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Two Stroke Addiction
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Discussion Starter #1
This post is as an "Up-date" from my Mini-Quad Post, I did a different thread because I feel this engine information could be of help to others building a PocketBike engine..and these folks may not be interested in reading my Mini-Quad thread but they always can read this, get some good ideas and colaborate to make this thread a good one.

Here we go......

I got this kit to modify an "stock" air cooled engine, the site said it was a BiG Bore Kit for Mini-Bike:



Once I disasembled the engine I did a "preliminary" comparation between all the parts..and this is what I found:

Both cylinders are 44 m.m. bore:


The BB kit has "boost ports", separate head assy but the intake ports looks same height and same size:

 

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Two Stroke Addiction
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Discussion Starter #2 (Edited)
Pistons seems to be identical except for the "windows":


Crankshafts are same "stroke", the new crank is "full circle":




By the 44 m.m. bore x 32 m.m. stroke(to be confirmed later) the engine seems to be 48.67 c.c., same disp. as before...if I'm not wrong, I don't understand WHY they call this a BB kit!!!marcelo
 

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Two Stroke Addiction
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Discussion Starter #3
Before I start to "drop" numbers for this built, need to confirm stroke, port heights, etc.

To make this the easy way, let's "built" a handy tool: A Set of "Test" Bearings!, this "test bearings" would allow to instal & uninstall the crankshaft in a snap...

Step 1:
Get your old bearings and your Dremel, using the right stone, grind the inner face of the bearing, trying to do it slow and evenly:



Grind the inner race until it drops into the crankshaft smoothly:



Step 2:
Grind the outer rce of the bearing in the same way:



Get a permanet marker to aid in this process:

 

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Two Stroke Addiction
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Discussion Starter #4 (Edited)
Paint the outer race so you can see if you are grinding evenly:


Grind until you can install the bearing on the half carter very smooth:



Step 3:
Once your set of bearings are ready, clean them very well with a degreaser, make sure they don't have ANY metal debris, we are going to use these bearings with the new crank and we do not want ANY contamination:



Step 4:
Now we have a Set of Test bearings ready to work with!

 

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Two Stroke Addiction
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Discussion Starter #5
These bearings will be very handy every time we work on a new engine:


Next step will be to "run" some serious numbers to determinate stroke and port heights....
 

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Two Stroke Addiction
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Discussion Starter #6
Did some research and now I know there are 43 c.c. stock engines and 49 c.c. stock engines...this BB kit was intended to "upgrade a 43 c.c. engine, every day You learn something new :)

Lets install the "Test Bearings" on the new crancksahft:


Now installed inside the carters, using only two opposed bolts:


Now I attach the engine to this custom fixture(This fixture was developed to "hold" scooter cylinders while doing port job)


Try to set the engine as evenly as possible
 

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Two Stroke Addiction
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Discussion Starter #7
Now let's built another "tool" from the old starter motor armature:




Got it!:


Now You are wondering what do I want the shaft of the motor for, right?
 

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Two Stroke Addiction
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Discussion Starter #8
Simple.....to check for ports height(degrees):





More to come tonight...I need to get some more bolts and nuts this afternoon ;)
 

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You did good got a TM cylinder w/ your kit. I have that piston in my Blue Demon motor, didn't like ring stop locations not far enough apart, look at your old piston grooves look where the pins are. You have a 4 port. They call it a Big Bore kit cause it was for 40mm bore, 47cc ( 40cc ) old Cags.
 

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Two Stroke Addiction
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Discussion Starter #10
You did good got a TM cylinder w/ your kit. I have that piston in my Blue Demon motor, didn't like ring stop locations not far enough apart, look at your old piston grooves look where the pins are. You have a 4 port. They call it a Big Bore kit cause it was for 40mm bore, 47cc ( 40cc ) old Cags.
Thanks for the comments EPR:)...I will look closer to those ring stop pins
 

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Two Stroke Addiction
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Discussion Starter #11
Now, let's find the TDC....Instll the piston and gasket:



Wow!, looks like theres room for some porting here, What Do You think?:




 

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Two Stroke Addiction
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Discussion Starter #12 (Edited)
Perfect TDC:



All for today...not too much, but It's late...



CAM2: I will appreciate your advise on what timings, CR, etc. are o.k. for this engine, I'm going to run on pump gas (93)

As for the pipe: PBU doesn't have those nice pipes anymore...just the "crappy" pipes, I gues my best choice is to get those JetPro pipes CAM2 recomended at e-bay...I was going to buy both pipes this afternoon but I hesitate because they say "Jetpro pipe for 47cc pocket bike side car"...and I'm wondering if those "pocketbike side cars" use same pipe shape a CAG's?????...PLEASE ADVISE....

Thanks!
 
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All the side car racer Cag I have seen are just a cag w/ a side car and 3rd wheel added, If it has that S shape its probably OK.
 

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Two Stroke Addiction
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Discussion Starter #14 (Edited)
All the side car racer Cag I have seen are just a cag w/ a side car and 3rd wheel added, If it has that S shape its probably OK.
Thanks EPR...problem is that the "seller" doesn't want to send me some pics of the pipe "out of the plastic bag" and the pic at e-bay doesn't really show the pipe....I don't want to spend on the pipe and freights just to find out it doesn't fit my application...
 

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No matter what you get it may not fit with out some mods. had to mod the Jet Pro to fit my A2 cag but bolts right up to my A1, and won't fit my Lucky 7 at all.
 

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Two Stroke Addiction
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Discussion Starter #16
No matter what you get it may not fit with out some mods. had to mod the Jet Pro to fit my A2 cag but bolts right up to my A1, and won't fit my Lucky 7 at all.
I see...does this looks to You as a pipe I could install, maybe with some mods?...I don't want to have to "cut & weld" the complete pipe and end doing almost a complete built pipe:

Jetpro pipe for 47cc pocket bike side car NEW | eBay

I may go for one of these?:
http://www.pocketbikeplanet.com/f82/more-help-pipes-60919.html
 

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You might be right, that pipe might go at a different direction on a side car away from the monkey rather than out the back, it does not look right, and I know nothing about the other pipes, but I do like the one that the muffler tilts up.
 

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Two Stroke Addiction
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Discussion Starter #18
You might be right, that pipe might go at a different direction on a side car away from the monkey rather than out the back, it does not look right, and I know nothing about the other pipes, but I do like the one that the muffler tilts up.
Thanks EPR...I have been looking to tht pipe for hours and the shape doesn't look similar to those pipes You show me before...I will forget about it and go for the Zocchi M1
 

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wow this thread is awesome!!! lots of good info in it with detailed pics. way to go mexicano im gonna be posted to this one
 

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Two Stroke Addiction
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Discussion Starter #20
wow this thread is awesome!!! lots of good info in it with detailed pics. way to go mexicano im gonna be posted to this one
Thanks Johnson712!...please feel free to do any contibution to this thread to make it grow
 
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