by uawelder » Sun Mar 25, 2018 5:47 am
Basic 2 stroke Tuning
by Eric Gorr
Think of a reed valve like a carburetor, bigger valves with large flow-areas work best for high rpm power bands. In general, reed valves with six or more petals are used for high rpm engines. Reed valves with four petals are used for dirt bikes that need strong low end and mid range power.
Boyesen Dual Stage reeds have a large thick base reed with a smaller thinner reed mounted on top. This setup widens the rpm range where the reed valve flows best. The thin reeds respond to low rpm and low frequency pressure pulses. The thick reeds respond to higher-pressure pulses and resist fluttering at high rpm. A Boyesen RAD valve is different than a traditional reed valve. Bikes with single rear shocks have off-set carbs. The RAD valve is designed to redistribute the gas flow to the crankcases evenly. A RAD valve will give an overall improvement to the power band.
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So with that being said, the benefits of a rad valve were a secondary consideration for my situation.
Due to the changing elevations and temp's where I will be riding at, I want to install a lectron carb to free me from playing the jetting game. Yes I am aware of the possibility of having to change the needle height in a lectron, but that is a far cry from replacing main & pilot jets.
With the new carb I will lose oil injection and must go to premix. I didn't want to risk air leaks from capping the port on the manifold, so a new manifold is required. I contacted Boyesen to see if they had a Rad Valve set up for the Beta's yet. They confirmed that they had been in production for only a couple of weeks and no info had been released yet. The oil injection removal kit from beta is about $15 less than what I paid for the Rad Valve. When the Rad Valve arrived & I found that it was shorter than the OEM part, that was just icing on the cake.
From my perspective this was a no brainer. YMMV