Spark plug thread busted

50cc · 02-08-2013, 09:34 AM

Hey everybody, seems like the last time I was plug-chopping the damn thing I over-tightened the spark plug and today, when I was changing it again, it felt like the thread is wrong, also there were some aluminum stripes left inside the threads of the old spark plug... I put the new one and this time it took too many turns to tighten it good.. Anyway, seems tight now, but I think one or two more spark plug changes and it'll go to hell. So what options do I have? A new cylinder head only or I can re-thread it somehow without removing the top end? Thanks.

**inuyasha** · 02-08-2013, 10:17 AM

Hi
http://www.helicoil.in/helicoil.htm
Take care and ride safely dear friend
Yours Hank

qwertydude · 02-08-2013, 11:44 AM

At the price and potential hassle of a helicoil for $30 I'd just buy a new head for $45. And more importantly torque your spark plugs correctly. You can tighten them and then do the quarter turn past hand tight only one time on a new plug. After the crush washer is crushed then you have to torque them and it is a very light torque, lighter than most people assume. For 10mm threads you're asking 7-8 lbs-ft max.

50cc · 02-09-2013, 04:11 AM

thanks to both, could you tell me how much torque is that in Nm?

bloodymomo · 02-11-2013, 03:42 PM

I had same problem. Tried helicoil and it blew out 1 mile down the road. Just get a new cilander or a big bore kit

prodigit · 02-11-2013, 04:16 PM

For mine it's very simple.
Just make sure you turn the spark plug in correctly, screw it in by hand. If it has any resistance, it's probably not screwed in correctly.
Then at the end use a small wrench, and tighten it. As long as you have the copper sealing ring, anything that feels tight, is tight. Doesn't have to be a precise torque, nor overtight.

rigger71 · 02-13-2013, 04:22 PM

I took my head to a machine shop and paid $20 and never had another problem

flu · 02-14-2013, 04:59 AM

A good rule of thumb with spark plugs is hand tighten then grab a wrench and give it 1/8 to 1/4 turn.

02-08-2013, 10:17 AM	#2
inuyasha Join Date: Sep 2012 Location: West Haven CT Posts: 1,165	Hi http://www.helicoil.in/helicoil.htm Take care and ride safely dear friend Yours Hank __________________ "4wheels move the body 2 wheels move the soul" Duty, Honor, Country. Those three hallowed words reverently dictate what you ought to be, what you can be, what you will be. Douglas MacArthur
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02-09-2013, 04:11 AM	#4
50cc Join Date: Oct 2012 Location: Germany Posts: 140	thanks to both, could you tell me how much torque is that in Nm? __________________ 50cc 139QMB, 7g sliders, manual petcock w/ transparent lines, Naraku CDI, Naraku belt, high output racing coil, 18.4mm CVK clone w/ #85 mj and #38 idle, needle @ leanest, OEM pipe mod, Kenda tires, NGK Iridium, lots of LED mods, 2.61L/100km (90 MPG)
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02-11-2013, 04:16 PM	#6
prodigit Join Date: Jul 2012 Location: Miami, FL Posts: 389	For mine it's very simple. Just make sure you turn the spark plug in correctly, screw it in by hand. If it has any resistance, it's probably not screwed in correctly. Then at the end use a small wrench, and tighten it. As long as you have the copper sealing ring, anything that feels tight, is tight. Doesn't have to be a precise torque, nor overtight.
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02-13-2013, 04:22 PM	#7
rigger71 Join Date: Apr 2012 Location: burlington n.c. Posts: 6	I took my head to a machine shop and paid $20 and never had another problem
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02-14-2013, 04:59 AM	#8
flu Join Date: Feb 2012 Location: Anderson, SC Posts: 19	A good rule of thumb with spark plugs is hand tighten then grab a wrench and give it 1/8 to 1/4 turn.
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