Confused about replacing spark plug on YD 100

noah9988

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Jul 3, 2021
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178
Hi, new to forum. I've browsed on here for troubleshooting help while building my bike. I read about spark plugs, and everyone says to get an NGK B6HS. Problem is that the hex on the plug is apparently 13/16" (didn't measure it myself, but that's what the specs say), while the one I have (Z8C) is around 3/4". I compared them and it is noticeably bigger. That's a problem because number one, I don't have a wrench that is 13/16". Second, with the bigger hex I don't know if I have the clearance around the plug to tighten it down. Also, the NGK has a longer reach, which worries me. I've also read about the E3.10 plug which is also 13/16" and has an even longer reach. The plugs are obviously not the same specs. What gives?

Edit: Actually I just found a thread of someone having the same problem. He says there's not enough room to tighten in down on the YD 100 engine. How do I find a b6hs with a 3/4" hex?
 
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noah9988

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Jul 3, 2021
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178
Welcome to MotoredBikes... Try a auto parts store or a place that sells ATV's
Thanks! I did some more research, and for future reference for anyone else with the YD 100: the BM6A (or BMR6A for the resistor one) should the same thread, pitch, hex, and reach as the stock Z8C that came with your engine. The confusion comes from other kits using a Z4C plug that has a longer reach and bigger hex. I'll update in a few days on if that plug will work. My exhaust gasket blew out today and need to wait for the replacement to come before I can test it
 
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DAMIEN1307

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Jul 23, 2020
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My exhaust gasket blew out today and need to wait for the replacement to come before I can test them.
Use the O2 sensor gasket from Toyota Highlander instead...just widen the stud holes a little wider with a bolt slightly larger than the holes.

Make sure that you install gasket with the side that has heavier amt. of metal is against the exhaust pipe not the engine head.

Here is the current Toyota dealer parts#/stock#, for that gasket...89466-20020-83.

If you shop Autozone, etc., its a "Dorman" brand part number ...Dorman 47021

This gasket is far superior to that chinese crap gasket your ordering online...been there, done that...lol...DAMIEN
 

noah9988

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Jul 3, 2021
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178
Use the O2 sensor gasket from Toyota Highlander instead...just widen the stud holes a little wider with a bolt slightly larger than the holes.
Yeah I've heard of people doing this. Along with the gaskets I also got high temp threadlocker, because the reason for the gasket blowing is because of the studs backing out... after it blew out I could remove the studs with my fingers. I also got ultra copper rtv. If I somehow blow them out then I'll switch to the O2 sensor gasket, lol.
 

DAMIEN1307

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Staff member
Joined
Jul 23, 2020
Messages
3,036
Yeah I've heard of people doing this. Along with the gaskets I also got high temp threadlocker, because the reason for the gasket blowing is because of the studs backing out... after it blew out I could remove the studs with my fingers. I also got ultra copper rtv. If I somehow blow them out then I'll switch to the O2 sensor gasket, lol.
I changed out my studs by using stainless steel allen head bolts instead and using split ring lock washers...much improved and stays in place...They havent backed out in hundreds of miles now.

Those chinese junky studs sub-standard metal studs do not last.

I would seriously recommend to do it the way i have done...no more problems with loosening and leakage, plus cleaning that RTV stuff off after its been used is a B$%^ch to get it smooth again...just do it right the first time so you dont have to do it right the next time around...lol...DAMIEN

Heres a couple of pics of my build:

IMG_0353.jpg
IMG_0348.jpg
 

Easydrifter

New Member
Joined
Sep 12, 2021
Messages
29
Hi, new to forum. I've browsed on here for troubleshooting help while building my bike. I read about spark plugs, and everyone says to get an NGK B6HS. Problem is that the hex on the plug is apparently 13/16" (didn't measure it myself, but that's what the specs say), while the one I have (Z8C) is around 3/4". I compared them and it is noticeably bigger. That's a problem because number one, I don't have a wrench that is 13/16". Second, with the bigger hex I don't know if I have the clearance around the plug to tighten it down. Also, the NGK has a longer reach, which worries me. I've also read about the E3.10 plug which is also 13/16" and has an even longer reach. The plugs are obviously not the same specs. What gives?

Edit: Actually I just found a thread of someone having the same problem. He says there's not enough room to tighten in down on the YD 100 engine. How do I find a b6hs with a 3/4" hex?
Luckily they included a plug wrench with my YD-100. My 19mm deep socket also fit it as did my chainsaw tool. A 3/4 did not work for me though.
 
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