Topic: Master cylinder identification ?

[Erny]

Preparing for dual disc conversion for my CB750 K7, got MC that is declared by seller as coming from GL1000.
I'll need to buy new master cylinder set (piston, seals..), so need to be sure what to order.

attched some pics of MC, it has already switch for brake light, I identified it as coming from GL1000 model 1978 : https://www.partzilla.com/catalog/honda/motorcycle/1978/gl1000-a-gold-wing/front-master-cylinder

can somebody confirm my findings?
If so, would you recommend non OEM cyl set (for example from Tourmax) or stick only to OEM Honda (quite expensive!)

[robvangulik]

Gl1000 and cb750F2/3 had indeed the same master, as far as I know the only ones with the high reservoir, and those will work very well with two larger piston (40.6mm) calipers like you have on the K7. On earlier 38mm calipers the normal 14mm master works nicely, but that may have too much travel/be too soft with the larger  piston ones.

[Erny]

So is the one I have definitely GL1000 '78?

[bryanj]

Looks like it to me and same as the one i have, try Dave Silver for pattern kit its where i got mine

[754]

It is 78 or later .. 77 did not have brake switch.

[scottly]

Gl1000 and cb750F2/3 had indeed the same master, as far as I know the only ones with the high reservoir, and those will work very well with two larger piston (40.6mm) calipers like you have on the K7. On earlier 38mm calipers the normal 14mm master works nicely, but that may have too much travel/be too soft with the larger  piston ones.

The K7 calipers had 42.8mm pistons, and will work with a 14mm master, but, as you say, may be a bit on the "soft" side. The Gl/late F had a huge 11/16" master, which will work, but with a much stiffer lever feel. Why Honda coupled an 11/16" master with dual 38mm calipers is a mystery to me.

[bryanj]

All the 1000 wings i worked on had a switch

[robvangulik]

The K7 calipers had 42.8mm pistons, and will work with a 14mm master, but, as you say, may be a bit on the "soft" side. The Gl/late F had a huge 11/16" master, which will work, but with a much stiffer lever feel. Why Honda coupled an 11/16" master with dual 38mm calipers is a mystery to me.

Ah, I couldn't remember the caliper piston size exactly last night (it was well after midnight ) , it can well be 42,8. 11/16 isn't that huge, at 17,4mm, I still think that will combine fine with 2 42,8 calipers, I have a chart somewhere, single piston brakes work usually well with a ratio between 12 and 18, if I remember correctly

[Erny]

Thanks all, so I'll prepare to rebuild GL MC