Helicoil insert for a stripped spark plug hole: Difference between revisions

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If you don't have a lot of mechanical experience, you may want to consider the alternatives:

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1. Replace the head. If you can get a completely assembled used head in good condition, you should be able to replace the head in about the time it would take to helicoil both plug holes, and with a whole lot less aggravation. A new head gasket, an o-ring for the coolant stub to the thermostat, and some coolant should be all you'd need.

2. Find someone else to do it. It might be difficult, though. You'd have to find a good mechanic who is also a machinist, or a machinist who is also a good mechanic, and there are fewer people like that all the time. The cost of labor has gotten so high that it's no longer practical to make parts fit, as in the days before the Japanese started making bikes where every part made for a certain bike would fit every bike that the part was made for. People used to have to hand fit every part, but that generation is dying off now and it's harder to find someone like that.

Probably the best place to find someone to do the job would be a shop that specializes in old European bike repairs. Unless you can't find a good used head, it probably wouldn't be would be cost effective. At today's shop rates, both helicoils would likely run you over $500. The helicoil does make a stronger than stock hole though; the BMW factory used to helicoil all their plug threads.

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==What you need==

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==Modifying the tool==

Because our plugs are so small and so far down in the head, you have to modify the insertion tool in two areas. The body has to be cut down somewhat, so it'll even go in the hole leading to the plug. Then the tip has to be cut down, so it will go into the little recess where the body of the plug seats.

Because our plugs are so small and so far down in the head, you have to modify the insertion tool in two areas. The body has to be cut down somewhat, so it'll even go in the hole leading to the plug. Then the tip has to be cut down, so it will go into the little recess where the body of the plug seats. This one was done by putting the tool in a drill, spinning it around, and using a grinder to remove the material. A lathe would be much better, if you have access to one.

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~~I don't have access to~~ a ~~lathe anymore~~, ~~so I managed with drills to spin the tool~~ and a grinder ~~or file for cutting~~.

[[image: IMG_7355.jpg|150px]]

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==Preparing the helicoils==

~~[[image: IMG_7355.jpg|150px]]~~

Before you even start, prepare the helicoil(s) you're going to use by cementing a 16" piece of upholstery thread to the little insertion tang, as you have to break it off and retrieve it after the coil is inserted. Since it is stainless steel, it isn't magnetic, so there isn't a good way to get it out after you break it off.

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 If you don't have a lot of mechanical experience, you may want to consider the alternatives:
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+. Replace the head. If you can get a completely assembled used head in good condition, you should be able to replace the head in about the time it would take to helicoil both plug holes, and with a whole lot less aggravation. A new head gasket, an o-ring for the coolant stub to the thermostat, and some coolant should be all you'd need.
+. Find someone else to do it. It might be difficult, though. You'd have to find a good mechanic who is also a machinist, or a machinist who is also a good mechanic, and there are fewer people like that all the time. The cost of labor has gotten so high that it's no longer practical to make parts fit, as in the days before the Japanese started making bikes where every part made for a certain bike would fit every bike that the part was made for. People used to have to hand fit every part, but that generation is dying off now and it's harder to find someone like that.
+Probably the best place to find someone to do the job would be a shop that specializes in old European bike repairs. Unless you can't find a good used head, it probably wouldn't be would be cost effective. At today's shop rates, both helicoils would likely run you over $500. The helicoil does make a stronger than stock hole though; the BMW factory used to helicoil all their plug threads.
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 ==What you need==
@@ Line 32: / Line 31: @@
 ==Modifying the tool==
-Because our plugs are so small and so far down in the head, you have to modify the insertion tool in two areas. The body has to be cut down somewhat, so it'll even go in the hole leading to the plug. Then the tip has to be cut down, so it will go into the little recess where the body of the plug seats.
+Because our plugs are so small and so far down in the head, you have to modify the insertion tool in two areas. The body has to be cut down somewhat, so it'll even go in the hole leading to the plug. Then the tip has to be cut down, so it will go into the little recess where the body of the plug seats. This one was done by putting the tool in a drill, spinning it around, and using a grinder to remove the material. A lathe would be much better, if you have access to one.
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-I don't have access to a lathe anymore, so I managed with drills to spin the tool and a grinder or file for cutting.
+[[image: IMG_7355.jpg|150px]]
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+==Preparing the helicoils==
-[[image: IMG_7355.jpg|150px]]
 Before you even start, prepare the helicoil(s) you're going to use by cementing a 16" piece of upholstery thread to the little insertion tang, as you have to break it off and retrieve it after the coil is inserted. Since it is stainless steel, it isn't magnetic, so there isn't a good way to get it out after you break it off.