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what size parts will fit, and why did my last motor blow

2130 Views 9 Replies 4 Participants Last post by  EPR, 
L
hey guys greetings from ontario:)

i have a rear wheel friction drive kit on my bicycle, that came with a stock gx35 knockoff, it was underpowered and sucked, and the crank eventually snapped in half! i got 2 different pocket bikes for parts, i threw the first engine on, ran in with a 40:1 mixture, and it seemed ok, but it wasnt powerfull, eventually it lost compression and died, i pulled it apart and it was cooked, it was clearly running to lean, anyways, i have another engine i wanted to use, i took the top end off of it and tried to switch the pistons and head over, but as it turns out, one piston is much smaller than the other, i read about the 44mm pistons and the 40mm pistons, but here is where im confused, the engine i blew has 40 clearly stamped on the inside of the piston skirt, and it has an arrow on the piston, the engine i currently have on my bike has an unmarked piston, with no arrows, however its a decent size smaller than the 40mm piston, it looks just like any normal pocket bike engine from the outside, i got it all together and it runs good, but i want to prevent it from blowing, also i dont have the stock muffler, i have a canister style muffler from a 49cc piston port engine, will this work ok? and what engine do i have? do they make pocket bike engines with 35mm pistons? how many cc is this thing, if the 40mm piston was 39cc then this must be like 30cc or something, i didnt know they came this small, thanks guys!
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CAM2
40mm piston is a 43cc engine...The chinese used to try and confuse the USA customs into beleiving the engines were only 39cc to get them imported into other countries faster........Eventually they tipped their hand and now the newer bikes have the truer spec plaques and engine size markings...........

Both of the the Dax reps and the Mitsubishi rep engines that come on most chinese made pocketbikes come in either 40mm(43cc) or 44mm (49cc)...Theres mitsubishi rep scooter engines that are 23,,26 and 33 cc's aswell

In order to keep your engine from seizing and burning up you must mix the gas and oil ratio right aswell as keep it in tune with the lowspeed and highspeed needles on the carb if it has a pumper carb...if it has a floater carb I suggest getting a pumpercarb retrofit kit for it.......Break-in is 28:1 mix for 4 tankfuls of variating but gentle riding...I like to heat cycle mine a few times before introducing a load to it..After break-in you can safely run 42:1 even 50:1 but a safe mix ix 40:1.....Good Luck and post up some pics of what ya got.............Photobucket is the best way.....
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C
That's some good info
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C
By pumper carb, do you mean the one with a primer bulb on the bottom?
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EPR
3
Yes Walbro style carbs.

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CAM2 said:
40mm piston is a 43cc engine...The chinese used to try and confuse the USA customs into beleiving the engines were only 39cc to get them imported into other countries faster........Eventually they tipped their hand and now the newer bikes have the truer spec plaques and engine size markings...........

Both of the the Dax reps and the Mitsubishi rep engines that come on most chinese made pocketbikes come in either 40mm(43cc) or 44mm (49cc)...Theres mitsubishi rep scooter engines that are 23,,26 and 33 cc's aswell

In order to keep your engine from seizing and burning up you must mix the gas and oil ratio right aswell as keep it in tune with the lowspeed and highspeed needles on the carb if it has a pumper carb...if it has a floater carb I suggest getting a pumpercarb retrofit kit for it.......Break-in is 28:1 mix for 4 tankfuls of variating but gentle riding...I like to heat cycle mine a few times before introducing a load to it..After break-in you can safely run 42:1 even 50:1 but a safe mix ix 40:1.....Good Luck and post up some pics of what ya got.............Photobucket is the best way.....
Click to expand...

ok thanks cam!! it does have a floater carb but im sure i can get my hands on a carb with adjustment needles, il work on the pictures, thanks!
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L
CAM2 said:
40mm piston is a 43cc engine...The chinese used to try and confuse the USA customs into beleiving the engines were only 39cc to get them imported into other countries faster........Eventually they tipped their hand and now the newer bikes have the truer spec plaques and engine size markings...........

Both of the the Dax reps and the Mitsubishi rep engines that come on most chinese made pocketbikes come in either 40mm(43cc) or 44mm (49cc)...Theres mitsubishi rep scooter engines that are 23,,26 and 33 cc's aswell

In order to keep your engine from seizing and burning up you must mix the gas and oil ratio right aswell as keep it in tune with the lowspeed and highspeed needles on the carb if it has a pumper carb...if it has a floater carb I suggest getting a pumpercarb retrofit kit for it.......Break-in is 28:1 mix for 4 tankfuls of variating but gentle riding...I like to heat cycle mine a few times before introducing a load to it..After break-in you can safely run 42:1 even 50:1 but a safe mix ix 40:1.....Good Luck and post up some pics of what ya got.............Photobucket is the best way.....
Click to expand...

hey i had a gas skateboard, it had the 49cc piston port engine, gsmoon engine covers, i have the pumper carb from that, will it just fit right on? and then i run lines to the carb, one for return and one for gas? does my tank have to be air tight? will this carb work on the standard reed induction pocket bike engine i have on my bicycle? this pumper carb has a small hole that lines up with a hole in the plastic manifold on the gsmoon engine, will it work without that hole attached to the reeds?
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L
EPR said:
Yes Walbro style carbs.
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i have the exact same carb in picture #1. do i just mount it like in the picture? and it will work?
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CAM2
3
Youre gonna need a cag pumper carb intake manifold to fit the pumper carb you have...All my cags have pumper carbs on them now and the ease of start-up and tuning gives the cheapo crap a new spotlight now the ones that run are used more than theyre worked on...... once you acheive that status youll be fready for another pocketbike to add to the collection......Good Luck





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EPR
Yes, the first photo is a 15mm Walbro SHA China copy carb, on a Plastic Cag to 15mm manifold. The same carb came on my 49cc piston port scooter engine. You can get a Cag manifold at morethanhundreds on Ebay or MBPN online. $8.95 + $3 S/H or something. They used then on some small Cag ATV 4 wheelers.
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