Horstman Secondary Disassembly

Mini Bike & Go-Kart Parts

#1
I am trying to disassemble a Horstman secondary and I am hoping someone here can point me in the right direction.

Attached are photos of a Horstman secondary on a Terra Trail Topper mini bike. I have not been able to find an identical Horstman
replacement and I want to keep the bike as original as possible.

I am now trying to figure out how to disassemble the secondary and attempt to restore it. In looking it over, there are no set screws or
other removable hardware on the secondary. The only thing I can come up with is the spyder (the 3 eared thing...) was pressed onto the
main clutch mounting shaft. The secondary is riveted together, so this is the only thing jumping out at me.

Assuming this is the best way to disassemble this thing, the spyder is aluminum while the rest of the clutch is steel... given the amount of rust
on it, I hate to think how much electrolysis has set up.

I may be missing something obvious, I have zero experience with secondaries. If so, please let me know!

Thanks in advance for any help!
 

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mustangfrank

Well-Known Member
#2
I am trying to disassemble a Horstman secondary and I am hoping someone here can point me in the right direction.

Attached are photos of a Horstman secondary on a Terra Trail Topper mini bike. I have not been able to find an identical Horstman
replacement and I want to keep the bike as original as possible.

I am now trying to figure out how to disassemble the secondary and attempt to restore it. In looking it over, there are no set screws or
other removable hardware on the secondary. The only thing I can come up with is the spyder (the 3 eared thing...) was pressed onto the
main clutch mounting shaft. The secondary is riveted together, so this is the only thing jumping out at me.

Assuming this is the best way to disassemble this thing, the spyder is aluminum while the rest of the clutch is steel... given the amount of rust
on it, I hate to think how much electrolysis has set up.

I may be missing something obvious, I have zero experience with secondaries. If so, please let me know!

Thanks in advance for any help!
Step one is getting the clutch off the jackshaft...good luck, it looks rust fused. Spider/cam might be threaded on, I'm not sure on that but they're removeable for spring and button service.
 
#3
Step one is getting the clutch off the jackshaft...good luck, it looks rust fused. Spider/cam might be threaded on, I'm not sure on that but they're removeable for spring and button service.

Thanks mustangfrank... I do have the secondary off the jackshaft, so I have been able to make that much progress. If the spider is threaded
on, I assume it is RH thread? Lefty loosie/rightie tightie?
 

mustangfrank

Well-Known Member
#4
Thanks mustangfrank... I do have the secondary off the jackshaft, so I have been able to make that much progress. If the spider is threaded
on, I assume it is RH thread? Lefty loosie/rightie tightie?
Wait for someone that has actually worked on a Horstman, I'd be too chicken to guess if it were mine.

The company is still in business, give them a call?
 
#5
Wait for someone that has actually worked on a Horstman, I'd be too chicken to guess if it were mine.

The company is still in business, give them a call?

I called them today... and spent 10 minutes explaining what a minibike was! Unfortunately the one person who might be able to help me
is out this week, so I will try them at the beginning of next week.

At least they are still in business!
 

mustangfrank

Well-Known Member
#7
I called them today... and spent 10 minutes explaining what a minibike was! Unfortunately the one person who might be able to help me
is out this week, so I will try them at the beginning of next week.

At least they are still in business!
Seems odd, they still make clutches although they only mention karting. Metal surfaces looks better than I expected them to look.
 
#8
Attached are some updated photos of the secondary after a couple of days in Evaporust. The spring is not in good shape and will need to be replaced for sure. If I can get it apart, I will like to clean and re-plate all of the components.
Evaporust is some good stuff. In my experience you should only leave parts in it for about twelve hours or so (room temperature, less effective in colder temps). Otherwise you get that blackening of the metal.

Getting it apart is easy. Stick a junk jackshaft in your vice, then slide the clutch on. Spray the cam with penetrant of your choice (PB Blaster, Deep Creep, Aerokroil, Gibbs etc. NOT WD40) Wrap a strap wrench around the cam and spin it off. If you don't have a strap wrench a pipe wrench or channel locks will work, but it'll mark up the aluminum.

Plating is another problem altogether. The outboard sheave (steel) and bottom of the cam (aluminum) are factory riveted together and are not a serviceable unit. The plating solution has a PH that won't jive with the aluminum (basically an acid) and etch it, not what you want.
 
#9
Evaporust is some good stuff. In my experience you should only leave parts in it for about twelve hours or so (room temperature, less effective in colder temps). Otherwise you get that blackening of the metal.

Getting it apart is easy. Stick a junk jackshaft in your vice, then slide the clutch on. Spray the cam with penetrant of your choice (PB Blaster, Deep Creep, Aerokroil, Gibbs etc. NOT WD40) Wrap a strap wrench around the cam and spin it off. If you don't have a strap wrench a pipe wrench or channel locks will work, but it'll mark up the aluminum.

Plating is another problem altogether. The outboard sheave (steel) and bottom of the cam (aluminum) are factory riveted together and are not a serviceable unit. The plating solution has a PH that won't jive with the aluminum (basically an acid) and etch it, not what you want.

Thanks Mark G, I appreciate the insights! One question: are the threads on the cam left-hand or right-hand? I would hate to potentially damage the cam by going the 'wrong way' trying to spin it off. Thanks in advance for your help!
 
#10
I believe it should be right hand thread. Been a while since I've had one apart.
If it were me, I would soak it in penetrant for a few days, then I'd try to TIGHTEN it just a smidge- enough to crack the bond. Then work it s l o w l y back and forth until it moves freely. Good luck
 
#11
Update on the Horstman secondary... I finally have it apart (thank you Mark G!). The spider does unthread (RH threads by the way) and it came apart with relatively little effort.

One issue: there is a plastic (Delrin? nylon? something else?) spacer that the movable sheave rides on to slide back and forth. The existing part is shot and I need to find or make a replacement. Does anyone know what these things are made out of?

Thanks!
 

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