First build: Two stroke 80cc mountain bike with jackshaft

Hey guys! Glad to have found this place.

This week, I started my first build, a Wildcat PK80 with a Sick Bike Parts jackshaft kit. The base is a 1997 Gary Fisher Mamba that belonged to my mother...she was about to throw it out, but I saved it from this grisly fate to give it a second chance. Right now I'm waiting on the right size chain breaker to show up; in the meantime, I plan to hang out here and pick up whatever tips and tricks I can.

Eventual plan is to add a complete electrical system with headlight, brake light, speedo, and horn, possibly with a dynamo. The grip shifter dangling off there will most likely become a tank shifter.

 

[FurryOnTheInside]

I have read the posts about the GT LTS builds. I have read very nearly every post on the forum (that isnt about 4-strokes or friction drive!) in the correct order lol.
The development of the original Shift Kit leading to the creation of Sick Bike Parts is an interesting story.
The newer Shift Kit mount plates are an improvement on the SBP guys' original design. The older and not as good version is currently being ripped off by the Chinese jackshaft kit. I think the Shift Kit plates have advantage mainly in reduced flex. (Really important, that flex can throw your chain)
I always wished for a seriously stiff yet light aluminium box to mount the jackshaft through.
Would you modify your frame to make the jackshaft bearing mount integral to the frame? Or engine mount integral to the frame? Does jackshaft height need to be adjustable? What exciting new stuff can one do when one commits to actually modifying the bike frame itself?

 

[rover528]

Furry is right. The peddle chain has nothing to do with the engine drive, peddling will only help the engine. In fact, often when I'm going down a steep hill where I don't need the engine I will cut it off and hold the clutch handle in and just glide down the hill to save gas only using the peddles if needed.

Does the motor shut off when you do this or just go into idle mode.

 

[FurryOnTheInside]

Does the motor shut off when you do this or just go into idle mode.

Its up to you. Pull (and/or lock) the clutch lever in and release the throttle to idle the engine. Or press the killswitch too, if you want silence.

Personally, I do like to kill the engine and enjoy the quiet time. I assist the bike to extend (slightly) the deceleration from 30-35mph down to around 15mph before I want it faster again. Then I bump start the engine again (starts instantly) and accelerate, and repeat.

 

[Tyler6357]

Does the motor shut off when you do this or just go into idle mode.

I usually hit the kill switch to kill the engine completely.

 

[Tyler6357]

Its up to you. Pull (and/or lock) the clutch lever in and release the throttle to idle the engine. Or press the killswitch too, if you want silence.

Personally, I do like to kill the engine and enjoy the quiet time. I assist the bike to extend (slightly) the deceleration from 30-35mph down to around 15mph before I want it faster again. Then I bump start the engine again (starts instantly) and accelerate, and repeat.

Yea, it's never a bad idea to kill the engine and let it cool down.

 

[Captain Rainmaker]

What the crap happened to my thread?

Anyway, quick update. Still runs awesome. Considering some upgrades like a reed valve, expansion muffler, IGH (like one of Shimano's e-bike hubs), and a larger cog on the jackshaft, but I'm also perfectly content to just leave it alone.

 

[CrazyDan]

Internally geared hubs are a godsend, no lag in the shifts. Just don't shift under power or grindy grindy happens.

 

[FurryOnTheInside]

This internal hub needs torque on the pedals/ power applied to shift...

Watch "Shimano Alfine.mpg" on YouTube

They have 4 or 5 different models too choose from,,, we can add the heavy application sproket and heavy duty chain ...

It is the widest hub at 165mm,,, our machine shop friend can make outter steel housings/ spacers for my fat tire 200mm width ...

Two 17.5mm spacers for either side of the Alfine...

Bull low speed for off road,,, direct drive for casual outtings,,, OD too get back to staging area ...

Im still game planing...

Don

Theres some interesting comments from (afaik) actual owners experiences under that video, as well as the usual opinion stuff....

I believe the experience and I agree with the opinions around the overcomplication inability to home/ roadside service.
I'll stick with derailleur and cassette on a pawled free hub.
The Halo 6D is possibly the king of the pawled freehubs. I have just one of these, on a 48 spoke 559x30 double eyeletted Halo SAS rim.

Plus I need that QR axle to attach my single wheel trailer.

 

[5-7HEAVEN]

My first gas bikes were friction drives.
Then I found Scooterguy and installed my engines in the upper mid frame. I also used the shift kit.

 

[Captain Rainmaker]

Rev2.

So after the included crappy plastic Chinesium throttle stuck open and sent me careening over a curb (I'm okay), I figured it was time for some upgrades. New aluminum throttle from Sick Bike Parts (very nice piece), and I figured as long as I was ordering parts from them I might as well grab their expansion pipe while I'm at it. Extremely pleased with it.

The cylinder is black now because I snapped an exhaust stud in the old one while installing the pipe and I decided it'd be a lot easier to swap on the jug from the old busted Wildcat instead of drilling and tapping for a new stud.