Looking for a unicorn horn

Master Hack

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Well, not exactly but might as well be.
i would like to find a 9 tooth 3/4 bore sprocket to fit the jackshaft on a series 40 TC. After exhausting searches and phone calls, l have concluded that the above mentioned horn might be easier to find!
Does anyone know if such an animal exists and/or where one might be sourced? l’m ready to buy a 5/8/bore sprocket and bore it out to 3/4.
 

karl

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There is not enough room for the chain to fully engage the teeth on 3/4 bore 1/2in pitch sprocket.

That would be why it does not exist, I would look into jackshafts or a bigger axle sprocket.
 

karl

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I hear ya , this will do

 

Master Hack

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Thanks! But am l missing something? So you suggesting changing the driven and the jackshaft and using a 9t x .625 x #40/420 sprocket? How is that different than boring a .625 sprocket to .750?
 

karl

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Yeah once you bore the center out bigger, there is no room for the key way or enough room for the chain to wrap around the sprocket.
Have you thought of decreasing the tire diameter?
 

Master Hack

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Have you thought of decreasing the tire diameter?
Yeah, that or increasing HP. The latter sounds like more fun. I can fix the key issue when boring the.750 lD. l would gladly exchang a little top end for a bit more on the bottom. Its heavy (900 lb) and its just a kids buggy. lt’s just me, trying to make it the best possible. the kids don’t know it could be bettter, they’re just happy to have a toy.
l’ll come up with a plan B. I now know 9T ain’t happening without some serious 3AM engineering.
 

Denny

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No, I haven’t heard. But the unicorn tear market must still be going strong because the gas companies are still using it by the prices they charge. Filled up my truck yesterday, over $80.00.
 

JimD

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Martin Sprocket makes a 9 tooth but the bore is a 1/2" (41B9) . Opening up to 3/4" and putting in a keyway takes away from the structural strength which might crack the sprocket at the keyway. You will not know until you try it.
 

Master Hack

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l’m a beginner at this stuff, so this has been an education. I thought this would be easy.
You are correct that there would be nothing left after machining. I would gladly trade a little top end for a little more bottom. The alternative is adding more power, which would be more fun anyway. I’ll leave this one alone as its just a kids kart and it works good enough. When the kids get bigger and drive better l’ll have to do something.
So, version 2.0 will get underway when l get done building a trailer.
Looking for 650-1000cc motorcycle engine….
 

JimD

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More bottom end than add a larger rear sprocket on the kart. Azusa Engineering in CA makes some bigger axle sprockets.
 

Master Hack

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Thats good info, thanks! Unfortunatley there is no room for a bigger sprocket. Thats why l was looking for a smaller drive sprocket. I should get a pic. The problem when ya engineer on the fly with no real plan, sometime ya get backed into a corner with nowhere to go. It works reasonalbly well though, for such a heavy pig
 

AlbertAmont

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Sometimes, trying to track down these niche parts feels impossible. I had a similar problem once with a project, and after a lot of searching, I ended up modifying a part to fit. Boring it out could work, but you might run into issues with the keyway and strength. Also, if you're looking for something a bit more fun to add to the build, check out train horns. They’re a blast and perfect for when you want to give it some extra character.
 
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bob58o

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They kinda exist as b-style sprockets in chain pitches starting with 5.

Although 5/8” pitch doesn’t really help if you can’t use a larger sprocket in back.

Don’t these threads lock after a few years?
Somebody brought the good penetrating oil.
No Diddy Jokes.
 
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