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JackJoshua

Joined:

Jul 12

Posts: 8

JackJoshua says:

up jet

i up jetted my 50cc nrg mc3 air cooled bike from a 60 to a 72 and it was running fine not bogging or backfiring but i was riding about with a mate for about 3 hours and then it just started to backfire and a major loss of power any ideas at all?:shock:

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  • Posted 3 years ago (06 July 2012 13:44)

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jaffa90

Joined:

Mar 09

Posts: 8890

jaffa90 says:

up jet

Welcome Jack,your spark plug will tell you a story.

Not sure about your carb but are you talking the main jet or the slow running jet?

If main jet why not set the needle a bit higher for more fuel.

If you give it more fuel what changes have you done to the air intake or exhaust?

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ally600

Joined:

May 09

Posts: 2538

ally600 says:

jack

as jaffa said check your spark plug..............i do not doubt your bike is now running way to rich and has fouled the plug:wink:

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AdieR

Joined:

Apr 08

Posts: 3042

AdieR says:

Is it

2-stroke or 4-stroke?

What was the reason for the jet change (was it OK before the new jet?)?

(Bear in mind that many 50cc bikes will be restricted performance-wise by exhaust resonators and other methods).

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JackJoshua

Joined:

Jul 12

Posts: 8

JackJoshua says:

upjet

i had to upjet because it was popping and it kept bogging out on me and after i put a 72 in it was fine but i had a look yesterday and its sparking but wouldnt start, i think its overfueling how could i sort this, thanks for your response guys very helpful:biggrin::biggrin::biggrin::biggrin:

[This Reply has been modified by the Author]

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JackJoshua

Joined:

Jul 12

Posts: 8

JackJoshua says:

up jet

how i do i set up  my main jet to the correct torque its a 6mm 72 or i have a 6mm 74 which is best and to the correct amount of turns?

[This Reply has been modified by the Author]

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jaffa90

Joined:

Mar 09

Posts: 8890

jaffa90 says:

main jet

turns,torque you`ve lost me.

Have you a diagram of the carb?

Also you no answer mine or AdieR questions.:blink:

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JackJoshua

Joined:

Jul 12

Posts: 8

JackJoshua says:

upjet

ive changed the main jet and its a 2-stroke it was fine for about 3hours after i rejetted then started backfiring loads i checked the plug yesterday and it sparks but when i put it in and try it wont start but when i take it out it soaked:upset::upset::upset::upset: i dont know what the problem is:/

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AdieR

Joined:

Apr 08

Posts: 3042

AdieR says:

When you say

" it was popping and it kept bogging out on me", what does this mean (reluctant to start / hesitant on the throttle / cutting out)?

To be honest I would say that an up-jet in these circumstances is a waste of time because there's an underlying fault which you haven't addressed. As its a 2T motor your oil / fuel mix may now be out (the oil is also a coolant so hope you haven't done damage).

By my reckoning, your main jet should be 53 and not 60.

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JackJoshua

Joined:

Jul 12

Posts: 8

JackJoshua says:

upjet

it doesnt want to start it has a spark but when i try to start it wont and when i take it back out its soaked, it also hesitates on full throttle, and cuts out when standing, but now it just wont start x

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AdieR

Joined:

Apr 08

Posts: 3042

AdieR says:

First thing to do

is change your jet back to the original 60 - to get anywhere, you need it back at a known standard, otherwise you're on a wild goose chase.

If you have an automatic choke, make sure it's working (you'll need a multimeter for this).

If that spark plug is of significant age, renew it.

Make sure your fuel lines (including any in-line fuel filters if you have any) are clear.

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