Min Crank for clutch

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fokai1008

New Member
#1
#1
I just got a GX160 from a friend and want to use it on my first minibike build that im working on.
1. Shaft is 3/4" and 1 1/4" Long. Will a standard clutch fit on this?

2. It does have a keyway but no bolt hole. I am planning to get one threaded in. Anyone know what size bolt should be threaded?

This is my very first attempt to build a mini bike.

Thanks in advance for any help.
 
MB165

MB165

Active Member
#2
#2
It should work you may have to mount the clutch so the chain is outside. make sure you have good engegment with the key
tap it 5/16"-24
 
F

fokai1008

New Member
#3
#3
Thanks

Thanks for the response. I really needed to know that I didn't have to replace the crank. just to clarify- what does the 24 stand for?
 
MB165

MB165

Active Member
#4
#4
24 is the amount of turn per inch (thread pitch)
That short shaft, its gonna be interesting to see how it works out...
 
F

fokai1008

New Member
#5
#5
Last one

Do I have tO go that deep on the threads? What do you think about using a shorter thread with lock tight on the bolt end? The bike will not be a speed demon but just something to putt around on.
 
Last edited:
Rapidrob

Rapidrob

#8
#8
I think you are confused on "Thread Pitch". When someone post 5/16 x24, what that means is the threads per inch are 24. This is called a Fine Thread. 5/16x18 is a Course Thread.
The greater the number of threads, the stronger the "hold" the bolt will have. By having more threads per inch will also help prevent the bolt from coming loose as it has more threads ( friction) than the course thread bolt. Fine threads also help prevent you stripping ( pulling out) the bolt as you tighten the clutch onto the crank shaft. Use a hole at least 1" deep to hold the clutch on. Deeper is better.
Always use a strong bolt. Bolts are in "Grades" The higher the grade, the stronger the bolt the higher the number. All bolts are marked on the head of the bolt. You can look up the markings on the internet. Use at least a Grade-8 bolt on your engine. 99.9999999% of the hardware made today is made in China. The standard plated bolts sold at Home Depot and other discount places are CRAP! They are way too soft and will strip their threads or snap off in a heart beat. Get quality bolts form a shop where professionals buy their bolts. A buck spent there will save you hours of grief in the long run.
Good luck on your build. Sounds like you have a strong,well made engine as a start.:thumbsup:
 
F

fokai1008

New Member
#9
#9
Modification

Thanks Rapidrob and MB165 for the assistance. I learned new things from this thread. I will have the Machine shop cut threads into my crank 5/16 X 24 X1" and get a grade 8 bolt from the local Cat shop.

I did find a solution to the short crank situation thanks to Rick Norris (Snowmangsx1100). look him up on the internet. I will be building a copy of his Lil Indian/Taco minibike. Yellow one.

Solution: Cut 3/4 thick wall pipe to the length needed for the clutch install. File a keyway into the pipe. Join the pipe to the crank and align the keyways. Insert the clutch over the crank and the pipe and install the key. Use the bolt to secure and tighten the pipe, crank, and clutch in place.

No welding required. The keyway and bolt helps to support the whole system and you wont risk damaging the crank seal and also wont run the issue of having a hard time removing the crankcase over if needed.

Also rapidrob or MB165, did I measure my crank right? Is there a big difference between 25mm and 3/4 inch?

I took a piece of 3/4" OD pipe and butted it up to the crank, it seemed to be correct at 3/4".

Thanks everyone.
 
F

fokai1008

New Member
#10
#10
crank measurement questions

I figured out the answer to the question I had regarding the 3/4" to 25mm difference.

I do have a 3/4" crank as it is no where close to 1" and it lined up great with my 3/4" OD pipe.

Thanks again!
 
F

fokai1008

New Member
#12
#12
Torque Converter Driver 20 30 Series Cover Guard Insert 3/4" Aftermarket Part | eBay

Torque Converter Driver 20 30 Series Cover Guard Insert 3/4" Aftermarket Part | eBay

How would I use this? Is it inserted from the outside of the clutch when installing then bolted to the short crank shaft?
 
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