MOPED ARMY

The general consensus is that metal reeds are bad because they break off and ruin your cylinder. However, when you switch to carbon fiber reeds, you have to decide on reed thickness. From what I’ve read, stiffer reeds work well at higher RPMs (because they reduce reed float/flutter), and thinner reeds work better at low RPMs. Is this similar to gearing, where you just have to choose acceleration or top speed?

Yes to some point it is the same

On a related note, what about dual stage, or multi stage reeds? They would seem to solve the problem of choosing one thickness of reeds, but I haven’t heard much talk about them, other than people simply stating that they are running them.

True multistage stage reeds give you a little more performance in everything under WOT and you can see how ni this picture

they arnt dual stage reeds!

dual stage reeds (such as the boyesen ones) have a thick reed on the bottom with a hole in and a thin reed on top that covers the hole.

the thin reed opens easily at low rpm and therefore gives you good throttle response/low end and the thick reed, on the bottom, takes over at high rpm when there is enough air flow and allows you to run at high rpm with less risk of reed bounce

My experience with Boyesen reeds was not a particularly good one. But from what I've read, my case was an anomaly. I put a set of Boyesen dual stage reeds in my Tomos and, at first, they worked great. There was a noticeable improvement in throttle response. However, after a week my bike started running like crap. When I pulled off the reed cage, one of the petals wasn't laying flat. I tried wet-sanding them slightly and turning them over (which supposedly is a no-no once your reeds have been used). I never could get the top petal to lay flat again. So, right now I have the 4 petal reeds that came with my Airsal kit in, but I have a set of the Malossi carbon reeds that I am going to try this week when I put on my 19mm phbg.

I've read Jennings, but not Bell. I didn't really feel like Jennings really got into reedvalve tech too much, because it simply came later than when his book was published.

I posted this in puchforum as well (with some help from Rodka), and he said, concerning higher number of reeds improving performance:

"More reeds allow a lower lift height, but the same volume of mixture can pass through. And the lower the lift height, the faster it closes. Also the reed weight plays some part in this."

which neatly explains why more reeds are better, especially at higher RPMs.

Elliot, how many petals were on the block where you tried the boyesen on one side, thick reed stock on the other? According to the polini website, the white carbon stock is 0.40mm. A guy on puchforum by the handle of lvs said that 0.3 and .35 work well, but that when you go up to .45 and .5, you lose top end. Perhaps you've found the thickest practical reed stock. Either way, I think the idea of using 2 thinner reeds, and two thicker reeds on a 4 petal setup is intriguing. It's like having dual stage reeds, but without the added fragility.

From what you guys have said, it seems like the dual stage reeds are the quintessential racing parts. They work great for a very limited amount of usage (a race or two), and then they need to be replaced (during vehicle prep for the next race), and replaced regularly.