with spare parts.

 

im low on C12 fuel, the MON 108 (british) RON 116 (stateside) 112 averaged octane level fuel ive been ruinning in this machine. i have a full five gallon can and then another that is composed of two opened cans from wearlier. C12 is pretty volatile, so ill use the open can in the BSA.

i get three runs out of my 5-litre tanks before i have to refill, so i have four fills or twelve runs before i run out, if i use the open can in the LSR

but i still have four cans of the infamous Q16: MON 116, RON >120, average octane 118. this is a the oxygenated (methanol -laced) nasty poisonous stuff i tried to run last year that didnt help. but it didnt hurt, either, and now i know what the jetting is for it. so when i run out of C12, ill jump from 160 to 195-200 mains and keep running. i already tried changing the spark timing for the Q16 and didnt get anything, so ill keep it at 30-31 BTDC.

fuel is an issue because im running high compression and the prehistoric triumph combustion chamber. to get 11.75 to 1, i have to have domes as high as st pauls, and that means i have a serious obstruction at overlap. i compensate for the dome by using two spark plugs per cylinder, but its a fix that helps combustion, not mixture distribution.

darkman has suggested the old-style TT pistons-- 11 to 1. somewhat lower compression but cleaner domes and so a much better mixture distribution. im wondering about that. everything is a tradeoff this high up in the horsepower range, but im thinking that that when i wear these pistons out (and theyre about due, with maybe 300 miles on) that i might try the lower compression and a more advanced spark. after all, these pistons were used successfully all through the 1960s with these motors. with newer springs, i dont know where ill be. my competition runs lower compression, except for a BSA guy that has 14 to 1. but he's up in 750, so i dont worry about what he does. hes faster than than shit tho. he's been tanking his transmission for years, but this last july it all came together and he took his exquisitely built BSA to 142. very, very good.

so we'll see.

i have to fetch the teenager and get him to help me load the trailer. he's 18 years old, with a reversed day/night cycle. but its afternoon, so maybe he's finally awake.

 

we ll just have to see, bud. really, the only serious change is to a more consistent electronic ignition.

but im thinking of radically changing the chassis over the winter: hardatil, lowering with the 17 inch wheels and no shocks.

maybe that would get more out of the wind. im the only one in LSR running a triumph with a swing arm.

ive decided to run just the Q16 fuel, not worrying about the C12. thats one less thing to be thinking about.

 

but we ve arrived in maine, and will go to tech tomorrow in the morning after we set up. then maybe some runs in the afternoon, hitting it hard the morning after

 

yes. ive been running 020 on the plugs, compared to a stock setting of 025.

with a plug gap of . . . i dunno . . . 028? ill have a larger initial flame kernel, which is like advancing the spark without the consequences of detonation, aiui. i have a friend who would open em up to 35 or so. and he went 134.

ill start with the same 30 btdc, and see how it works. i tried 28 and 27 btdc with the Q16 fuel and got either nothing or less. but with the cleaner ignition i might di better. certainly is much easirr to set the ignition tonthe earlier timing accurately

andy at pazon in new zealand recommends setting the ignition at 34 BTDC (compared to 38 stock). but you know, none of this is fixed. the only way to know what the motor wants is to try out different settings, and it will tell you what it likes. sometimes its easy to make these changes, like with jets and timing and exhaust pipe length. sometimes its not so easy, like with cam timing. but the only way to know is to test.

 

got to the race course

1080-something miles.

its pissing down rain here



nothing has happened today nor will it. we ve just looked at the satellite images and it aint getting any better

 

that building in the distance is a hanger that holds two complete USAF B-52s, complete. the building is immense.

its at least a quarter mile away

 

shit fire wee're back. some 2500 miles of driving to get there and get home again.

lots of stuff there. the fastest motorcycle was a 240 mph hayabusa. dont recall the fastest car. well over 200. the record there for bikes in the standing mile is 311, and for cars its 265.

 

shit i give up on pictures. its just too slow and awkaward to upload from my phone. i dont have issues anywhere except here,.





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wednesday was rain, and thursday there wasa 20 mph headwind. terrible. all day.

anyway, the triumph wopuld not pull over 6000 rpm in fourth gear, which was about 105 mph. nothing i could do changed that. changed jets. no. changed fuel from Q16 to c12. no. tried different plug gaps. no.

th ebike would rev freely to about 5500, then begin to break up. if i held it open i could 6000, a ragged top end. sometimes it would slow to 3500, as if there was a fuel flow problem.

but i popped of the carb drains and opened the petcocks. the fuel poured out of the 3/8-inch taps, so no problem there.

i suspect either the pazon transistor box is bad, or one or both of the coils. i dont know how to tell whether a coil is bad, if it works sometimes and not others.

but a friend of mine from oz is sending me an ignition he makes. hes an old engineer, and all i have to do is get a machinist to make me a rotor. no waste spark, so it fires two sides separately, has an adjustable rev limiter and adjustable spark curve (by him). working on that now.

but in spoite of the headwind, the bike would still do the ton, so i said to the boy

want to ride it?

and he did. slow. 78 mph.

i said, this isnt the 250 ninja. open the throttle in first for five seconds. there will be reversion at 3100, and the bike will burble and misfire. hold it wide open and at 4100 it will clear. shift into second at 6000, then hold it open until it wont go any faster to shift into third.

he tried again, but didnt believe me. slow again.

then on th ethird run, he held it open through the reversion, and i could hear the motor catch. a good run. 100 mph.

he came back and said

when it gets through that it really acclerates. it almost threw me off.

yes, i said.

thats how it works. if youre not hanging on when the motor clears the pipes, you can be in trouble.

so we're back again, and im contemplating other changes besides the ignoition.

but thats it for racing for 10 more months. just wrench work until then.

 

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we came back in the morning and the wind had destroyed it.

if you tie it down the wind pulls it apart.

if you dont it isnt there when you look next.

but a new tent every three years isnt bad. if i had a closed trailer we d just use thst

 

we ll see. most important is to solve the ignition