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| Our Forums | | | | 2 Stroke Bicycle Engines & Kits 2 stroke motorized bicycle engine kits need careful installation and setup, find out how from our professionals here! | replacement spark plug-rethreading Discussion at Motorized Bicycle Engine Kit Forum in the 2 Stroke Bicycle Engines & Kits forum. Had some problems with my recently purchased 2 stroke kit..Removed the plug to determine its condition and noticed that several ...  | | 
09-19-2009, 08:04 PM
| | Motorized Bicycle Newbie | | Join Date: Jun 2009 Location: New Mexico
Posts: 12
| | replacement spark plug-rethreading Had some problems with my recently purchased 2 stroke kit..Removed the plug to determine its condition and noticed that several of the threads in the head were stripped -also noted that the spark plug threads of the Chinese plug were not as protruding as those on an US plug.
Two questions- Is there an US replacement plug(long threads) that is compatible with the Chinese plug? Due to to the stripped threads,will have to install a helicoil or similar insert
in the head. Has anyone every done this and what is the procedure. Have notified the supplier and hope that they will supply a new head and a new plug but we all know how that goes.
Thanks | 
09-19-2009, 08:30 PM
|  | Master Bike Builder & Forum Sponsor | | Join Date: Dec 2007 Location: Duvall, WA PNW
Posts: 2,848
| | Re: replacement spark plug-rethreading There are several plugs that will work excellently NGK B6HS is a good starting point. | 
09-20-2009, 12:44 AM
|  | Motorized Bicycle Elite Member | | Join Date: Jun 2009 Location: Washington St.
Posts: 391
| | Re: replacement spark plug-rethreading The threads are regular sparkplug threads. A good tool place can supply you with a heli-coil kit if they go really bad.
__________________ Put something FUN between your legs.. | 
09-20-2009, 01:59 AM
|  | Motorized Bicycle Elite Member | | Join Date: Jul 2009 Location: Mi
Posts: 678
| | Re: replacement spark plug-rethreading Regular spark plug threads can be 7/8"-18, M10-100, M12-125, M14-125 and M18-150. | 
09-20-2009, 03:37 AM
|  | Motorized Bicycle Elite Member | | Join Date: Jun 2009 Location: Washington St.
Posts: 391
| | Re: replacement spark plug-rethreading Ok I'm sorry I thought we were talking about the plug threads in HT motors. Not every plug made.
__________________ Put something FUN between your legs.. | 
09-20-2009, 07:19 AM
|  | Motorized Bicycle Elite Member | | Join Date: Jul 2009 Location: Ontario
Posts: 407
| | Re: replacement spark plug-rethreading there is a special tool out there for us engine builders called a thread chaser, it has a magnetic tip on it that will collect the chips on its way up.
its a must have!
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<code>"isuck@code"</code> | 
09-20-2009, 10:33 AM
|  | Motorized Bicycle Elite Member | | Join Date: Jul 2009 Location: Mi
Posts: 678
| | Re: replacement spark plug-rethreading Quote:
Originally Posted by Humsuckler there is a special tool out there for us engine builders called a thread chaser, it has a magnetic tip on it that will collect the chips on its way up.
its a must have! | That only works on iron heads not aluminum. It's a good practice no matter what the material the head is made from to coat the tap with a liberal amount of grease to collect the shavings. | 
09-21-2009, 01:41 AM
| | Motorized Bicycle Elite Member | | Join Date: Jul 2009 Location: australia
Posts: 112
| | Re: replacement spark plug-rethreading I haven't done any helicoiling for years, but, what fantastic technology!
do not pass go; move directly to a helicoil kit; it's easy to do, and gives a superb result ... a result that improves upon a virgin head...
in fact.
You'll love helicoils. | 
09-21-2009, 02:19 AM
|  | Motorized Bicycle Elite Member | | Join Date: Aug 2009 Location: So Cal
Posts: 588
| | Re: replacement spark plug-rethreading I have had waaay too many heli-coils unscrew with the fastener.
Now given I did not install them, I do not know if they were incorrectly installed.
I greatly favor time serts. Properly installed they will never come out.
Antique Volkswagen and dune buggy afficinados will know them as case savers. They are commonly used in the avaition industry as well.
They are a hardened tool steel cylinder with the threads you want on the inside and special threads on the outside.
They install similar to a heli-coil, but not quite.
Due to the cost of a kit, it would be best to have a machine shop or engine repair shop install it.
The actual insert is only about $5.00 US, but the special tools are pricy. | | Thread Tools | | | | Display Modes | Linear Mode |
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