I've had my clutch cover off so many times this year sorting out the slipper clutch that I've managed to ruin the threads on the engine casings.

Got a set of GB racing covers and when I was fitting them I noticed that a few of the bolts didn't feel like tightening up properly. Having had a bit of experience of this over a long career of engine work I backed them out to find the start of aluminium swarf in the threads. I've found a local bike shop that has the helicoiling kit but just wondered if anyone has had the same experience or if there is a better way of doing this now? Clutch doesn't leak because of the 'o" ring but I don't like the idea of doing to much riding with only half the bolts done up really tight.

Yep - had exactly that problem with the GB cover - try using slightly longer bolts (add the depth of the cover to the OE length) or, if that doesn't work for some or all, ask Paul (ex-Bracken) to helicoil them (as he did for me) or for his advice re do's and don'ts.

in the future you may want to use Anti-Seize on threads . I think friction has a way of breaking down the little aluminium threads sometime.

cheers

I've always used Helicoils with good success but it's never too late to try something else. I might try TLS_Russ' suggestion next time to see how they
go. Theres always a next time

Time-Sert, Heli-Coil, whatever - all good if properly installed. And that's where most people go wrong: DIY on these isn't for all ... used them both on many a part design, and engines. On most occasions, I have machinists install them. BTW "Machinists" <> "Mechanics". Particularly if it was dimensionally critical (e.g. having to line up a clutch cover or other part with several fasteners afterward).

I tend toward Heli-Coils for lesser load applications (like engine case threaded holes where a clutch or stator cover are secured). Properly installed, Time-Serts work great for things like exhaust studs, but require more material removal, and on space-premium, low load applications, the risks outweigh any real advantage (=none). They are also are a little trickier to install.

That said, with either approach, threads will be better than those in the cases as they are from the factory, in both resistance to pull-out and thread durability. The only caveat is perhaps when using a stainless steel insert with a stainless steel fastener - there is a risk of galling. Use of these inserts are de-facto on air-cooled Porsche rebuilds wherever studs go into the cases.

Not enough material for Timeserts. You're gonna have to go Heli-coil. Wouldn't sweat it as they work fine and are straight forward to install.

To get your depth right on the pilot drill hole and threads apply electrical tape (several layers thick) to the drill bit and tap at the proper distance from the end to get the proper depth in the cases. If I didn't make that clear let me know and I'll shoot you a picture of what i'm trying to describe.

Good luck (although you won't need it, dead easy to do). Just take your time (especially on the pilot holes). Imperative you keep the drill perpendicular to the cover sealing surface. Shoouldn't be too much of an issue as you are only removing a small amount of material.