Spark plug gap in English please By mthomas (Read 43,921 times)

[mthomas]

Does anybody know what the plug gap is in English? The manual says .7-.8MM. I put an new NGK plug in and since my gap tool is in English and I tried to take the gap off the old one but it does not seem to run as good. I checked it today and the NGK is at .032 and I think .7mm is about .027". Anybody know fo sho?

[mikebpnw]

Divide MM by 25.4 to get the number in inches, and vice versa.

You are correct that 0.7mm = 0.0275"

[mthomas]

Thanks for info guys. Mine is at .032 but the manual says .7-.8 which is .028-.032. I noticed a small miss after adjusting the valves. SHould I close up the gap to .28 to see if it's a bit hotter and stops the miss or should I leave it and look elsewhere? Seemed like it ran better with the Autolite plug.

[mthomas]

I was wrong. I pulled out the old plug which was an NGK not an Autolite and the gap was actually was about .028. I regapped the new plug and put it back in and it ran much better. Wierd

[mthomas]

OK...you were right and I was wrong. I took the old NGK plug and wire brushed it and re-gapped to .032. I put it back in and it ran better. I think what happened is when I put the new plug in, I was afraid to strip out the soft Chinese head and because of the crush washer, did not tighten it as well as I should have. Still hard to start once it got warm even though I adjusted the valves.

[Bashan]

What do you have the valves at? I've found hard starting or stalling after it warms up, and then starts OK after it sits is the valve set, at least it was on mine. People often blame the auto-enricher but that simple little gadget is working most of the time. I had my valves at .006" exhaust and .004" intake, I reset to .004" both and it started fine when warm. I think the theory on the wider set on the exhaust is that it's hotter on that side (exhaust gas) so the gap needs to be wider for the stem to expand as it warms; this doesn't seem to be true it practical use. I think the engine is so small that there's just not much of a temperature differential between intake and exhaust. So the set at .006" is too wide, the valve doesn't open enough, poor running and staring. JMO, Rich

[mthomas]

They are both set at .004, did that last week.

[speedracer]

I just purchased a NGK Iridium plug and the gap was factory set at .026. According to NGK the Iridium gap should not be changed due to damage to the tip.

[speedracer]

On my old NGK plug I set the gap at .032 and did nothing with the Iridium plug.

[speedracer]

Dr that was no misprint. My Iridium is .026, in fact the one before it the gap was .026. I don't have a special tool and I sure don't want to break off the tip. I emailed NGK about the gap and will post when I hear from them.

Speedracer

[wildman]

speedracer
If your Iridium spark plug gap is .026" it's fine.. I have 3 different manuals for GY6 157QMJ engine w/ NGK C7HSA or Iridium spark plug that recommends a gap of .6mm (.024") - .7mm (.028").. Now I do have one manual for 125cc GY6 w/ a CR8EH-9 spark plug recommending a gap of .8mm (.031") - .9mm (.035")..

The Chinese standards are all over the place, & the same goes for the information written to CD or even the Haynes repair & service manuals..

Now w/ all that said, that doesn't mean you can't play around w/ your plug gap... Some times a different gap w/ make a difference for the better..

Now if you're using a standard NGK C7HSA spark plug or similar plug, I recommend side gaping the plug w/ a gap of .014" - .018", which will preform nearly as well as the Iridium spark plug & is tougher.. Side gaped spark plugs have been used for high performance racing & in 2 stroke engines for many years.. So for those of you who don't have the $12.00 to spend on a high performance Iridium spark plug, I recommend side gaping your spark plug..

David Sr.

[wildman]

The 4 NGK Iridium plugs I've bought, came w/ a gap of .027", same as NGK C7HSA plug..

David Sr.

[wildman]

These GY6 engines are pretty simple engines, but if you ask me it's easier to tune a Briggs & stratton lawnmower engine.. ;D

David Sr.

[Bashan]

David, thanks for the mini-tutorial. Now, what is side gaping? I never heard of it. Also, I'm trying to get some definative info down in tech; is there something one's scoot would be doing that would make you think "ah, gotta regap the plug" or is part of the usual suspects list (another thing I'm going to work up). Rich

[wildman]

3 year warrant for the lawnmower!! That explains it all then!! Did it come w/ an operator to?? Because the 3 year warranty tells everyone in the scooter world you must own at least one, or possibly more then one Chinese Scoot w/ a GY6 engine, because if you didn't you would surely have time to fix a lawnmower.. I know w/ owning 3 Chinese scooters, LORD HELP ME if anything around the house breaks.. Need a full work force if you're going the own Chinese Scoots.. ;D ;D

David Sr.