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MickeyMoto wrote: ↑01 Jan 2022 21:40 ...but not for the master cylinders.

Norbert says 16mm for single disc, I am saying 16mm for single disc, you have quite clearly stated 14mm for a single caliper.

Am I missing summat?

You might want to read what Norbert and I wrote agian.

14mm is standard for the 250 twin, which uses the same wheel disc and calliper as the 350, but has a better brake feel.

And I do believe that a 14 mm mc would also be worth a try with a double disc. For me and my small hands a 16mm mc didn´t have a good feel and my current 13mm mc to me is a bit to agressive/dangerous when panic breaking.
Rocinante with this 13 mm mc was without use during the last 18 mounth and will be reactivated in spring, because I left the silver Dulcinea in Spain till I´ll drive her to the north in june passing for Morano, if it will be posible. That will be a strong change from the geat drum brake to the 13 mm mc! It took me some time to realy trust the drumbrake after decade with doblediscs. You have to change your riding style somehow.
The most important thing to have in mind is that most of us have reached an age that won´t pardon going to the ground like 20 years ago !

All the best for you and your folks for this 2022!!! It will be dificult that it turns out worse than the last year, but that is what we are thinking all our live

Yes, I have read it all again. In your post you state 16mm but do not state that this is a replacement for a 19mm mc. It is like a fill in the gaps if the full information is not printed. Norbert is very clear on the original sizes, you just make a statement with no qualification that you are stating a recommendation and not the original sizes. That is why I am confused.

My 16mm m/c, unlike the later 18/19 mm has no electric hook up for a front brake light.
If I use this on my K1 what’s the recommended solution?
What did the 1970’s bikes fitted with these master cylinders have?

My K has a cylindrical screw-in switch which screws into the brake lever mount. This type of thing, maybe a cheaper version....Think I got a few as they pack up every few years. Heat shrink on the terminals and away I go. You can either put a washer on or dremel the end of the piston lightly to get it to activate at the right moment if needs be. You may not have a compatible lever mount though. John

https://www.bay.co.uk/itm/125025536595? ... SwA3dYPwMh

My 19mm m/c is exactly the same casting as the 16mm one (except the piston bore of course) but whereas the 19 has the cylindrical screw in switch on the lever mount the 16 doesn’t have the threaded hole to fit the switch.
I imagine there must be some other way to solve the problem or this type of m/c wouldn’t exist would it?
My 16mm unit came off a 1970’s 350 sport so how do those bikes’ front brake lights work?

Mark wrote: ↑05 Jan 2022 19:22 My 19mm m/c is exactly the same casting as the 16mm one (except the piston bore of course) but whereas the 19 has the cylindrical screw in switch on the lever mount the 16 doesn’t have the threaded hole to fit the switch.
I imagine there must be some other way to solve the problem or this type of m/c wouldn’t exist would it?
My 16mm unit came off a 1970’s 350 sport so how do those bikes’ front brake lights work?

Oh! I can answer that one-they didn't. At least until 1977 or a little later there was no switch fitted. The law didn't require one then (till about 1980 I think?) The first ones I saw fitted were on the twin disc models with the hydraulic splitter on the bottom fork yoke. There was a switch mounted in a port on that splitter. Some people fitted those switches that doubled as a banjo bolt on the master cylinder. But that can foul things on clip on bars and looks a bit obvious and messy on stradas.

Thanks for that clarification Steve.
No way have I got room for one of those banjo switches and I’ve just fitted two new lines so don’t fancy buying a new set of three with a splitter, assuming I could find a splitter anyway.
Hmmm, back to the shed.

Can the mounting be drilled and tapped like the other type or is there not enough metal?
You wouldn’t want to compromise the brake lever.

Mdina have new old stock 16mm master cylinders. https://www.mdinaitalia.co.uk/grimeca-f ... -16mm.html

You'd have to check with Doug if his parts have the tapping for the microswitch, can't quite see in the picture, but it does looke like there is a slightly square looking protrusion in the casting which is the bit where which my K1 is drilled and tapped for the microswitch.

However, from the MOT inspection manual it is not an MOT requirement to have both a front and rear brake light switch on motorcycles made before 1st April 1986. And even motorycles made after this date are only required to have both switches if it was manufactured that way. So provided you have a rear switch, if you have an original front Grimeca master cylinder with no switch provision, then it is not a requirement to have a brake light switch on the front circuit. If there is a switch fitted it MUST operate, but if there is no provision for a switch I think you are ok.

If you fitted an aftermarket or modern master cylinder with no switch provision then it would be harder to argue that the bike was made that way.

Of course, it's a good safety feature to have a front brake light switch, so regardless of MOT requirements you may decide you want to find a solution for this. If drilling the master cylinder for a microswicth acting on the lever is not an option, then since there is not normally room at the master cylinder banjo end, a banjo pressure switch in a yoke mounted splitter would be neatest solution but as a stop-gap you could probbly fit one at the caliper end, although it would look a bit odd.

From https://www.gov.uk/guidance/mot-inspect ... -equipment :

4.3.2. Switching

Motorcycles first used on or after 1 April 1986 must have a stop lamp that switch on from both brake controls. However, a small number of motorcycles first used from this date were approved with the stop lamp switching on by only one control. You should fail the stop lamp only if you are certain that it was originally manufactured to switch on from both controls.

All stop lamps should light up immediately when the brake is applied and switch off immediately the brake is released.

Additional stop lamps, over and above the mandatory requirements, must be tested. However, if there is doubt as to whether they are connected, the benefit of this doubt should be given.

I have a 19mm with the screw in switch as an example and it looks like it may be possible to tap the 16mm m/cyl in the same place although there is more meat at that point on the 19mm unit which is otherwise an identical casting.

In legal terms it’s gratifying to see the info you dug up Tom as my bike is from 1983 so a period grimeca 16mm with no front brake switch seems to be legal even if it’s not the 19mm the bike originally came with.

This is a 16mm (error: it´s a 13 mm!!!) mc that was destinated for my 500 Frankensteinproject. Before I used it with my 350K and it had a thread for the switch. Of course in that times it was not that shiny
A friend of mine, who will do the electronics on the bike, drilled the thread to 8mm so he could import an 8 mm aluminium tube in which he glued a Reed-Switch (with a very small magnet in the lever). Underneath there is a grub screw to adjust the switch (distance switch-magnet).

Oh sorry the first foto is a 13mm mc for clipons. But I will not use it with the dobledisc of the 500. It´s the same I´ve mounted on Rocinante with double disc (that one with a certain danger when panic breaking).
But the 16mm mc of the second foto, that I used before mounting the 13 mm one, also had the thread for the switch.

Splitter on e bay at the moment
https://www.ebay.co.uk/itm/175187179340 ... Sw0PBiIy2v
I know you said you didn't want to go this way but may be worth a thought - Duncan

I would not doubt, it´s a fair price I think , and brake light switch included