Caliper Seals

[panteradave]

I've just finished (I thought) rebuilding the front master cylinder and calipers on my '82, bench bled the system, and was getting ready to re-mount everything back on the bike. But I have encountered an inconsistency. When I disassembled them, the calipers had one o-ring seal per piston, even though there are two grooves in each cylinder bore (the outer groove contained no o-ring). Since my CBX is very low mileage, I assumed that the single o-ring was as from the factory. The rebuild kits actually contain four o-rings per caliper, but two of the seals are thinner and slightly smaller in diameter so don't really seem to fit the pistons. I figured that the rebuild kit was designed for more than one bike and therefore had extra parts in it, hence the 2 smaller o-rings.

But I have just noticed a Honda service manual illustration that indicates the '82 calipers have 2 o-ring seals per piston. So which is it - 1 or 2 o-ring seals per piston?


Dave

[daves79x]

Dave:
Each caliper bore requires a thick seal and a thin one. No idea why yours didn't have the thin one. The outer thin one is a wiper and seals the piston from the elements. Install them both.

Dave

[panteradave]

I disassembled both calipers (again) and sure enough the extra o-rings fit the outer grooves in the cylinder bores exactly. Everything is now back together and back on the bike. It looks like my bench bleeding wasn't completely successful though as the lever is still a little mushy. I can't quite lock the front wheel up on a hard stop, though the tire howls pretty good. I'll try strapping the lever open over night and see if that lets some more air escape. If not, then more bleeding (my wife is becoming less and less fond of the brake bleeding excercise).

Thanks for the heads up on the seals.

Dave