LH Mirror Thread Repair

[hudson]

hey guys. The LH handlebar mirror threads in the handlebar perch pf my 71 R75/5 are stripped and the threads on the stem are in bad shape. What size die and tap do I need? 10mm? What thread - 1.50 or 1.75? It definitely is not fine threads. I am having trouble finding resources for LH thread repair for a die & tap. Any resources in the US you know of? I guess I need a LH helicoil kit. LH die- I have no idea. BTW, the previous own had a helicoil in it.


Thanks!

[gspd]

According to Max fiche, your mirror stem goes right through the perch and has a 10mm nut on the end.
Is this correct?

[Rob Frankham]

Are you sure that the perch should be threaded? The BMW parts list suggests it isn't, that the OEM mirror just fits through a plain hole with a nut either side. I know this to be the case with the later perches and it looks like it's the same with those used on the /5... perhaps another owner can confirm. The shaft size is M8 x 1.25. Is it possible that some PO has modified it for a mirror with a 10mm shaft?

Rob

[Kurt in S.A.]

The thing I wonder about is that the /2 perches had a threaded insert for the left hand mirror...nothing for the right. How far into the /5 era might have BMW continued with that? I notice that on RealOEM, the underside nut/washer is grayed out, typically meaning it's not applicable for that model. The fiche for the '74 /6 shows the underside hardware.

Kurt in S.A.

[PAS]

MAXBMW shows mirrors with nuts. I cant post a picture. Diagram 51_5471
https://shop.maxbmw.com/fiche/DiagramsM ... d=09082020

[gspd]

I think hudson's bike has the older (/2) type perch, which would explain the confusion.
Maybe the first run of r75/5's came with the older type?

Anyhow, if the threads in the perch and the mirror stem are bad, JB Weld can be used to hold the mirror in place.
As long as there are enough cavities and irregularities for the JB to 'bite' into, it will be strong enough to hold the mirror securely.

[Kurt in S.A.]

On my '69 R69S, I first tried a left mirror only screwed into the perch and just couldn't get used to it...kept looking right but saw no mirror! The bike came with some mirrors that clamped to the handlebars that I removed just to try the single mirror. Went back to the clamp-ons...mo' better!

Kurt in S.A.

[hudson]

Hey guys! It definitely threads in on both LH & RH. The stems are threaded at the bottom and the inside of the perch hole has threads. There are nuts that you screw down to tighten once the mirror is threaded in and you have it at the desired position. The thread in the perch and also on the stem are roughed up, pretty good. The thread on the mirrors are definitely 10mm (the dropped in easy in the bolt gauge tool that I have (even though it is a cheap plastic version). The threads on the stem are large and spaced apart -definitely a course thread. Can't remember if it is 1.5 or 1.75 off the top of my head. I can post pictures when I get home later today.

It also appears the previous owner actually already used a helicoil in the LH side. I don't think I would need to ream the perch hole a size up from what I can tell- the in-tact part of the current, broken helicoil seems to want to fit ok but can't because of the damaged threads-but I am not sure. I don't know what size the perch hole was enlarged to for this prior 10mm helicoil.

I know the inside of the helicoil is 10mm (or standard equivalent) - the outside diameter for the drill bit and tap would be? So I need to find the proper size with a LH thread. Also, I guess I need a 10mm LH thread chaser/die? If I can't find metric, can I use standard equivalent ( I have no idea what size this would be)? Or will that mess up the mirror stem threads? IN the event I can find these LH tools, I assume you drill, tap and die counterclockwise (I know a stupid question). Thanks,

[Rob Frankham]

MAXBMW shows mirrors with nuts. I cant post a picture. Diagram 51_5471
https://shop.maxbmw.com/fiche/DiagramsM ... d=09082020

That's interesting... The '81 parts list only shows 8mm threads. The 2001 ETK shows everything as being obsolete but lo and behold, the 2006 ETK show the same diagram as in the MaxBMW. Unusually, the later list seems to be more up to date than the one that's almost contemporary. I have to stand corrected.

Can't help with left handed taps and dies in the US but, if you get desperate, they are listed at https://www.tracytools.com/taps-and-die ... -taps-dies located in Devon in the UK... Very helpful people and, if they don't sell it, you'll be pretty lucky to get it anywhere. Incidentally, FWIW, a standard Metric coarse 10mm bolt is 1.5mm pitch... but don't assume... there are three other possibilities to choose from.

Rob

[Seth]

Maybe a Timesert will work better than the helicoil.
It’s probably a little thicker than the helicoil and wouldn’t require anything else to anchor it into the perch. If you do go in that direction, I suggest red threadlocker to set the timesert in permanently. Of course, the timesert tools aren’t cheap.