Dear all, in another threat i wrote about limited rpm´s of my DT, didn´t get more than 6000. Suspicious to me was the silencer. I purchsed another Silencer on Ebay, which was quite gutted and yes, much better driving. But loud as hell.
The stock silencers in Europe are different to US. There is no possibility to open it, all is welded together as a unit. And no spark arrestor.
So the only chance was to open my fine looking Silencer. Despite burning it to clean, lots of coal was inside, but i couldn´t find any real blockage. Gave it a sand blasting and tried to follow up the route, gas is taking. As i have a gutted spare, now, there is the idea to build a stock-looking silencer with "modern " inner life, but more silent. Any suggestions, how to ? I could cut it on the red line, weld a perforated tube inside trough whole lengh and pack it with Glass Fibre, like in the drawing. Similar to the FMF aftermarket pipes . The end-cap should be removable screw-on. Think the flow would be better, but maybe even more noisy?
Do you have some more ideas? My experience in this is zero.
Forgot , i am waiting for my sleeper pipe from Dave Meis very courious about that.

Nobody any comment ? Anyway, i will start rebuilding my spare silencer. As the smallest diameter in the pipe is the place, where the O-ring sits (connection between pipe and silencer), i will continue with this diameter till the end of the silencer. It´s 25mm. I ordered 80mm pipe for outer tube, and 28x1.5mm stainless for the perforated inner tube. I started with the end-cap, bend from 1mm sheet.

I wondered if a "modified" silencer would help or hurt the performance of a Sleeper Pipe ? Or just make it louder with no improvement. Louder is not my goal, smoother performance is. Over the years i have collected 3 spare silencers, #1 stock,#2 spark arrester "cone" removed, #3 totally hollow. Will resident exhaust gurus please comment? All three fit my 75 dt250 and 75 dt400

Thank you Mace. Think you are right, the Sleeper works best with original pipe, as Dave Meis wrote:

The Sleeper cone is optimized to be used with a stock pipe....so removing the spark arrestor would reduce performance and make the pipe quite a bit louder.
We have built some DT/RT Sleeper Pipes without the spark arrestor turbine assembly and
they are loud and make less low end midrange power.

So not optimal....


Ok. i could go with the original pipe, i opened and sand blasted. But this , even it´s stock Yamaha, is different from the US Silencers, which have a spark arrestor. Does anybody have a picture, how the US Silencers look inside?
Just for interest, i will parallel finish my custom silencer, As the end-cap is removable, i can try several setups. later.

That silencer is looking good Wessi. Please keep posting your build process as I’d like to attempt something similar for a AT1. One question. How did you bend that cone on the wooden form so smooth? Did you hand form it then start the lathe with an attachment to finish it?
As regards your making an perforated tube glass fiber type...to adjust the back pressure without trial and error method of making up different diameter tubes a small adjustable damper can be installed. Much like the damper in a wood stove flue pipe. I have such setup on a two stroke snowmobile engine & can get pictures if anyone wants to see one.

Yes, i bend the sheet template over the wood form, welded together and smothed it on my Lathe. Finally hammered a 50mm round steel through the funnel. Good idea, to try different diameters inside later to fine tune the silencer. I started yesterday to cut the old silencer, as i need the inlet pipework as a base to start with. That´s the only part on this old thing, left in good shape. It seems that generations of DIY welders tried to work on it.
Cutting it on the Lathe leads to exact 90° angle.
After, i welded 2 pieces of steel pipe in the right angle to center the perforated pipe, later.
Meanwhile, i made the 2 bolts, which fix the silencer to the holder

After sand blasting the inlet, i fixed the pipes in the inlet center and hard-solderd it inside.
So now waiting the ordered outer and inner tube to arrive, to continue.

Two deliveries arrived yesterday, the outer tube and the half dome. The half dome luckily is available on Ebay in 50mm diametera for 2€. I cut the outer tube and fitted the end cap. Today, i will start welding

You are a very skilled craftsman Wessi! Nice work!

Thank you, Mark.
Took longer, as expected. I made 2 brakets, to weld on the perforated tube, later to the end cap to center and hold it in place.