modified 66cc Ht bicycle engine in bmx

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dylan1024

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Oct 29, 2010
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Re: modified 66cc Ht in bmx

we did our final ballancing and assembly this weekend, it needed 6.6grams removed from each counterweight on the crank

test runs in the street outside proved positive... and that we had very long gearing, 1block was not long enough to get on the pipe

we found a deserted set of service roads at a local racetrack and continued testing there......

the chain came off about 6 times, it destroyed itself.

on the last run we hit 59.8km/h on the gps, then the chain came off halfway up the straight, it was just starting to come onto the pipe. i have a feeling that 65km/h is easily possible

this thing is bloody scary!! it needs a disk brake up front, as stopping doesnt happen with the rear only v brake setup.


pics and more progress to follow later
 
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matthurd

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Dec 13, 2010
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Re: modified 66cc Ht in bmx

ohh man that thing looks like its practically a rocket ship, fricken sweet :D bet with that sprocket on the back the thing flies.

that pipe looks AMAZING too. i want one D:
 
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dylan1024

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Oct 29, 2010
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Re: modified 66cc Ht in bmx

its awesome :D and scary!

i built a spot welder to make the tuned pipe, its desined for a nice wide powerband round the 8grand mark, and from our test runs so far it seems to work

will keep you all posted once we get the chain sorted out
 
Bike Monster

Bike Monster

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Jun 4, 2010
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Re: modified 66cc Ht in bmx

your bike gave me some inspiration so i took a couple of pics edited cut them and put them together to make this.... if i had fab skills and the tools to make it i would... lol ps why did you go with 2 pipes on the side instead of making one to go up and over????
 

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dylan1024

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Oct 29, 2010
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Re: modified 66cc Ht in bmx

its running a Walbro pumper carburettor 15.6mm

not sure of the model number
same style as on most weedwackers


the two tubes.. it was my mate Dan's idea, he did most of the fab work
its because we didnt have access to a pipe bender to make a tube go over the top.
they are cut from an old Mini's exhaust and braized on.
 
LS614

LS614

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Dec 22, 2009
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CT and MA
Re: modified 66cc Ht in bmx

Cool build :) There's something about the compact size of BMX bikes that I really like when I see them motorized :) Good job! A lot of custom fabrication work I can see :D
 
Bike Monster

Bike Monster

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Jun 4, 2010
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Conneticut
Re: modified 66cc Ht in bmx

dylan1024 said:
its running a Walbro pumper carburettor 15.6mm

not sure of the model number
same style as on most weedwackers


the two tubes.. it was my mate Dan's idea, he did most of the fab work
its because we didnt have access to a pipe bender to make a tube go over the top.
they are cut from an old Mini's exhaust and braized on.
Click to expand...
couldn't you cut and weld the pipe at an angle????
 
LS614

LS614

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Dec 22, 2009
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CT and MA
Re: modified 66cc Ht in bmx

looks cool! More of a pocketbike than a motorized bicycle but still seems like a fun and fast ride :) Good job
 
foureasy

foureasy

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Jul 9, 2009
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tucson
Re: modified 66cc Ht in bmx

Nice try with the head. That sure is some poopy aluminum. Perfect on the crank weights as well. How much does the bike weigh?
 
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matthurd

New Member
Dec 13, 2010
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manchester NH
Re: modified 66cc Ht in bmx

dylan1024 said:
some not so great videos:

YouTube - 66cc ht bmx test ride
YouTube - modified 66cc ht in a bmx chain jumps off



PS: how the freak do i embed the vids in this post?
Click to expand...
on other forums that use the same system it would be [movie]Nm9scyiciZ4[/movie] but paul has it disabled. i doubt he makes tons of money with the site and the extra bandwidth of viewing videos from the site rather then going directly to youtube would probably run up his bill.

that bike flies though, pretty cool.

where are you from btw? at first i thought you were being reckless then i saw the car driving on the other side of the road too.
 
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foureasy

foureasy

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Jul 9, 2009
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tucson
Re: modified 66cc Ht in bmx

Decipher this mess and build a pipe. Its a nice low rpm pipe that makes peak hp around 8k and limits at 10-10500. Shorten the parallel wall section to three inches long though, I never made that correction on the paper.

 
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dylan1024

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Oct 29, 2010
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Re: modified 66cc Ht in bmx

i just dont think the welder completely understood what i wanted to do on the original head, or didnt care anyway.
the button head is much better! and it looks cool :)

foureasy: not sure of the total weight, its light though ill weigh it when we get a chance

We live in South Africa, hence the "wrong" side of the road riding ;)

thanks for the pipe info, i have some tricks up my sleeve for the future. sticking with our original project outline the next pipe will probably be made when we convert the motor to run on Methanol, so all the numbers go out the window due the the reduced EGT's



we now have the heavy duty chain back on it and it seems to be behaving itself, plastic wheels and a front disk brake are waiting for us at the bike shop :)
 
foureasy

foureasy

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Jul 9, 2009
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tucson
Re: modified 66cc Ht in bmx

Ethanol didnt change the hit of the pipe that much. My first pipe didn't really care which fuel it had.
 
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