Lawn mower plug head (what)

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hwybikedon

hwybikedon

New Member
Mar 25, 2012
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Florida
I just have an extra few heads so this is what I did.

I noticed the plugs that I have did not reach the bottom of head when screwed in.

Just a thought. My bike and lawnmower plug little different.

After a bit of work, stock bike plug now sticking out of the head a little.

Here I needed to work some more to get lawn mower plug to do that.

Ok before I go any further. I ran with both plugs in this head before and after the work was done. With the stock head there was a five mph difference with allot of break up with the lawn mower plug before work. Do to that plug tucked up in the head I think? Not a tech here just tinkering around.

With the head work done, running two stock plugs and two baby lawn mower plugs. There is no change in running that I can tell, mph stayed the same no break up on any of them.

With. all that said, head work is not finished!That was just a test now that it worked I will go further. The pocket will be larger when finished and on a sertin angle where fuel will be distrubited correctly in the head. Allot cleaner but sand blasted when complete for fuel suspention. No spell check please see ya.
 
2door

2door

Moderator
Staff member
Sep 15, 2008
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Littleton, Colorado
I'm not following your reasoning. Instead of modifying the head to fit the plug, why not use a plug that fits the head the way you want it to? There are plugs available with extended electrodes (reach) Most of us use the NGK B6HS and the engines run fine on them. Get rid of the kit suppled plug. They are notorious for early failure and poor performance.

Tom
 
rustycase

rustycase

Gutter Rider
May 26, 2011
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Left coast
Don, I've noticed that on my 48, the b6hs does not have sufficient thread on the plug body to read the end of the cut threads in the cylinder head.
I think... the b6es has a longer thread.
Yes, it would be better if the electrode was within the combustion chamber for best flame path. AND, the exposed threads collect combustion debris, which will bake off and create probs when ejected.

It seems you are on your way to creating a squish band. Which is a good thing!
A squish band will be created in conjunction with the piston top dome shape, configuration of the head's combustion chamber, and adjusted level of the head, which could be done by lapping it on sandpaper, which would also raise compression.

As above, a quality plug is very important.

Best
rc
 
M

multipaul

New Member
Mar 31, 2012
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Germany
In my opinion the sparkplug shouldn't be longer than the thread. A little bit shorter is not as bad. The best is, it fits exactly. If a plug is too long it will collect coal from the burned oil. This is very hard and when you turn out the sparkplug it can happen that the thread in the head is damaged.

Multipaul
 
hwybikedon

hwybikedon

New Member
Mar 25, 2012
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Florida
2door said:
I'm not following your reasoning. Instead of modifying the head to fit the plug, why not use a plug that fits the head the way you want it to? There are plugs available with extended electrodes (reach) Most of us use the NGK B6HS and the engines run fine on them. Get rid of the kit suppled plug. They are notorious for early failure and poor performance.

Tom
Click to expand...
Hello Tom, there is no reason, thats why. Just to see what would happen? Partly bored, extra heads around. Yes could have changed plug and did many times. The E3 for me has been the best! Stock plugs x 2 ok I guess, 4316 Autolite seem to make motor run hot, J19LM CHAMPION 2nd best. This after I messed with the head.

Why was the E3 the best in my test? After many miles of riding the E3 plug would allow the motor rev as high as I wanted it to, the others topping off like rev limiter?
 
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