Brad The Bike Boy: Timing belt adjuster thread failure and repair 2V models

Saturday, July 4, 2026

Timing belt adjuster thread failure and repair 2V models - a Pantah in this case.

I had a Pantah in for valve clearance check and belt replacement, and undoing the tensioners got me the day wrecking jammed bolt and torn out heli-coil of love.

I looked into Time-serts, but the hole the heli-coils had torn out was about 9.6mm and that's about the od of the Time-sert, so the only option there was a Big-sert. But the 14mm or so deep blind hole was possibly an issue when using the shortest insert (11.7mm, Time-serts come in shorter options) with the supplied taps and finishing tools, and the Big-serts have a little pin that pushes out and locks as part of winding the inner finish tool in, meaning that if it wasn't right, it'd be a bigger mess to undo.

Looking at another set of early style cases I had kicking around, it looks like the horizontal hole is in line with the boss for the case half screw from the LH side, and the vertical is almost into the stud boss. As such, they possibly could go deeper without issue, but I wasn't too keen on finding the oil so played it safe.

I figured the strongest thread to put into the case would be a fine M12, so went out and bought a couple of M12x1.25 taps (inter and bottoming) and some M12x1.25 bolts as donors and had at it. Starting with the inserts - drilled and tapped with M8 internal hole, cut to 13.5mm lengths with opposing leads as required.

Cases drilled with 9.6, 10, 10.2 then 10.5mm drill bits and tapped to M12x1.25. The charts I found gave 10.8mm as the M12x1.25 drilling size, but the taps went in so easily at 10.5mm that I'd be inclined to start with the 10.2mm hole next time to see what happens. No point giving up material at the minor diameter if you don't have to. I've been watching "Ralfy Customs" on Youtube, and bought some Anchorlube from the local supplier to try. Seemed to work as well as anything else I've used.

Cleaned all the holes, fitted my inserts onto an M8 bolt with a top hat spacer to allow them to be tightened inside the case with some blue Loctite on the outside. I did consider the Wurth green, but removal is generally not an option once fitted with that. Shortened some M8 hex bolts to give maximum available length without bottoming (as per the initial cause of said mess) and Bob's ya aunty.

Belts fitted and tensioner bolts torqued to 25Nm. I was rather pleased with my result.

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