Reeds??

[girlsbike]

I understand what they do,but how does the condition of the reeds effect bike performance.What is the difference "torque" reeds and others.How does the reed tension and stiffness effect power.
The reeds in my bike look good but i'm wondering if they loose tension over time and change power.

 

[David Trustrum]

Generally speaking fibre reeds -unless they are delaminating or fraying, need not be replaced until they show such wear. I have home-made some which I believe did get contaminated probably due to unsuitable resin & they did seem to go off but I doubt that will ever be a problem to you.

Reeds are an excellent aftermarket product to sell. They are relatively cheap to make in quantity & easy enough for the owner to fit but hard enough (& sold expensively enough) that they have ownership in the job so they are likely to ‘feel’ an improvement. The alternative is you have just spent a sum of money & time for no benefit, which is often largely the case.

A particular engine prefers a given thickness of material to match the size of reedblock & carb etc. The reed stops are matched to this so the reed operates within its limits. You can rest assured that the stock set up has been carefully chosen.

 

[canyncarvr]

They do lose tension over time. That's indicated by them being 'sprung'..not seating on the reedblock 'at rest'.

So, it takes back pressure by the piston to close them instead of them tending to close themselves. That effect is going to be more pronouced on the bottom end than the top just due to the speed of things happening.

The stiffer they are, the harder they are to open..but the easier they tend to shut. That would tend toward a good thing for hi-rpm operation.

Conversely, a reed that opens easier (but by that nature would tend to stay open, too) will tend toward enhancing the bottom end.

The more 'petal area' you have, the less they have to open (and flex) to get the same amount of 'air' through. The less the petal opens, the sooner it can get back to where it started (closed).

THIS sounds like a good workup for a combination of lo AND hi rpm power!

Enter the DFII!!!
:)

 

[David Trustrum]

Quite.

The problem with reeds is that they form an obstruction to the inlet port. The reed-block by nature is an obstacle impeding a straight constant-speed passage of air movement. Worse -as you have just done all this fine work upstream in the carburettor, atomising the fuel in an attempt to produce a suitable mixture to provide flawless combustion over a wide rpm range;

& then the mixture splats into these flat reeds like a bumble bee on your windscreen, the fuel falling out of suspension of the gaseous mixture into wet drops so you have to jet up to produce the correct mixture. Direct Fuel Injection would remove this problem as well as clearing up emissions. (When I come up with something better I’ll let you know :cool: ).

Of course with the FIM banning its use at road race GP level, development was not a priority for the factories. So now our future lies with fat farty four-strokes. Boo.

CCvr. Point taken about the curly reeds. It’s been so long since I have seen any like this I’d almost forgotten about that. I do wonder how much mixture is really lost as the pressure build-up will be pretty quick & in the same way that a piston rings tension is not a real contributor to the seal it creates I suspect the same applies. Course I have been wrong before.

Once.

And that was disproven. :p

 

[canyncarvr]

Agreed.

Seems all kinda silly, don't it. .....the 'splatt' part?

All of which could be reduced by reducing the º the reeds present to the incoming charge.

Maybe TWO blocks stacked on top of each other?

ENTER THE DFII !! :)

heh heh......

I think there is considerably more pressure on a ring from combustion compared to tension on that ring than there is on a reed by virtue of piston displacement vs: the incoming charge.

You get a good HP boost losing some tension on oil scuppers. As long as you're building a motor that you're going to be changing the oil in every 1/2 mile...who cares if you blow some by? ;)

Yeah...that's along the line of:
'I've never made a mistake. I thought I did once, but I was wrong.'

 

[Tom Ludolff]

Can you get a decent low end boost or low & high end boost by just replacing the reeds in the stock block? This would be much cheaper wouldn't it?

 

[canyncarvr]

If your reeds are 'weak', meaning they could well stand to be replaced, you will get a decent 'boost' by replacing them......period. That applies to using oem reeds in the stock block, too. Might as well use something along the line of boyesen 607 power reeds on the stock block as long as your replacing stuff.

Cheaper? Yep. Likely 20-25% of the cost of an aftermarket replacement assy.

If you want your bike to run as well as it can, might as well apply that 20-25% to a new valve if you're going to end up with one anyway.

That doesn't make replacing the reeds on the stock block a BAD thing! They're consumable items! They need to be replaced just like your tranny oil does. It's just the cost of 'doing business.'