SuperTrapp Silencers

[Daniel P. McEntee]

I'm working on adapting a used SuperTrapp silencer to the pipe on the 400 Penton project. It's in good shape, just need to weld a proper end on it to attached to the end of the pipe. It is a three inch diameter version and it only has four discs in it right now. I have no experience with this silencer but I'm guessing that four discs won't be enough for it. I have another one I just got off eBay that has eight discs in it. Any one using a SuperTrapp on a 400 and can give me a good starting point for the number of discs? Several vendors on eBay have them available, just need an idea on how many to have on hand, and maybe how to tune them.
  Thanks in advance,
  Dan McEntee

[john durrill]

Dan,
give speedy a call. he had a lot of bits and a great deal of knowledge
about traps. he had what we needed several times.
john d.

[Farmjohnny]

Back in the day, we would start with the most you could fit under the screws, pulling them out till you hit your db. then jet accordingly.  Your results may vary.

[ALB]

I had a Supertrapp on my Jackpiner pipe. I had the dealer weld it on back in the mid 70's. It was the longer style that used fiberglass packing inside it. I believe that I only used 3 of the discs. The 4 stroke bikes use a lot more discs. Your 400 will most likely use only the 4 discs.
NOTE: One of the problems that I had with my Supertrapp was with the long rod in the center to secure the end cap. When the pipe would get hot (also from the vibration when you hit the power band) the rod would expand causing the discs to rattle and the nuts (double nutted) would loosen up. There were a couple of times when I was riding where the nuts came off spilling the end cap and discs along the trail. I always made it a point to check that the nuts were still tight during my rides.

Alan Buehner

[Daniel P. McEntee]

Thanks for the feed back.

Al, I would have never thought four would be sufficient for the exhaust volume of a 400 Penton. I think I'll just get a six pack of them to have on hand. Better to have 'em and not need 'em than to need 'em and not have 'em! They are not that expensive. I think a cotter pin or safety wire through the acorn nut on the end of the rod would help keep from loosing things. I plan to email the company and ask about different spring rates for the retaining spring. I would have to guess that a lighter spring would do the same job as more plates? With in reason of course.

  John Durrill! Great to hear from you! Hope all is well with you and yours. Hope to make a Reunion Ride with a whole flock of Pentons once we get these two finished. Everything from a steel tank Berkshire through a '97 KTM JP Special Edition. Just gotta figure out how to haul the all safely and securely. I'll drop Speedy a line and see what the Schnellmeister has to say.
 
  Thanks again folks,
   Dan McEntee

[brian kirby]

Supertrapps are not ideal for two strokes, I would go a different direction unless you just have to use it for nostalgia reasons.

Brian

[SouthRider]

By the end of the 70's Supertrapps were on just about every 400 KTM engine bike we would see around the shop, and they were just about universally paired with a Lectron carb (great air flow, mikuni like floats, easy to tune).

I seem to remember putting a stiff spring between the end cap and the double nuts to help with vibration(like a small valve spring).

They worked great for sound tests. You could carry a couple discs in your tool box and add or subtract based on the sound check for each club, then tighten or loosen the nuts as needed. Some guys would leave the starting line with a piece of inner tube around the discs that wouldn't be there by the end of the day.....


Clark

_____________________________________________________________________________________

"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]

quote:Originally posted by brian kirby

Supertrapps are not ideal for two strokes, I would go a different direction unless you just have to use it for nostalgia reasons.

Brian

   I think it will work OK for a old toad like me! I'm not going to weld it to the pipe. I'm adding a support bracket to it to attach to the normal tab on the back of the frame. If someone else down the line wants to try something different, easy to change out. In fact, I have a couple of Skyway silencers that I will adapt the same way so I can try them out. I was cleaning out the garage a bit today and came across one that I forgot I had. They are aluminum bodies so just got to find the right size tubing to weld on the end to make the clamp out of. I was trying to rebuild what was left of the silencer that came with the bike, but in cleaning up all the garbage and old, bad welds, it just didn't fit right any more and the insides were pretty well shot. I had been collecting some possible replacements including two SuperTrapps, and after seeing how one looked on Andreas' 250 in the threads about his bike, I thought I would try one of those first, and just make it interchangeable with the other Skyway units I have.
  Thanks again for the input,
  Dan McEntee

[Lew Mayer]

I have the sheet that came with them. I'll look up what it says for a starting point for # of discs on a 400. I have one on my Rokon.

Lew Mayer

[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