Repair broken manual starter spring - without spare parts!

Patrik · 21 July 2011, 22:07

Hi all

I seem to have gotten an engine that I can't get spare parts for. It's a Yamaha 5BS 661. 2 stroke, 5 hp with air cooling. The exact serial/model number is unreadable, don't know if it's been willfully removed or if it's just worn off. So I don't know what year it's made, but between 1974-1980.

However, the thing is that the spring has broken, that retracts the rope after you've started the engine. So the rope just hangs there and looks stupid.

Could I replace the spring with a part from another engine? Construct something myself? What to do?

benc · 21 July 2011, 22:53

Upload some pictures of the engine, and the broken parts, location of it etc... im sure someone will be able to help

Patrik · 21 July 2011, 23:01

Took a bath with my iphone in my pocket yesterday when fiddling with my other engine... But I will try to take some pics with some other camera tomorrow and post them! Thank you

9D280 · 25 July 2011, 09:21

As a going in thought I would think that repairing the spring may or may not be feasible - I ghuess it;s probably broken at the bit where it engages i neither the recoil pulley or the case. The biggest oproblem is by bending it back (if you even can without snpping it again) is that it will likely become a recurring theme..... Now, I donlt know what;s under there, but one option maybe to somehow clamp the broken end with a block / screw arrangement, ut that wonlt work if it pokes trhough a tiny slot.

On the plus side, yam are usually pretty good at not changing stuff for change's sake, so you will likely find the same spring has been used for years across a multitude of engines. Have a dabble in the parts lists and see how often the same part number pops up. While you are there, have a look at the case etc pics, you may be able to figure out it's vintage form there.

willk · 25 July 2011, 09:37

Quote:

Originally Posted by Patrik

What to do?

Yamaha 5BS - I wonder what the BS stands for?

Anyway, let my Googlefinger point you in the right direction:

Link

willk · 25 July 2011, 09:46

So once you find the model number on there (619-15713-01-00 SPRING,STARTER), you will find (I'm sure) the cheaper part in the USofA. Probably you can't get that shipped to Schweeden either

Link

jwalker · 25 July 2011, 11:19

I've done this. Right, it depends where the spring is broken. If it's somewhere near the centre of the spring it will be more difficult because you'll need a weld and that bit of spring will loose it's temper and won't be so springy. I found it very difficult to retemper the welded area without destroying the surrounding spring. Anyway, mine broke a distance from one end and the above was how I initially tackled it, unsuccessfully. But it was fine when I heated the end of spring to redheat and reformed it to the original shape. I made no attempt to harden and temper it because that part doesn't really flex much. There is one limitation though, because of the loss of some spring length, the distance the starter cord can be pulled out is less. I didn't find it much of a problem once I adapted to not hauling it full length.

The spring can easily be brought up to red heat in the flame of a stove or blowtorch but it must be allowed to cool slowly to anneal it so it can be formed cold. Because the spring is thin it doesn't hold much heat so cools too quickly, simply turn down the flame and gradually allow it to loose red heat as slowly as possible. I reformed the end when it was cold and it was fine showing no sign of cracking.

Getting the spring back in and the cord rewound the correct distance is the tricky bit.
Good luck.

doggypaddle · 25 July 2011, 19:24

Quote:

Originally Posted by jwalker

I've done this. Right, it depends where the spring is broken. If it's somewhere near the centre of the spring it will be more difficult because you'll need a weld and that bit of spring will loose it's temper and won't be so springy. I found it very difficult to retemper the welded area without destroying the surrounding spring. Anyway, mine broke a distance from one end and the above was how I initially tackled it, unsuccessfully. But it was fine when I heated the end of spring to redheat and reformed it to the original shape. I made no attempt to harden and temper it because that part doesn't really flex much. There is one limitation though, because of the loss of some spring length, the distance the starter cord can be pulled out is less. I didn't find it much of a problem once I adapted to not hauling it full length.

The spring can easily be brought up to red heat in the flame of a stove or blowtorch but it must be allowed to cool slowly to anneal it so it can be formed cold. Because the spring is thin it doesn't hold much heat so cools too quickly, simply turn down the flame and gradually allow it to loose red heat as slowly as possible. I reformed the end when it was cold and it was fine showing no sign of cracking.

Getting the spring back in and the cord rewound the correct distance is the tricky bit.
Good luck.

done this a few times....works a treat