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

[megawatt]

Try sticking two fingers or your thumb in the bearing centre to make sure it turns smoothly?

[Guest]

The Speedfight problem is a carb that needs a very good service. I've pulled it out (without removing most of the pipes), pulled the throttle needle out, jerked it back in, let some petrol drop, put it back in, and the bike started... for a short time, then it turned off again and stayed off. At least I know it's the carb.

I may or may not have time to look at the tRusty Aubergine today.

 

Crap in the float jet.

[KingRoach]

The Speedfight problem is a carb that needs a very good service. I've pulled it out (without removing most of the pipes), pulled the throttle needle out, jerked it back in, let some petrol drop, put it back in, and the bike started... for a short time, then it turned off again and stayed off. At least I know it's the carb.

I may or may not have time to look at the tRusty Aubergine today.

 

Crap in the float jet.

 

That's my current diagnosis. I was able to get it running again for a good while today but it's very dodge and the idle goes up and down on its own. I've ordered some carb clearning sprays and hopefully will give the carb a detailed cleanup inside and out once they arrive.

Unfortunately, I haven't been able to touch the Yamaha today. Temperature drop, some rain, and family stuff. I just couldn't.

[KingRoach]

I'm confused about headlight bulbs. My bike is probably a 1996-1997 bike and the bulb that's already in it is the pear-shaped thing with 2 electrodes on its end.

Wemoto lists several bulbs, and also on eBay, with different models for different years, and there is a confusing overlap in the years specified for each bulb from one page to another.

for demonstration purposes, here are both styles on Wemoto:

http://www.wemoto.com/bikes/yamaha/sr_125/99-03/picture/bulb_headlight/

http://www.wemoto.com/bikes/yamaha/sr_125_se/92-94/picture/bulb_headlight/

http://www.ebay.co.uk/itm/1x-Yamaha-SR-125-10F-1996-2002-Neolux-Dipped-Main-Beam-Bulb-Headlight-Lamp/391860447589?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2055119.m1438.l2649

A bulb like this is more like the modern ones, with a gobo/reflector inside the bulb surrounding one of the filaments. This kind of bulb has three electrodes on its end. One page specifies this bulb for 1996, another specifies the pear bulb for the 1996. Was there two variations to the sockets?

Or are they interchangeable?

[Mr Fro]

None of the bulbs you linked are interchangeable - the seat and the connections are different.

Can't you just do a direct replacement of the current one (should be numbers on the bulb somewhere).

[Guest]

None of the bulbs you linked are interchangeable - the seat and the connections are different.

Can't you just do a direct replacement of the current one (should be numbers on the bulb somewhere).

Agree....just take the old one to Halfrauds.

I'm starting to think that the biting off has exceeded the chewing capacity.....(not having a go, but it sounds as if this is the first big project you've done?....We will, of course, be here to help if it's needed......it's all valuable experience!)

Edited November 8, 2017 by Anonymous

[KingRoach]

Of course I can. While this one may have been an obvious one, the confusion was because the newer model of bulb was actually listed as a fit for my bike's year in one place. I had to ask in case I missed something.

What do you mean the biting off has exceeded the chewing capacity? I'm doing this at my leisure, for fun and education, and gaining as much info on the way as possible. I will ask about EVERY detail I don't yet have an answer for. This is what a forum is for. Please let me know if asking questions bothers anybody on this forum.

[Guest]

Hi KR please see my edit above........

PS - do you have the Haynes manual for the bike?

Edited November 8, 2017 by Anonymous

[Tango]

Just keep asking mate......If we can help, we will.......

My first "project" was my Triumph Bonneville I had many years back.......I needed the bike to get to work and to see my girlfriend, and I was an apprentice, so wasn't exactly flush with cash......but I learnt a lot from working on that bike.....it's all valuable experience. .....

[KingRoach]

Hi again. Yes [mention]Speedy23[/mention] this is the first "deeper" project I do. Not that it's that deep anyway, I still have not had to dismount the engine and take it apart. I will admit the SR is not a complicated bike. It's more about the little details that one is afraid to miss here and there.

I've done small things before on a Honda SX50 5 years ago (carb, drive, rollers), and also small things on the Speedfight 2 100cc (break pads, stem valve, exhaust). The Yamaha is the first geared bike that I ever have, and the fun part of it is that I want to get it on the road with my own hands. I don't have the Haynes manual but I do have the Service Manual that is available online, which is very helpful for specifying all the manufacturer's torques, but nothing beats hands-on experience. By the time I upgrade to a bigger CC with a full license, I will know a lot more what to look for on every corner of the bike.

Re: wheel alignment, I think it's more the tyre now. The rim, if it's moving at all, is much less and hardly noticeable, so I'll leave it.

Last problem on the drive: what does it mean if, when the bike is in 1st gear and the rear wheel is free to run (bike is raised), the drive/wheel gets "jumpy" every now and then.

Thanks a lot [mention]Tango[/mention]. That's a nice bike.

[JRH]

Last problem on the drive: what does it mean if, when the bike is in 1st gear and the rear wheel is free to run (bike is raised), the drive/wheel gets "jumpy" every now and then.

 

This is probably due to the power pulses for a single cylinder engine. Pulls the wheel on the power stroke then the next 3 stroke the wheel is coasting and probably going faster than the engine so the chain is pushed, then on the next power stroke the chain once again is pulling the wheel. so the whole chain is moving in a series of pulses.

Hope that make sense.

Probably if you operate the back brake slightly to put some load on the wheel the drive will tend to smooth out.

[megawatt]

Check to see if the cush drive is worn.

[Guest]

Hi KR, thanks for reply, if you can get a look at the Haynes manual, I suggest you do so - these books are written from the amateur mechanic's (i.e. most of us on here) point of view and can give advice on things the official w/s manuals will not address (like how to remove stubborn nuts, etc.). I learnt a lot from these books and I'm sure they will be a good source of information for you. Might even be available from your local public library (if you still have one - thanks, Tories! ) for free. "Jumpy" drive sounds like worn chain with tight spots....your sprockets look OK, so someone might have tried to get away without changing chain as well. False economy.

[Guest]

Last problem on the drive: what does it mean if, when the bike is in 1st gear and the rear wheel is free to run (bike is raised), the drive/wheel gets "jumpy" every now and then.

 

This is probably due to the power pulses for a single cylinder engine. Pulls the wheel on the power stroke then the next 3 stroke the wheel is coasting and probably going faster than the engine so the chain is pushed, then on the next power stroke the chain once again is pulling the wheel. so the whole chain is moving in a series of pulses.

Hope that make sense.

Probably if you operate the back brake slightly to put some load on the wheel the drive will tend to smooth out.

 

How many rpm does this engine turn over at idle? It ain't a Panther......

[KingRoach]

Sorry I've been away/busy. Yesterday I REALLY felt like I wanted to do some work on the bike. The weather's been dry for a couple days right?

So I remembered the speedo drive unit isn't working and I decided to dive into it today.

But today wasn't as dry. ¬_¬

Sorry you're not here for the journal.

I took the speedo drive unit apart and delved right into it. Both gears were ceased and it took a lot of knocks and hits and bashes and throwing around to get one moving, until I could finally take it out. The last gear, I was REALLY hoping I wouldn't have to take it out, so I soaked it in some WD40 for a short while and kept knocking on it until it finally moved.

Cleaned up the whole thing and applied new grease (moly grease because it's all I have, but it's rated 2 so should be alright) and now that it's all back together, I have a working speedometer.

Another repair at a cost of £0 and a couple hours.

What's left?

- New headlight bulb and confirm chain sprockets and everything area alright.

- what seems like oil leak from the engine. Take photo and post here.

I can't think of anything else that needs doing, let's keep fingers crossed.

[KingRoach]

After wasting a few days for me with some frustration on top due to their horrible order/delivery service, and 3 roundtrips, Horrible Halfords finally got me a light bulb. All that fuss!

Anyway, headlight is good to go. I should inspect the beam.

But oh the small things you discover every now and then. My side stand kill switch is NOT THERE! The wire is there but it's been cut and taped and tucked away behind the stand. I need to replace that, and also considering replacing the main stand as it hasn't seemed to hold the bike straight up very well.

Besides the leak on the forks which seems to have become negligible, I don't see much else that needs doing before an MOT.

[megawatt]

Fork leak probably negligible because all the oil has leaked out.

[KingRoach]

Fork leak probably negligible because all the oil has leaked out.

 

C'mon, don't be pessimistic. It's dampening nicely and previous signs of leak were probably because the cracked cap caused: a) dirt in seal, b) rainwater accumulating under cap, and c) previous owner using newspaper to stuff under the seal, and so the visible previous leak was probably the water, slightly oily and dirty because of the paper squeezing out.

Since cleaning the seal with a plastic tool and keeping the bike under cover from the rain, it's not been the same.

Be optimistic.

[megawatt]

Never heard of an oil seal healing up? You obviously know more than me. Good luck with your mot and your handling.

[KingRoach]

Never heard of an oil seal healing up? You obviously know more than me. Good luck with your mot and your handling.

 

It doesn't "heal up" if it's cracked or leaking due to deterioration or age or hardening or getting brittle or any of the bad things that happen to seals, but if the leak is caused by dirt getting in between the seal and the fork shaft, then cleaning that up may sort that the issue if the seal itself is still in good functioning condition.

I don't know more than anybody else. I'm just a guy learning and sharing experience and thoughts.

[Guest]

Never heard of an oil seal healing up? You obviously know more than me. Good luck with your mot and your handling.

[Guest]

Fork leak probably negligible because all the oil has leaked out.

 

C'mon, don't be pessimistic. It's dampening nicely and previous signs of leak were probably because the cracked cap caused: a) dirt in seal, b) rainwater accumulating under cap, and c) previous owner using newspaper to stuff under the seal, and so the visible previous leak was probably the water, slightly oily and dirty because of the paper squeezing out.

Since cleaning the seal with a plastic tool and keeping the bike under cover from the rain, it's not been the same.

Be optimistic.

 

Errr....point "c"? Have fun.