20mm shaft

[Byynow]

While working to resurrect an old, abused, partly cut up Yerf Dog for the grandkids to run around in, I've been lurking here soaking up much good information, but I want to verify what I think I have learned. I have an engine I want to use. It appears to be Lifan 6.5 hp. It has a 20mm output shaft, and from what I gather, no torque converter style drive is available for that size shaft. I did find a centrifugal clutch in that size but I think the kart is to heavy for that.

Also, is there a thread or a writeup that thoroughly explains the governor on these small engines? I've worked on cars and motorcycles all my long life but have yet to deal with small engines and their unique devices. Please school me.

 

[madprofessor]

How the Small Engine Governor Works - YouTube

 

[panchothedog]

Are you sure it's 20mm and not 3/4. I think Lifan is just another brand of clone
engine. There are many. What size are the rear tires. I have owned a couple of
Yerf-Dogs and they bought had 18 x 8::50 x 8 rears. Way to big for a centrifugal clutch. If it is 20mm that is so very little above 3/4" it would almost seem like you could file it down.

 

[Byynow]

Are you sure it's 20mm and not 3/4. I think Lifan is just another brand of clone
engine. There are many. What size are the rear tires. I have owned a couple of
Yerf-Dogs and they bought had 18 x 8::50 x 8 rears. Way to big for a centrifugal clutch. If it is 20mm that is so very little above 3/4" it would almost seem like you could file it down.

Output shaft measures 19.98 mm (.7870 in), close enough to 20mm for me. .037 is a lot to file, and keep it true. I see where another member here used an angle grinder on the shaft while the engine was running! I’m not that brave. I have other engine options but I sure wanted to use this one. It’s off a snowblower with very low hours, and has an electric start. It’s branded “Sanding” model 168F II but when I google it I find it is a Lifan 168F-2.

My other choices are, a Central Machinery 6.5 hp, which seems to be in pretty good shape, a Tecumseh Power Sport model OHH 60 that looks to be rode hard and put up wet, and a Honda GX140 which is 5hp. All of those are 3/4” shaft.

The tires are 18x9.50-8, which stand about 17” high.

 

[Byynow]

How the Small Engine Governor Works - YouTube

Exactly what I needed! Thank you. In principle, it works like the governor in an automatic transmission. After watching the video a few minor questions came to mind but I can probably find the answers on my own. If not I know where to ask.

 

[panchothedog]

With tires that tall you need a torque converter. You will tear up a centrifugal clutch in no time. I would be afraid to use a angle grinder on a spinning shaft also. I have heard of people using a file on a running engine, BUT must honestly say I have never seen or even heard about the final result. To eliminate
.037" you're only removing . 0185" of material from the surface.

 

[Byynow]

With tires that tall you need a torque converter. You will tear up a centrifugal clutch in no time. I would be afraid to use a angle grinder on a spinning shaft also. I have heard of people using a file on a running engine, BUT must honestly say I have never seen or even heard about the final result. To eliminate
.037" you're only removing . 0185" of material from the surface.

I thought about it. But the amount of effort doesn't seem worth it. Tearing the engine down, mounting the crankshaft in my cheap almost worn out chinese lathe, then spinning it unbalanced without a correct weight bobweight on the small journal (havoc?), probably wouldn't have the desired outcome. I think option #2, the Central Machinery engine, is the one.

 

[Master Hack]

You could have a shaft extension made. .7874 (20mm) x .7500 that and a few spacers and yer all set. Any machine shop could turn one out for a few bucks. You have a lathe, go for it!

How to fix your shaft

If your shaft has been damaged, hacked or just isn’t as long as it should be, get your mind out of the gutter and follow along. the shaft on my lttle Briggs motor was all of the above, so l wittled out this little fix. lt looks like this on the Briggs. tomorrow l’ll make some spacers and...

www.diygokarts.com

 

[karl]

I see where another member here used an angle grinder on the shaft while the engine was running! I’m not that brave.

Are you referring to me? lol. But yes I have done that. If you got nothing to lose, it's worth a shot , right?
Worked for me.

Anyway, why not just swap the crank? 30min job under $30

https://www.ebay.com/itm/164230237553?hash=item263ce28d71:g:bsAAAOSwtVpe18m6&amdata=enc:AQAHAAAA4C5zN38GitWnhYkn9gopQCgxNF22V35YeVWASiHfRcfgE0i6Bzz+cy9KVhi8N4ARI57nxTw58Wu3qK4+JKR5GMbIsec8YvBrbGZ4qtzecRQp+0wQSekOdXE95I+oI1a48p6NjhZP5lJp0hdqJxLQCwk8ZAzFApYoeg5c94dU7Hodq6ksqXDAqUvzBnSnLeFuKGVcaylUsY987RMRBdredWDvK+x07DKg4HeEEhK+5tfZpZ0O5cDr3X3OO8godQvhjwiR16guNiyxhKAHlLiQJssbxWoTAtd+k6fLCInuMmmT|tkp:Bk9SR4jN8PmmYQ

 

[karte_m0lim]

I used file and engine on high rpm

 

[Byynow]

You could have a shaft extension made. .7874 (20mm) x .7500 that and a few spacers and yer all set. Any machine shop could turn one out for a few bucks. You have a lathe, go for it!

How to fix your shaft

If your shaft has been damaged, hacked or just isn’t as long as it should be, get your mind out of the gutter and follow along. the shaft on my lttle Briggs motor was all of the above, so l wittled out this little fix. lt looks like this on the Briggs. tomorrow l’ll make some spacers and...

www.diygokarts.com

Hadn’t thought of that.

 

[Byynow]

Are you referring to me? lol. But yes I have done that. If you got nothing to lose, it's worth a shot , right?
Worked for me.

Anyway, why not just swap the crank? 30min job under $30

https://www.ebay.com/itm/164230237553?hash=item263ce28d71:g:bsAAAOSwtVpe18m6&amdata=enc:AQAHAAAA4C5zN38GitWnhYkn9gopQCgxNF22V35YeVWASiHfRcfgE0i6Bzz+cy9KVhi8N4ARI57nxTw58Wu3qK4+JKR5GMbIsec8YvBrbGZ4qtzecRQp+0wQSekOdXE95I+oI1a48p6NjhZP5lJp0hdqJxLQCwk8ZAzFApYoeg5c94dU7Hodq6ksqXDAqUvzBnSnLeFuKGVcaylUsY987RMRBdredWDvK+x07DKg4HeEEhK+5tfZpZ0O5cDr3X3OO8godQvhjwiR16guNiyxhKAHlLiQJssbxWoTAtd+k6fLCInuMmmT|tkp:Bk9SR4jN8PmmYQ

And this is why I’m here! Thank you karl, replacing the crank is just what I’ll do.

 

[Byynow]

UPDATE: Installed a replacement 3/4" crankshaft. What an easy and inexpensive way to solve my problem. I didn't know there was such a supply of parts for these engines, thought they were throwaways. Haven't ran it yet but everything went together so smooth I can't see a problem. The only surprise I had was when I found that these engines don't use rod bearings! I haven't seen that since I took apart a model airplane engine.

 

[phopnick]

UPDATE: Installed a replacement 3/4" crankshaft. What an easy and inexpensive way to solve my problem. I didn't know there was such a supply of parts for these engines, thought they were throwaways. Haven't ran it yet but everything went together so smooth I can't see a problem. The only surprise I had was when I found that these engines don't use rod bearings! I haven't seen that since I took apart a model airplane engine.

Can you share the part number for the crankshaft? I am in the same scenario. 168F diesel engine with 20mm bore on the output shaft. I was getting ready to sand it down until I saw your update

 

[Denny]

You’re going to need to find the correct crankshaft for a diesel. I don’t think gasser cranks are the same.