I have quite a few of the 80cc Mac engines which use the screw on clutch the bearing section is 5/8" and has a course UNC left handed thread and i wish to run a Max-Torque type clutch now the million dollar question did anyone make an adaptor to do this conversion or where would a fella get one or two of these adaptors i plan on using these so my young fella can run these engines in his mini bike.
Mc Bob.
Mac Screw on clutches
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Terry Sullivan
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mcbob
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Re: Mac Screw on clutches
Thanks Terry i have fired off an email to Jim ...................
Mc Bob.
Mc Bob.
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Dennis Turk
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Re: Mac Screw on clutches
Just yesterday I emailed Jim Donavon and ordered three clutches for Clinton chain saw motors. I had previously sent him high quality cad drawings of the Clinton chain saw crank shafts as there are several different versions. Three hours after I sent the email I got a call from Jim telling me that they clutches were done and in UPS to be shipped the very same day. Now that is what I call really fine service.
Dennis Turk
Dennis Turk
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Mark Havery
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Re: Mac Screw on clutches
Hi MC Bob,
If you want to it is possible to turn down the bearing area with a ceramic bit to fit the Rev-Grip clutch drum, then use the screw on clutch with it. Make sure to form a radius at the shoulder and make a small spacer with a relief inside it to clear that radius. I did this when doing an article covering a conversion of a MC Super 250 for kart use. It took about 15 minutes to turn down the bearing area and another 15 to make up the spacer.
Mark Havery
If you want to it is possible to turn down the bearing area with a ceramic bit to fit the Rev-Grip clutch drum, then use the screw on clutch with it. Make sure to form a radius at the shoulder and make a small spacer with a relief inside it to clear that radius. I did this when doing an article covering a conversion of a MC Super 250 for kart use. It took about 15 minutes to turn down the bearing area and another 15 to make up the spacer.
Mark Havery
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Mark Havery
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- Joined: Wed Jun 20, 2007 6:25 am
- Vintage Karting items owned: Poison Arrow, Chaparral, McCulloch R-1
Dart Mean Machine and the "Mongrel Kart"
Re: Mac Screw on clutches
Hi Dennis,
Jim and I worked out the first clutches for the Clinton chainsaws. I sent him the crankshaft so they would fit perfectly. After that I wrote an article covering the conversion of a D-65 for kart use. Later on Steve Line installed the D65 on his Fox and ran it at Deans Turkey Trot last year. The clutch performed perfectly. The only
thing you must look for on installation is chain clearance next to your mount as it is an inboard clutch. My mounts upright is 1/4" thick so I had to use standard #35 chain for clearance. Now, Russ Smith says his clears with space chain using the identical mount I made him. If you use a sheet metal mount this wouldn't be an issue.
Mark Havery
Jim and I worked out the first clutches for the Clinton chainsaws. I sent him the crankshaft so they would fit perfectly. After that I wrote an article covering the conversion of a D-65 for kart use. Later on Steve Line installed the D65 on his Fox and ran it at Deans Turkey Trot last year. The clutch performed perfectly. The only
thing you must look for on installation is chain clearance next to your mount as it is an inboard clutch. My mounts upright is 1/4" thick so I had to use standard #35 chain for clearance. Now, Russ Smith says his clears with space chain using the identical mount I made him. If you use a sheet metal mount this wouldn't be an issue.
Mark Havery
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Dennis Turk
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- Vintage Karting items owned: Dart D-300
Persival wild cat
Clinton engines
AH 47 power products
820 West Bend
Re: Mac Screw on clutches
Hi Mark
There are two different length Clinton crank shafts. One moves the clutch .270 farther away from the crank case. These are the versions I have had Jim make clutches for. The short crank shaft is more often found on the D-35 saws and that would put the sprocket very close to the case. If you looked at the for sale section you will see the Clinton E-65 motor mounts we have replicated. These are just like the originals and give you all the clearance you need even for the short crank. I have also modify the long crank by turning the .625 diameter back an additional .270 and this gives you a better mounting of the clutch. Also the short crank shaft uses left hand threads on the end and the longer version use right hand thread. Both threads being 7/16 - 20.
what I am using to build replica E-65 motors is the block from a D-65 and also the forged steel rod and crank. I am using the side plate fan shroud and air baffles as well as the recoil starter from the D-35. There is one chain saw that is a belt drive and is actually a left hand motor. This saw will provide you with the side plate fan shroud and air baffles to make up a left hand E-65. Right now I cant remember the model of saw it is. You will still have to use a D-65 block as this saw power head used the D-35 block. You can also use a D-55 Super saw block as this model has the 2 1/8 bore. Most D-55 engines are the smaller 1 7/8 bore models.
Also on Mac 250 with the screw on clutch you can build an adapter that screws on to the thread that has a keyway in it and you can mount a standard clutch only it will have the sprocket on the inside rather than the outside.
Dennis
There are two different length Clinton crank shafts. One moves the clutch .270 farther away from the crank case. These are the versions I have had Jim make clutches for. The short crank shaft is more often found on the D-35 saws and that would put the sprocket very close to the case. If you looked at the for sale section you will see the Clinton E-65 motor mounts we have replicated. These are just like the originals and give you all the clearance you need even for the short crank. I have also modify the long crank by turning the .625 diameter back an additional .270 and this gives you a better mounting of the clutch. Also the short crank shaft uses left hand threads on the end and the longer version use right hand thread. Both threads being 7/16 - 20.
what I am using to build replica E-65 motors is the block from a D-65 and also the forged steel rod and crank. I am using the side plate fan shroud and air baffles as well as the recoil starter from the D-35. There is one chain saw that is a belt drive and is actually a left hand motor. This saw will provide you with the side plate fan shroud and air baffles to make up a left hand E-65. Right now I cant remember the model of saw it is. You will still have to use a D-65 block as this saw power head used the D-35 block. You can also use a D-55 Super saw block as this model has the 2 1/8 bore. Most D-55 engines are the smaller 1 7/8 bore models.
Also on Mac 250 with the screw on clutch you can build an adapter that screws on to the thread that has a keyway in it and you can mount a standard clutch only it will have the sprocket on the inside rather than the outside.
Dennis
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mcbob
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Re: Mac Screw on clutches
Thanks fellas had a yarn to my local machine shop and he came up with the same thoughts on that type of shaft he suggested that we assemble the clutch onto the shaft after fitting the clutch itself to the adaptor locking into postion with the key then screw the clutch assy onto the crankshaft. But by the time i purchased the taps and dies it works out pretty expensive so i'm waiting on a response from Jim as he's checking through his drawings as he has built a couple in the past.
Mc Bob.
Mc Bob.