Helicoil insert for a stripped spark plug hole: Difference between revisions
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The initial fix was to JB Weld a new plug into the head, in the hope that it would last for the rest of the life of the engine. Didn't work. | The initial fix was to JB Weld a new plug into the head, in the hope that it would last for the rest of the life of the engine. Didn't work. | ||
'''Before we go any further:''' This is not something for the faint of heart. | '''Before we go any further:''' This is not something for the faint of heart. The potential to mess up something really bad is very high. [https://www.ninja250.org/Dailyrider Dailyrider] has this advice for someone attempting this: "This is not a novice job. I've been a motorcycle mechanic for over 50 years and it wasn't an easy job for me. Modifying the tool and inserting the helicoils are both very intricate jobs. Take your time and think a lot about what you're doing." | ||
If you don't have a lot of mechanical experience, you may want to consider the alternatives: | If you don't have a lot of mechanical experience, you may want to consider the alternatives: | ||
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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. | 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 | 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 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. | ||
==What you need== | ==What you need== | ||
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[[image:CYLINDER HEAD.png|100px]] | [[image:CYLINDER HEAD.png|100px]] | ||
The tower completes the plug cavity from the head to the valve cover. It's a part of the exhaust cam bearing. The two cam bearing bolts hold the bearing | The tower completes the plug cavity from the head to the valve cover. It's a part of the exhaust cam bearing. The two cam bearing bolts hold the bearing with the tower to the head. There is an o-ring between the tower and the head, but it should be ok to reuse. | ||
Because the tap has an extension on it that threads into the existing threads, the cylinder needs to be as close to bottom dead center as you can get it. When you're positioning the piston for the cylinder you're working on, turn the engine over until the intake valve rocker arm will just wiggle a little. That way both valves will be closed, but the piston will be well down in the bore, so it won't cause any interference with the Helicoil tap. Since the thread tap is a three-part tool (guide, reamer, and thread tap) there will be a good bit of it sticking down in the bore, and you don't want it running into anything. | Because the tap has an extension on it that threads into the existing threads, the cylinder needs to be as close to bottom dead center as you can get it. When you're positioning the piston for the cylinder you're working on, turn the engine over until the intake valve rocker arm will just wiggle a little. That way both valves will be closed, but the piston will be well down in the bore, so it won't cause any interference with the Helicoil tap. Since the thread tap is a three-part tool (guide, reamer, and thread tap) there will be a good bit of it sticking down in the bore, and you don't want it running into anything. | ||