MTB pitbike build - AUS

damonjackson_spl

New Member
Dec 2, 2008
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Hoebart Australia
Pitbike MTB Build
alloy duel sus/ MTB
49cc pitbike engine rack mounted
solid bar rack with 4mm plate mounts on industrial vibration reduction clamps (thanks bro *cough hydrualics engineer *cough)
need to order another length of chain and probably a bigger chainwheel as the teeth number are tiny, more like a timing chain than bike chain!






enjoy..

cheers

Damon
the tassie devil
 

Brains

New Member
Jul 21, 2008
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Adelaide Australia
Done well Damon, I have found with my custom builds when utilizing poket bike motors that they are very severe on vibrating mounts to death, all my mounting brakets & cradles are constructed utilizing 6mm plate steel, welded at all points, no bolted brakets
 

damonjackson_spl

New Member
Dec 2, 2008
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Hoebart Australia
g'day brains!

how much can you get me a race engine for again?

yeah i am excited to see how the clamps go as they are designed for holding hydrauilcs lines etc/ to limit vibration, frame is alloy hence the mild steel rack, hopefully more forgiving than 6065 alloy!

also the motor has electric start so should be smooth sailing starting the motor..

what gearing are you running? you have 20" wheel?
 

Brains

New Member
Jul 21, 2008
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Adelaide Australia
I build all my pit bike conversion on steel frames (only had a mig) but I have got a AC/Dc Tig so aluminium is possible, standard set up for me is 6 tooth front & 72 sproket.

I have never worked on the type of pocket bike motor you have used, so will be intresting to see what results you attain

Keep me posted with an update once you have test driven your new baby
 

damonjackson_spl

New Member
Dec 2, 2008
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Hoebart Australia
ok, have bought a new pocket bike engine, the 47cc which is actually a 40cc..

had to fab up new mountings and luckily the gearbox i had fitted onto the centreifugal clutch and funnily enough it is perfect for RH drive!!

so i welded a 12t bmx cog onto the pocket bike cog (which is on a spline with sirclip) so i can experiment with different ratio's etc/

then i welded a 56tooth 415 sproket from one of my left over kits onto a 22T cog from a dismantle 7sp cluster, this way I can move the sprocket into perfect alignment by sliding it down the splined shaft of the shimano cassette..

anyway so the rear end freewheels on the rear shimano cluster and also have a 20T cog on there as well for the pedals, so all i need to do is make freewheel cranks so when i am motoring it doesnt make my pedals spin around ;)

pics
 

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damonjackson_spl

New Member
Dec 2, 2008
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Hoebart Australia
edit:

took it for 1st voyage and it is very nice!! freewheeling is awesome!! NO DRAG!!

had to make a alloy chain deflector to stop chain from jumping off, but after getting the sprocket alignined properly it now stays on everytime!!

it is very camparible to the 66cc chinese engine but it only 40cc!!

so end result very very happy, you can pick the motors up very very cheap and created a nice full sus/

will pull it down for paint shortly/
 

damonjackson_spl

New Member
Dec 2, 2008
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Hoebart Australia
took it for a full throttle run tonight..

MAYHEM, allot faster than the 66cc chinese motors and this is only 40cc, I am now going to defintely explore these engines more and buy some modified race engine parts from an AUS site.. you can get big bore kits to make the motors genuine 49cc, billet flywheels and carbon fibre reeds etc/ you can get thes engines up to 8HP aparently, but they are 39cc watercooled race engines only about $400 AUD!!

will keep you posted as I build another one soon!