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LM3 rear brake light switch

Printed From: guzziriders.org - moto guzzi forum
Category: Technical
Forum Name: Big Block Tonti
Forum Description: Spada, Le Mans and Cali
URL: http://www.guzziriders.org/forum_posts.asp?TID=3773
Printed Date: 28 Mar 2024 at 13:42
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Topic: LM3 rear brake light switch
Posted By: Hustler
Subject: LM3 rear brake light switch
Date Posted: 15 Feb 2016 at 18:47
I've just invested £3 in a new secondhand rear brake light switch and today went to fit it.
It is larger than the current non working switch and shown in the foreground of the picture.
So I start to unscrew the old switch (shown in the photograph with the red plastic cap on the end) and brake fluid starts to leak from the loosened fitting.
This is no great problem really as I can drain the fluid from the non linked rear brake, replace the brake light switch, fill with new fluid, bleed and job done.
But I was wondering if there was a clever way to replace the switch without draining the brake fluid.
I can't think how that could be achieved but just interested really.
Thanks very much. 





Replies:
Posted By: NeilD
Date Posted: 15 Feb 2016 at 20:06
not totally familiar with the LM3, but on the LM 2 the original switch (which youve bought) fits in the splitter manifold  on the lefthand side  of the frame by the lift handle.. the switch you currently have fitted is an aftermarket switch which incorporates the banjo bolt...

have the brakes been de-linked ? just in the process of doing this to my LM 2 and am fitting the set up you have with the switch on the master cylinder


Posted By: Jim Mac
Date Posted: 15 Feb 2016 at 20:19
every switch I have changed meant loss of fluid etc

-------------
V85 TT Trzvel    BMW R45
Too old to die young


Posted By: Hustler
Date Posted: 15 Feb 2016 at 20:28
Originally posted by NeilD NeilD wrote:

not totally familiar with the LM3, but on the LM 2 the original switch (which youve bought) fits in the splitter manifold  on the lefthand side  of the frame by the lift handle.. the switch you currently have fitted is an aftermarket switch which incorporates the banjo bolt...

have the brakes been de-linked ? just in the process of doing this to my LM 2 and am fitting the set up you have with the switch on the master cylinder
Thanks very much Neil,
I haven't had the bike long at all and not sure I've even got a lift handle.
Be exciting if I have and will check it out tomorrow.
I'll also have a look round for the splitter manifold while I'm there.
I saw the fitting I've photographed and just assumed that's where the new switch must fit.
My brakes have been de-linked but by a previous owner although personally I'd rather have them linked.
I shall report back tomorrow with my findings and thank you.



Posted By: theone&onlymin
Date Posted: 15 Feb 2016 at 20:29
I went to this method a few years back so I did.
[IMG] http://s821.photobucket.com/user/theoneandonlymin/media/IMG_0665.jpg.html" rel="nofollow"> [/IMG]

Cheers
Min


Posted By: Hustler
Date Posted: 15 Feb 2016 at 20:35
Originally posted by Jim Mac Jim Mac wrote:

every switch I have changed meant loss of fluid etc
 
Thanks Jim,
The fluid did look a little mucky in the master cylinder so I'll change that whatever the outcome of this brake switch.





Posted By: NeilD
Date Posted: 15 Feb 2016 at 20:40
Originally posted by Hustler Hustler wrote:

[
I'll also have a look round for the splitter manifold while I'm there....


doubt you'll have one if they have delinked the brake as i guess they have run a brake hose direct from the rear caliper to the master cylinder.... gutsibits amongst others sell the switch you currently have fitted

steine dinse have online parts lists if you want to see how you brake system was originally laid out :)

http://www.stein-dinse.biz/eliste/index.php" rel="nofollow - http://www.stein-dinse.biz/eliste/index.php


and Min... nice mod :)


Posted By: Hustler
Date Posted: 15 Feb 2016 at 20:43
Originally posted by theone&onlymin theone&onlymin wrote:

I went to this method a few years back so I did.
http://s821.photobucket.com/user/theoneandonlymin/media/IMG_0665.jpg.html" rel="nofollow"> " />

Cheers
Min
Thanks Min,
That's interesting.
I don't have that setup attached to the frame and I also see you have 2 connectors on top of the brake cyclinder cap whereas I only have the one.
So maybe I'm missing a wire which is why the brake light isn't working and nothing to do with the switch.
Should be in for some exciting times tomorrow in the garage.
 


Posted By: Hustler
Date Posted: 15 Feb 2016 at 20:46
Originally posted by NeilD NeilD wrote:

Originally posted by Hustler Hustler wrote:

[
I'll also have a look round for the splitter manifold while I'm there....


doubt you'll have one if they have delinked the brake as i guess they have run a brake hose direct from the rear caliper to the master cylinder.... gutsibits amongst others sell the switch you currently have fitted

steine dinse have online parts lists if you want to see how you brake system was originally laid out :)

http://www.stein-dinse.biz/eliste/index.php" rel="nofollow - http://www.stein-dinse.biz/eliste/index.php


and Min... nice mod :)
My new / secondhand switch came from gutsibits.

I'll have a look at the stein-dinse link as well so thanks for that, appreciated.


Posted By: exsmokingbiker
Date Posted: 15 Feb 2016 at 20:49
the 2 wires on the top are not brake light the are fluid level indicator in case it runs low


-------------
For all your engineering- ultrasonic and aquablasting needs see WWW.bike-aquablasting.co.uk


Posted By: Hustler
Date Posted: 15 Feb 2016 at 20:54
Originally posted by exsmokingbiker exsmokingbiker wrote:

the 2 wires on the top are not brake light the are fluid level indicator in case it runs low
Of course, obvious really when you point it out.
Thank you.


Posted By: Ken-Guzzibear
Date Posted: 15 Feb 2016 at 22:19
pm  sent brake light sw is behind top of rear left shock on frame downtube there , the switch ontop of master cyl is the low level switch  replacedtop with sealed one as these often cause air to get in they get fine cracks in them the only bikes with switch on master cyl have got de linked brakes
 
 


-------------
The Older i Get, The Better I Was


Posted By: Hustler
Date Posted: 15 Feb 2016 at 22:56
Originally posted by Ken-Guzzibear Ken-Guzzibear wrote:

pm  sent brake light sw is behind top of rear left shock on frame downtube there , the switch ontop of master cyl is the low level switch  replacedtop with sealed one as these often cause air to get in they get fine cracks in them the only bikes with switch on master cyl have got de linked brakes
 
 

Thanks very much Ken.
What a good selection of very helpful replies I've received today.
Let's just hope I'm up to making sense of it all in the garage tomorrow.
I will report back whatever I find though.
Thanks again one and all. 


Posted By: Ken-Guzzibear
Date Posted: 15 Feb 2016 at 23:01
useful tips tell you how to reverse bleed the brakes takes seconds big syringe tubing take fluid out of mast cyl, cover top I use cling film fill syringe new fluid fit to nipple flick syringe a laa dr does air goes up ... open nipple at caliper slowly push fluid in till it appears in mast cyl lock off nipple job done ....

-------------
The Older i Get, The Better I Was


Posted By: Hustler
Date Posted: 15 Feb 2016 at 23:15
Originally posted by Ken-Guzzibear Ken-Guzzibear wrote:

useful tips tell you how to reverse bleed the brakes takes seconds big syringe tubing take fluid out of mast cyl, cover top I use cling film fill syringe new fluid fit to nipple flick syringe a laa dr does air goes up ... open nipple at caliper slowly push fluid in till it appears in mast cyl lock off nipple job done ....
 

I have seen that on the forum although I'll probably use my Mityvac bleeder kit.

Need to nip out and buy some brake fluid first though.
    


Posted By: NeilD
Date Posted: 16 Feb 2016 at 07:30
Originally posted by Hustler Hustler wrote:


My new / secondhand switch came from gutsibits.

[/QUOTE]

guess they sent what you asked for , a brake switch for a Lemans 3, but unfortunately yours doesnt have a standard one Smile  not wanting to teach you to suck eggs etc, but presume you have checked that it actually is the switch thats duff ?




Posted By: Hustler
Date Posted: 16 Feb 2016 at 09:06
Originally posted by NeilD NeilD wrote:

Originally posted by Hustler Hustler wrote:



My new / secondhand switch came from gutsibits.


guess they sent what you asked for , a brake switch for a Lemans 3, but unfortunately yours doesnt have a standard one Smile  not wanting to teach you to suck eggs etc, but presume you have checked that it actually is the switch thats duff ? 
 
Neil,
I'm quite happy to be taught how to suck eggs.
In fact I've never sucked an egg come to think of it.
My workshop ability is basic. 
I like to service my bikes and a few extras like brakes, electrical faults and always looking to do a bit more but serious stuff goes to a man that knows about these things.
I was buying a rear brake disc from gutsibits which I need, knew the back brake stop light didn't work and they had these switches for £3 so I assumed / guessed that would be what I needed but for £3 pushed the boat out and went for it.
If nothing else it's been, for me, well worth the £3 for the education I've gained on this forum with my question.
But no, I don't know if the switch itself is actually duff.   
PS sorry. When I first got the bike it went to a man that knows about these things as the carbs. were out and a few other things and I got him to go over the bike as well and he said I needed a brake light switch.


Posted By: NeilD
Date Posted: 16 Feb 2016 at 09:24
not sure why anyone would want to suck an egg :)  tis a strange expression :)  gutsibits are a good bunch so you've made a good start in your guzzi education :) 


Posted By: italianmotor
Date Posted: 16 Feb 2016 at 09:24
I might copy that Min. My rear brake switch on the S3 hasn't worked for years and I haven't replaced it because I just can't face/be bothered with all that bleeding business. Might get meself a switch and hook it up like yours instead.

Originally posted by theone&onlymin theone&onlymin wrote:

I went to this method a few years back so I did.
http://s821.photobucket.com/user/theoneandonlymin/media/IMG_0665.jpg.html" rel="nofollow"> " />

Cheers
Min


-------------
Guzzi lover doing my own thing: http://www.italianmotormagazine.com" rel="nofollow - http://www.italianmotormagazine.com


Posted By: Hustler
Date Posted: 16 Feb 2016 at 09:32
Originally posted by NeilD NeilD wrote:

not sure why anyone would want to suck an egg :)  tis a strange expression :)  gutsibits are a good bunch so you've made a good start in your guzzi education :) 

I'm not quite new to my guzzi education as I also have an old V50 Monza in need of a little work that I really must sort this year. 
That will wait until the warmer weather though. 


Posted By: Barry
Date Posted: 16 Feb 2016 at 09:55
Can't imagine why you'd want to de-link the brakes myself, but it's your bike!

If you *are* going that route, and your bike is pre-86, I think that the MOT requirements are such that you only need a stop lamp that is operated by one of the controls, that being the primary control. With linked brakes that would be the foot brake on a Guzzi, but if de-linked that would be the front-brake lever.

This came up when I got my Spada MOT'd and the foot brake-operated switch had failed. In that instance, the switch is on the proportioning valve and wasn't too much of a hassle to replace, given an extra pair of hands!

Just something to consider - and to verify for yourself, of course!

"Machines first used before 1 April 1986 must have a stop lamp that operates from at least one brake control."

http://www.motuk.com/bike/1-3.asp#Menu_Top


Posted By: italianmotor
Date Posted: 16 Feb 2016 at 10:20
Correct, which is why my bike has always passed its MOT with just the front brake switch operating. I only really use the front brake anyway!


-------------
Guzzi lover doing my own thing: http://www.italianmotormagazine.com" rel="nofollow - http://www.italianmotormagazine.com


Posted By: Dukedesmo
Date Posted: 16 Feb 2016 at 10:36
Originally posted by Barry Barry wrote:

Can't imagine why you'd want to de-link the brakes myself, but it's your bike!

 
I de-linked the brakes on mine because, after nearly 40 years of riding with conventional brakes I found the setup awkward (and different to my other bikes) and really wasn't happy with the front brake lever stopping ability.
 
In doing so I changed both master cylinders, using a similar design but smaller bore rear that is a little shorter in the body so the banjo brake light switch fits onto it whilst keeping within the frame (original was on the splitter valve).
 
I used a Brembo RCS radial master cylinder at the front (15mm) and, combined with a complete overhaul (new pistons, seals, pads & braided hoses) the setup suits me much better and the front brake can actually stop the bike quite well (for an old bike) and I can still use the front/rear combination if I want.
 
 


-------------
Le Mans 2
Ducati 916

Ducati M900


Posted By: Hustler
Date Posted: 16 Feb 2016 at 11:32
Originally posted by Barry Barry wrote:

Can't imagine why you'd want to de-link the brakes myself, but it's your bike!

If you *are* going that route, and your bike is pre-86, I think that the MOT requirements are such that you only need a stop lamp that is operated by one of the controls, that being the primary control. With linked brakes that would be the foot brake on a Guzzi, but if de-linked that would be the front-brake lever.

This came up when I got my Spada MOT'd and the foot brake-operated switch had failed. In that instance, the switch is on the proportioning valve and wasn't too much of a hassle to replace, given an extra pair of hands!

Just something to consider - and to verify for yourself, of course!

"Machines first used before 1 April 1986 must have a stop lamp that operates from at least one brake control."

http://www.motuk.com/bike/1-3.asp#Menu_Top
Thanks very much for your reply Barry.  
My LeMans3 is 1982.
I didn't de-link my brakes as they were like that when I bought the bike late last year.
I would prefer they were still linked and may, if it isn't too expensive, revert back to the linked arrangement.
If I don't need the light for the rear brake then I may not bother.
It certainly passed it's last MOT like that, well I think it did anyway.
I shall have another look round later today and go from there.


Posted By: Hustler
Date Posted: 16 Feb 2016 at 11:37
Originally posted by Barry Barry wrote:

.....

"Machines first used before 1 April 1986 must have a stop lamp that operates from at least one brake control."

http://www.motuk.com/bike/1-3.asp#Menu_Top

And thanks for the MOT link Barry, most useful.


Posted By: Pharisee
Date Posted: 16 Feb 2016 at 15:50
Originally posted by Dukedesmo Dukedesmo wrote:

 
I de-linked the brakes on mine because, after nearly 40 years of riding with conventional brakes I found the setup awkward (and different to my other bikes) and really wasn't happy with the front brake lever stopping ability.
 



I'm in exactly the same situation, although I've been riding a little longer... over 50 years in my case.
I'm currently riding the LM2 with the linked system but as I'm so used to braking with my right hand, it just seems alien to be using my foot as the main braking force.
I'll probably de-link mine in the not too distant future so any advice on which master cylinders to use would be greatly appreciated.


-------------
Light travels faster than sound which is why some people appear bright until they open their mouth.


Posted By: Dukedesmo
Date Posted: 16 Feb 2016 at 16:23
Originally posted by Pharisee Pharisee wrote:



I'll probably de-link mine in the not too distant future so any advice on which master cylinders to use would be greatly appreciated.
 
As the rear cylinder is a 15mm bore for 2 calipers, I used a Brembo RCS 15 at the front to keep the same size for 2 calipers (front and rear calipers are the same) and it works really well. The RCS is the 2-position which allows you to change the effective length between 18 & 20mm for a different feel but you don't need this type, any 15mm or 16mm (maybe 17mm?) would be fine IMO. I wouldn't go any smaller or you'll have too much lever movement and be back to the bars before you get full pressure.
 
I have the RCS on the faster setting meaning I get less travel and it is fine even for 2-finger braking but on the slower setting it is close to trapping my other 2 fingers, so based on this I think a 16mm master cylinder would be good but not smaller (the original for 1 caliper is 13mm I think).
 
For the rear you want something smaller bore or you'll have a real on/off action, there is also the issue of what fits.
 
Both Ducati & Laverda used that same design of rear master cylinder with a single P08 caliper (same type as Guzzi used) and they used the smaller 12mm (or 13mm?) version.
 
The only problem is that they fitted it the other way round - with the exit facing forwards so (unless there is another version that I'm not aware of?) the counterbore is on the wrong side and the bolt/nut combination for the lever pivot is also on the wrong side, this involves some engineering work; i.e. cutting a counterbore in the opposite side and threading the other side of the pivot bolt holes? not a great deal, I did it myself in the workshop.
 
As for the master cylinder I got mine from a US ebay seller who seems to have had a batch of NOS parts as a year later he still has some for sale;   http://www.ebay.co.uk/itm/161078529356?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT" rel="nofollow - http://www.ebay.co.uk/itm/161078529356?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT  although I got the one without the low fluid switch as I don't think it's necessary any more with de-linked brakes and it gives an easy way for moisture to enter the reservoir (you could always fit your old switch cap if required?).
 
This master cylinder is a little smaller but with the required engineering fits perfectly and being shorter means you can fit a banjo switch without it 'peeping' out from behind the side panels.
 
Obviously you need new lines and to remove all the linked gubbings (splitter and link pipe from splitter to the front of the bike), I use Goodridge 'build-a-line' as you can get almost any length with bolt-on fittings and banjos.
 
I also found the pistons in mine had corroded and replaced them with the new updated alloy parts to prevent it happening again.
 


-------------
Le Mans 2
Ducati 916

Ducati M900


Posted By: NeilD
Date Posted: 16 Feb 2016 at 17:17
 I bought one of those 13mm rear m/cy as per that link you posted  fits a treat :)  ive gone for a new 15mm front m/c with the oblong built in resevoir... fits under the fairing nicely and as a bonus has built in brake light switch... brakes on my darmah with twin p8 calipers and standard 15mm m/c are really nice which swung it for me..


Posted By: Pharisee
Date Posted: 16 Feb 2016 at 22:19
Thanks very much for the info. It's much appreciated. Smile


-------------
Light travels faster than sound which is why some people appear bright until they open their mouth.


Posted By: Hustler
Date Posted: 16 Feb 2016 at 23:40
Just a quick update as I posted the original question yesterday.

As Barry pointed out in a previous post I only need a stop lamp that is operated by one of the controls, which the front brake does quite successfully, so I've decided to leave things as they are, at least for now.

Got plenty of other things to get on with without creating unnecessary work. 

And in answer to one of NeilD's questions I don't have a lift handle although unsure if I should have one or not for this model.

Thanks for all the replies people, most appreciated.



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