Well being new...
... Slickbike gear changer ...
... give your thoughts as to how reliable they are.
Thanks Fly
Hi Fly, welcome.
Is this your first build?
A jackshaft (shift kit) works great, but reliability is solely dependent on your mechanical skills and tools.
It is not a piece you just 'bolt on', it is box with like 50 parts that have to fit perfectly together and that requires filing and grinding.
4-stroke jackshafts are pretty easy, here are a few I have done.
http://kcsbikes.com/KCsBuilds.asp?motor=4-stroke&Drive=Yes
2-stroke jackshafts are another story.
The base of the jackshaft first attaches to the engine which is no small feat and it has to be perfect.
Here a few 2-stroke shifters I have done.
http://kcsbikes.com/KCsBuilds.asp?motor=2-stroke&Drive=Yes
In either case you have to pull your existing pedal system out, then assemble the new one and install it.
If you are new to these engines and building I suggest you just build a simple direct drive first.
If you don't like the hassle of them to begin with you aren't out weeks of frustration and a couple hundred bucks.
If ya dig 'em, cool, sell yours while it is still fairly new and look into building a shifter.
Or of course you can just dive in head first and go for it as gears change everything on a motorized bike.
Just read the instructions and don't skip steps and it will be reliable.