Hello,
very recently got my bike back on the road (many thanks to all who helped).
I do have one little issue, I have a leak from the front brake master cylinder, evidenced by DOT 5 down one side of the petrol tank. Where it is coming from is a bit of a mystery, no evidence of a leak at the banjo bolt or anywhere else come to that, but there it is, on the tank following every ride out.
Any idea's?

side question - are all front brake master cylinders the same/ compatible? Is there any advantage to fitting an XB master cylinder?

Many thanks

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Today my pet mouse Elvis died ..................He was caught in a trap
There are two types of people in this world, those that can extrapolate

If it definitely is brake fluid (have you tasted it?) it must be coming from either
i) the line out (banjo seals which you've checked)
ii) the lid seal
iii) past the piston seal and on to the heel of the lever
iv) the window seal (unlikely)
Get it clinically clean and dry with brake cleaner on a tissue, then look again after a ride, it doesn't evaporate so it must leave a witness.

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'98 M2 Razorback, it's a keeper.

If you replace the m/cyl, note that 96-97 models had a 5/8" dia m/cyl. The later ones had 1/2".

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Try doing this to yer fueller...........

Why don't you admit that you are addicted to it?

Have the brake lever ziptied and see if there is showing some fluid afther a while.

Is the rubber piece that sits under the reservoir cover still in good order?
if it's sweating it could be leaking through there.
(well most is allready suggested by Rik

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The sound of a V-twin engine braking is music to my ears!!

Thanks for the help,

If it definitely is brake fluid (have you tasted it?) (checked /yes it is)
i) the line out (banjo seals which you've checked)(dry as a bone)
ii) the lid seal (checked and good)
iii) past the piston seal and on to the heel of the lever (Top hat style seal looks pretty perished - no sign of brake fluid, but a possible)
iv) the window seal (unlikely)(dry as a bone)
Get it clinically clean and dry with brake cleaner on a tissue,then look again after a ride (Will do, i plan on lightly covering all the possible leakage areas with paper for inspection)

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Today my pet mouse Elvis died ..................He was caught in a trap
There are two types of people in this world, those that can extrapolate

Good plan.
If it was the piston HP seal, there'd be evidence inside your tatty dust boot.
My money's on the lid gasket...

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'98 M2 Razorback, it's a keeper.

Bellow which seals the lid doesn't have the plastic insert on pre 98 bikes......ie. bellow gets 'sucked' in, leaks are common

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Mithered ta death.
92 MB
96 S2T
98 S1W
00 M2
01 X1
03 P3
10 CR

Would this not be DOT 4 or DOT 5.1 fluid

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2017 KTM 690 Duke
2001 M2
2019 Street Triple RS
2004 Monster S4R
Wilier La Triestina

I know my '98 is DOT 5, not 100% sure of the earlier ones... but if it was DOT4 or 5.1, I don't think Graeme would be quite so relaxed about it getting over his tank!

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'98 M2 Razorback, it's a keeper.

Thankfully Dot 5 (never thought i'd say that).
Still waiting for the opportunity to take her out for a spin to find the leak.

Maz 'lid doesn't have the plastic insert on pre 98 bikes' -no sure what the insert looks like, can this be retro fitted to my M/C? (always looking to upgrade)

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Today my pet mouse Elvis died ..................He was caught in a trap
There are two types of people in this world, those that can extrapolate

Yes.

_________________
Mithered ta death.
92 MB
96 S2T
98 S1W
00 M2
01 X1
03 P3
10 CR