Reed valve on the cheap

I recently completed a homemade reed valve setup and tested it for the first time tonight. It is compiled of 100% recycled material I had collected .

The reed itself came out of a discarded homelite Super 2 chainsaw with a Walbro HDA carb. I wanted to try it with the stock carb first and eventually utilize the Walbro.

The block is made out of a bracket from a pipe hanger that I cut three pieces out of. I traced the reed valve onto them and drilled out the pattern and filed the edges until it fit. There is gasket paper between each piece of the block.

This is still in a test phase but so far the setup functions like its supposed to.

The engine is a lot quieter, the throttle is more responsive, and overall acceleration has improved.

I will post more info and a video on it over the next few days. I intend to refine it a great deal, but part of my experiment was to see just how grassroots this mod could be done and still work. So far I think I have about $7.00 and all day Saturday and Sunday tied up in it.

I made the whole thing using a cordless drill, a dremel tool, and a few hand files.

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keep us posted on how it runs.

looks very cleanly dun so far . I like the looks of that nice!

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That looks like an easy to do and very worthwhile mod that anyone can do.

Keep us updated fo'sho'.

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If it ain't broke, and you mess with it long enough, it will be.

Does it have a powerband?

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I anticipated a little bit of tuning was going to be involved to get this application dialed in just right. Being that I had already done some mods. the engine itself is well past its prime and the reed has definitely brought new life to it. With the little bit of riding I did just the motor "feels" more reliable not to mention how much quieter it is.


As soon as you let the clutch go there used to be a little hesitation as the motor engaged and tried to get with it. That is is all gone. A lot more pull when just starting off.

There is no more chunky sluggishness in the low RPM range just before getting on the pipe. It is all quiet smoothness right into the pipe's power-band.

I'm going to find a road this afternoon to "Stretch it out" to WOT and see what happens.

Well, it took longer to warm up than I was expecting. Lost the adjusting screw on the carb somewhere. Put in a replacement and it ran pretty well. The throttle cable is binding up somewhere and needs to be worked out. I the pressure in the crankcase is considerably higher. I can see the gasket is getting moist in some spots, which was to be expected. I will be checking the crank bearing seals soon I'm sure. It definitely winds up tight and fast.

At wide open throttle it starts to surge a little bit. I haven't noticed an increase in over all top speed but getting there is a bit quicker.

A few more pics.[IMG][/IMG]

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Update:


I made some adjustments to dial it in and performs really well so far. Initially, the plug was showing a lean condition and I wasn't quite getting to the same top speed. I took the block apart and plugged the hole for the pump on the carb it came with and cleaned and reapplied RTV. I also moved the slide needle clip down a notch to raise the needle. I also added about an inch to the exhaust header. This combination has restored the top end of the motor yet the idle is a little ruff.

the torque is definitely stronger. It has this little hop to it now where the front wheel comes off the ground a few inches when you let the clutch in and throttle up.

It is maxing out the rpms without hitting WOT and I will probably be getting a smaller toothed sprocket to help out.

I still believe there is some uncorked goodness in the engine that can be gained from doing some porting. Before I get into all that I am going to hook up the walbro and try running it to see how it performs before pulling the cylinder off.


So far so good. The only thing I would really like to change about the set up is having a chunk of plastic, like the reed valve is made of, instead of using those metal plates. I have 50cm intake studs now with 1cm anchoring the other 4cm on there. But hey, it least its working.

I got a WJ-116 Walbro here. I called numbers on the phone over the internet to get this part number! It officially dials up to 80cc without overkill. So the the carbs jetting screws should be on the map with this one as I can dial it down. Yet another project i got a couple of aluminum blocks already mocked up for it. Your making me wish I had reeds about now!

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One can do anything you set there mind to.... Do a good thing...

Can you explain, in theory, how this works?

I thought that, less lenght between the in port of motor, and the carb, is the most perfect conditions to improve overall performance, but how you describe, you put 3 pieces of metal..i didn't get how this improve the performance.

Sorry of my noob terms

thanks in advance