INDIAN 741, 600cc Metanol-fueled, Supercharged, Bonneville Land Speed Record Special.
A Build Diary.
I'm telling you, visiting Bonneville is totally intoxicating. I came home still high on motorcycles of all kinds, intoxicated by all the magnificent sights and sounds and smells and wonderful people. You know what intoxication does to you - makes you irresponsible ever so stupid and inclined to do weird thing, that seems absolutely brilliant. At the time. Like wanting to build your own Bonneville racer.
Being a romantic old fart - and now an intoxicated one to boot - it had to be an Indian, didn't it? It all seemed 'meant to be'. Immediately after I got home, my friend Allan called to inform me that a 741 engine was for sale in the Blå Avis (local free ad paper) at a reasonable price, and at the same time I got a call from Moen, that he happened to have this frame for sale. The frame was built a few years back by IPE, in a successful attempt to build a 101 look-alike based on the relatively cheap and plentiful 741 engine and trans. Two were made. This particular one had its wheelbase stretched 4”. Who could resist?
So that's how it started: I now had a bare frame and a not-so-complete engine, missing the oil-pump and quite a few other essentials.
...and a transmission apparently not missing any parts.
The engine was immediately
ripped apart (nope; the ”thingy” in the upper left corner wasn't part of
the deal - more on that later).
...and a closer look at the pistons/bores revealed that this wasn't just an ordinary 500cc 741-engine. No sir; this was probably (and hopefully) the worlds first and only 534 (or whatever) cc 741-engine... auuurgh!
After a 2675 hour lecture on Indian engines in which Moen, with great patience and incredible knowledge, introduced me to the mysteries of these splendid contraptions, plans were laid. A complete rebuild was in order and, the stock 741 not being the fastest thing to come ever out of a motorcycle factory, plans were made for a few up-grades like boring to 600cc and something as bit more radical - deciding to throw in a supercharger and a SU carb initially meant for a Triumph I was building. Low-rpm power and high gearing was the way to go to make this thing run a bit faster.
At the same time
it was decided to run this thing on alcohol (methanol), first of all to
cool the engine and secondly for a bit of extra wrooomph. Methanol engines
run surprisingly cool. This is a special set of aluminum Scout heads for
a 45" alcohol burning hill climber. As developed by Clem Murdaugh on his
way to a national AMA #1 champion hill climber in 1940. The clever ones
among you will note the absence of cooling fins.
While engine parts were send off to Moen and his machinist to be fixed, rebuilt and upgraded (more on that later), me and my friend Kenneth started working on the frame. A LSR (Land Speed Record) bike needs to look fast (it all helps!) and as the big monster to fight is air-resistance, one wants to be seated a low as humanely possible, so we built a cowling placed right over the rear wheel on which to put the seat:
Moen was kind enough to lend me a dummy crank case and transmission, and Mads of ALMA fame equally kindly lent me a set of cylinders, so we had something to measure on and fool around with while my own engine was away.
Let's start with the supercharger/blower. Now after a LOT of head-scratching and dead-ends we finally decided how to run the blower. A tube was welded to the engine drive shaft sprocket with a bore big enough to still be able to get the nut in there and attach it to the shaft (tube seen here in mock up is just tack welded on)
...a plug was made to insert in the crank-case
...with a center punch inserted
enabling us to determine the center of the necessary hole in the side cover
...and Kenneth machined a cap for a double-lip oil-seal to keep the oil in there where it belongs
The tube will hold a toothed-belt wheel and the belt will run the supercharger. It was now a small matter of finding a suitable position for supercharger and carburettor
and a mount for the supercharger
was welded to the frame
At the BUB Motorcycle Speed Trails at Bonneville one can run according to, either the AMA (American Motorcyclist Association)-rules, or the FIM (Federation Internationale Motorcycliste) rules. The FIM-rules stipulates that there must be a minimum 3mm thick steel plate shield between the supercharger and the rider. Hence the combined mount/shield.
The next challenge was how to actually get the the fuel from the supercharger into the cylinders. Obviously the original intake was no good so we started fooling around and at one point Kenneth made this fine looking intake
...on which we intended to mount a 90 degree tapered tube bend leading to the supercharger. One reason for coming up with another solution was that one wants a large plenum/intake, ideally around 150-200% of cylinder volume, on a supercharger V-twin, according to all the clever old folks who did this back then.
Victory Library is THE source for advice on blowing an old bike, and I've read a couple of books on the subject: Supercharging Cars and Motorcycles by Maurice Brierley (from the late sixties, I believe) and A Do-it-yourself Guide to Street Supercharging by Pat Ganahl, as well as a few sections from other books.
The blower/supercharger generates pressure-pulses at a certain rate per second. The engine opens up the intake valves at quite a different rate. So you need a 'boost-storage tank', so every intake-opening takes in the same pressure every time and also equally for each of the two cylinders. So we messed around with some straight and bent tubes
...and finally came up with the (obvious) idea
to cut the sides off
...and make two holes and attach two intake tubes leading to the intake
...the weld on the 90 degree tube bend
...and - presto! - a supercharger intake for a 741 is a reality.
...it fits in... just!
...and of course it uses the original nuts on the cylinder nipples.
...and it doesn't look too bad.
Now at the blower-side a straight piece was brutally hammered
...and welded to a flat piece of aluminum with a cutout matched to the blower outlet port.
...then mounted to the blower.
Still need to match the two together with an reinforced rubber-tube and we need to build a pop-up vent. It will be something like this
…basically a washer, held down by a spring, covering a few holes.
The washer will pop up to relieve the pressure should (gawd forbid) something terrible happen; a back fire or a stuck valve etc. With no pop-up; the back fire will have nowhere to go but back into the blower, and will rip the teeth off your belt and, in worst case, things could turn real ugly and blow up your blower... auuurgh!
Next installment: finishing the intake and tearing into the engine.
Main Salt Cracker Page
Links to Earlier Parts of the Story:
8 April, 2009: Presentation.
Indian Land Speed Racing Reading on the VI:
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This is no hi-tech CAD design enterprise. We're talking angle grinder/hacksaw jobs.
Low tech design drawings for intake:
...and it gets worse: plans for gear change system
My first, more or less, complete set of inch tools. This is nuts. Who came up with the silly idea that it would benefit mankind to invent a tool named a ”Twentyfivethirtytwopartsofaninch”-socket???
Trying desperately to circumvent the non-streamlining rules!
The bikes running at BUB Bonneville are divided up into classes in witch you aim to set a record.
According to frame type, cylinder displacement, engine type, age, presence or absense of streamlining devices, forced or naturally aspirated induction, type of fuel etc, you can play around with these parameters and you end up having 1100 classes.
My bike will run in the 650 A-VBF class.
That means max. 650 Cc / Special-build frame/ Vintage / Blown / Fuel.
Vintage basically means the engine is build prior to 1956. Must retain the O.E.M. Heads and cases. Blown mean... yes, blown, and Fuel means I don't have to run gasoline but can run it on whatever I want.
Here's a guy who still (!) holds the record for the 1000 S-AF class (1000cc / Streamlined / Modified engine / Fuel)
Silly bugger dreaming about a record
The engine today 19 May 2009. Test assembly.