I have one of the 1970s coalman mini bikes and ive been searching for a larger sprocket option since I don't have the origenal motorcycle like motor. I plan on using a highly modified briggs inteck 206 over head valve motor. The old sprocket this bike has would be way to small to provide the proper gear ratio for the new setup even with a jackshaft and torque converter added. the Gemini mini bike and Arunthetic charger electric mini bike both use the same wheels and have laerger sprockets but the sprocket alone is imposible to find. I happened across a picture of a sprocket for the new coalman mini bikes. and noticed it happend to use the same 3 hole pattern as the old coalman mini bike. I took a chance and orderd the sprocket and it lines up! so the vintage coalmans and the new ones do share one detail in common the hole pattern for the sprocket!
I thought this discovery may be usefull to anyone else building a vintage coalman or any bike that shares these wheels who needs a sprocket.
The only issue is the holes in the newer sprocket are slightly larger than the bolts for the old wheel, that may or may not be an issue, I may have to do some creative problem solving for that. maybe make some bushings or re tap the wheel to a larger thread size.
The fit and finish on the new sprocket leaves something to be desired. It wasn't deburred very well with most of the edges being almost sharp, it wasn't coated in anything protective as far as I can tell and on most spockets they angle the top of the teeth to reduce chain ware and reduce the risk of derailing if the chain isn't quite lined up perfect, This sprocket dosn't. It also feels very light like is made of aluminum wich dosen't make alot of sense, aluminum is soft and week, it macines and therefore wears far easyer than steel so for a wear component like a sprocket its a bad choice. Aluminum is also more expensive then steel and its probably not titainum that would be to expensive.
I'll have to see how well this spocket holds up before making any final judgements.
I thought this discovery may be usefull to anyone else building a vintage coalman or any bike that shares these wheels who needs a sprocket.
The only issue is the holes in the newer sprocket are slightly larger than the bolts for the old wheel, that may or may not be an issue, I may have to do some creative problem solving for that. maybe make some bushings or re tap the wheel to a larger thread size.
The fit and finish on the new sprocket leaves something to be desired. It wasn't deburred very well with most of the edges being almost sharp, it wasn't coated in anything protective as far as I can tell and on most spockets they angle the top of the teeth to reduce chain ware and reduce the risk of derailing if the chain isn't quite lined up perfect, This sprocket dosn't. It also feels very light like is made of aluminum wich dosen't make alot of sense, aluminum is soft and week, it macines and therefore wears far easyer than steel so for a wear component like a sprocket its a bad choice. Aluminum is also more expensive then steel and its probably not titainum that would be to expensive.
I'll have to see how well this spocket holds up before making any final judgements.