Question for the engineers out there.

Geoff Hastings · Post by **Geoff Hastings** » Tue Dec 04, 2018 2:33 pm

I've got a ca77 engine in bits and thought while its apart I put some new rings in it. The bores are not worn enough to warrant a rebore, nice and straight and not barrel shaped. Anyway I got a new set for not a lot of money only to realise that they are thicker than the ones currently fitted. My question is, is it viable to just skim off the .3mm from the lands to take the new rings?

rrietman · Post by **rrietman** » Tue Dec 04, 2018 10:26 pm

I think not. the spacing is different early/late thick/thin. what with the oiling grooves etc you run the risk of breaking a piston. this stuff is low$$$ and readily available, just get the right parts imho.
Good luck
Randy

Geoff Hastings · Post by **Geoff Hastings** » Wed Dec 05, 2018 5:06 am

Cheers Randy but, the source of cheap parts doesn't extend to the UK. A pair of pistons are £64 plus a set of rings, another £60 plus pins £10 each. If I'm buying new Pistons I might as well go for the rebore too. I look enviously at the price of spares in The USA then I look at postage, £25 for a gasket. I've seen a right hand case for as little as £8 but £60 postage, it's obvious some of the dealers are jacking the price of the postage up, I can't believe it costs £25 to put a gasket in an envelope with perhaps a piece of cardboard to protect it.

G-Man · Post by **G-Man** » Wed Dec 05, 2018 1:16 pm

Geoff

What size rings do you need? I may have some for you.

It's quite possible to turn the grooves in the piston to take the thicker rings and also I have seen people put the rings on a grinder (magnetic fixture) and take material off . Whilst either of those would be an interesting and fun excercise, probably easier to just get some more rings for someting like the Honda.

If you have not done so, get a copy of Radco's 'The Vintage Motorcyclist's Workshop'. Plenty of pragmatic Engineering solutions in there for engines much rarer than 60s Hondas..... :-)

https://www.ebay.co.uk/p/The-Vintage-Mo ... 929&chn=ps

Expensive in print but I can help....

Drop me a PM and we can discuss availability of rings. I'll be in the USA in Feb so I can pick up some up as a last resort.

G

Geoff Hastings wrote:I've got a ca77 engine in bits and thought while its apart I put some new rings in it. The bores are not worn enough to warrant a rebore, nice and straight and not barrel shaped. Anyway I got a new set for not a lot of money only to realise that they are thicker than the ones currently fitted. My question is, is it viable to just skim off the .3mm from the lands to take the new rings?

Seadog · Post by **Seadog** » Wed Dec 05, 2018 3:20 pm

G-Man wrote:If you have not done so, get a copy of Radco's 'The Vintage Motorcyclist's Workshop'. Plenty of pragmatic Engineering solutions in there for engines much rarer than 60s Hondas..... :-)

Good read. Get it in .pdf format at https://www.billymegawatt.com/uploads/6 ... rkshop.pdf

Geoff Hastings · Post by **Geoff Hastings** » Wed Dec 05, 2018 4:19 pm

Cheers guys,I had a quick look on Amazon at buying a copy, Prices varied from £60 to an eye watering £320. I had a look at the online PDf and it does look very interesting.

border0_3 · Post by **border0_3** » Thu Dec 06, 2018 8:33 pm

Hi Geoff,

We've been caught out by this difference in the past also.

The early CA pistons/rings were slightly thicker. Later CA and I think all CB and most common are the thinner type.

There'd be something on the subject on this site. G-Man and LM are go to gents on such subjects.

Best regards - Richard

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