Doc Sprocket
*********
I thought I'd post this seperately from my clone thread, as a lot of people struggle to make a good throttle connection once the governor is removed. Here's my take on it, and it cost nothing.
Even if you don't have all the parts laying around, this will be cheap.
To begin with, I re-used the original linkage rod that goes from the governor arm to the carb. I put that funny Z-bend into it for two reasons, 1) To locate the rod where I wanted it, and 2) Because of the way the rod slots into the carb's throttle arm, there is a danger of the rod popping out at idle, facing straight forward. The fisrt bend prevents this, the second bend puts the rod where I want it. It does miss the factory fuel line location, but in my case the line's not staying there anyway, so it doesn't matter to me.
I made the bellcrank from a strip of 16ga steel. This is what converts the cable's pulling action into the rod's pushing action. It pivots on a stud bolted through the fan shroud. The nut on top is a Nylok nut, so that it can be left loose enough for the bellcrank to pivot, but it won't back off. The cable attachment actually was a factory part on my clone that I re-used. There are lots of ways to do this.
The return spring is just hardware-store stuff I had laying around.
The cable bracket was made from a strip of 14ga steel I had laying around. The hole that the cable barrell passes through has been drilled and tapped to 1/4-20 thread for the cable barrell. It is currently attached to the fan shroud with sheetmetal screws for mock-up only. They will be changed either to rivets or small bolts. Sheetmetal screws will NOT stay in, don't do this.
Also, be very careful here- the clearance between the shroud and flywheel in this area is very minimal. To avoid damaging the flywheel, mark these holes and remove the shroud before drilling. Also make doubly sure that these fasteners will not interfere with the flywheel. Check it, then check it again.
The cable barrel is another homebrew item. I fully intended to use one from a bicycle brake system, but try as I might, I couldn't find one around here. (funny bit- I found one about a half-hour AFTER finishing this rig) I used a 1/4-20 bolt, with a 3/4" long threaded portion. This is quite easy with a drill press. I did one by hand years ago, but it's harder. You can use a plastic, brass, aluminum, or steel bolt. If you use steel, be sure to select a crappy, ungraded hardware store bolt. Much easier to drill through than one that's graded.
Once the bolt was lined up in the drill press, clamped down and centrepunched, I drilled a 3/32" hole through it's length. That done, I drilled a 1/4" hole down into the head, for the cable end to seat in. Assembled, the take-up in the cable is adjusted by turning the bolt, then locked in place with the jam nut.
For throttle cables, I tend to use bicycle brake cable and the related casing. If you look closely at the black and yellow bits- that's a 1/4" nylon cable clamp from the hardware store. The yellow is a few wraps of electrical tape around the cable casing to make it a tight fit in the clamp.
If you really stare at things closely, you'll notice a light spring going from the carb lever to the blower housing. I tend to overengineer things. If the rod should pop or break out of that plastic lever, this will close the throttle. This spring was an original part from the governor arrangement. I am probably going to remount it a little more cleanly.
Cheers- Chris
Even if you don't have all the parts laying around, this will be cheap.
To begin with, I re-used the original linkage rod that goes from the governor arm to the carb. I put that funny Z-bend into it for two reasons, 1) To locate the rod where I wanted it, and 2) Because of the way the rod slots into the carb's throttle arm, there is a danger of the rod popping out at idle, facing straight forward. The fisrt bend prevents this, the second bend puts the rod where I want it. It does miss the factory fuel line location, but in my case the line's not staying there anyway, so it doesn't matter to me.
I made the bellcrank from a strip of 16ga steel. This is what converts the cable's pulling action into the rod's pushing action. It pivots on a stud bolted through the fan shroud. The nut on top is a Nylok nut, so that it can be left loose enough for the bellcrank to pivot, but it won't back off. The cable attachment actually was a factory part on my clone that I re-used. There are lots of ways to do this.
The return spring is just hardware-store stuff I had laying around.
The cable bracket was made from a strip of 14ga steel I had laying around. The hole that the cable barrell passes through has been drilled and tapped to 1/4-20 thread for the cable barrell. It is currently attached to the fan shroud with sheetmetal screws for mock-up only. They will be changed either to rivets or small bolts. Sheetmetal screws will NOT stay in, don't do this.
Also, be very careful here- the clearance between the shroud and flywheel in this area is very minimal. To avoid damaging the flywheel, mark these holes and remove the shroud before drilling. Also make doubly sure that these fasteners will not interfere with the flywheel. Check it, then check it again.
The cable barrel is another homebrew item. I fully intended to use one from a bicycle brake system, but try as I might, I couldn't find one around here. (funny bit- I found one about a half-hour AFTER finishing this rig) I used a 1/4-20 bolt, with a 3/4" long threaded portion. This is quite easy with a drill press. I did one by hand years ago, but it's harder. You can use a plastic, brass, aluminum, or steel bolt. If you use steel, be sure to select a crappy, ungraded hardware store bolt. Much easier to drill through than one that's graded.
Once the bolt was lined up in the drill press, clamped down and centrepunched, I drilled a 3/32" hole through it's length. That done, I drilled a 1/4" hole down into the head, for the cable end to seat in. Assembled, the take-up in the cable is adjusted by turning the bolt, then locked in place with the jam nut.
For throttle cables, I tend to use bicycle brake cable and the related casing. If you look closely at the black and yellow bits- that's a 1/4" nylon cable clamp from the hardware store. The yellow is a few wraps of electrical tape around the cable casing to make it a tight fit in the clamp.
If you really stare at things closely, you'll notice a light spring going from the carb lever to the blower housing. I tend to overengineer things. If the rod should pop or break out of that plastic lever, this will close the throttle. This spring was an original part from the governor arrangement. I am probably going to remount it a little more cleanly.
Cheers- Chris
Attachments
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throttle.jpg
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