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Discussion Starter #1
Over the weekend I found that my spark plug was seized. When it came out (warm engine – bad idea), the top set of aluminum threads came out of my head welded to the steel spark plug. In assessing the damage, I cleaned up the spark plug by filing off the stuck-on aluminum with a needle file. Then I carefully screwed the newish-looking plug back in without tightening it too much just to check the thread and the fit. Unbelievably, the plug seized the instant I tightened it and when I tried to coax it back out, the threaded steel base broke off 2/3 still in the head! Gah!


Okay, not terribly difficult to pull the head and work with it on a table. I tried filing the steel plug base that was stuck in the head in half but that did nothing – it wasn’t too tight, it was just seized at the molecular level so I had to drill it out. Don't ask how I know that a common M10-1.5 helicoil kit won't work. The stock plug is a M10-1.0 (fine threads). There are plugs that are M10-1.25 (medium threads) but no M10-1.5 (coarse threaded) plugs that I'm aware of. I looked around and couldn't find a M10-1.0 helicoil kit. Maybe a shop would have a comprehensive Time-Sert repair kit with the right insert but I just dived in and ordered the Trail Bikes 143cc Big Bore/Race Head V2/manifold adapter kit direct from TBparts.com.


My advice – 1) Only remove spark plugs from a cold aluminum head and 2) Always use anti-seize paste on plugs going into aluminum heads. I’ve changed dozens and dozens of spark plugs and found one seized like that, especially not on a new bike with under 500 miles on it. My habit is to always use anti-seize paste on my plugs and I’ll damned sure do that every time from now on.


I'm not sure that the plug was ever out from the factory. I bought it at 220 miles with Chimera/Yosh/Bazzaz already on it. The Bazzaz map was only the default map which is kind of lame so I updated that straight away. I also noticed that the rear axle had been heinously over-tightened. The previous owner, a Delta A&P mechanic, must have cranked down on the axle like it was a lug nut on a 747.
 

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i have never had this issue. my plug has been out many times but i the first time i took it out they were un reasonably tight for no reason. u could probably just time cert it and it be ok
 

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Discussion Starter #4
When life gives you lemons (in the form of a seized spark plug), a Trail Bikes Big Bore Kit with Racing Head V2 is how you make lemonade. 56mm piston vs 60mm piston. The exhaust valve is 3.5mm larger in diameter while the intake valve increases from 24mm to a whopping 30mm. Ports are correspondingly larger too.
 

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