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What size to tap? Stripped oil drain

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The threads are striped on where the oil drain plug goes, the bolt was 12x1.5. When I tap it do I tap it to 12x1.75 or do I have to increase the hole diameter to 14 by whatever? 

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4 hours ago, Je55e1996 said:

The threads are striped on where the oil drain plug goes, the bolt was 12x1.5. When I tap it do I tap it to 12x1.75 or do I have to increase the hole diameter to 14 by whatever? 

What Kyle said. A timesert is better than a coil, but more expensive. 

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10 hours ago, P84ONE said:

What Kyle said. A timesert is better than a coil, but more expensive. 

So I can get a m12x1.5 helicoil kit and I'll be good to go, correct?

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26 minutes ago, Dane Richardson said:

How much would that cost to do just curious

Every machine shop would be different. 30-50 I would think. 

The kits cost a few hundred. 

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Make sure you find an experienced mechanic that's done a bunch of them, to do the job.

I had a timesert installed that leaked and then came out with the drain plug, first time I tried to remove it.

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The previous owner of my bike installed a Helicoil which eventally failed:

2rzq9v5.jpg

33uykie.jpg

The thread of the hole was so damaged that it looked like a 12 mm hole with bad roughness:

2nu1sh4.jpg.

I tapped it to the size 1/4 Gas (1/4 is not 1/4"), with the intention to just use a 1/4 G plug. The drill size was something less than 12 mm, 11.8 IIRC, so 12 was close.

125hxmc.jpg


2uhoo4h.jpg

In order to keep the tap straight I used a caliper on the sides where i could place it (there is not much room to work there, even if the engine was disinstalled from the bike):

15f0jnq.jpg

And, to turn the taps (I used a set of two: taper tap and second tap, IIRC), I utilized one of these adjustable wrenches:

33420210.jpg

The local shop wasn't able to provide me with a suitable tap wrench and extension fast and so I just decided to utilize that wrench because it worked. Definetely not the proper way to go, I know. The problem is that, as I've already written, there is not nuch room to work down there, because the axis of the hole has a big angle, so I just couldn't use a common tap wrench: I either needed one with a ratchet or one with an extension.

Then, I removed as much swarf as possible utilizing a straw as an extenzion of a vaccumm cleaner crevice tool:

Maybe from the video it seems that it didn't work; well, this was recorded just for future reference, but when I could use my both hands to keep it in position, it worked and removed all the visible swarf. You know, between the straw and the crevice tool there was a piece of bycicle tube, so it was not rigid and needed one hand on the tool and one on the straw.

I also poured some old oil into the engine, drained it in a container, re-poured it in the engine, removed the swarf from the bottom of the container and repeated the process until I was not able to see swarf in the oil. I didn't have other cheap ideas to flush the cases.

I used the bike for some hours and then I split the cases to replace the crankshaft (so that was not related to this) and I found some swarf behind the bearings of the gears drum, so apparently not all the debris had been removed.

This is the final result:

el49yr.jpg

It leaks like a couple of drops per week unless I use a teflon tape on the thread (I wrap it around only the threads closest to the copper washer). Probably, it's not perfectly straight and so the washer doesn't mate perfectly with the surface of the case.

I used a plug whose length is not enough to cover the radial hole I noticed when I removed the Helicoil:

15645yq.jpg 

Edited by Theo
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