My 80cc Bmx Build "The Reaper"

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TxKx0

New Member
Apr 27, 2011
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Chicago IL
Hey guys, here is my Specialized Fatboy 80cc Bmx build. Went with rear engine, no frame mod mount. Took a little bit of engineering but it works great, runs like a champ even tho the engine sat around for 3 years in my garage :p. Only part i am not totally happy with is the gas tank placement, it kind of throws off the sleek look i was going for but awell. Feel free to comment.




 
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TxKx0

New Member
Apr 27, 2011
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Chicago IL
And btw, i still need to do finishing touches, i plan to replace the cables for the accelerator and maybe the clutch. Plus other cosmetic improvements.
 
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msrfan

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Sep 17, 2010
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Yeah! That looks like a wheelie machine. You can still put the tank where it belongs. Just takes a little more engineering. What I mean is, you can purchase an impulse fuel pump that will pull the fuel uphill to the carb. Just tap into the crankcase and screw a small hose nipple into it and run a hose to the pump. The impulses from your motor works a small diaphragm with two valves to move the fuel. Probably would cost around $35 or so.
 
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TxKx0

New Member
Apr 27, 2011
8
1
0
Chicago IL
msrfan said:
Yeah! That looks like a wheelie machine. You can still put the tank where it belongs. Just takes a little more engineering. What I mean is, you can purchase an impulse fuel pump that will pull the fuel uphill to the carb. Just tap into the crankcase and screw a small hose nipple into it and run a hose to the pump. The impulses from your motor works a small diaphragm with two valves to move the fuel. Probably would cost around $35 or so.
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Thanks for the suggestion, is this what you were talking about?
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=120709135228&viewitem=#ht_500wt_956
 
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DuctTapedGoat

DuctTapedGoat

Active Member
Dec 20, 2010
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I really like how you got it to work behind the rear axle - out of curiosity and concern though, how did you modify the clutch plate, there's no clear pic of the underside. On the same note but on the concerning side, it worries me a bit seeing no bottom screw - how does the clutch work when it's not tied down at all 3 points? The pressure would push that cover out a bit on the bottom.

Lastly, I'm super interested in those mounting brackets you fabbed up - care to share?
 
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TxKx0

New Member
Apr 27, 2011
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Chicago IL
Later today i will get some closer pictures of the clutch plate, me and my friend who helped me a ton(and that's an understatement, props to E.G.) in putting this together were both a little worried about removing that bolt but as it turns out that the clutch plate is solid and doesn't seem to be effected. It was ether remove that bolt to allow clearance for the return chain or create a odd sprocket setup to clear both sides of the chain.

As for the mount it was a mix of measuring , eyeballing, and luck :p. If you want specifics like measurements on it or any thing i can try to get those for you.
 
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BarelyAWake

BarelyAWake

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Jul 21, 2009
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Posts made by new members that contain links need to be approved by staff first, an automatic feature of our antispam security - nothin' personal, it'll stop messin' with ya once you've been here a lil while ;)
 
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TxKx0

New Member
Apr 27, 2011
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Chicago IL
BarelyAWake said:
Posts made by new members that contain links need to be approved by staff first, an automatic feature of our antispam security - nothin' personal, it'll stop messin' with ya once you've been here a lil while ;)
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Gotcha, i figured it was something like that, but i was second guessing if i hit the delete button instead of saving it (edited the reply) :p
 
DuctTapedGoat

DuctTapedGoat

Active Member
Dec 20, 2010
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TxKx0 said:
Later today i will get some closer pictures of the clutch plate, me and my friend who helped me a ton in putting this together were both a little worried about removing that bolt but as it turns out that the clutch plate is solid and doesn't seem to be effected. It was ether remove that bolt to allow clearance for the return chain or create a odd sprocket setup to clear both sides of the chain.

As for the mount it was a mix of measuring , eyeballing, and luck :p. If you want specifics like measurements on it or any thing i can try to get those for you.
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Now my brain is thinking how you could use a carriage bolt and a mini roller to keep it pinned down on the bottom - but these china girls don't give you much room to work with.

That'd be super cool to have measurements - not only for myself, but for anyone else who might want to make some jigs.
 
dag_29307

dag_29307

New Member
Jul 1, 2009
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Enoree, Sc.
Totally sweet set-up! I was wanting to see a 20" build. I was thinking it couldn't be done. How's that thing ride? Is the balance/sway of the steering affected by the weight being that far off the rear wheel?
 
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TxKx0

New Member
Apr 27, 2011
8
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Chicago IL
dag_29307 said:
Is the balance/sway of the steering affected by the weight being that far off the rear wheel?
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So far it doesn't seem to be, but i also haven't really done any hard cornering on it yet. One of my friends was rocking it around the block a bunch after the build was done and he didn't say any thing but how much fun it was :p.

moonshiner said:
cool build ....what was the reason you mounted the engine that far back behind the axle ?dnut
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I wanted the engine to be away from my booty lol, its a small bike and when you sit on it your body ends up past the seat since you kind of slouch. It did end up a little farther back than i was picturing in my head but i am happy were it is.
 
dag_29307

dag_29307

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Jul 1, 2009
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Enoree, Sc.
Nougat said:
I was thinking about the logistics of a rear wheel HT setup myself. I was thinking stand the engine up, so that the chain sprocket points at the rear axle, roughly the way it points when in-frame. This would make the cylinder point about 45 degrees to the rear instead of 45 degrees to the front. Then turn the intake over so the carb would be upright. I imagine you could turn a stock exhaust upside down and have it going up and over on the right without difficulty, too.
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If you do try this please let me know about the thread I would love to see that. I have often wondered if different angles would affect the performance of these motors. Not the angle of the carb., just the motor.

Thanks
 
dag_29307

dag_29307

New Member
Jul 1, 2009
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Enoree, Sc.
Really? Oh wow, now see you got my creative mind all fired up.;) So essentially by turning the motor around you almost eliminate the need of a jack shaft, just another "free wheel" sprocket of sorts right? Man! I'm gonna have to go and buy another kit now! My wife's gonna hate me. LOL

I'll get back to you on this....hopefully.
 
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