Confused with centrifugal clutches

[Stelios]

Hello, im new here. I decided to build a minibike with a frame i found in a scrapyard. I chose this 6.5 HP kraft engine https://ergalia.gr/khpos-agrotika-kinhthres/19192-23468-208cc.html The site is in Greek. The engine has a 3/4" shaft but im a bit confused with the clutch. How should i lock the clutch on the shaft? With set screws or bolt it on the crankshaft? Do all engines have holes in their crankshafts for bolts to lock the clutch? Does the key come with the clutch or not?Do all cltuches support set screws?

Sorry for my bad english:

 

[Smerft85]

Luckily I have a few projects around, and hopefully the pictures should help. Most honda clones such as the one you are looking at come with a keyed shaft and the key is included, clutches for the same size shaft normally have a matching keyway. The engine shaft will likely be threaded and you should use a flat washer along with the correct bolt, this will keep the clutch from falling off the end of the shaft. Some clutches come with a built in key, and some will have set screws, some wont. The clutches that don't have set screws may require a bushing between the engine and clutch to keep it out far enough to stay on the drive sprocket.

Hope this helps out, and welcome to the forum!

 

[J.S.@SMS]

Some people only use the set screws, but I've had too many of them fall out on me, so I use a spacer behind the clutch to get the chain alignment correct (washers work quite well, though it isn't always necessary) then use a bolt and washer to hold the clutch on the shaft, and I'll install the set screws just because I can. And the key usually comes with the clutch.

Not all engines have a threaded shaft, but most of the honda clone engines, like that one, do. Occasionally you'll find one that has an externally threaded part on the end of the shaft, those use a castle nut and a cotter pin, and are reliable, but for the most part they're drilled and tapped for a bolt.

And you speak English better than most.

 

[Stelios]

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Luckily I have a few projects around, and hopefully the pictures should help. Most honda clones such as the one you are looking at come with a keyed shaft and the key is included, clutches for the same size shaft normally have a matching keyway. The engine shaft will likely be threaded and you should use a flat washer along with the correct bolt, this will keep the clutch from falling off the end of the shaft. Some clutches come with a built in key, and some will have set screws, some wont. The clutches that don't have set screws may require a bushing between the engine and clutch to keep it out far enough to stay on the drive sprocket.

Hope this helps out, and welcome to the forum!

Thanks for the help! What bushing should i put between the engine and the clutch to lock it in place using a bolt on the crankshaft?Do i really need the bushing or i just can align the engine with the rear wheel sprocket without the bushing?

 

[Smerft85]

If the clutch comes with set screws you wont need the bushing behind it, if it doesn't you could use a washer or two behind it to take up the space and keep it lined up.

 

[mckutzy]

Its reccomended that you use the bolt on the outside of the shaft... use blus semi-permanent thread locker.....
I found clear nail polish works for this in a pinch... Just make sure the bore is clear and you have the right threads for the bolt... It could be a metric or a standard fine thread in the shaft... so be sure to check first..

 

[Stelios]

Its reccomended that you use the bolt on the outside of the shaft... use blus semi-permanent thread locker.....
I found clear nail polish works for this in a pinch... Just make sure the bore is clear and you have the right threads for the bolt... It could be a metric or a standard fine thread in the shaft... so be sure to check first..

How to choose the right bolt?

 

[mckutzy]

Your link doesnt work, so I cant see what it might be... look at the manual to see what the shaft says...

 

[Smerft85]

Your link doesnt work, so I cant see what it might be... look at the manual to see what the shaft says...

Link worked for me, looks like a honda clone based over seas (KRAFT on tank), I'd guess it's the same threads on the predators or hondas, but I know the bolt as "the one that fits", I'm guessing a fine thread metric.

 

[ashleymooree]

Great job ahead of you! I hope everything turned out great

 

[JimD]

When ever possible you ALWAYS want to hold the clutch on with a bolt and washer. No one takes the time to read the donut instructions on the clutch because "we know it all". The set screws are ONLY for a crankshaft that is not drilled and tapped and most crankshafts today are drilled and tapped. American engines as well as many Honda are 5/16-24 and some Tecumseh are 3/8-24 but what ever the case, use the bolt and washer and let the clutch float on the crankshaft. Don't try and fix it in place, the Max-Torque clutch is 2.220" long and the standard crankshaft is 2.297" long. You want the extra .070 to be clutch float because rear sprockets on the axle be it a go kart or a mini-bike never run true, there is always wobble in them and you want the clutch to move in and out so you don't put extra pressure on the chain and shorten the chain life.
The set screws were in there for the cranks that were not drilled and tapped. We quit putting set screw holes in the clutch 2 years ago since the engines are now drilled and tapped and it is rare you find one that isn't. The good news is you can easily drill and tap an American engine since they don't heat treat them like Honda. When you use set screws you mar the crank making it hard to get the clutch off or a new one on.

 

[moe91]

Hello new to the site was wondering what kind of clutch do I put with a 50 tooth rear sprocket and if I need a third wheel to convey the chain

 

[pearl111]

Hello new to the site was wondering what kind of clutch do I put with a 50 tooth rear sprocket and if I need a third wheel to convey the chain

Welcome, ... please start your own thread with your new question.
Also, you need to give a lot more detailed info. on the project that you are working on.
You need to post pictures, of the project and aera that you're working on.
No one can help you without this information.