Modern Vespa

So, apparently some time ago I'd unknowingly stripped threads on the case where the belt cover attaches, most likely from careless use of my impact driver

Anyway, wanted to mess around with a helicoil ...yes, I know the bolt isn't really needed, but it does hold a hose clamp in place.. So, procured a kit (specific to that size), and in looking it over I checked it against the bolt, which didn't seem to align that well. I thought I'd do a test insert on a scrap of aluminum, but the bolt jammed pretty fast. After messing with it a bit, I noticed that the spring coil will spread slightly against the bolt threads and thus align. Also decided to try to measure, and got 1mm on my bolt and tap, but from what I can see with my aged eyes the coil seems slightly less. My understanding is that "fine" threading is 0.75mm? Wondering if its possibly an error where I got the wrong threading on the coils? As I'm totally green in this area, thought I'd see if anyone here has thoughts...it's entirely possible I'm doing something wrong. Seems to me it should be a pretty simple process, at least for putting the pieces together.....

Finer threading depends on the diameter. It is not always x0.75. (Or x1 for regular threads.)

I hope this loads correct and helps....

This Helicoil set has saved our butts so many times. It shows what drill size to use with the corresponding tap for the coil. And it's metric. Does that make sense?

I don't think case bolts in aluminum are ever fine threaded
Loose helicoils should very easily thread onto the bolt, i
Installing helicoils reduces the id some, this is part of what keeps them in place. Breaking the tang off the helicoil after installing, also helps.

M6 x 1mm is the right size.

Thanks for the input, everyone.

My concern is really about the size of the coil I have vs. the bolt...the threads don't align with the resting position of the spring....threads on tap and bolt seem to match fine, spring will only align if stretched slightly. That doesn't seem to work once the coil is installed.

I'm tempted to purchase another kit just to give it another shot....

I have had poor results in the past using heli coil type products. TimeSert is a much better solution although much more expensive, they work well every time.
Ted

Helicoils should be fine once the coil is inserted and the end snapped off, so it's squeezed out and down.


But Timesert all the way, if the budget can support it. I had one stripped head bolt hole on a Subaru engine - the kit was $550 to buy, so I rented one for $125. Well worth it!

Good suggestion, though for one non-essential fastener it doesn't seem worth it.

Is the scooter essential?

I guess not if you have half a dozen 🤠

Interesting question...with 4 inches of snow outside.

And Max, I'm halfway there, so, yeah...

Personally I'd just leave it blank. Nine out of ten screws is plenty still.

I would were it not also the fastener for a coolant hose.

....and a bit of boredom this time of the year....

Well, all ended well. I redid my trial, noticed a bit of aluminum on the bolt that likely came off the case, that possibly made insertion difficult and make me panic a bit. Just put the belt cover on, and gingerly installed the bolt in question that went in easily and snugged right up. Easy peasy.

One less drama behind me.

Well done.

Nice! I noticed the M6 was missing from the set I posted. At work we practice with the Helicoil sets, so now everyone brings us there their stripped out or broken off bolts. Again, great job you got it sorted.

I have Taps & dies and run them over any threads which are questionable.
Melting the plastic slightly on a nylok will give it new life
Loktite 290[green] is for assembled fasteners, stronger than blue, not quite as strong as red