Motorcyle Racing Engines (antique)

[Keith Morganstein]

I'm wanting to learn more about antique motorcycle racing engines.
The board track racing engines 1910's through 1920's are particularly interesting to me. They seem to be quite advanced in some ways. 4 valves per cylinder, some OHC of different designs. Some with full pressure lube systems.

I'm amazed at the speed these boardtrack racers were achieving on these machines. Average lap times over 100mph.


Also very interesting is some unusual mods done to the engines. They seem to have been very concerned with getting the exhaust out of the cylinder, but go about it by drilling extra exhaust ports through side of the head, drilling holes in the bottom of the cylinders. There is fire coming out of all of them.

I know from some Indian motorcycle ad copy (Indian sold factory race bikes), the engines were sold without these extra ports.

I don't know if these engines copied airplane engines of the time, or were unique to motorcycles. Anyone on here have more knowledge or know where I can learn more?

Here is a couple of videos, lots more of different makes running on youtube.

https://www.youtube.com/watch?v=4Dl_kJZuO1Y

https://www.youtube.com/watch?v=TfEZyCccKTs

[PackardV8]

That's a new old one to me.

So, do we think the holes in the side of the head are drilled into the exhaust port to which the exhaust header is connected?

FWIW, call the Barber Motorcyle Musuem in Birmingham, AL. http://www.barbermuseum.org/ Not only the world's largest collection of motorcycles, but much literature and history as well.

[engineguyBill]

For information on this subject, contact Dave Reed at Otto Gas Engine Works in Elkton, MD 410.398.7340 He has tons of information and parts fro antique engines.

[panic]

The genesis AIUI is the board track IOE racers of the twenties, which had 1 or 2 cylinder ports for auxiliary exhaust. Nice advantage, being able to completely drop the cylinder pressure to ATM at BDC - reduces cylinder temperature, reduces the pumping load from BDC up, and extends the work cycle later in the downstroke without pumping loss.
However: these bikes ran on or off, low vacuum or closed throttle - no mid way.
if you ported the cylinder, what would prevent air from entering at BDC on the intake stroke where there is generally unsatisfied vacuum?
This would be harmless (except for the local temperature problem: intake and exhaust using the same port) at full throttle, since you could just play with mixture to compensate.
But... at part throttle, a huge percentage of charge would be pure air, and almost impossible to compensate for since the regulatory factor (engine vacuum) would be missing. An EFI en-gine could adjust based on a UEGO or knock sensor but IDT a carburetor could do it.
If there were a way to effectively close it off except at full throttle it might work, but that area typically doesn't have much metal to work with (since there's not much cylinder pressure). Perhaps a stub leading to a solenoid, long enough to drop the temperature a bit? I'm not sure if I would want it to join the exhaust, since that means that the intake stroke would pull in exhaust gas at BDC.

[Keith Morganstein]

The extra ports in head, look to be drilled into the exhaust port alongside the exhaust valves. I guess the engine designers may not have worked with exhaust scavenging and intake charge ram effect at the point. I wonder about cam timing events in those engines.

The ports in the bottom of the cylinder are more intriguing.

I'm not so sure any fresh air get back in to the combustion space, it would allow fresh air in to cool the cylinder and underside of the piston. At first I thought the ports were so low, crankcase venting and cylinder cooling was there purpose. However, the "night video" is pretty clear that combustion is present at the ports.

Panic presents some point to ponder, including they may have thought it a good idea to drop cylinder pressure to ATM at BDC.

I did read that board trackers often ran with the throttle pinned wide open, only using the ignition cut out for speed control. (Add direct drive (no clutch) no brakes, no susp, crap tires, Well over 100mph top speed, must have been a wild ride. At least the road race versions had a throttle, clutch and a brake.)


I'll have to follow on the resources suggested.

[pamotorman]

may be they serve the same purpose as the windows in the LS block for getting rid of cylinder pumping pressure

[Keith Morganstein]

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repop head 4 valve, unusual one larger valve, not much chamber.

[Keith Morganstein]

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[Keith Morganstein]

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Spark plug in the cylinder.


Other makes of these racing bike are as interesting and many have the ported lower cylinders (the repop above are stock not ported)

There seems to be more info about the Indian eight valve to study

[grandsport51]

All the antique engines both car and motorcycle are fascinating

you are correct mechanical details do not abound but last year I found a fascinating blog

http://dlmracing.blogspot.com

I found the construction of a replica HD 1921 engine and complete bike fascinating episodes 8 and 21

along with the old movie footage of the HD factory team at Daytona on the beach in 1920 fascinating!!

Great Subject

Dave B

[grandsport51]

Just found this you tube video which shows individual exhaust headers on each valve on HD 1914 8 valve racer

Really Cool

Dave B

[grandsport51]

Oops link didnt post
https://www.youtube.com/watch?v=hedv8RGcvMQ

[Geoff2]

Yup, there were some clever people & engines around in the early days. Some of the ideas have been refined/improved for today's engines.

The Rudge engine with two exh valves...
H-Ds, needle roller lifters in 1929...

[MotionMachine]

I've bored/sleeved a lot of JD Harleys and made a fixture to do them on my CNC. With the same fixture I've bored some Ace and Excelsios's also, all blind cylinders. What surprises me about all of them is how square the base flange is to the bore, they indicate extremely close top to bottom.

[Keith Morganstein]

image.jpg

Interesting patent drawing for a Harley four valve racer. The valve angle would suggest a hemi type chanber. The lifters look like a roller with lever or finger. Cams have a lot of high lift duration. I've found no evidence of lower cylinder porting on these. It seems in this design, they were more aware of airflow and scavenging.