Reed testing on a stock 31158 reed cage

My next batch of tests were 6 different reed sets on a stock 31158 WB820 reed cage.

The top 4 sets are the ones that Ryan Courts sent to me for evaluation. I will test the G.E.M. G1158 reeds as soon as I figure out where I put them.


My calculations show that a WB820 needs 38.0 CFM at 8,000 RPM. The Boyesen 620 results surprised me. Might need to dust off one of the engine dynos. :^)

Mower parts

Part of this flow testing project is to find better flowing filters for my space restricted JLO powered Nethercutt MK1s.

I was hoping for a better number from the Tecumseh 35066 filter because it is small, fits HL carbs, is cheap and is still available brand new. 

It flows 39.0 CFM which is better than the 36.0 CFM 29661 Tecumseh foam filter and the 35.0 CFM cut down A11552 CASE filter that I have been using for over a decade. The adapter has an 11/16″ bore that I will punch out to 3/4″ and try again on the bench.

This filter is stock on some Tecumseh TVS lawn mower engines. The early TVS engines use the same recoil that we are currently using on our WB820s to replace the troublesome FM recoils. The later TVS engines use the 35000A cup that we also use on the WB820s.


Pretty much spent the weekend repairing fences so I was only able to sneak one test in. 

I expected the HL-375A racing carb to post a big number. I just did not expect it to go off my calibration scale.

It flowed 105 CFM which is more than double a stock HL-173A.

All my testing is per SAE J607, 3″ Hg pressure drop corrected to 29.92 Hg and 60° F.

820 flow bench testing

I flow tested 3 Tecumseh air filters, 1 Wacker cover, 1 West Bend housing and an Azusa velocity stack last night. I ran the tests on the HL-173A carb that Wilma sent me since it is bone stock and is what most Rokon 820 engines have. I did not use an elbow. I am looking for an air filter system that is currently available that does not hurt horsepower too much. I will run more tests on larger carbs since I suspect some of the Kart guys might also be interested in this.

Found info dating the 82001 engine to 1961

I was looking at an old Power Bee manual trying to find a part number when I noticed that it dated the 82001 engine as being originally built in 1961. Until now the earliest 82001 build documentation I could find was from March of 1962. Since the engine serial number is 1017 I suspect this is the 17th 82001 engine built and it was probably built in 1961. Possibly the MK0 is a 1961 bike???

Another HL-134A to look at

Don Junoska sent me a HL-134A carb that he thinks came off of a piece of small railroad equipment; rail saw, rail drill or impact wrench. This is the same model that my MK0 82001 engine came with and has a few special parts that I have only seen on this model Tillotson. It has an intact 2 screw throttle shaft which is what I broke trying to straighten on my MK0 carb. It still has the gold paint that I found under the yellow and Hunter green paint on the MK0 HL-134A carb.

My Tillotson application list shows that the HL-134A was used on 61001, 61002, 82001 and 82002 go kart engines. The 61001(CW) and 61002(CCW) were 99.9 CC iron sleeved engines built for a 100 CC go kart racing class. The 82001(CW) and 82002(CCW) were Chrome plated bore Aluminum engines. All 4 engines look the same from the outside and use a lot of the same parts.

The air filter base has the same hack job off center modification that my MK0 has so I am less inclined to blame the Nethercutt crew for this.

Vespa selector showed up

The 4 speed Vespa shift selector showed up yesterday and I held it up in front of the Plunger shifter to get some idea of how much work I have gotten myself into. I thought I was going to have to move the clutch brake but the selector has to be spaced out about an inch and a half from the Plunger gearbox so the brake can stay where it is. The left side mounting bolt can be fastened to the clutch brake mounting bracket. I will have to make a simple bracket to fasten the right side mounting bolt.


I started looking at my MK8 trying to figure out how to mount the shifter, run the cables and quickly noticed that the frame is cracked again.

This is the 3rd or 4th crack in this frame not counting the Autograb cracks. This will get repaired when the Plunger gearbox is out of the frame.