What replacement spark plugs do you use? (chinese 2-stroke)

srdavo

Well-Known Member
Joined
Nov 4, 2006
Messages
3,162
here is the list I compiled a couple years ago.

NGK B6HS & B5HS
Champion L86C
Champion CJ7Y low profile ( I like these)

Autolite 425
ND W2OFS_U
Bosch W9EO

The plugs in bold print are the ones I have personally and successfully used.
does anyone use any of these?
has anyone found more to add to the list?

I want to confirm my list, but NAPA only carries the 1st three .
thanks
Dave
 
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OldPete

Guest
One should not use plugs that place threads inside the combustion chamber for two reasons.

1- The thread/s can fill with carbon and start damaging fragile aluminum cylinder head threads when removed. It can get so bad the plug threads go into a bind at removal.

2- With extended heavy load on a hot day the thread that is exposed inside the chamber can glow just enough to induce deadly detonation. This leads directly to a holed piston or a piston seizure. Bad stuff for sure.

(I have seen a seizure cause by a Heli-coil plug hole repair that was hanging into the chamber by half a thread.)

Solution? Use an old gasket along with a new one or use a solid copper ring to space the plug out enough. This is the only image I could find on a quick search. Called index washers. They are used to place to open side of the plug gap directly at the incoming air charge when the plug is tightened.

1633_index_1.gif


srdavo, delete this if you wish. :cool:
 
G

gone_fishin

Guest
my ngk b6hs is exactly the right length on my dax70.

can anyone confirm any of the other numbers? we wanna make sure the manual is correct.
 
H

Herrmanator8

Guest
!!!!!!!!!!!!!!!!!

I have an 80cc bike motor that i bought from kingsmotorbikes and it came all stock and the spark china plug is stock. Is the stock spark plug the right length, id like to know whats the best/highest performance spark plug i can get and it must be the right length because i dont was and engine seizure or any other problems in addition to the ones i already have. so can someone please tell me what i should get plz, and maybe some good advicel.

Thanks, Jon Herrmann
 
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Guest

Guest
NGK B6HS OR B5HS are the best direct replacements.

I have fitted an Autolite 4093 with no problems, but haven't checked to see if it goes into the cylinder at all.
 
M

MotorbikeMike

Guest
spark plugs

I have not messed with these in years, but I can tell you that I remember that not all of the heads are threaded the same depth, and in many cases the orig plug is actually too short,. Mike
 
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OldPete

Guest
Re: spark plugs

MotorbikeMike said:
I have not messed with these in years, but I can tell you that I remember that not all of the heads are threaded the same depth, and in many cases the orig plug is actually too short,. Mike

Every home-brew mechanic should have one of these, they can be had in plastic, from Harbor Freight for <<$10. A vernier caliper w/depth gauge.


1633_gauge_1.jpg
 
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