De-snagging an SL125

Hi All.

Well it has been a long time coming, but further to my original posting, I have had some success altering/reducing the noise emitted by the SL 125 silencer.

I tried a plain extension tube - no good. No room to put in a perforated baffle as per my original post - so no good

I then found a piece of copper pipe that was a 'snug fit' inside the outer pipe of the silencer outlet, if that makes sense. See sectional sketch of muffler outlet - above - for details.

I managed to make and insert three baffles into the copper pipe and the whole assembly was lightly hammered into the tailpipe. I had intended to put some wire wool into the inlet side of the muffler - but decided against that - it just didn't seem right in this case. The exhaust sound is now quieter and the harshness of the note has gone, so I am happy.

So this is what I ended with ..........

Copper tube hammered into place. The visible extension is about 2.5 inches long - 3.25 inches overall length.

View on end of extension pipe, with baffles inside.

I hope the final result is of interest to you.

Thanks again to everyone for their input - I am pleased with the result.

All the best.

Alan.

Edited By Alan Donovan on 12/06/2022 21:11:35

Edited By Alan Donovan on 12/06/2022 21:12:07

Edited By Alan Donovan on 12/06/2022 21:14:19

I had an SL125 in 1973 - brand new. It was very quiet. That removable part '6' was described as a 'spark arrestor' compulsory in the States. If you have a one piece head that is usably unworn you are very lucky. Most of them were scrapped by youthful over tensioning of the cam chain when the engine was cold, as the engine heated up the alloy head expanded , but the steel chain pulled the cam down into the head, eventually ruining it. A great little bike , it would go anywhere I was brave enough to point it.

I have a 1976 xl125K with the trials TL type front mudguard that has the same one piece head, amazingly the head is still in good condition and survived the big end bearing failing. Completely rebuilt the engine some ten years ago however have never ridden it since. I can’t see myself ever getting rid of it!

Edited By Twf on 20/06/2022 18:56:44

I would check out the legality of using copper tube in an exhaust system. There are many quotes of it producing toxic fumes. In that location I doubt it would be an issue but if it is illegal then you don’t want to give the plod an opportunity to cause problems for you.

Mike

do you honestly think that average Mr plod could tell copper from anything else let alone if its legal or not.

I can offer guide to 'How quiet the SL125 was when new'.

Back when the bike was new a friend had one, and got it stuck in some very soft ground in Wales. We took perhaps 20 minutes struggling to get it out, and then, as it was put on its side stand om firm ground, there was a cry of astonishment. 'Well I'll be blowed - the jolly little device is still running'.

So yes, it was a really quiet bike at tickover at least, when new.

Cheers, Tim

I recently acquired most of a 1978 XL125 from the scrappy. Missing the back wheel, the petrol tank, and the gear and kickstart levers. Pretty much the same bike as the OP's SL125, except this one has the two piece head, It also has a bit much play in the camshaft bearing, so I might have to build that up with a bit of TIG. Not the only work it will need, but having owned a CB100 back in the day I couldn't resist rescuing this one. The CB100 was also the same engine, apart from the bore. The experience back in the day was that the 100 was just as quick as the 125, mine was even quicker once it got a hot cam, a bigger carb, and a 125 barrel.

John