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Author Topic: Project "walrus" Yam XS 750  (Read 36026 times)

Offline datadavid

  • Posts: 1149
Re: Project "walrus" Yam XS 750
« Reply #70 on: Aug 15, 2016, 01:55:05 »
The piston seal is only just about the most important point of a hydraulic brake😁

Offline XS750AU

  • Posts: 328
Re: Project "walrus" Yam XS 750
« Reply #71 on: Aug 15, 2016, 08:01:36 »
Agree Dave
They have got to fit into the caliper body - not on the piston.
The seals in my calipers are not leaking so I will take the spares out for when needed.
Thanks
Tim
“Engineering is the art of being approximately right rather than exactly wrong.”

Yamaha XS750-2D
Yamaha XS896
Husaberg FE550
Yamaha TT250
Yamaha IT200N

Offline Ryan Stecken

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Re: Project "walrus" Yam XS 750
« Reply #72 on: Aug 15, 2016, 14:55:30 »
Agree Dave
They have got to fit into the caliper body - not on the piston.
The seals in my calipers are not leaking so I will take the spares out for when needed.
Thanks
Tim
Agree.

Today I dissaasembled another brake (rear).
Rubber washer sits in piston,reakly important to clean all the dirt thats behind seal.I use a dremel with a rubber polishing device,works nicely.
The rubber boot sits in a notch on the piston and getd pinned down with clip.

Think I found out why it was impossible to put the rubber boot back,I used petroleum on the other brakes in order to clean.....BIG mistake...seems to mess with the rubber.

They get new kits anyways...

Would you recommend buying stainless steel pistons,my stock ones look brilliant after I cleaned them...




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Offline semmins

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Re: Project "walrus" Yam XS 750
« Reply #73 on: Aug 15, 2016, 15:12:09 »
If there's no pitting on the outside of your stock pistons, no need to replace them.

Offline Ryan Stecken

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Re: Project "walrus" Yam XS 750
« Reply #74 on: Aug 15, 2016, 15:13:55 »
If there's no pitting on the outside of your stock pistons, no need to replace them.
I heard that they do tend seize easier than the stainless ones...but I guess this only happens when you leave then unused for a long time.

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Offline jpmobius

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Re: Project "walrus" Yam XS 750
« Reply #75 on: Aug 15, 2016, 15:42:11 »
Brake fluid (most types) are quite hygroscopic which means it attracts and absorbs moisture.  That's why the pistons corrode if you don't swap out the fluid once in a while.  Stainless helps a lot to stop this (stainless still rusts under this sort of situation) but the fluid performance can go terribly wrong if allowed to accumulate enough water so you still need to change fluid at regular intervals.   I wouldn't use any sort of power tool on any interior brake part unless I was honing a bore which is these days pretty much a last resort.  I also don't let any sort of chemical near any brake components except brake fluid (anti-squeal vibration dampening goo and grease for sliding pins and housings being the exception), and commonly have a little bowl to dunk parts in as they get assembled.
Mobius


On a long enough timeline, the survival rate for everyone drops to zero.

1973 RD350 Yamaha build  http://www.dotheton.com/forum/index.php?topic=66498.0

Offline Ryan Stecken

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Re: Project "walrus" Yam XS 750
« Reply #76 on: Aug 17, 2016, 12:18:15 »
Thanks Mobius for chiming in!

I´ve been busy with minor things (life), the last days but i´ve collected a variety of new parts.
Just ordered new seal kits for the brakes,forks et cetera.

How do you guys decide if a fork needs servicing or not?
My fork seals seem to be good in shape (no oil or dirt whatsoever),the chrome on the fork legs is good, no pitting or scratches.
Would you guys just drain the fork oil and let it be?the forks seem to be a bit saggy, but that could also be because of the weight of the bike...there are some kind of adjusters on top, maybe i can just readjust them.

thanks in advance!

Offline XS750AU

  • Posts: 328
Re: Project "walrus" Yam XS 750
« Reply #77 on: Aug 17, 2016, 18:54:00 »
Hi Ryan
Don't let forks scare you, 1970s forks are very simple. As a minimum drain the oil and replace with new. After 40 years with a heavy bike resting on them the springs will have sagged. So a new set would make a difference. They are easy to get out. You may need to spray some penetrating oil around the end plug to free it up.  You push the end plug down 1 or 2 mm and with a small blade screw driver lever  out the retaining clip. The spring can then be removed. Once you have removed the spring you can wash the fork out and flush out any rubbish. New oil and springs at the correct length will make a difference.
Cheers
Tim.

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« Last Edit: Aug 18, 2016, 05:47:03 by XS750AU »
“Engineering is the art of being approximately right rather than exactly wrong.”

Yamaha XS750-2D
Yamaha XS896
Husaberg FE550
Yamaha TT250
Yamaha IT200N

Offline Ryan Stecken

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Re: Project "walrus" Yam XS 750
« Reply #78 on: Aug 19, 2016, 04:43:51 »
Hi Ryan
Don't let forks scare you, 1970s forks are very simple. As a minimum drain the oil and replace with new. After 40 years with a heavy bike resting on them the springs will have sagged. So a new set would make a difference. They are easy to get out. You may need to spray some penetrating oil around the end plug to free it up.  You push the end plug down 1 or 2 mm and with a small blade screw driver lever  out the retaining clip. The spring can then be removed. Once you have removed the spring you can wash the fork out and flush out any rubbish. New oil and springs at the correct length will make a difference.
Cheers
Tim.

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Thanks Tim!
Then I guess I will do the forks too.What do you think about Progressive Springs for the XS?generally new springs are darn expensive (100 euros here in austria)...

Offline XS750AU

  • Posts: 328
Re: Project "walrus" Yam XS 750
« Reply #79 on: Aug 19, 2016, 21:16:54 »
Hi Ryan
Originally they did not have progressive springs. I fitted Progressive Suspension part number 11-1117 to the 750 when serviced my forks. The XS factory spec states the free length was 503mm as you can see in the photo the original springs measure closer to 493mm. Not much sag but still have sag. The  Progressive Suspension 11-1117 free length is 521mm with a progressive rate. That meant a 18mm preload - they do bottom out (and thats not on the Paris to Dakar either!). I weigh 90Kg so you can judge from there how they would suit you.
Unfortunately there is not a lot of choice on spring rates that I have found. I believe Hagon sell fork springs but I have not got the data on them. Progressive do make a higher rated spring (11-1107) but it is only 457mm long, so would need a 50mm spacer, which is doable.
The longer springs you can see in the photos are from the XS750SE which is the basis for the 896 which I am building up. Their specified free length is 606mm and they are measuring 600mm. I am going to have a play with the 2D  springs which are currently measuring 493mm to see if I can reset them to 500+mm. Involves stretching and heat - just got to confirm the heat process. I believe it is just low temperature stuff though!! Anyone out there that has reset their springs???
Cheers
Tim
“Engineering is the art of being approximately right rather than exactly wrong.”

Yamaha XS750-2D
Yamaha XS896
Husaberg FE550
Yamaha TT250
Yamaha IT200N