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SurfLung
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Gas Engine Drive Train

Wed Jul 25, 2018 12:47 pm

Gas Engine Drive Train
- I'm considering hooking up a neat little Go-Kart engine to my RIX SA-3E compressor. I was wondering if it is acceptable to use a centrifugal clutch or is it usually done with a direct drive? The clutch would give the engine the ability to idle without the compressor running. And the throttle could then act like an On/Off switch. I seem to remember these 2-strokes develop their power on the high end so idling on the low end seems logical.

Back Story:
- I converted this Lawn Boy F-Series engine to horizontal shaft several years ago when my oldest son and I built a vintage style go-kart. This was probably 1988 when I checked out a 1961 book on How-to-Build-Go-Karts from the Library. Back in'61 they used the West Bend 580 2-cycle motor... Which I had no source for in 1988. I noticed the Lawn Boy F-Series is almost identical to that engine. So I bought a used Lawn Boy mower and took the engine off. We re-ringed the piston, reamed out the carbon from the exhaust ports, removed the governor... And Holy Cats that thing was fast.
- The Go-Kart frame itself has long since disappeared but I made a point of saving the engine as I was most proud of that. Like the West Bend 580, the Lawn-Boy F-Series is a 3.5 horse. My manual for the RIX lists two engines: Honda GX-120 and GX160... Which according to the specs are both 3.5 hp. So...
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SurfLung
The Freedom and Simplicity of Vintage Equipment and
Vintage Diving Technique are Why I Got Back Into Diving.

tbone1004
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Re: Gas Engine Drive Train

Wed Jul 25, 2018 3:05 pm

no reason you can't use it. They're usually direct drive, but if you want to use a clutch so it can idle and warm up before you start the compressor or want to idle the motor while you switch tanks instead of start stop, or actually want to use the variable speed for noise reduction you'll get a bit of efficiency loss but nothing major. I would probably be nice to your neighbors though and put a much bigger muffler on it....

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captain
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Re: Gas Engine Drive Train

Thu Jul 26, 2018 10:48 am

Most gas powered compressors and gas powered equipment in general use engines with governor speed control to maintain engine speed constant with changes in applied load.
Captain

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SurfLung
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Re: Gas Engine Drive Train

Fri Jul 27, 2018 10:10 am

- Thanks Tbone and Captain. Interesting that "quiet" was one of the big selling points of Lawn Boy mowers... This is because they ran the exhaust straight down thru the mower deck into a larger round muffler... So not only did it have a good muffler, it was also muffled by the deck and the grass. Our GoKart conversion simply rotated the carburetor mounting to make the shaft horizontal... But this also rotated the exhaust port to the side. The original big muffler wouldn't fit because it wrapped around the shaft and didn't leave enough room for a clutch. The straight little muffler we ended up using actually worked pretty well... It was much more quiet than no muffler at all. I think I can fit a bigger one on it now.
- The original governor on these motors was interesting... And I think it played a role in keeping down the noise level. It basically was a wind vane connected to the throttle and sticking up into the cowling next to the fly wheel. The air flow from the fly wheel controlled it. So, when the mower came under more load, the wind from the flywheel would slow down, and the wind vane would open the throttle to apply more power. Pretty slick.
- Of course, we had no tolerance for any sort of "governor" when seeking to use this engine for a Go-Kart ! :)
- I'm thinking I can use my laser RPM meter to find the right throttle setting to run the compressor at the specified 2300 rpm. Then just start it up and push the throttle to the mark.

More Back Story... This is actually the third or fourth Lawn Boy engine I converted for GoKarts back then. The first one came from the used mower and it even had electric start... Cost me $91. My son was able to just turn a key and start it up. One day, the engine was running exceptionally well. He was just screaming back and forth on the dirt road out front when... BANG! The engine blew up! He learned the importance of using mixed gas in 2-cycle engines from that. Father was not happy with him that day... He wrecked my beautiful little engine :(
- I told this to a friend at church and he said the local junk yard had three old Lawn Boys just sitting there. The junkyard sold them to me for $5 each so I was able to convert a couple of them... one for my son and one for the neighbor kid. Man, those kids got an education from those gokarts... They'd race back and forth and around the yard until until something broke. Then they'd have to haul their karts into the garage and weld or wrench on them to solve the problem. :D
SurfLung
The Freedom and Simplicity of Vintage Equipment and
Vintage Diving Technique are Why I Got Back Into Diving.

swimjim
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First Name: Jim
Location: Belgium WI

Re: Gas Engine Drive Train

Fri Jul 27, 2018 8:23 pm

Man, those kids got an education from those gokarts... They'd race back and forth and around the yard until until something broke. Then they'd have to haul their karts into the garage and weld or wrench on them to solve the problem. :D

Yep, I learned a lot by blowing things up and then fixing them. Those were the days!

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