Helicoil insert for a stripped spark plug hole: Difference between revisions
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[[image: IMG_7355.jpg| | [[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. | 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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Tie the string to the tang first, then rotate the knot to the bottom side and glue it there with some silicone seal or something like that; you don't want it to be knocked off when you break the tang off with a screwdriver. | Tie the string to the tang first, then rotate the knot to the bottom side and glue it there with some silicone seal or something like that; you don't want it to be knocked off when you break the tang off with a screwdriver. | ||
[[image: IMG_7349.jpg| | [[image: IMG_7349.jpg|150px]] | ||
An alternative to this is to get a long, thin hemostat clamp to hold onto the tang while breaking it off. | An alternative to this is to get a long, thin hemostat clamp to hold onto the tang while breaking it off. | ||
[[image:hemostat clamp.jpg| | [[image:hemostat clamp.jpg|100px]] | ||
==Bike preparation== | ==Bike preparation== | ||
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Get the bike stripped down basically to where you would be doing a [http://faq.ninja250.org/wiki/What_is_the_adjustment_procedure%3F#Getting_to_the_valves valve check], and then go one step further and remove the gasket and tower on the spark plug hole (two bolts). Be sure to '''not''' have both of these off at the same time, otherwise the exhaust cam won't have anything holding it in. | Get the bike stripped down basically to where you would be doing a [http://faq.ninja250.org/wiki/What_is_the_adjustment_procedure%3F#Getting_to_the_valves valve check], and then go one step further and remove the gasket and tower on the spark plug hole (two bolts). Be sure to '''not''' have both of these off at the same time, otherwise the exhaust cam won't have anything holding it in. | ||
[[image: IMG_7348.jpg| | [[image: IMG_7348.jpg|150px]] | ||
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. | ||
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(This would be a picture of the tap loaded with grease and aluminum if the focus had been correct): | (This would be a picture of the tap loaded with grease and aluminum if the focus had been correct): | ||
[[image: IMG_7356.jpg| | [[image: IMG_7356.jpg|150px]] | ||
Even though the tap has a built-in guide, always make sure the tap stays centered in the spark plug cavity while you're reaming and cutting the threads. That thread MUST be square with the seat for a good plug seal. | Even though the tap has a built-in guide, always make sure the tap stays centered in the spark plug cavity while you're reaming and cutting the threads. That thread MUST be square with the seat for a good plug seal. | ||
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Put the insert on the insertion tool and thread it into the guide so that it is flush with the bottom, as seen in the picture. | Put the insert on the insertion tool and thread it into the guide so that it is flush with the bottom, as seen in the picture. | ||
[[image: IMG_7353.jpg| | [[image: IMG_7353.jpg|150px]] | ||
[[image: IMG_7358.jpg| | [[image: IMG_7358.jpg|150px]] | ||
Now comes the fun part. Take the insertion tool out and get the thread (string) into the cylinder. One way to do it is to ball up the thread and put a dab of grease on it to keep it bunched up, then put the guide into the spark plug well and use a piece of safety wire modified into a reverse hook to push it down. You don't want any of the thread sticking up, because when you insert the helicoil it will cut the thread, and then all your hard work to get it in is gone. | Now comes the fun part. Take the insertion tool out and get the thread (string) into the cylinder. One way to do it is to ball up the thread and put a dab of grease on it to keep it bunched up, then put the guide into the spark plug well and use a piece of safety wire modified into a reverse hook to push it down. You don't want any of the thread sticking up, because when you insert the helicoil it will cut the thread, and then all your hard work to get it in is gone. | ||