For today's regular dose of bike talks, we will explore a valve train set up on early 4-stroke motors termed intake over exhaust or IOE. IOE systems had been famous at the turn of the last century and exist on many motorbikes up until the mid-1930s.
For an IOE engine, the pipe valve is placed near the cylinder, as on a typical flathead engine, which is opened up by a tappet. The lifter is taken care of by the engine's camshaft with a lobe, then forces the valve up after which lets the valve springs to move the valve down. An IOE air intake valve is located right over the exhaust valve and may be operated several other ways.
The pioneers in motorbike engines have atmospheric intake valves, which is a pretty smart deal in comparison with modern intake valves. Rather than having a push-rod or a lifter open up the valve, this design uses a low valve spring. When the piston flows straight down its cylinder on its intake stroke, the pressure section built up in the cylinder opens up the intake valve. Once the piston shifts the other way around the cylinder, the drive in the cylinder rises, and the weaker stress of the spring can yank the valve closed up from its seat.
The intake valve setup on a single-cylinder motor engine is enough at best if all things are in working order, but has some issues. In case the spring has too much or too little tension, the motor will not likely work correctly along with the air-fuel mix will probably be inaccurate. When companies began testing multi-cylinder machines, a mechanically controlled intake valve was necessary in order to eliminate some aspects from the valve timing.
In 1908, Indian twins had a mechanical intake valve that utilizes the very same tappet as the exhaust valve. This design has drawbacks and was a deal that took just a year. The following year, the exhaust valves once again had their particular tappet, and the wigwam included a tappet for the intake valve. This particular has a push rod within it that enters into a rocker arm on the top of the cylinder head. The rocker opens the valve when it's time to bring cleaner air and fuel mixing into the motor engine.
Indian used this setup on its twins when it came out with the Powerplus motor. They extended to make use of the IOE setup on its fours until 1935. Couple of years later, Indian switched the setup making it an exhaust over intake (EOI) setup instead.
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