Jackshaft Shift Kit Questions for anyone thats allready installed one

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Jun 3, 2013
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#1
Hi people. Doing my 1st install and have some questions maybe someone knows the answers?

1. What size chain do you run on the engine to jackshaft sprocket?
I'm trying to use 415 from the engine kit, It looks like its going to rub the jackshaft plate. The engine sprocket wont accept 410 bmx chain, my guess the sprocket to wide? if using 415 do you use extra washers to space the jackshaft sprocket further to the outside?

2. Can you use a 1/2 link on the engine to jackshaft that has a tiny cotter pin without that link failing?

3. What size sprocket do you have on the engine output? Mine has 10 teeth, my engine to jackshaft chain wouldn't fit with any combo of the included shims. After days scratching my head I milled the spacer down from 1/2 to about 3/8, took me about 3 hours last night with a piece of glass and sandpaper and now I have no problems fitting it, has anyone else had to do that?

This is where I am at in my install as of tonight. I am taking my time trying to get it right the first time. This is my first motor bike too so the engine is brand new also.
 
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Fabian

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#2
You do not mill the spacer down.
You file the part of the engine case where the spacer sits onto. This part of the engine is typically not flat, so it needs to filed down about 3mm to get it perfectly flat and square to the inner face of the clutch housing.

Use the 415 chain supplied with the shift kit. It will not rub on the shift kit plate if the 17 tooth sprocket is lined up with the 10 tooth engine output shaft sprocket. The shims are included to give you the ability to get the alignment perfect.

The 10 tooth engine output shaft sprocket is the only one that seems to be available.

A good tip is to use glue (i used super glue) to attach a piece of 4mm (hard) rubber to the (standing from behind the bike) left hand side of the inner jackshaft plate, thereby allowing the plate to transfer twisting force directly to the seat post tube.
If you do not make this small modification the twisting motion (especially if you are using the SickBikeParts optional high torque gearing) will pull the engine and jackshaft in a downwards arc which will cause chain alignment problems; either derailing the chain or punching out chain side plates.

Do a Google search for:


"Additional stability for the Sick Bike Parts shift kit"


and


"Chain Tensioner for 2-stroke engine and SickBikeParts (SBP, Sick Bikeparts) shift kit"


and


"Chain tensioner for chainwheel side of SickBikeParts (Sick Bike Parts SBP) shift kit"





and this beneficial modification if you travel on rough surfaces:


"Chain Stabilisation Device in conjunction with SickBikeParts, SBP, Sick Bike Parts, shift kit"
 
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#3
Yea I filed the motor mount pad on the actual motor casing. It was already pretty flat to begin with. I cant see filing that down 3mm with the file I had, It would have been really uneven so I just milled the spacer. The SBP install manual shows a 11 or possible 12 tooth engine output sprocket on there install example. Thats why I thought maybe I have an uncommon sprocket that cause me not to be able to fit 15 links correctly.
The shift kit comes with a 410 chain for the jackshaft to crank. I tried to fit that to the engine to jackshaft, the engine sprocket doesn't like it.
I email the tech guy at sbp all these questions but didn't really get any answers.
I'm not new to any of this tech stuff, Maybe a little rusty.
There must be differences in the 80cc (66cc) engine kit I got from engines online shop why I had to modify this thing to fit. I just worry about that chain being to wide, I don't want it rubbing the jackshaft plate. If I could fit the 410 thinner chain it would be great but I guess I have to change that engine sprocket?
 

Fabian

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#4
If the shift kit comes with a 410 chain, then fit the 410 chain.

All of the Chinese Bicycle Engines are different, even from the same manufacturer - some of them can have seriously different (external) dimensional measurements.
I have had to file down every one of my engine cases to get the mounting area flat and true.
With a steady hand and a small (engineers) hand square and attention to accuracy you can get the engine to jackshaft mounting surface perfectly flat and true. On one occasion i spent 3 hours getting it perfect in all dimensions and for proper chain fit and a heck of a lot of material had to be filed away.

The SickBikeParts sprockets (and optional sprockets) are "exclusively" for the right hand side of the Jackshaft kit, except for the 17 tooth left hand side sprocket.
 
Joined
Oct 23, 2007
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#5
Fabian, thanks for all your help getting this customer good information. Just to clear up a point. All Chinese 2 strokes come with 10 tooth output sprockets and so that is what is shown in our instructions. As the instructions state we recommend using the chain that came with your engine kit for the left side chain and the 410 chain that came with the shift kit for the right side chain.

As was noted not all engines are the same which is why we give some direction in the manual and shimming options with the kit. Typically what works is the 1/4 inch spacer with the two holes and the two 1/8 shims but sometimes a little material removal from the back of the engine is required and as Fabian said recommended to get proper mating and alignment. If you have any more questions feel free to contact me directly through our website.
 

KCvale

Motorized Bicycle Vendor
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#6
Just wait a day or so, maybe even a week as it so much, for pics and tips.
I have built a couple dozen JS builds 2 and 4 stroke and just doing another 2-stroke now and taking pics and notes for a new assembly guide for my shop.

It is an art bud, no ****, about 30 steps and each progressive step requires that each previous one was done right and in order or you will find yourself just wandering in circles or with a precision raw power transfer assembly that fails in short order because of improper assembly.

I post this same warning in every JS related topic.
'Jackshafting is not for the faint of heart or mechanically challenged'.
It can however be done well with the SBP parts supplied and gears change everything ;-}
 

Fabian

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#7
One of the best tools to have in your tool collection is a digital vernier caliper. With some basic maths you can measure up dimensions then add or subtract numbers to find out if things will fit or if they will not fit when installed.

It saves on having to use the method of an ever larger hammer to make things fit together.
A digital vernier caliper can be purchased for as little as $20.
 
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#8
Has anyone ever used aluminum pie tins or cans cut out for shims? Im sure I could have got it to fit if I had some different sized shims.
 
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#9
Also no one has replied about my chain thickness. Right now the sprocket is dead inline with the engine sprocket but the chain is so wide its really close to the jackshaft plate.Is it ok to put a washer/spacer there or will I have problems? How close is your chain? pictures? I just dont trust that being so close.
 

Fabian

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#10
Use the 415 chain supplied with the SickBikeParts shift kit.

My assembly required the use of 2 large washers and one thin washer to get perfect alignment with the 10 tooth sprocket, so i guess there must be 3 or 4mm between the chain and the jackshaft plate.


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sickbi10.jpg


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sickbi16.jpg
 
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