"motorizing" a Trek FX 7.2

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1dave1

New Member
Nov 29, 2012
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San Diego
Long time listener, first time caller.

A month or two ago I bought a 2 stroke engine from Motovelo (guy does have good customer service and fast shipping, not sure why the immense hate on here for him but, I digress...) and installed it on an old rickety beach cruiser. I love it for a first time install but I want something safer and something more rideable.

I just got my hands on a Trek FX 7.2 fitness bike. Here is a youtube link of the bike I got.

http://www.youtube.com/watch?v=NhbOGy-KRVs

Do you see any issues w/ a future installation on this bike? I know I will have to drill into the frame to mount the motor but anything other then that? Are the tires too narrow? Will this be more dangerous? Its my second go around at this and I might be missing something. Any hints would be appreciated. Also, should I do a four stroke or two stroke? I live in Cali and need shipping.

Thanks
 
paul

paul

Well-Known Member
Dec 23, 2007
5,547
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Kalamazoo, MI
not sure why you would have to drill holes in the bike. the fx 7.2 has a fairly nice triangle on it. tires and stuff i would not be concerned with however new bikes are made to be as light as possible and if you drill holes in them i would think it would weaken that spot especially with the constant vibration from the engine and cause a dangerous situation.

also welcome to the site. great to have you with us, i am sure some other the others that are much better motorized bicycle builders will give a hand also
 
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1dave1

New Member
Nov 29, 2012
36
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0
San Diego
Thanks for the advice Paul. It does have a nice triangle but I was thinking I would have to drill into at least one part of the frame because it looks too wide for the normal motor mount. I might be wrong but it looks wide to me. I would love to not have to but I'm not 100% sure. I guess if I have to drill into the frame, I might as well not risk it. I never thought of the effect the light weight + vibrations + drilling would have the structural integrity.
 
mdlee1958

mdlee1958

Member
Feb 22, 2009
204
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18
Fort Collins, Colorado
One thing that almost everybody forgets to talk about is spoke count. If this bike has 32 spoke wheels it is going to be very difficult to mount the drive sprocket to the hub, most sprockets have a 9 hole mounting pattern and I don't know about your universe but in our universe (The Rocky Mtn "High" state of Colo.) 9 does not divide well into 32. Just something to consider.
 
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1dave1

New Member
Nov 29, 2012
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San Diego
interesting. I did not think of that. In California our kits have the same 9 hole mounting pattern. Any ideas? Different sprocket?
 
BikeBerryKelci

BikeBerryKelci

New Member
Oct 25, 2012
37
0
0
brea
1dave1 said:
Long time listener, first time caller.

A month or two ago I bought a 2 stroke engine from Motovelo (guy does have good customer service and fast shipping, not sure why the immense hate on here for him but, I digress...) and installed it on an old rickety beach cruiser. I love it for a first time install but I want something safer and something more rideable.

I just got my hands on a Trek FX 7.2 fitness bike. Here is a youtube link of the bike I got.

http://www.youtube.com/watch?v=NhbOGy-KRVs

Do you see any issues w/ a future installation on this bike? I know I will have to drill into the frame to mount the motor but anything other then that? Are the tires too narrow? Will this be more dangerous? Its my second go around at this and I might be missing something. Any hints would be appreciated. Also, should I do a four stroke or two stroke? I live in Cali and need shipping.

Thanks
Click to expand...

Yes it looks like a multiple speed bike, and with a motor installed that can change gears w/ your bike. The bike chain can gear pop or even break if you gear too high or too low.But other then that you should enjoy it!
 
J

JonnyR

New Member
May 13, 2012
1,203
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ronkonkoma, new york
BikeBerryKelci said:
Yes it looks like a multiple speed bike, and with a motor installed that can change gears w/ your bike. The bike chain can gear pop or even break if you gear too high or too low.But other then that you should enjoy it!
Click to expand...
it is a multi speed bike if he said he wanted to do a shift kit i might think about the chain/derailleur but he seems to want to do a standard chain kit and me personally wouldn't want to do a single speed bike because i have had to ride the bike with the motor dead 3-4 times and shifting down and up is so nice also i love my rim brakes so i think he has chosen a great bike for this project light weight and multi speed
 
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1dave1

New Member
Nov 29, 2012
36
0
0
San Diego
also something i had not thought of. My last build was beach cruiser, this one has 24 speeds. Im semi confused though. Do you mean if I rev the engine to around 10 mph and pedal fast in a low gear the chain is likely to pop off? I'm new to multi speed bikes and I like the simplicity of the one speed. Can you think of a part, perhaps a simplified gear shifter or maybe even a way to lessen the number of speeds? The last thing I need is to get used to hand brakes, a new engine and 24 speeds. Thanks for input
 
1

1dave1

New Member
Nov 29, 2012
36
0
0
San Diego
oh yeah. I'm doing a standard kit w/ out any shifting. So, Jonny, I hate when the chain pops off, especially on night rides, do you forsee me having any issues with either chain, bike or engine? If so, how should I remedy them? Thanks
 
J

JonnyR

New Member
May 13, 2012
1,203
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ronkonkoma, new york
i have a 10 speed cruiser and never have had a pedal chain issue only cheap Chinese engine side chain issues that i fixed with a heavier chain kmc HD410 or 415 is a nice chain also i like the 415 from the hardware store or #41 from tractor supply/grainger stores
 
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