Spark plug gap

never bothered measuring the gap. i just take a peek, see a gap, stick em in... as long as it isnt huge or too small... 0.5 to 1mm.

it makes literally sweet eff all difference. we arent running points ignition on these things!
 
you'd be surprised. I tried the factory recommended .028 for a giggle once and it just missed and surged and all manner of nasty things
 
0.028...lemme see now...

divide by 25.4, multiply by something um...

0.7mm? um? thats a standard plug gap...
or 0.07? arrrrg!

you know i refuse to follow any plans that are measured in that horrible unit, though i always found it amusing to call a 4x2 a "3 35/64 x 1 49/64"...(finished size is 90x45 over here...)
the number of customers that were amazed i could use both units (when i worked in a timber yard) was astonishing. but thou just hurts my head... even if my lathe is imperial, i hate it hate it hate it! ever tried cutting metric threads on an imperial lathe? you cant take it out of gear! forwards, stop, backwards, stop, forget to back tool off, snap, regrind tool, re-align tool, snap, repeat process, give up and wait two weeks for a weird sized die to arrive off e-bay... M9x1? wtf?

nope, i still say as long as its about the same as a credit card is thick...its fine. never had an issue.

have burnt plenty of ignition coils out by going over 2mm though...
 
it's a standard gap, but it doesn't work well at all in any of my engines. I just did some tests on my race bike and went 50 on flat land with stock gearing using a .039 gap, lost a whopping 5 mph with an .028, and it took me a whole lot longer to reach top speed.

and then the engine overheated and started losing power, but that's neither here nor there. it's still got my winter plug in it, not too nice when it's 90 degrees instead of 30

I love thou, it's easy to think in for me. especially gapping spark plugs, one thou in any direction makes enough of a difference that using millimeters or even tenths of a millimeter isn't sufficient, but going down to hundredths of a millimeter just complicates my thought process.

I can think in either unit just fine but all my precision instruments are imperial.
 
you'd be surprised. I tried the factory recommended .028 for a giggle once and it just missed and surged and all manner of nasty things

My little stock motor bike runs great on .025 to .030. It will even pull my 220 pound
butt up step hills. Never tired a bigger gap but will for the fun of it.
 
I have a 220 pound butt as well, and my bike doesn't notice a difference between it and my racing buddy's 130 pound butt. I actually get better acceleration than he does, because I'm less afraid of destroying the clutch.

my race bike makes a buttload of power and the top speed is only restricted by gearing. it can damn near climb a vertical wall and and in the quarter mile it outruns some cars
 
I am getting ready to open my plug up a little to see how it does. Will report back after I test it.
 
Butre are you running a stock or up graded CDI? I am guessing up graded. The one on mine right now is stock. Only thing on the motor that is not stock I am running a SHA clone carb. Changed the gap from .025 to .032 took her for a 4 mile ride. It seems to have better low end torque but might be lacking on top end torque a little but not 100% sure. Idles the same very good. Have the fan on it going to try opening it up to about .038 to see how she does. I am running a NGK B7HS.
 
Last edited:
Butre are you running a stock or up graded CDI? I am guessing up graded. The one on mine right now is stock. Only thing on the motor that is not stock I am running a SHA clone carb. Changed the gap from .025 to .032 took her for a 4 mile ride. It seems to have better low end torque but might be lacking on top end torque a little but not 100% sure. Idles the same very good. Have the fan on it going to try opening it up to about .038 to see how she does.
stock. none of the aftermarket CDIs are built for 11500 rpm. I use a jaguar on my street bike which only turns around 9800.
 
Last edited:
Back
Top