SuperTrapp Silencers

[Andreas Piepke]

Hi All,

That's an interesting discussion. It so happens that I am just tuning a re-built 1973 Hare Scrambler, also equipped with a Super Trap. How many disks are a good starting point for that engine? Lew, if you have a data sheet perhaps you could look up the recommendation for both 250 and 400 ccm KTM engines? My Super Trap came installed on an old exhaust with 7 disks and that's how I left it. After reading through these posts I suspect that's too much.

Thanks

Andreas

[Lew Mayer]

Andreas, I think you're close. I'll check.

Lew Mayer

[SouthRider]

The supertrapp is after the exhaust, and not a part of the tuning - other than if you remove too many discs it will choke the engine down.

The amount of discs simply changes the amount of noise emitted. You want as many as you can without the bike being too loud. That said - at a certain point adding more doesn't make any more difference.

The exhaust systems on Pentons were designed to be quiet enough for the ISDT, which was very strict on sound, thus they were overly restrictive. That's why you find very few of them today with intact OEM exhaust systems. Woods model Huskies had the same problem.

American races were not near as strict on sound as in Europe, so American riders did what they do best - they un-restricted them to make them run better.

The skyway, like the xdusor didn't get used much. Mostly on small bore early 70's jap bikes, and they somehow seemed particularly fond of Hodakas.

The supertrapp was heavily marketed by Hi-Point (& John Penton specifically) as an alternative to the stock silencer for KTM engine Pentons, but also mostly for open class bikes that needed to breathe better. That's why they also pair well with a Lectron which was the best breathing carb of that era. They ultimately ended up as original equipment on a few of the last Penton GS models.

Because they are open around the circumference they tended to dribble 2 stroke spewl all over the fender, seat, and number plate - as well as the aforementioned vibration problems and rattling (again - the bike is less restrictive when you leave the nut a little loose).

70's tuning was a constant battle between restriction for noise versus letting the engine breathe.

The supertrapp was an excellent compromise that let the bikes run but was easy to throttle down when needed to pass a sound test. Many enduro riders could be seen a mile or so after the start of a race on the side of the trail loosening the nut a little.

The Supertrapp was also a natural spark arrestor which was another inspection point at the sound test. At that time most spark arrestors caused 2 stroke oils to congeal and stop up the exhaust systems causing constant maintenance. The trapp discs could be easily removed, washed in a varsol tank, and glass  beaded to remove carbon, unlike most other systems that required repacking every time you dared pull them apart.

They worked well until they were ultimately replaced by the large diameter bolt-on aluminum bazookas of the 80's with the removable Krizman style spark arrestor cones in them.



_____________________________________________________________________________________

"We the willing, led by the unknowing, are doing the impossible, for the ungrateful. We have done so much, for so long, with so little, that we are now qualified to do almost anything, with nothing."

1972 Penton Berkshire 100
1983 Husqvarna 250 XC
2011 Jayco 31.5 RLDS
2009 Chevy 2500 HD Duramax

[Lew Mayer]

KTM/Penton
-------Racing----trail

125cc--5discs-----3
175cc--6discs-----4
250cc--6discs-----4
400cc--8discs-----5

You need to balance power vs. noise.
One more disc can be added with the quiet core insert and resonator.

Lew Mayer

[Andreas Piepke]

Thanks for the info. I'll take some disks out.

Andreas

[Daniel P. McEntee]

"The skyway, like the xdusor didn't get used much. Mostly on small bore early 70's jap bikes, and they somehow seemed particularly fond of Hodakas."

   I had one of the Xducers on my 100 Berkshire with the square barrel  back in the day. I can't remember if it was a stock pipe or not, but had a "stinger" and had a problem getting it quite. The Xducers came out, were pretty reasonably priced for a teenager, and did a good job of quieting the bike quite a bit and as I recall, didn't hurt the power, or at least not enough for me to notice. The round shape wasn't a big favorite with a lot of guys but I didn't mind it. Wasn't Xducer the forerunner of SuperTrapp? Just interested in a bit of trivia. Of all the vintage stuff you see around, I have never seen one of those since I have been back involved with dirt bikes. Must not have been made for very long or in great numbers.
  Type at you later,
  Dan McEntee

[SouthRider]

Dan, I don't think I ever saw or fooled with either the skyway or xdusor - other than seeing them in magazines. I don't recall them being related to super trapp. I'll bet that Dane would have known where they came from, also possibly Jackie, or Larry Maiers.

Somehow along the way I ended up with a bag of xdusor tuning discs in my toolbox, which I still have.

They are NOS in their original bag, and are free to a good home if anyone wants or needs them.

_____________________________________________________________________________________

"We the willing, led by the unknowing, are doing the impossible, for the ungrateful. We have done so much, for so long, with so little, that we are now qualified to do almost anything, with nothing."

1972 Penton Berkshire 100
1983 Husqvarna 250 XC
2011 Jayco 31.5 RLDS
2009 Chevy 2500 HD Duramax

[Daniel P. McEntee]

I never had to take mine apart, and wasn't aware that they were tunable with discs like that. They were just so unusual looking. I thought that they kind of resembled a land mine! I just have a memory of reading somewhere that the Xducers were the predecessors to the SuperTrapp.If I ever find one, or one finds me, I'll let you know.
  Type at you later,
  Dan McEntee

[rd400pi]

Per the SuperTrapp instructions, there is a spring that goes between the End Cap and the nut/acorn nut on the end of the Hook Bolt.  It is actually supposed to be tightened until the spring closes completely (blasphemy!) so that when the unit gets hot there will still be tension on the discs.  I have the 4 page instructions and tuning guide if anybody is interested.  Cheers.

  Mike H.

[Andreas Piepke]

Hi Mike,

That's very interesting. Could you scan and post the instructions and tuning guide? This probably would be useful for many.

Cheers

Andreas

[Farmjohnny]

That's very cool stuff, Mike!
Thanks for sharing!!!!

[rd400pi]

Ok, now I'm in hot water!  I can scan with no problem but, I'll have to flail around a little while I learn how to post them.  To be continued...

  Mike H.

[Daniel P. McEntee]

I would be interested in that file also. Email it to me if that is easier. My email is dpmcenthusiast at aol dot com.
  Thanks a lot,
  Dan McEntee

[Lew Mayer]

I got mine scanned but I also have to figure out how to post them.

Lew Mayer

[Daniel P. McEntee]

Just got off the phone with Mike H. and he's having some computer issues, but has a hard copy of the tuning info that he is going to snail mail me. Once I get them, I'll scan them into my computer and email them to interested parties, unless I can figure out how to post them also! I suck at that kind of stuff! So, stay tuned for further developments as they become available.
  Type at you later,
  Dan McEntee