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Yamaha SR 125 - putting an old bike back on the road


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Hello forum!


I've just got a very rusty Yamaha SR 125 that I'm very excited about getting back on the road and using for casual commuting. It's my first geared bike, and I hope to be able to keep it for a year or so until I get a full licence, then maybe I could get something bigger but only if I decided bigger is a need.


The bike is full of rust, but upon closer inspection, it's all external and cosmetic and can be scrubbed and painted on the chassis or wiped off in other areas. The chromes are affected sadly. The worst corrosion is in the headlight. Other than that the bike seems to function like it should.


The one big problem is has is a front-brake problem. It's not braking. The guy I bought it from pointed to the caliper being the problem, and he said he tried bleeding it to remove any possibility of air, but that didn't sort out the problem. Surely enough the bleed nipple is snapped but it's inserted in the middle and is capable of bleeding the caliper.


What I found out is that if I pull the brake repeatedly, it brakes properly on the third pull. Then if I let it go and wait a couple seconds, it requires 3 pulls again.


I've inspected the caliper and it's working. Lost a bit of fluid but still got enough. He said he bled it so let's trust him and say there's no air in the system, and the caliper is good, so what does that leave? Yes, I suspect it must be the master cylinder.



:idea: Is it possible to buy the bleed nipple alone and only the seals in the master cylinder kit to save money?



I've been looking at 2nd-hand parts, but I would like to save as much money as I can right now since I've not recovered yet from the shock of spending too much on bikes (my other bike is a scooter that's failed MOT and I got screwed by sellers and lost the 10-day grace period and bought an exhaust that turned out to be blowing too and the welder asked for as much as the exhaust costs and then somebody stole my batter, and this came after I had my helmet and gloves stolen from the seat box too, etc, etc, etc. Now I'm looking at 2 bikes that need MOT and some parts. I'm paying at least the price of another bike just for these!)

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:idea: Is it possible to buy the bleed nipple alone and only the seals in the master cylinder kit to save money?

Yes. Wemoto sell them - think I paid about £2.5 for a nipple (arf) and £20 for the MC rebuild kit.


It does sound like you've got air in there though. You'd notice if the MC needs doing because there would be fluid leaking from it.

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HI Mr Fro. Thanks for the reply. Are nipples a standard fit across makes and models? If not, could you link me to an Sr125 one?


As for the master cylinder kit. I found it for £20. I'm wondering why can't one just be able to find the seals? Because that's all that needs replacing really, isn't it?



Is what I described the symptom of air? and is the only failing of a MC manifest as a leak? I'm asking to troubleshoot. I don't want to have to buy a part I don't need. Extremely tight budget here, and I HATE postal times. :)

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Yeah, repeatedly pumping the lever compresses the air to a point that it's negligible volume to allow the fluid to compress and the brake to work. Leaving it for a few seconds allows the pressure to release back in to the reservoir and you're at square one again.


Just look at wemoto.com and navigate to your bike - it's not difficult because even I can do it! You might find that a local bike place has the nipples in stock as it's not uncommon to shear them off.


Personally, I would hold off on the repair kit unless you can see it's leaking fluid. If you peer past the lever and it's dry then it's likely fine.


Can you get the remains of the old nipple out by the way?

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does sound like air in system with brake actually working when you pump it a bit can you see any bubbles in the reservoir window? that bleed nipple may be allowing a slight leak in if its snapped.


worth trying bleeding the system with a replacement nipple for the cost of one before you go into more expensive repairs i would think :). Its easy enough job


oh and welcome back to biking, fellow sr rider myself :D

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Great input, thanks a lot to both of you! There is no leak, so maybe as you say it is still an air issue. I might be able to do it where there is a nipple placed (on the banjo bolt in the middle of the caliper). Just need to get some fluid I guess, then.


The sheared nipple is still inside. I don't have any direct means to pull it out, but if I put my hands on a reverse-screw (screw removal) kit, I might be able to pull it out, though I would still need to flush the system to do it, so I guess fluid should be made a priority.


Is there any fluid I should avoid? (on my 2T scooter, I was told to avoid Carlube 2T oil for being too light).




By the way, wemoto doesn't have the bleed screw for older bikes. Mine is 1993 or 1996, I forgot.

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im using DOT 4 synthetic in my sr 500ml from halfords is £7.99 still got well over 2/3rds of a bottle left after flushing the whole system and works a treat for me :).


oh and these guys have the nipple you need fits the 92-2000 models they say.


http://yambits.co.uk/sr125-custom-brake-caliper-bleed-nipple-front-p-5964.html


this one on ebay should do it also but couldnt be 100% without measurments :)


http://www.ebay.co.uk/itm/Stainless-Steel-Bleed-Nipple-M8x1-25-Bleed-Nipple-Stainless-Steel-YAMAHA-/360426004949?epid=1354199373&hash=item53eb1061d5:g:E7YAAOSwLN5WlWTJ

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The two links seem to offer two different bleed screws. The first on ebay is M8x1.25 and just says "Yamaha all models", while the other is M7x1 and states "SR125". I wonder if the first is referring to modern Yamahas and if the company changed the standard screw pitch and width in their calipers. This is exactly why I'm asking on this forum. Bless the forum.

 

I think king is referring to the type of 2 stroke oil he should be using.

I was asking about brake fluid brands in general, if there's any particular one I should avoid. For example, on my two-stroke scooter, I was rightly told to avoid a certain brand of 2T oil which causes engines to go bust. Just wondering if a high-end brand of brake fluid vs. cheapo brake fluid is as important.


There's a motorcycle shop just behind where I live. I wanna go and ask if they have brake fluid (or go to Halfords) but I know I still need a vinyl tube. There's one on eBay for £3 with a one-way valve (doesn't seem important if you just use a bottle/jar), but it's from China. The same in the UK is a stupid £7. Why? :scratch:


Oh, and I've just received the last missing light bulb in the mail and I'm guessing the bike is near complete other than brakes. My chain/sproket will need to be replaced, do you think MOT will make a big fuss about it if I don't replace them first? I'm not experienced but it does not seem to me, visually speaking, that they are worn out. I have the replacements already but don't wanna remove the rear wheel due to a lack of a proper torque-wrench in my arsenal. Which reminds me, it does seem to require a clean up and grease anyway. One more item to buy.

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yeah why i said on the ebay one im not sure cause cant see the measurements if they differ on the pre 2002 customs, the first link should be fine for your though says 92-2000 model sr :).


the manual for the bike says dot 4 so thats what i went with :) branding im not sure if it will make a major diffrance.


tubing for draining the plug i actually used some spare piping i had frm my fishtank pump lol XD done the job perfectly ^^

Edited by mike_1984
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There is an alternative fix for a broken bleed nipple and that's a bleed bolt. This is simply a banjo bolt with a bleed nipple built in.http://i.imgur.com/otBgi5R.png like this.

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B&Q sell the tube you need by the metre. They do various sizes so be careful which one you get.


I used the glass jar half filled with fluid method when i bled my brakes, works a treat. Just make sure you pinch the bleed nipple back up after every pump to stop any air being sucked back in.


Oh and make sure you keep the master cylinder topped up otherwise you'll be back at square one!

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There is an alternative fix for a broken bleed nipple and that's a bleed bolt. This is simply a banjo bolt with a bleed nipple built in.http://i.imgur.com/otBgi5R.png like this.

 

Unfortunatly with these the air isn't forced out of the caliper, it's short circuits from brake line to bleed nipple. You have to rotate the caliper so air migrates up to the nipple then open it and allow the air to rise naturally .

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That banjo/bleed thing is exactly what I have on my caliper right now.


I think you are saying that, even though I've bled it completely to the point that I see no micro air bubbles coming out at all, there will still be some air inside of the caliper because of the different location of the bleed. If that is true, then this must be what is causing the problem. I will look into bleeding the caliper again while it is unmounted. How do you recommend placing it for this job?

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[mention]KingRoach[/mention]


Take the caliper off the bike and gently rotate it so that the new bleed nipple it at 12 o'clock in relation to the caliper cylinder. The gently open the bleed nipple.DO NOT OPERATE THE BRAKE LEVER.

Brake fluid should start to rise into the bleed tube gently rock the caliper and look for bubbles in the fluid. Hopefully you will see some.

Close nipple

Check fluid level in master cylinder.

Repeat the above till no more air appears.


If you operate the lever during this time you will

A push air back into the caliper and

B push the pads right out as the brake disc is not there to stop them.


HTH

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Great news guys! The brake is now working! Thanks to all of you. :thumb:


[mention]JRH[/mention] , I did it earlier this morning so a bit different from what you said but same concept.


I took the caliper out, turned it so the bleed nipple/bnajo is upwards, gave it a few taps to make sure any air goes upwards towards the nipple.

Attached the bleed hose, put the other end under brake fluid, cracked open and operated the lever until a huge bubble of air came out and it was mostly fluid again.

I was depending on the amount in the reservoir to go down the pipe.

I did allow some micro bubbles to stay because I was in a hurry.

Locked everything back, pushed the pistons back to zero position (I could already discern a difference in piston reaction with the lever).

Put everything back and pumped the lever until it gripped. Now it's braking like pincers!


I even took it out for a ride (to refill the tank). Oh boy what a ride!


I will just need to top up the reservoir to be on the safe side. The micro bubbles might be staying in there right now as it's acting like there's none.


Again, thanks to all of you for helping me with this one.


Now only the other smaller jobs:


- electronics: neutral, speedo and dipped lights. All three need attention.

- speedo doesn't work. Could be wheel unit.

- chain/sproket: now cleaning chain to see if it will need replacing or not.

- fork seal being observed to determine it will require replacement just cleaning and gaiters.

- exhaust has two very tiny leak holes that will need blocking.

- might be some leak in the engine/piston area. Could be one gasket. Will observe later.

- overall rust removal and cleanup.

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Congratulations me for finally being able to see some chain under the mass of grime that was so thick and so black my bike almost seemed driven by a rubber belt.


In case anyone is wondering I used wd40, lots of, and an old toothbrush, then water from a bottle. No jet no hose. Lube can is there waiting but i need to determine whether this thing needs retentioning or replacement. Will post pics but can i post a video?


Only small jobs these couple days due to rain:

Speedo light located. Only blown bulb. New bulb ordered.

Dipped light confirmed to be simply a blown filament in the headlight. Will replace.

Neutral light playing up: found a weak/corroded connection in wires and strengthened it but seemsblike it is still playing up.


Speedo cable and clock are both fine. Speedo drive unit must be the reason why. I dont suppose yhis thing is repairable. Will save this job for when i make a final dexision on forks.

 

Glad you got it sorted buddy :) You be rocking your sr in no time :D i fixed a hole in my exhaust can recommend gun gum exhaust paste, done the job perfectly and has held fast.

i saw your other post (likes) in which u mentioned this. That was the first time i even heard of that thing. I had since got one tin and repaired two exhausts on the Speedfight 2 100cc.
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Great news guys! The brake is now working! Thanks to all of you. :thumb:


@JRH , I did it earlier this morning so a bit different from what you said but same concept.


I took the caliper out, turned it so the bleed nipple/bnajo is upwards, gave it a few taps to make sure any air goes upwards towards the nipple.

Attached the bleed hose, put the other end under brake fluid, cracked open and operated the lever until a huge bubble of air came out and it was mostly fluid again.

I was depending on the amount in the reservoir to go down the pipe.

I did allow some micro bubbles to stay because I was in a hurry.

Locked everything back, pushed the pistons back to zero position (I could already discern a difference in piston reaction with the lever).

Put everything back and pumped the lever until it gripped. Now it's braking like pincers!


I even took it out for a ride (to refill the tank). Oh boy what a ride!


I will just need to top up the reservoir to be on the safe side. The micro bubbles might be staying in there right now as it's acting like there's none.


Again, thanks to all of you for helping me with this one.


Now only the other smaller jobs:


- electronics: neutral, speedo and dipped lights. All three need attention.

- speedo doesn't work. Could be wheel unit.

- chain/sproket: now cleaning chain to see if it will need replacing or not.

- fork seal being observed to determine it will require replacement just cleaning and gaiters.

- exhaust has two very tiny leak holes that will need blocking.

- might be some leak in the engine/piston area. Could be one gasket. Will observe later.

- overall rust removal and cleanup.

 

As far as the chain and sprocket goes, is your sprocket hooked? If it is, it is knackered. Does the chain have the right number of links? Has it run out of adjustment? Replace chain and sprocket(s) at the same time, as running a new chain on old sprockets will knack it in short order.


S23

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As far as the chain and sprocket goes, is your sprocket hooked? If it is, it is knackered. Does the chain have the right number of links? Has it run out of adjustment? Replace chain and sprocket(s) at the same time, as running a new chain on old sprockets will knack it in short order.


S23

 

Hi Speedy. Thanks for your advice. The sprockets are not hooked, they seem fine. After cleaning the chain to the point where it looks like a chain, I can see the upper half (the tensioned part) is slacking a bit and does a dance when the wheel is turning. A few side links have some surface rust on them, but all O rings seem fine. How do I know if it's the right number of links? Do you actually count them or just make sure it's the right tension?



Today's update: all electronic little things sorted including the twitching Neutral light. Here's what I found out today:


">



Funny haha. The weak link turned out to be under the seat. Yeah the only electronic problem remaining on this bike is to change the headlight bulb (dip light filament is broken), and maybe to sometime tidy up all the wires behind the headlight as most of them seem to be "tucked in there". I was wondering if they should all be exposed that way from behind (between the petrol tank and the steering bar).


Next up: clean the fork seal properly.

Speedo drive unit.

Chain/sprokets (I don't have the right size socket for the back wheel. ¬_¬) Do I really need a torque wrench for factory specifications for this? e_e

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Could just need adhusting, is it in the usable range window on the chain guard, and do you have any more numbers left to adjust to on back adjustment plates?


As for wires yeah mine are same I sealed them up with some tape. your on the older model if I remember, square clocks? You should have some fairing to cover them if so, on mine the 2002 model they have nothing covering them! Lol

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I don't have the chain guard so have to guesstimate. I saw the illustration in the manual and should be able to estimate better. I tend to think an adjustment should do, to be honest. The worst thing I'm seeing is some surface rust on the outer links in the chain. Only some of them.


I haven't been able to look at the smaller front sproket. The two screws holding the cover seem to have their phillips heads stripped and they are already too tight. I need to find a way to remove those two (if anything, I can give the sprocket area a good clean).


In any case, I will need a 22mm socket to loosen the rear wheel axel for any of these jobs and the biggest I have is a 19mm. :( I went to carboot today and looked but the biggest socket that I could find with any numbers on it was a 21mm.


And that damn torque wrench! Gotta have one!


[mention]mike_1984[/mention] yeah my bike was first registered 1997 so I guess should be made either 1997 or 1996. Square clocks indeed.

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