jjeeff
New Member
I have a trek 7.2 fx with disk breaks, what engine kit should i get?
what should i get??
- Thread starter jjeeff
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KCvale
In memory of KCvale 1959 - 2019
Are you talking about this Trek 7.2 with front and rear discs?
If that's the case it's a no-brainer.
A jackshafted 2-stroke is the way to go.
You keep both disc brakes and your engine can use the 7-speed gears on the rear wheel.
This is a similar build.
~$400 for a DIY build and a rewarding ride if you have the building skill and tools to install the shift kit properly.
Just my opinion as always, meaning what I would do with said bike.
If that's the case it's a no-brainer.
A jackshafted 2-stroke is the way to go.
You keep both disc brakes and your engine can use the 7-speed gears on the rear wheel.
This is a similar build.
~$400 for a DIY build and a rewarding ride if you have the building skill and tools to install the shift kit properly.
Just my opinion as always, meaning what I would do with said bike.
No place more than MAB's have I found the saying "you get what you pay for" is more true.
As Darwin said, you need to figure a few things out first.
I will add: the more complex, the more things to come loose.
If you like to tinker, frame mount china girl, if you want to ride FD or GEBE WITH quality engine.
If you're going to do any kind of serious jumping, frame mount is the only real option.
Any and all are fun fun fun.
As Darwin said, you need to figure a few things out first.
I will add: the more complex, the more things to come loose.
If you like to tinker, frame mount china girl, if you want to ride FD or GEBE WITH quality engine.
If you're going to do any kind of serious jumping, frame mount is the only real option.
Any and all are fun fun fun.
jjeeff
New Member
KCvale: so that top trek bike is defiantly the one im talking about. So do I buy the 2 stroke engine separately and then buy the jackshaft kit?
I've seen disk break kits specifically designed for motorized bikes. The rear disk is significantly larger so they can fit over the engine kits rear sprocket. Don't know if that would work on most bikes tho. Frames with disk breaks are usually made in such a way that if you want a motor on it you'd need to switch to a V break. If your worried about breaking power most of that comes from the front break anyway so keep that a disk break and change out the rear for a V break. I plan on fitting my GT Dyno Deuce cruiser with a motor in a few months and that bike only has a rear coaster break but I can swap out the front fork and front hub for ones that are disk break compatible because I wan to keep the original rims.
from what I've read about jack shaft kits, a jack shaft kit is good for going faster changing gears and helps you keep both front and rear disk breaks but most states if you want to ride a motorized bike without a license, registration, and insurance it can only be one speed from the engine to the rear wheel. In most states the legal definition of a moped/motorized bicycle that doesn't need a license, insurance etc. is often a bike that has an under 50cc engine with fully operative petals and no gears.
from what I've read about jack shaft kits, a jack shaft kit is good for going faster changing gears and helps you keep both front and rear disk breaks but most states if you want to ride a motorized bike without a license, registration, and insurance it can only be one speed from the engine to the rear wheel. In most states the legal definition of a moped/motorized bicycle that doesn't need a license, insurance etc. is often a bike that has an under 50cc engine with fully operative petals and no gears.
Last edited:
KCvale
In memory of KCvale 1959 - 2019
Yep, some states specifically state no gears, Arizona is not one of them ;-}
Yes you buy the motor and shift kit separately, mount the jackshaft base to the back of the motor, then mount the combo into the bike.
Is this your first build?
Are you really good with tools?
If it's your first build and you are not handy with tools it might be a bit more than you can do.
If you want to give it a go get the deluxe kit.
It has the specialty parts and tools you'll need.
http://www.sickbikeparts.com/catalo...ducts_id=29&osCsid=1p44nkm9g95j9ej1jgc7v6qc84
You have 3-piece cranks on the Trek so that makes the bottom bracket easier.
It's still a complex job though, there is no room for error or slop when you are redirecting ~3HP of spinning force around.
READ THE INSTRUCTIONS TO SEE WHAT IS INVOLVED!
http://www.sickbikeparts.com/Manuals/SBP2 Manual001 Rev A.pdf
Good Luck!
Yes you buy the motor and shift kit separately, mount the jackshaft base to the back of the motor, then mount the combo into the bike.
Is this your first build?
Are you really good with tools?
If it's your first build and you are not handy with tools it might be a bit more than you can do.
If you want to give it a go get the deluxe kit.
It has the specialty parts and tools you'll need.
http://www.sickbikeparts.com/catalo...ducts_id=29&osCsid=1p44nkm9g95j9ej1jgc7v6qc84
You have 3-piece cranks on the Trek so that makes the bottom bracket easier.
It's still a complex job though, there is no room for error or slop when you are redirecting ~3HP of spinning force around.
READ THE INSTRUCTIONS TO SEE WHAT IS INVOLVED!
http://www.sickbikeparts.com/Manuals/SBP2 Manual001 Rev A.pdf
Good Luck!
jjeeff
New Member
yes this is my first build. i was going to pay someone to put it on for me because i am not the most handy with tools, but that is proving to be just as hard as finding out what i need to buy. But i think im gonna go for it im going to get the jackshaft delux kit a 50cc engine and find a mechanic who i think is up to the job. Thank you for your insight and help
Arty
Well-Known Member
I agree with KC. Installing the shift kit isn't rocket science, but you do have to be careful with chain tension, sprocket alignment etc., and for me anyway, it took a bit of tweaking after first assembly, and obviously, there's more to go wrong than with direct drive.
They are fun though, and it's easier to keep the bike on the pipe at varying speeds, and to keep from thrashing that poor little engine at high RPM at road speed.
I do miss engine braking though, because of the extra freewheel on the pedal crank.
They are fun though, and it's easier to keep the bike on the pipe at varying speeds, and to keep from thrashing that poor little engine at high RPM at road speed.
I do miss engine braking though, because of the extra freewheel on the pedal crank.
jjeeff
New Member
KC: If it isn't to much to ask could you send me a materials list for the Gray Trek 8.3 48cc Shifter that is on your website? Im just confused if there is a specific type of 50cc engine i need, they all look different. And the gas tank and exhaust pipe? Will any of them fit onto any 50cc motor? I feel like its a elementary request but i just don't wanna buy something that wont work.
