Ngk plug performed worse?

shiveralex

New Member
Apr 11, 2017
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Illinois
I replaced the stock plug that came with my 49cc 2 stroke china motor with a ngk b5(or 6)hs. i noticed that it doesn't not accelerate as quickly nor does it reach a higher rpm. With the stock plug my motor reached around 2900 but with the ngk it stop at 2400.
 

bairdco

a guy who makes cool bikes
Aug 18, 2009
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living the dream in southern california
Check the gap (baseline is .025,) check that it's tight and seated properly, make sure your plug wire is tight, and check the headbolts.

If the headbolts were never retorqued, it might have wiggled loose from removing or installing the plug.

If nothing helps, put the stock plug back in and see if it works good again.

You may have a faulty plug (doubt it, but possible.)
 

MotorBicycleRacing

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Jul 28, 2010
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I replaced the stock plug that came with my 49cc 2 stroke china motor with a ngk b5(or 6)hs. i noticed that it doesn't not accelerate as quickly nor does it reach a higher rpm. With the stock plug my motor reached around 2900 but with the ngk it stop at 2400.
Never use a B5 unless you are riding in frigid temperatures.
B6 is OK if you are in a temperate climate and riding easy.

What tach are you using? You must have it on the wrong setting as your
rpm's are less than half of what they should be.

Did you put the original plug back in to see if it really was "2900" after
using the NGK?
 

shiveralex

New Member
Apr 11, 2017
14
1
0
Illinois
Never use a B5 unless you are riding in frigid temperatures.
B6 is OK if you are in a temperate climate and riding easy.

What tach are you using? You must have it on the wrong setting as your
rpm's are less than half of what they should be.

Did you put the original plug back in to see if it really was "2900" after
using the NGK?
Im using some cheap tach i found on ebay, i set it to 1 cylinder 2 stroke motor.
The head bolts were torqued and the plug was installed correctly. i put the old plug back in and got my performance back. either the new plug i got was gapped incorrectly or i should by the hotter plug.?
 

BobbyT

Member
Mar 16, 2014
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Santa Maria ca.
If you didn't gap the new plug it wasn't installed corecttly. You need to gap them yourself or atleast check the gap. Use B6,7 or 8 HS. If you go hotter then 5 goodluck to you.
 

MotorBicycleRacing

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Jul 28, 2010
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Im using some cheap tach i found on ebay, i set it to 1 cylinder 2 stroke motor.?
setting sounds like the right one but 2900 rpm is not.
Even 5800 rpm is a poorly performing China girl.
Should be at least 6 to 7,000 rpm even stock.

You have the tach on the wrong setting.

An NGK B5HS will make your motor run hot.
NGK's come gapped at 30 thou.
 
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