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Stripped manifold (non standard?) bolt holes

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Keanez
L Plate Warrior



Joined: 01 Sep 2019
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PostPosted: 13:06 - 01 Sep 2019    Post subject: Stripped manifold (non standard?) bolt holes Reply with quote
I've been replacing the exhaust downpipe on my Yamaha TW125 because the old one was a rusted mess with holes here, there and everywhere. After fitting the new one and tightening the bolts, they just keep turning and won't go tight.

I was thinking a helicoil insert would be best way to solve this but the bolts I'm using are these. Are there helicoil kits that would work with these or am I best using different bolts? Another issue is that the bolt holes are so close to the edge of the engine block that I'm worried if I drill a larger hole then it's going to crack open the side of the engine. (I hope I'm explaining this well enough)

If anyone has some good advice for the best way to fix this, I'm all ears.
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Pete.
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Joined: 22 Aug 2006
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PostPosted: 13:20 - 01 Sep 2019    Post subject: Reply with quote
There's nothing obviously non-standard about those bolts. Just buy the appropriate helicoil/recoil set and fit them.
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Keanez
L Plate Warrior



Joined: 01 Sep 2019
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PostPosted: 13:31 - 01 Sep 2019    Post subject: Reply with quote
Pete. wrote:
There's nothing obviously non-standard about those bolts. Just buy the appropriate helicoil/recoil set and fit them.


So which is the appropriate helicoil set? If I'm measuring these correctly, they're 5.5mm diameter
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Riejufixing
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Joined: 24 Jun 2018
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PostPosted: 14:06 - 01 Sep 2019    Post subject: Reply with quote
They're probably M6 coarse. Measure with the fatter part of the calipher's jaws not the tips.
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Pete.
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Joined: 22 Aug 2006
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PostPosted: 14:11 - 01 Sep 2019    Post subject: Reply with quote
Keanez wrote:
Pete. wrote:
There's nothing obviously non-standard about those bolts. Just buy the appropriate helicoil/recoil set and fit them.


So which is the appropriate helicoil set? If I'm measuring these correctly, they're 5.5mm diameter


As above you're measuring down in the thread grooves. Bolts are measured across the peaks and they will be about 0.1-0.2 smaller than the nominal size. Those look like bog standard M6 bolts, measure across the tops.
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Riejufixing
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Joined: 24 Jun 2018
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PostPosted: 14:19 - 01 Sep 2019    Post subject: Reply with quote
Riejufixing wrote:
They're probably M6 coarse. Measure with the fatter part of the calipher's jaws not the tips.


Sorry, didn't answer your question. This will tell you what you want to know:

https://www.amazon.co.uk/Helicoil-5546-6-Metric-Coarse-Thread/dp/B0002KKPXK

"The plug style tap is 3/8 – 16 that requires a ¼ hole drilled. The specs for the HEL570-6 tap is major diameter of 7.42 mm (outside thread diameter) with a 1 pitch (1 thread per mm). "

So you're going up by very roughly 1.5mm, so the radius of the "hole" at the outside of the thread diameter will increase by 0.75 mm roughly. I'd be surprised if you didn't have the "meat" for that oversize.

Picture?

EDIT: you will have to be careful to keep the axis of the hole in line with the original, and not let the tap bottom out.
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A100man
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Joined: 19 Aug 2013
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PostPosted: 21:26 - 03 Sep 2019    Post subject: Reply with quote
As a bone fide cheap-skate I bought one like this..

https://www.ebay.co.uk/itm/25-M6x1-0-Compatible-Helicoil-Thread-Repair-Wire-Insert-Taps-Drill-Bits-kit-box/392265683949

Seems to work fine in alloy at least..
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Old Thread Alert!

The last post was made 4 years, 236 days ago. Instead of replying here, would creating a new thread be more useful?
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