400ex spark plug size

[PismoLocal]

quick question what size socket is the stock spark plug on the 400ex?

[redexrider]

18mm, you should look for an 18mm spark plug socket, or a thin walled 18mm socket. Most standard 18mm sockets will not fit in there.

Originally posted by redexrider
18mm, you should look for an 18mm spark plug socket, or a thin walled 18mm socket. Most standard 18mm sockets will not fit in there.

That will work but It is actually a 13/16 socket but most people dont have them so an 18 will work just fine.

[GPracer2500]

Originally posted by EXking
That will work but It is actually a 13/16 socket but most people dont have them so an 18 will work just fine.

Nope.

13/16 is a little smaller than 21mm. 18mm is the correct size.

[BigMike]

Definately 18mm. I spent the last week looking for a socket to fit down inside the head. Finally found an 18mm, long shank, small diameter plug wrench for $5.99 at my local Cycle Gear shop.

Mike

[cals400ex]

it may take a thin-walled socket to fit down in the 400exs head as well.

Originally posted by GPracer2500
Nope.

13/16 is a little smaller than 21mm. 18mm is the correct size.

I have no idea why every body tries to debate this with me you just wait a second and I will get you some proof.

Whatever I will hand the win over to you because I cannot get any proof. FYI: IT WORKS ON MY BIKE!!!!!!!!!!!!!!!!!!!!!!!!!!:mad:

[BigMike]

The mechanic at our local shop told me that the NGK "D" series plugs are all 18mm. The plug wrench I bought is stamped "D" series. I am surprised that 13/16" fits in the head. Must be very thin wall. I also bought a 18mm Craftsman socket on closeout for $1.97 and subjected it to the bench grinder to get it to fit inside the head. After about 5 minutes of grinding, it works like a charm.

Mike

[underpowered]

Originally posted by EXking
Whatever I will hand the win over to you because I cannot get any proof. FYI: IT WORKS ON MY BIKE!!!!!!!!!!!!!!!!!!!!!!!!!!:mad:

what brand of plug do you run in your bike? NGK has is an 18mm socket. HOWEVER, if you run champion or an automotive brand it very well could be a 13/16 socket. but the correct plug for the bike is 18mm. and GPracer is correct, 13/16 will not work on an 18mm plug, it is about 2mm to big.

I use ngk but it is still 13/16

[-copyguy-]

if you use the correct NGK (NPR8Z) it's definitely 18mm...it spins around in the 13/16" socket...doesn't even make contact.

I just put a dial caliper on the plug and transferred the measurement to an 18mm socket...perfect fit.

[BigMike]

Originally posted by -copyguy-
if you use the correct NGK (NPR8Z) it's definitely 18mm...it spins around in the 13/16" socket...doesn't even make contact.

I just put a dial caliper on the plug and transferred the measurement to an 18mm socket...perfect fit.

I think the correct plug is the DPR8Z.

Mike

[-copyguy-]

Thanks Mike, I guess I typed it wrong...it'd be nice if I typed things correctly when I'm saying they are correct...

The Denso equivalent is X24GPR-U (and I double checked that one!)

[underpowered]

Originally posted by EXking
I use ngk but it is still 13/16

ok. there are 25.4 mm in one inch. divide 13 by 16 and then multiply by 25.4 to get that mesurement in MM. i come up with 20.64. over 2.5mm over 18mm. i know you can use a 3/4 inch socket for a 19mm if you need to. 13/16 is one size larger than 3/4 and even a 3/4 inch socket will not work to take out your 18mm spark plug. i doubt you could even get a 13/16 in the plug hole since you have to have a thinwall 18mm to get in there.

[MIKE400EX]

ummmm....it's 25.4 mm to an inch!:D

[-copyguy-]

Originally posted by underpowered
ok. there are 24.09 mm in one inch.

Actually, the conversion is 25.4 mm/inch. I use it regulary in programming. 13/16" = 20.6375 mm ...either way, 13/16 ain't takin out a 400ex standard plug! ;)

http://www.google.com/search?hl=en&q=convert+inch+to+mm

[underpowered]

Originally posted by MIKE400EX
ummmm....it's 25.4 mm to an inch!:D

sorry, has been changed. i was using 24.9 in my physics class the other day for some conversions, forget what for though. it was just stuck in my head.