2008 GSA stripped sump thread

magic dave

Registered user
May 24, 2015
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West Sussex, UK
Hi Guys
Got the bike all back together after the chain tensioner debarkle last week ( thanks to anoyone that suggested the throttle cable). Today was the day for first test ride so thought I'd quickly drop the oil and do a filter change. When I replaced the sump plug ready to refill it didn't tighten up. so I took it out and it's come out with a load of the sump thread.
These can be helicoiled right? Helicoil do a tap that screws in to the old thread and then cuts a new thread so you can rethread to the original size and don't need to use a drill, which I think is the better option given I don't want to take the engine out!!
I can't find one of these for a M16x1.5? Anyone have any suggestions?
The Helicoil kits I have used include the correct size tapping drill to size the new hole correctly for the thread insert tool.
Found these,

Never used one so cant say whether they are the right ones or suitable for what you want - they just came up in a search for the sizes you posted

Someone more knowledgeable in this type of repair may offer a better solution / rework method

have your tried talking to an indy BMW repair place or engineering shop to see what they would suggest??
I have a number of the V coil kits amongst many other makes the V coil make seem adequate.
I always helicoil with the part mounted on the milling machine, that way I can cut the seat to match the thread, often come across drain plugs leaking because this has not been done.
Make every effort if doing it on the bike to cut the new helicoil thread in the same plane as the original.
If its an in-situ repair I would be tempted to slowly hand ream the hole out in stages to the correct tapping diameter then helicoil it, rather than attempt to open the hole out with a drill bit and have it wander off course (or cut an oversized or oval hole). Its probably be a good idea to loctite the thread insert in place as it is probably fairly thin section casting if it has stripped already.

The casting may also need spot facing to give a clean mating face for the new plug to seal on ( I would probably make up a home made tool for this, or use a counterbore drill on slow speed).

FWIW I never use a torque wrench to tighten sump/drain plugs and prefer to do it by feel and sound judgment, YMMV.
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Don't forget that there isn't a removable sump.
The drain plug screws into the crankcase.
It's the kind of job that needs to be right first time.
I would suggest an experienced engineer or mechanic.
Someone who understands that it's not just a case of fitting a new sump if it goes wrong.
I have carried out hundreds of heli-coil repairs on bikes and aircraft. I have never come across a heli-coil insert that doesn't require drilling first and then tapping a new thread. The drill and tap are not a standard thread size. After fitting an insert thread you will have a stronger thread, this is why most aircraft engines have them. The advice posted earlier regarding drilling square is very good advice and should be followed. If you are not experienced in carrying out the machining then go to some one who is as the result if you don't get it right could be very expensive considering where the repair is.
I have done 'several' over the years. I used to go on sites and sort out some really badly attempted repairs, or a thread that some one had stripped. Some of the units were enormous and would have cost a fortune to dismantle. We could have charged pretty much anything and the company would have paid it. we never did though. Think it was about £50 back in the 90's.

If you are doing it by hand, there is a good chance you wont drill it or tap it square, the drill will bounce around the hole and then snatch and try to screw itself into the hole. If you are really unlucky, the drill will hit something inside and snap off or damage something inside.

For drilling by hand, I ground a diameter on the drill that went into the hole and then a taper on the drill so it would start in the hole, then I flattened the cutting edge off so the drill wouldn't snatch. I had an adjustable collar on the drill so I could control how deep the drill went when I started drilling and it wouldn't go in too far.

My drills had an attachment that I could mount small spirit levels on so I could drill square.

So, by all means have a go, but be aware it is not always a simple job.

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