Hello and silencer question

[Andy Higham]

Hello all.
I am rebuilding a 1970 250 which turns out to have 350 crank, barrel and primary gears.
This is my second Ducati, my first bike after a moped was a 1970 cadet 100. Ironically both bikes are from the Hannah batch.
I have fitted a Misano head and piston, 173 profile cam, shim rockers arrow rod, and 38mm carb.
I want a silencer that looks right, performs well and sounds right. I was thinking of getting the stainless steel downpipe and "Conti" replica silencer from Feked. Has anyone tried one of these? do they perform and sound right?

Cheers in advance
Andy

[Duccout]

It will sound right - bloody loud!


Colin

[LaceyDucati]

Hello Andy
Make sure you get the correct pipe, for the bike as there is a difference between Wide and Narrowcase, and some capacities. Either that or be prepared for some cut and shutting and bending. Genuine Conti's work well with a step from the standard single header into the larger twin silencer (just use a split collar to fit). Not sure about the Feked replica, may well be okay but no experience. The genuine Conti has a swirled series of notches in the inner pipe and a break in that pipe in the middle. If it looks like that (ie a close replica) then it should be fine. The genuine Conti is also of heavy gauge construction. I did some Dyno tests with a genuine Conti compared to some specific replica "specific" single Conti's and was staggered by the difference in the mid range, approx 3bhp.

I will add "silencer" is a relative term with a Conti

Nigel

[Andy Higham]

Looking at the photos of the Feked silencer, it has the spiral notches but I can't see a break in the middle

IMG_0704-1000 by Sigma Projects, on Flickr

[DesmoDog]

I've never heard one of those but speaking as someone who used to develop mufflers for OEM automotive companies, that louver tube design is, um, how can I say this... poo?

There is a time and a place for louvers and that isn't it. Not only that, but they're stamped in the wrong direction. They should not be punched into the flow, all that does is add flow noise and restriction. Sound does not need to be "scooped up" into the muffler, it'll find it's way through simple perfs all on it's own thankyouverymuch.

Sorry. Pet peeve.

But yeah, I'd expect that muffler to be relatively loud and not all that nice sounding. A megaphone will be louder. A typical glasspack will be quieter and have a less harsh sound to it. The stock muffler design will of course have the most stock sound to it... Captain Obvious told me that one...

[blethermaskite]

Andy, I'm sure I won't be the only one to recommend a suitable 'silencer' to you, nearly 50 years ago on my 350 mk3 I used a Dunstall decibel 'silencer' and found it to be 'good' in comparison to an open megaphone (which most Ducati singles like best). Now after running on an open pipe for the last 20 years or so I moved back from the countryside to an urban setting and needed to quieten things down a bit, so I managed to get another new (now old stock!) Dunstall decibel and with a bit of re jetting once again still pretty good with not too much power reduction and the noise level is down enough (for me anyway ). I used a Conti replica on my 250 desmo for a short time and frankly neither the bike nor I liked it , I found it flattened out the power curve too much taking the nice revvy edge of the wee engine, (that was running with a Gardner flat slide race carb).
I believe the decibel 'silencer' I am using is a standard factory fitment from a 1980s Triumph or maybe a Norton twin????.......but not sure, its the same as my 1970s one except it has provision for a flat disc baffle/diffuser type plate on the end outlet area (which didn't come with it and I didn't want it anyway!)
Cheers,
George

[Andy Higham]

Back in the days of old I used the "Dunstall style" silencers with the alloy reverse cone. Worked well on my Tiger Cub and also on my A10.
On the A10 I shortened the alloy cone by about half so the "nest of tubes" was visible. These silencers were re-buildable (read as easily modified)

[Andy Higham]

Want a giggle?
This is the silencer I removed from the bike, the dear departed previous owner repaired it many times

20240828_141004 by Sigma Projects, on Flickr

20240828_140944 by Sigma Projects, on Flickr

20240828_141022 by Sigma Projects, on Flickr

[blethermaskite]

Steam punk megaphone Cheers, George.

[Duccout]

Hi Andy,

I have been wondering how a Misano head would perform in a road bike, so you must let us know how it runs in general use, not just in performance terms, but also in tractability, although that 38 mm carb will make life interesting in town. Hopefully you have some nice clear roads near you.

Cheers,

Colin