1980s 3hp Briggs help. Looking for a clutch!

S

Slideaway

New Member
#1
#1
Hello everyone.

Im looking for some advice on fitting a clutch to my 3hp. I got this from a lpcal person and it was fitted with an alcon water pump.

Ive removed the pump to take a look at the output shaft. Its 2inches long, is part threaded and has no keyway.

Im confident enough to cut my own keyway using my dremel, however i just really want a bit of advice as to what centrifugal clutch i need to get.

Ive included a few pictures for you to take a look at. Sat next to one of my 2hp briggs motors for comparison.

Cheers

Joe

IMG_20170418_084901.jpg
IMG_20170418_085020.jpg
25ur1j7.jpg
2w1s1vk.jpg
 
jackeo21

jackeo21

Member
#3
#3
Looks like you scored on that 3HP! By the looks, it has the ball bearing crankshaft (much longer life over regular bushings). The motors with the ball bearing crankshafts also generally came with a cast iron cylinder sleeve, which as you may already know provide a much longer lifespan over the traditional aluminium bore. Score!

I've been in your situation multiple times before. I generally solve my problem by finding a new crankshaft (often difficult in New Zealand!) or locating a different engine. That 2HP engine looks to be in great shape, and would take a 5/8" centrifugal clutch, as would the 3HP, but as you have noted it would take some modification to work!

My advice would be to locate a clutch that uses two "grub screws" to mount instead of a key-way. Those crankshafts are very difficult to work with! Someone who has overcome this problem may chip in and give you some advice.

Good luck!
-Jack
 
S

Slideaway

New Member
#4
#4
Thanks for the reply buddy. Im fairly new working woth briggs motors, after deciding to build a classic minibike not some time ago. Would there be any performance advantage to my motor having a ball bearing crankshaft and cast cylinder sleeve, or is it just a reliabilty advantage?

Im going to get hold of a 5/8 clutch from my local parts place, however the ones they stock do not have any set screws. Ive learned also that attatching a clutch with just set screws risks slippage on the output shaft. Ive decided to attempt my own keyway, obviuosly a mill would be great! But im going to use what tools i have avalible. Worst case scenario, i need a new crank wich i might have had to replace anyway. Otherwise i. Saving myself lots of time and money.

I will post progress reports as soon as i start work on it.
 
Phil1958

Phil1958

#5
#5
Slideaway said:
Thanks for the reply buddy. Im fairly new working woth briggs motors, after deciding to build a classic minibike not some time ago. Would there be any performance advantage to my motor having a ball bearing crankshaft and cast cylinder sleeve, or is it just a reliabilty advantage?

Im going to get hold of a 5/8 clutch from my local parts place, however the ones they stock do not have any set screws. Ive learned also that attatching a clutch with just set screws risks slippage on the output shaft. Ive decided to attempt my own keyway, obviuosly a mill would be great! But im going to use what tools i have avalible. Worst case scenario, i need a new crank wich i might have had to replace anyway. Otherwise i. Saving myself lots of time and money.

I will post progress reports as soon as i start work on it.
Click to expand...

instead of cutting a keyway how about if you drill a hole under one of the
set screw holes and run screw into the shaft? just a thought!
 
S

Slideaway

New Member
#6
#6
I did think about it phil. Like i said though i am finding it difficult to find a 5/8 clutch with set screws in this country. Any ideas where i can find one?
 
S

Slideaway

New Member
#8
#8
Right here is the plan provided that i cannot locate a clutch with set screws... Ill use the dremel with a cutoff wheel to get the line depth, then use a small grinding stone to take the shape and finish off with a file. Thanks for sharing lawn-boy
 
danford1

danford1

#11
#11
If the crank is only 2" long AND you found a clutch with grub screws, you would have to mount it with the sprocket on the outside. That could cause chain alignment issues. The 2" crank May not be long enough to mount it the other way around.

Instead of a drilling a hole for the screws, you can also grind a small flat area for them to bite into.
I may even have a 5/8" clutch with grub screws, I'll look later today.

Danford1
 
creia

creia

#12
#12
KB2ROCKET said:
Buy a crank shaft
Click to expand...
Best answer right here^^^.
Also,
I doubt that your engine has a "cast cylinder sleeve" as stated by a previous reply. It is most likely a "Koolbore" all-aluminum block, head, and cylinder wall. Are there any numbers on the recoil shroud? If so post them.
Michael
 
Last edited:
danford1

danford1

#13
#13
danford1 said:
If the crank is only 2" long AND you found a clutch with grub screws, you would have to mount it with the sprocket on the outside. That could cause chain alignment issues. The 2" crank May not be long enough to mount it the other way around.

Instead of a drilling a hole for the screws, you can also grind a small flat area for them to bite into.
I may even have a 5/8" clutch with grub screws, I'll look later today.

Danford1
Click to expand...

I checked. I don't have one. Sorry.

Danford1
 
jeep2003

jeep2003

#14
#14
Cutting a keyway isnt that difficult. Give it a try. I think most 5/8" clutches dont have a removable key anyway. It is definately easier on a shaft that doesnt have an engine in the way. I would buy a clutch first then you can see how far you need to go with the keyway. They dont go all the way across so itll save you some work. Keyways dont have to be perfect either. especially if you have a bolt to tighten it down with. Crankshafts also drill and tap very easy so you might consider doing that aswell
 
You must log in or register to reply here.
Top