Mag Housing/Flange Stripped Threads

[Tony Hart]

I have managed to strip two of the threads on my mag flange which secure the flywheel cowling (twelve and three o'clock). I dropped the engine out at the weekend and am waiting for some m5 helicoils to arrive but have been thinking that there probably isn't enough metal to drill out to use them. That seems to be Plan A out of the window. Plan B will be to drill and tap two new holes a few centimetres from the originals. Is there a Plan C as I don't fancy Plan D of buying a new flange?

Managed well over a thousand miles since snapped exhaust bracket and sheared crankcase stud in April so for me the scooter is going great

Any ideas appreciated

Tony

[Warkton Tornado No.1]

There are several ‘bodges’ that I’ve used. Probably the neatest is to obtain shoulder bolts such as M6 (Ø8 mm) & drill M6 clearance holes (Ø6.6) through the back flange to allow them to be fitted up tight (with an M6 nut & washer) to the bottom of the stripped M5 holes. Look @ RS Components 292-300 which are only £2.51 for a box of 10! So far you will have an Ø8 shoulder snug up to the underside of the dodgy threads.

Then you need to mark the centre for re-creating the stripped M5 holes by marking through them on to the shoulder of the bolt just fitted.

Then, remove the shoulder bolts & drill Ø4 mm & tap M5 centrally & square a new hole in the shoulder. The shoulder has a hard surface so be careful in drilling. However, if I can do it, it can be done, even if you have to sharpen your drills & go in stages of drill sizes.

I then cut the head off the shoulder bolt & refit ensuring alignment with the stripped hole by screwing in an M5 fastener. Tighten up the M6 nut & washer on the back face. Job done!

If you struggle to understand what I’m prattling on about, say so, & I’ll try & post up a photo or two.

I hope this helps.

[Donnie]

im assuming you've ordered a m5 helicoil set and not just a set of the coils themselves? I ask as the tap needed is not a standard tap and the drill size will also be specific.

However, if you think there may be little meat for the drill, you may be able to use the tap directly in the current hole to recut it for the helicoil and you're done?

[Ian-B]

Well it took me a few minutes to work out what Warkton Tornado was on about there but it sounds like a good option. That's not a bodge, that's good engineering.

[bazza3004]

A few on mine were goose so i just tapped out to next size . Not had any problems since.

[Tony Hart]

Many thanks for the replies. W-T No1 a picture would help me no end as I don't have Ian B 's imagination. I have ordered the fixing kit for the helicoils Donnie, I seem to have quite a collection of them now! I might just look at re-tapping to m6 first as the easier option. Thanks again for all the input and I will let you know how I get on.

[rossclark]

Rivnuts?

[Warkton Tornado No.1]

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[Warkton Tornado No.1]

Hi.

Sorry for the delay in response & the image detached from this message.

There are other images I would have liked to add (via Dropbox) but they fail due to their size.

If anybody wants me to try that little bit harder, I will, or I'll even knock up a 3D model/drawing if required.

Which reminds me. Slightly off subject.

Are there any Lambretta enthusiasts with basic machining facilities available to do small batch prototype work? All with improving Lambretta in mind, of course.

Kind Regards

[Warkton Tornado No.1]

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Another view of a much repaired mag flange.

[Warkton Tornado No.1]

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Yet another view of a much repaired mag flange.

[Warkton Tornado No.1]

IMG_0210.JPG

....And yet another (blurred) view of a much repaired mag flange.

[rossclark]

That's quite a neat fix.