Jackshaft Shift Kit Questions for anyone thats allready installed one

sactownie

Member
Joined
Jun 3, 2013
Messages
168
That's the first time i've seen a magnet failure as described by your photos, and i've traveled over 30,000 miles in 3 & 1/2 years on my motorized bicycle in riding conditions from the good to the downright ugly.

I struggle to understand how such a magnet failure could happen given correct assembly of the parts?
Yea I used this forum as a bible when I put this thing together, I didn't want any failures I took my time and double checked everything. The motor was running fine, or so I thought up until it just died. I am hoping the place I got it from will at least send me a replacement at a discount price. If you haven't noticed yet I am unemployed and planned on using this to look for work, I used to be a auto mechanic so Im really good with mechanical stuff, there was no warning to this failure, I even checked that mag rotor bolt early in the build.
 


Fabian

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Joined
Sep 8, 2009
Messages
4,522
Basically you will need a new crankshaft, magnet and keyway and possibly a magneto coil to get the engine operational.

Magnet/keyway = approx $10
Crankshaft = approx $30
Magneto coil = approx $20

or you can get a complete replacement engine for $100. In the past i have done deals with my vendor to purchase some of his returned engines which have failed during the warranty period, of which most of them failed due to operator error = incorrect oil/fuel ratio or stress related failure from over revving.

I picked these engines up for $30; then disassembling and sorting through undamaged components to assemble a reliable engine.

Having said that, if you don't have a jig to press out the crankshaft from the engine cases and also to reassemble the crankshaft in the cases, you'll always have an engine plagued with excessive vibration.

Even if this is beyond your skills at the moment, at very least an alternative option exists to get the bike back on the road.
Worst case scenario is that you only damage already damaged engine parts in the learning and disassembly-reassembly process.
 

sactownie

Member
Joined
Jun 3, 2013
Messages
168
Out of curiosity, what was the installed air gap between magnet and magneto coil arms?
Unknown I never measured it but I eyeballed it when I checked out the motor before I installed it and it looked ok from top to bottom.
 

sactownie

Member
Joined
Jun 3, 2013
Messages
168
Basically you will need a new crankshaft, magnet and keyway and possibly a magneto coil to get the engine operational.

Magnet/keyway = approx $10
Crankshaft = approx $30
Magneto coil = approx $20

or you can get a complete replacement engine for $100. In the past i have done deals with my vendor to purchase some of his returned engines which have failed during the warranty period, of which most of them failed due to operator error = incorrect oil/fuel ratio or stress related failure from over revving.

I picked these engines up for $30; then disassembling and sorting through undamaged components to assemble a reliable engine.

Having said that, if you don't have a jig to press out the crankshaft from the engine cases and also to reassemble the crankshaft in the cases, you'll always have an engine plagued with excessive vibration.

Even if this is beyond your skills at the moment, at very least an alternative option exists to get the bike back on the road.
Worst case scenario is that you only damage already damaged engine parts in the learning and disassembly-reassembly process.
Yea im going to try to get a replacement from enginesonlineshop.com at this point I would be happy if they will send me a replacement for $100 or under, no one else will ship to california usa. As long as they will warranty the replacement for atleast 30 days ill make sure to put some major miles on it in that 30 days.
 

zwebx

Member
Joined
Mar 11, 2012
Messages
69
I have got a queston, for fabian or anyone that knows..
how long is your jackshaft kits bottom bracket? my current bottom bracket is too small also whats your spacing on the sprockets?
 

Fabian

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Sep 8, 2009
Messages
4,522
@ zwebx

Please take some hi-res photos so we can better understand what the issues are with your bottom bracket.

The spacing on the front chain wheels is very tight on my bike because i run 4 sprockets in the space that was originally designed for 2, thereby allowing my bike to retain the use of 27 gears.
 

zwebx

Member
Joined
Mar 11, 2012
Messages
69
IMG_0294[1].jpg
here is a placeholder for now i will go to where the bike is wednesday night and get some photos
im only attempting to put one drive gear on (to the rear wheel) for now because i dont have the room or the extra sprockets but i will ad a 8speed megarange rear to my rear wheel and retain some lower speed ratio to join you on your extreem rides.. im thinking of ditching my clutch welding it up and putting one off a qmatic drive on it
 

Pablo

Motored Bikes Sponsor
Joined
Nov 9, 2007
Messages
1,825
Oh, it's a 4-stroke. One thing for sure, your chainring is on the wrong side of the freewheel. We use the SBP 206 mm custom BB cartridge with keyway and FW adapter for wide 4 strokes.
 

zwebx

Member
Joined
Mar 11, 2012
Messages
69
Oh, it's a 4-stroke. One thing for sure, your chainring is on the wrong side of the freewheel. We use the SBP 206 mm custom BB cartridge with keyway and FW adapter for wide 4 strokes.
Its a custom gearbox, runs in reverse cost a bit of $$ but i think it may be better than a jackshaft
why the keyed adaptor when my freewheel is attached to my right pedal?
 

Fabian

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Joined
Sep 8, 2009
Messages
4,522
I see. It's a 4-stroke. That changes things completely.

I have no idea how that combination will work out as i'm old school and only mess with 2-stroke bicycle engines.

Never had any experience with 4-stroke bicycle engines and i never will.
 
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