Secondry master cylinder issues

Joined
Dec 16, 2010
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33
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Ireland
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2005 ST1300
Hey folks

Happy new year to one and all.

I am getting that familar clunk from the SMC when I go over bumps,I am hoping it is just an air in the system issue as I bled the brakes not long ago. My question is do I just need to raise the SMC at the forks and bleed the proportional valve by using the rear brake pedal or do I need to bleed the whole system from start to finish.

Thanks

Dub 24
 

Scooter

This space for rent...
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Since you just bled the brakes not long ago you would not need to bleed the two lines running from the front master cylinder but I would do all of the others in the proper order. You might want to exercise the SMC plunger a few times when you have the caliper off and tilted in order to get all of your air out. It might be worth your while to read this first...
 
OP
OP
Joined
Dec 16, 2010
Messages
33
Location
Ireland
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2005 ST1300
Hey Scooter thanks for the reply,

I read the article very helpful. I watched jfheath's video showing the amount of play there was in his SMC ,mine doesn't have anywhere that near amount of play all mine does is barely move but it moves enough to stop the rear wheel solid when applied which is what jfheath said was the conclusion he wanted on page 3 of that link you sent me so I am assuming the SMC is working properly and that the clunk noise I get going over a bump is telling me that the innards of the SMC needs replacing or do I possibly have an air issue as well ? .

If I do have an air issue I plan to follow jfheaths suggestion

Open the PCV and activate the SMC plunger, with a vacuum also on the line
and then I plan do both bleed nipples on the rear caliper with the above method as per jfheaths suggestion on the link you sent me.

Have I got his right



Sorry for all the questions

Thanks for your help

Ollie
 
Last edited:

Tom Mac 04a

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My 04 clunks over bumps too.... After a full bleed, the noise goes away for a few months but slowly returns.
I've tested my SMC and it appears to be fully functional , had it rebuilt / plunger changed.
Its been the same sincet he bike was a yr+ old , haven't beeb able to correct it over yrs, so I don't worry anymore.... I just do a bleed about every yr during normal winter maintanance.

When it does present a problem, I'll just drop in a new/replacement SMC (got one from a bike that had 3k miles on it)
 
Joined
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Dublin, Ireland
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Hi Ollie,

Hope you're keeping well..

My VFR used do the same. If your brakes are working OK I wouldn't worry about it.

John's guide to bleeding is excellent, but it's a bloody time-consuming exercise. Next time I'm doing mine I have a 4l bottle of brake fluid and expect to use it all, based on past experience. I hang a weight off the brake pedal and cable-tie the front levers overnight once every 2 or 3 weeks just to keep them biting. I also made up a 15 degree triangle out of a cornflake box to help with getting the smc in the right place when bleeding.

Did you ever get the bar risers?

Alfie
 
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I hang a weight off the brake pedal and cable-tie the front levers overnight once every 2 or 3 weeks just to keep them biting
I might try that too,I get that clunking noise on the VFR and on the ST1100,just accepted now that its because of the linked brakes and leave it at that.
the brakes seem fairly good but I'll try that tip of yours,the parking brake I just fitted on the ST will eliminate the need for a cable tie I think.
I think the linked brakes on the 1300 are harder to bleed though,isn't there a PCV or something buried under the plastics somewhere that needs bleeding too? anyway I don't think I'll ever be buying a 1300,if I ever get fed up with the 1100 I may go for an FJR,which I think would be a good compromise between the 2 bikes I have now. kinda going off the adventure bike idea now for some reason.
 
OP
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Ireland
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2005 ST1300
Hey Tom

Thanks for the reply I am just going to live with it and like you wait until it presents a problem.

Alfie

How was your trip last year. I ended up getting the bar risers from the UK rather than the ones from the USA and am very happy with them .

Thanks lads for all the advice

Ollie
 

Tom Mac 04a

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I wondered if it was possible for the plunger arm to have come unscrewed
Don't think so but one nevers knows... I think it may just be a little more play in some than others and somehow ( like mentioned ) air over time is working in. Mine makes no noise after a flush, but by end of season it's back... Rear brakes fine, no excess wear. I've just learn to live with it .
 
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Hi Alfie, did you see the thread where we where chatting about getting all the Irish pan owners we can organise to meet up some Sunday say in May or June, somewhere that's handy for everybody, like Sligo lol.
 
OP
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Ireland
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2005 ST1300
Hey folks thanks for all the replies

Broc I have replied to the meet up and am definitely interested in the meet up ( depending on if I am on leave ) .

Dub 24
 
OP
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Dec 16, 2010
Messages
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Location
Ireland
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2005 ST1300
Hey folks hope your all in good form

Well it seems this issue has come back to bite me big time.

My back wheel is binding a small bit when I apply the rear brake so I am going to replace all the seals and clean the pistons both front and rear.

when I put the bike on the centre stand and engage first gear and apply the front brake the rear wheel is not stopping yet when I get the war office to spin the back wheel by hand and I apply pressure to the SMC the wheel stops but is then also binding am I right in assuming the secondary master cylinder is not working properly as well and if so I plan to replace all the parts in it as well.

I read somewhere here that spraying WD 40 down into the boot of the SMC helps is it worth doing that for the moment while waiting for the parts to arrive.

Thanks for all the help
 

970mike

Mike Brown
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If I were you I would order the complete SMC and replace it after looking at mine and having it replaced under warranty due to the corrosion inside of it causing the rear brake to bind. WD-40 will not help your problem.
 
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