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Old 01-09-2012, 10:35 PM
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Venice Motor Bikes Venice Motor Bikes is offline
Custom Builder / Dealer/Los Angeles
Join Date: Mar 2008
Location: Los Angeles, CA.
Posts: 6,017
Default Re: Spark Plug reach-why not use longer?

*This has all been re-writen!!* I later installed these plugs in some engines & had some problems...

Ok... I got some comparison pics today of three different heads I have & the NGK B6HS (short) & NGK B6ES (longer) plugs in them.
First is a (older) Raw 'center fire' head that shows the difference between the short & long plugs... *edit*...The longer plug is too long & will hit the piston.

Next is a older Raw 'slant' head with a NGK B6HS (short)... The combustion chamber is much smaller on this head putting the spark plug much closer to the piston top, (& the reach looks perfect)!
I didn't even bother taking a pic of the longer plug because it was soooo far out that it was very obvious it would hit the piston.

& last is a new Raw 'slant' head (Grubee style) that shows the difference between the two plugs... These heads have a extremely small combustion chamber with more threads for the plug... (the longer plug fits perfect)!!
This is what i had on my bike for the Venice ride last Sunday... I rode more that 37 miles (much of it at WOT) with great success!
*Edit*... The engine i used this plug on was older Raw engine with a new grubee style head; it worked on this engine, but when I used this plug on a all grubbe engine the plug touched the piston. so I added a couple of extra crush washers to the new plug & then it worked good.*

So there you have it... Some heads will benefit from the longer plug & others will cause major problems. (I learned a lot from this)!
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Last edited by Venice Motor Bikes; 01-13-2012 at 08:57 AM.
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