Clutch bore size question

[mikums]

Hi all! Rookie go-kart guy here.

I was given a go-kart with burnt out clutch.
I bought a new clutch <details belo>:
Go Kart/Mini Bike Centrifugal Clutch 3/4" bore,12 Tooth + 4' #35 Chain & link

Problem:
The bore is too small.
The crank shaft is 7/8", so a bit to big for the 3/4" inch hole in the clutch. The seller of the clutch states they don't make 7/8" clutch bores, so I'd have to grind down the crank shaft.
I'm afraid I'd damage the crank shaft grinding it.

I've attached a pic of the size of crankshaft.

Any advice appreciated!!
Thanks,
Mike

 

[ML-TOYS]

Can you post a pic of your motor and shaft

 

[mckutzy]

Hello and welcome. If you want/need to stick with the OEM crank, you are going to need it to be machined down to the right diameter. Grinding it yourself will just potentially bugger it up, and it wont necessary come out true and concentric(oh the keyway will need to be adjusted aswell).

If not find a replacement shaft.

 

[mikums]

Thanks Mckutzy and ML-Toys. Mckutzy, I agree grinding it myself may mess it up completely. I'm hoping there is a stock size that fits that engine.

MLToys, i've attached a couple pics.

The engine is a:
Robin Subauru 6.5 hp
prod. no. ex170d500105467
Air-Cooled, 4-Cycle, Slant Single-Cylinder,
Horizontal P.T.O. Shaft, OHC Gasoline Engine

 

[ML-TOYS]

It looks to me that there is a sleeve over the shaft that is why you are measuring 7/8.
The actuall shaft should only be 3/4, see how the keyway slot is covered by it.

 

[machinist@large]

Remove the sleeve; it's part of the the dead clutch. The crank shaft is inside the sleeve ATM....

 

[rmm727]

Agree. The hub from the old clutch is still on the crank.

 

[mikums]

Oh my gosh. Embarrassing. You guys are a huuuuuuuge help.
So, that whole collar and sleeve should pop off?
Next question is how do i remove that sleeve? Think I need a hack saw or grinder?

 

[mckutzy]

Should be able to use a torch, and a couple of flathead screwdrivers. Heat the bush up pretty good and it should pry off easily. Make sure you direct the flame away from the shaft seal as much as you can.
Take a look just to see if there is any setscrews in the steel end of it.

 

[OzFab]

Think I need a hack saw or grinder?

No, you need one of these

 

[mckutzy]

A puller does work, and helps alot. I found when a basically a sacrificed part is needed to be removed(good example is this bushing here), using the heat gets it done quicker.

Used this method many time to remove pump seal bushings. They are machined real tight and basically a combo of locktite and shrink fit holds them on. This should be about the same but looser.


Im just saying its a good start, then if anything else use the puller.

 

[mikums]

Great stuff! I'll let you know how it works out!
Thanks again!

 

[OzFab]

Mckutzy, I wasn't saying no to your post, you posted while I was typing...

Yes, heat is a good idea if you have the equipment, then the puller finishes the job...

 

[mikums]

Follow Up:

ML-TOYS, machinist@large & rmm727, you guys were right.
The sleeve from the old cluch was still on the crank. I tried getting it off with a clutch-puller, but there was not enough grip.
I finally had success using an old wood chisel and hammer. I guess the metal on the chisel was stronger than the metal of the clutch sleeve. I just tapped away until it split the sleeve open. Thanks again!

 

[landuse]

ML-TOYS, machinist@large & rmm727, you guys were right.
The sleeve from the old cluch was still on the crank. I tried getting it off with a clutch-puller, but there was not enough grip.
I finally had success using an old wood chisel and hammer. I guess the metal on the chisel was stronger than the metal of the clutch sleeve. I just tapped away until it split the sleeve open. Thanks again!

Great!

 

[MidNightIllusions]

I have a engine in my garage, that was off a pressure washer.
Originally it was a vertical shaft. I changed it to horizontal shaft. Later on I found out it had a 7/8" shaft. Couldn't find a clutch for it so I never used it. Your lucky you had something to make one. Or you would of been screwed lol