175 top end overhaul

[ranton_rambler]

As mentioned previously, having completed the summer riding I've taken the head and barrel off my 175 to sort a couple of things out.

One is to repair some threads so the rocker cover gaskets will seal properly.

The other is to fit some new piston rings. It's been rebored to 63mm and Cox & Turner have provided the 2 compression rings, but I'm struggling to find the oil control rings. There are 2, one in the usual place and one near the skirt but both are 2.5mm depth. Gaps are about 0.9mm on both so I don't want to refit them. Any suggestions on where to try?

Ian

[veloduke]

You could try F W Thornton
https://www.fwthornton.co.uk/

[ranton_rambler]

I spoke to Duncan at F W Thornton and will pop over there next week to collect the single oil control ring they have. I suppose one good one will be better than none!

Also a schoolboy error. I forgot to undo the camshaft nut before I took it apart so will need to partially reassemble.

[ranton_rambler]

Somewhat delayed update. The bike has been back together for a few weeks now.
Rocker cover threads repaired with insert kits.
Compression rings and one oil control ring replaced with bits sourced from FW Thornton and Cox & Turner. Thornton's only had one suitable oil control rings so I had to re-use the better of the 2, and fitted it in the bottom groove below the gudgeon pin.
Original camshaft refitted and carburettor put back to previous settings. The "sport" camshaft did produce a little more top-end power I think, but I don't think I was getting the best from it with my small-valve head, and it was rather peaky and had no idle, hence a bit more difficult to live with.

It starts easily and settles to a steady idle once a bit warmed up. No oil leaks apparent so far but I have not had a chance to take it out for a shakedown run yet. The roads round here have now been gritted so it might be a while before I get out on it.

Ian P

[Duccout]

Well done Ian,

Got to be wary of road salt, it can do a lot of damage.


Cheers,

Colin