hi !
simply the best solution/choise is to get the 5:1 reduction box (from ebay or from dax).
i have tryed the option where i welded 10t 415 Chain/pitch sprocket over the Pocketbike 6t sprocket. with it is needed mahoosive Reduction jack shaft gearing, that is why 5:1 reduction nox is the easyest and best solution by many good reasons.
the 5:1 reduction box is also exellent as it has gear against gear inside the box, no chain(s) like some of the PocketBike reduction boxes have (the 3:2 reduction boxes from mx style pocketbikes and atv's)
it will not be durable option to use the PocketBike sprockets, it will also cause you various problems on Chain(s) and Reduction Box output shaft gear options.
bye
m
ps i have 26" mtb with Pocket bike 47cc Cagllari engine and i have the 5:1 reduction box etc parts and have build engine fittment parts etc all by my self including secondary gearing etc++
best tip that i can give as a starter after this is to go into this topic and pick some ideas:
http://motorbicycling.com/f36/front-mounted-minimoto-engine-16978.html
it will be uber important to make good engine plate fittment including engine top support like in the minimotos, not juts supporting/locking down the engine from its bottom as Cagllari pocketbike engines do vibrate alot and it would Crack your casings by time.
about the ebay Cag engine that you linked:
i would assume that you know the Carb on it is complitely bad, 1st the Fuel Switch will start to leak and the seal expands by fuel. Rather use the China clone/copy Dellorto SHA or PHBG19xx, both mentiond carbs are produced with intake manifold so they are Plug & play with fine tuning the jetting.
some of the Cag engines have really bad guality coil. worth checking the Coil model buy seeing if it has Silicon on the ht-lead fittment and what is the Coil barnd marking (to avoid the bad1)
What comes to tuning/exhaust options, ya have plenty to choose from like 5. Chainsaw style small box is available from Dax or you can use PocketBike exhausts that have real calculated Chambers for best power/torq/peak power/power band features.
in my opinion, the ebay linked Cag engine is over priced especially as it has the ****ty Carb on it.
What comes to the PullStarter cover, check that the Bendix is made from the Aluminium alloy and not the Plastic. in my opinion the Aluminium allouy PullStarter covers are the best because you can rotate the Pullstart into wanted direction as it has 3 bolts in it with 120degree placements.
in my own bike i have the engine on rear rack and as my Starter cover has the 120degrees 3 bolt fittment i can rotate the cover so that i can easyly pull/start the engine while pedalling.
