Minimum frame size?

[Matricon]

I've been planning to make a motorized bike for a while now. I'be been waiting for the perfect bike to show up on the local craigslist and it seems it's finally showed up! I want front suspension, disc brakes and 9 speeds, this bike has it all! It even has a top tube you could make into a gas tank like some felt bikes. Unfortunately this large top tube also seems to make the fit of the motor look like a squeeze. I just want some insight if this looks like the motor would fit ok or if it's to small to be motorized. Thanks for your help!
http://washingtondc.craigslist.org/mld/bik/3256425771.html

 

[The_Aleman]

Dave31 uploaded an engine template pic awhile back that came from another website, all original links are dead, but his upload still exists:

http://s390.photobucket.com/albums/...late/?action=view&current=engine-template.jpg

You may have to play around with the image size or settings on your printer before it comes out the right size.

The bike you posted is a pretty nice one, I think it'll fit an engine just fine. If you want to be 100% sure, print out the template on the link. You should be fine tho.

 

[Matricon]

Awesome! Thanks for the help. That is way more helpful than the sketch on bikemotorkit.com

 

[The_Aleman]

Glad that helps. The bike you're looking at appears to have near-perfect frame geometry and size for mounting a chinagirl engine, so I don't think you'll have a problem.

My second build used a similar-sized frame, engine fit like a glove

 

[Matricon]

The new bike! Picked it up on craigslist for 350, msrp 1400, what a steal! Anyway it is a 17.5 inch frame and as expected it looks a bit tight, any opinions on if i would need any modifications like offset carb or slant head? I was hoping to get an engine and mount a shift kit to the nine speeds in the rear. I was shocked how good the bb7 brakes worked, especially considering they were on 160mm rotors, while I personally find that adjusting mechanical brakes sucks and that self adjusting hydraulics are better these brakes are not lacking in power at all. Took it out to the local trail and the 130mm travel fork works real good to. all in all if i can mount everything its going to be a sweet ride!

 

[Matricon]

Just 2 more pix. A question though, will the standard rag joint fit 32 spoke wheels ok? also will the sprocket fit over centerlock hubs? the guy i got it from seems to have bought centerlocks but then put adapter for 6 bolts on. just wondering if i could use the standard kit as an interim while i build up cash for the shift kit.

 

[biknut]

My Cadillac MB had a 17" frame. The fit was so tight, I had to grind out the front motor mount to get it to drop a little lower in the frame. It needed a shorty manifold.

I'm not familiar with shift kits, but if it takes even 1mm of extra space you can forget about it. Without a shift kit you can use a Top Hat adapter for the rear drive, but you won't ba able to keep the rear disk unless you use a very small sprocket.

 

[Matricon]

Wow, nice bike. I see why they call it a cadillac. Where did you get the cadillac symbol for the transmission case? Also how is the manic mechanic head, more power or same?

 

[wheelbender6]

Konas are bullet proof. Never seen a broken Kona frame. Good choice, especially with XTR components. You can get an offset intake manifold from an on line engine vendor or ebay to help it fit that frame. You will need an oversized front engine mount or you can make one with a muffler clamp. Don't overtighten it and damage that down tube.

 

[Matricon]

So the oversized downtube clamp, do you mean the 5 dollar option on gas bikes site or the one from sick bike parts? Does it matter if the tube is more of an oval and not a circle?

 

[Easy Rider]

Take a look at Venice's race bike. That's about as small of a frame you can fit a motor in. Nice pick up. I like Haros.

 

[LazyDrunk]

hello, did you ever finish your project? i have just ordered my engine and the bike im going to put it on looks like a simular frame size to yours