20mm Crank

[qtband]

I see engines with a 20mm crank. Is it OK to use a 3/4" clutch on a 20mm shaft?

 

[Hellion]

Ah yes, the non-standard Chinese crank diameter. You might need to turn it down to .75”. Curious to see if a standard clutch fits with some loose tolerances and without hammering the thing on.

Have seen some 20mm bore clutches on the jungle store.

 

[Sparkwizard]

3/4 clutch will not even hammer onto a 20mm shaft. 3/4 is close to 19mm.
If you didn't buy one yet, avoid the dreaded 20mm, unless you are in Europe, where parts to fit it might be more readily available.

 

[Hellion]

How hard is it to turn the crank down 1mm+/- via the shade-tree mechanic way? That’s holding a file to the crank while it runs and checking with a caliper?

Wonder what the typical machine shop would charge? You’d have to crack the block open, extract the crankshaft and bring it in…

Otherwise they are available: https://www.amazon.com/Fuerduo-Centrifugal-Clutch-Chain-Engine/dp/B08BZ6T2ZJ

 

[Sparkwizard]

I had a couple of Hondas that came off rental karts. They had 2:1 gear reduction wet clutch boxes on them. We should have kept those, but we decided to remove them and reduce the 20mm shafts to 19mm. It proved to be really challenging to hold a file steady as it skipped over the keyway. Before we ruined them, we stopped and built a tool to hold a 4 1/2 inch grinder with a NEW wheel spinning against the rotation of the engine. It did not leave a smooth surface, but the clutches would cover them, so no harm.

 

[Master Hack]

20mm = .7874 inch 3/4= .750
difference =.0374 That means ya gotta remove .01875
thats a lot for a file and emory!

 

[Hellion]

....That means ya gotta remove .01875 thats a lot for a file and emory!

Sounds like a job for .............................. Master Hack!

 

[Whitetrashrocker]

Took .750 off a 12 bolt ring gear with a angle grinder still bolted in the housing. Put it on the lathe afterwards to true it up and found it was about .010 out of round.
Your over thinking it.

 

[Master Hack]

I think starting it up and using an angle grinder is an outstanding idea. I'm gonna have to try it.

 

[Sparkwizard]

WE built a fixture and bolted it to the side cover. Tried to use a C clamp to feed the grinder along the crank, but gave up and just fed it manually.
Was not pretty, but it worked.

 

[JimD]

Max-Torque will build you the clutch but it has to be held on with a bolt and washer because the clutch will be 2 pieces. Shoe assembly and a drum and sprocket. The sleeve holding the two pieces together is no longer there. The other thing we need to do is make the keyway bigger because they use a metric key and not the 3/16". Like someone said avoid buying the 20mm it is a pain-in-the a$$.
You can always do it yourself but you have to start off with an American clutch, Noram, Max-Torque, Comet that has a keyway- the china stuff with the built-in-key just ain't goner work. Good luck

 

[JimD]

3/4 clutch will not even hammer onto a 20mm shaft. 3/4 is close to 19mm.
If you didn't buy one yet, avoid the dreaded 20mm, unless you are in Europe, where parts to fit it might be more readily available.

You just haven't bought the bigger hammer yet. I have seen where they tried pounding them on and then tell me the drum doesn't spin and the clutch is defective. There are a lot of dumb asses out there and it is never their fault.

 

[Hellion]

I almost bought one of those 20mm crankshaft engines, one of the red with white gas tank “obvious Honda ripoff” models just because they were so cheap. I wanted to see just how cheaply you could get into this dangerous hobby of ours.

Dangerous hobby? It occurred to me that that means buying a 2005 or prior domestic manufactured go kart that was *so dangerous* they were litigated into oblivion by parents and bloodthirsty lawyers

 

[Hellion]

I almost bought one of those 20mm crankshaft engines….

Whoops, I DID buy one. I may want one of those Max-Torque clutches for it, Mr. Jim.

 

[Denny]

Better be nice to Jim than Hellion.

 

[JimD]

Hellion -- I can certainly make you one or walk you through what I do. The only clutches you cannot do it with are the china ones with the built-in-key. Most of the guys on this site are very clever to start with and walking people through it is fairly easy IF YOU OWN A LATHE.

Maybe that should be my next video I do and put it on my site. Write it out step by step or make a video?? What is the preference?

 

[Sparkwizard]

Please make a video and post a link to your site here, Sir!

 

[JimD]

Give me a few days, got to shave and look presentable.

 

[Master Hack]

got to shave and look presentable.

Why?