What is causing me to backfire

4971 Views 12 Replies 4 Participants Last post by N!pples, Sep 18, 2012

beansdaddy78

Discussion Starter · Sep 6, 2012

my motor backfires a little when i let off the gas. what besides timing might cause this???

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CAM2

· #2 · Sep 6, 2012

running too lean will cause backfiring while decellerating

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beansdaddy78

Discussion Starter · #3 · Sep 6, 2012

CAM2 said:
running too lean will cause backfiring while decellerating

this is a 4 stroke motor, im gonna try to put it on my 69 fox spoiler
do the 4 stroke motors have the problem with running lean also?

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CAM2

· #4 · Sep 6, 2012

beansdaddy78 said:
this is a 4 stroke motor, im gonna try to put it on my 69 fox spoiler
do the 4 stroke motors have the problem with running lean also?

Of course they do....When I had a dyno in my basement it took 3 hours to find out there is a tab in the floatbowl that holds the float high so the fuel just dribbles past the float needle...............

If you do the float restrictor mod and tune the carb richer you can eliminate the pop...........

Theres mods to make your stock carb perform way better...Theres an air/fuel adjustment screw next to the idle screw...stock factory setting is 2 full turns out....You can richen it or lean it out up to 1 full turn in either direction if you have to adjust for conditions

Theres a c-clip on the mainjet needle,,factory setting for the chinese is dead middle on the 3rd notch...You may have to go to the 4th notch to get rid of any off idle stumble....

You basically want your bike to start-up and rev like this bike..........

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beansdaddy78

Discussion Starter · #5 · Sep 8, 2012

Great Cam2 im very glad you had time to answer, and cant tell you enough how much i appreciate the pics and descriptions. you basically make it moron proof for me. thanks again man im gonna try it all.

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CAM2

· #6 · Sep 8, 2012

beansdaddy78 said:
Great Cam2 im very glad you had time to answer, and cant tell you enough how much i appreciate the pics and descriptions. you basically make it moron proof for me. thanks again man im gonna try it all.

No problem...let me know if you want to know how to modify the atomizer tube.....................

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beansdaddy78

Discussion Starter · #7 · Sep 8, 2012

hey CAM2, can you look at this carb for me and tell me if it would fit on my cat eye pocketbike, and also a quad i have laying around? also its only $10 and the place is only 7 miles away so i can pick up and save on shipping.

also if this carb would work how come its so cheap is it not as good as the stock carb that cost me $28 with a walbro rebuild kit for another $8-9

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beansdaddy78

Discussion Starter · #8 · Sep 8, 2012

CAM2 said:
No problem...let me know if you want to know how to modify the atomizer tube.....................

of course i want to know

he he he yes keep it coming, anything you know that i can do to a cat eye or just to the motors in general please let me know. and the pics are awesome.

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beansdaddy78

Discussion Starter · #9 · Sep 8, 2012

beansdaddy78 said:
hey CAM2, can you look at this carb for me and tell me if it would fit on my cat eye pocketbike, and also a quad i have laying around? also its only $10 and the place is only 7 miles away so i can pick up and save on shipping.

also if this carb would work how come its so cheap is it not as good as the stock carb that cost me $28 with a walbro rebuild kit for another $8-9

not sure if im allowed to quote myself but there it is. I forgot the link to the carb i was asking about here it is. i hope i dont get in trouble for it.

http://www.buyatvsonline.com/two-st...r-chinese-pocket-bikes-pb-carb-02-p-9497.html

this place is so close to home it makes parts affordable

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EPR

· #10 · Sep 8, 2012

That carb is for a Cag reed port engine, it's a 12mm carb and your stock one is 15mm. Not going to help get more power, don't know if it will run right on the piston port engine.

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beansdaddy78

Discussion Starter · #11 · Sep 8, 2012

EPR said:
That carb is for a Cag reed port engine, it's a 12mm carb and your stock one is 15mm. Not going to help get more power, don't know if it will run right on the piston port engine.

ahhh i see, i had no idea. thats why i love these forums, any other time i would have probably ordered it without checking just because it was in the pocketbike section and the price was very low. now speaking of 12 and 15mm am i able to go larger than 15mm and it have a positive effect on the motor or am i only able to use a 15mm carb?