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Old 03-26-2020, 12:06 PM
Stelios Stelios is offline
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Default Confused with centrifugal clutches

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-ki...468-208cc.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:
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Old 03-26-2020, 12:40 PM
Smerft85 Smerft85 is online now
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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!
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Old 03-26-2020, 12:47 PM
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J.S.@SMS J.S.@SMS is offline
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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.
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Old 03-26-2020, 12:57 PM
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Originally Posted by Smerft85 View Post
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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?
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Old 03-26-2020, 01:11 PM
Smerft85 Smerft85 is online now
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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.
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Old 03-26-2020, 01:59 PM
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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..
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Old 03-26-2020, 03:17 PM
Stelios Stelios is offline
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Quote:
Originally Posted by mckutzy View Post
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?
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Old 03-26-2020, 05:32 PM
mckutzy mckutzy is online now
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Your link doesnt work, so I cant see what it might be... look at the manual to see what the shaft says...
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Old 03-26-2020, 06:08 PM
Smerft85 Smerft85 is online now
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Quote:
Originally Posted by mckutzy View Post
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.
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