My First build. Done finally. Some nice upgrades

burrus

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Okay, I purchased a 49cc Cruiser style motorized at the beginning of summer and was hooked. But after going on the forums, and seeing what was out there, I decided I could do better. So I scoured Craigslist for the right bike and found a Specialized Crossroads (XL frame as I'm 6'3") that had been used about 5 times. I got a steal on it and decided to go with the Skyhawk 66cc for an engine. I had a couple of chain/tensioner issues with the first bike, so I purchased 10' of #41 roller chain from Tractor Supply (21.99) and a spring loaded tensioner off ebay. ($20.00) Also got a dual brake lever/throttle assembly with built in kill switch. ($19.99) The quality of it is fantastic and it is METAL! Much more solid than kit throttle, which is all plastic. What held me up the most was finding the right gas tank. I just don't care for the peanut style tanks. I found this one(41.99 incl shipping) which came primed and I painted it to match the bike. Also upgraded the plug wire and boot with a set of high performance copper core wires from Advance Auto. (38.99 for 8) Took it out today, and rides like a dream. Love the front and seat suspension. Soooo much more torque than the 49cc and quieter too. Very happy. So far......
 

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Serious question about the tensioner up on the engine:
Since your chain clears the chainstays enough to use that style, why do you need a tensioner at all?
If I had that much clearance, I'd shorten my chain and eliminate my stock tensioner even though I've had no problems with it.
 
Serious question about the tensioner up on the engine:
Since your chain clears the chainstays enough to use that style, why do you need a tensioner at all?
If I had that much clearance, I'd shorten my chain and eliminate my stock tensioner even though I've had no problems with it.
I think I can see why: He has vertical dropouts which lack the fine adjustment of chain tension that you would have with forward slanted or rear facing horizontal dropouts. Full/half links are big steps and would miss the sweet spot.
This is why there are adjustable tensioners available for vertical dropout geared bicycles converted to single speed. However they don't require a spring because the sprockets are perfectly concentric.
Goggle: "single speed conversion kit"
Changing the rag joint to a better system of rear sprocket mounting could eliminate the need for the spring. A slotted flat bar could be made to apply the necessary tension without causing unnecessary resistance. The bike would be a tiny bit faster under power, easier to pedal, and would certainly freewheel further without the spring (if sprockets are concentric).
 
I think I can see why: He has vertical dropouts which lack the fine adjustment of chain tension that you would have with forward slanted or rear facing horizontal dropouts. Full/half links are big steps and would miss the sweet spot.
This is why there are adjustable tensioners available for vertical dropout geared bicycles converted to single speed. However they don't require a spring because the sprockets are perfectly concentric.
Goggle: "single speed conversion kit"
Changing the rag joint to a better system of rear sprocket mounting could eliminate the need for the spring. A slotted flat bar could be made to apply the necessary tension without causing unnecessary resistance. The bike would be a tiny bit faster under power, easier to pedal, and would certainly freewheel further without the spring (if sprockets are concentric).
Well said Furry,
You're right on vertical dropout front. Also, I've owned motorcycles, dirt bikes and street bikes since I was 10 years old. Wow! That's 45 years! Probably have ridden and owned about 75 bikes in that time. I've seen talk on the MB forums about "chain stretch". What mainly happens is the metal on the sprockets will gradually wear, resulting in a looser chain. Simple friction physics. Newer bikes have the adjustments to tighten, but many older ones don't. Trust me, it's no fun pushing a Husqvarna WR 250 about a mile through mud to get back to the street after you've thrown or broken a chain. Also, on my first MB, it seemed like my biggest issue was always that damn stock chain tensioner. So, for $20 and 5 min of installation, and something that still looks aesthetically ok, I'm going with it. Thanks.
 
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That is awesome! Thanks, Randall. I liked the first bike, which came already done. But this one I am loving. Not just because it's superior bike and engine wise, but because I built it and know anything that may go wrong, will be much sooner identifiable and fixable. Plus, the satisfaction you get when you make something yourself, it works, AND it's very enjoyable.
 
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Nice build. Does your speedo/bike computer work with the engine running? I tried to put one on my bike but got bizzare readings with the engine running.
 
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