I was just curiuos as to how loud our Pentons are? NETRA is adamant about the 96 db noise restriction and it is strictly enforced. I installed a db Dawg in my Honda for this reason. Thanks, David.
1973 Penton Six Day
1973 Penton Jackpiner
1982 Yamaha XT200
1982 Yamaha XJ650J Maxim
1987 Yamaha YZ490
2005 Honda CRF450R
They are louder than 96db, and a lot of it is the air cooled cylinders. The water cooled cylinders dampen a lot of the mechanical noise you hear on air cooled engines. Even if you can get the exhaust quiet it would be very hard to get an air cooled bike down to 96db for that reason.
Brian
'72 Berkshire
Brian,
Cut 8 mm id black fuel line up just wide enough to squeeze between the fins. Run that top to bottom between the fins on the 4 corners of the cylinder and you will be pleased with how much noise it knocks down.
The head is harder to do with the fins cut. Fat rubber bands cut from inner tubes work on full radial heads. You could get creative with the 8 mm fuel line and do some good with the head also though.
Paul ,Jack and Speedy can give you ways to quiet engine noise. They had to deal with it for the ISDT. 96 db would hurt you in points.
john d.
True the cooling fins are like tuning forks, I actually found that by touching the third fin on the left side of the engine at idle it quieted right down. The 2007 NETRA standard is set at 96 dbA at 20 inches from the rear of the silencer at a 45 degree angle, and at 50% of the engine RPMs that the motorcycle reaches at its maximum horsepower. For the CRF450R this is 4500 rpm and with the db Dawg measures 92 dba, stock pipe is 102 db. Any Jackpiner or Six-Day numbers available?
We support grass roots organizations in order to keep our trails open and I certainly don't want to rock the boat with loud equipment. Thanks, David.
1973 Penton Six Day
1973 Penton Jackpiner
1982 Yamaha XT200
1982 Yamaha XJ650J Maxim
1987 Yamaha YZ490
2005 Honda CRF450R
In addition to the rubber ideas John gave, I would also pass along an idea Dwight Rudder gave me that I never would have thought of. When they are doing the test, try to stand with your body between the meter and your engine. Those original Penton enduro exhausts are not real loud and if repacked are pretty darn quiet for their era, but the engines are a huge source of noise.
I went through all this a few years ago when I was toying with the idea of entering some AMA ISDE Qualfiers with a '79 Maico. I came to the conclusion that it was pretty much impossible to pass the sound test with an air cooled bike.
Brian
'72 Berkshire
WOW! I remember the days when we would ride with just a plane old expansion chamber (spelling?) because that is the way the bikes came off the showroom floor. The bike would echo for miles on a good day. After the neighbor complained a few times, and the police "advised" me of the disturbance, I finally ordered a SILENCER from JC Whitney for about $12. It was amazing that the small clamp-on device cut the noise in half. I think the following year, maybe in 1972, SILENCERS became mandatory at the local race track. That was OK with me. I learned to build my own silencers out of old spray cans. joe
The STOCK penton exhaust system not only had a unique timber to it ,it was amongst the quietest in the industry.One reason I loved my first new penton a 72 six day,as I had to ride it to a practice track a mile from the house never did get hasseled but plenty of my friends did.I personally believe since the test is administered from the rear towards the expansion chamber and silencer, engine noise should affect the test minimally.Back then the cry was less sound more ground I even had a tee shirt with the logo.I would say if were gonna keep our riding areas open we ought to adopt it again.
Dave
A quick story about a recent sound test and bike inspection.
A good friend of mine rode his Six-Day in a very prestigious enduro a couple of years back that had mostly modern bikes in it. He nervously took his 125 Six-Day to the inspection tent, concerned about all the requirements. To his amazement the chief inspector instantly went nuts at seeing the Penton and just could not stop telling about his Penton days from years gone by. My friend offered him a ride on the Penton, the chief inspector climbed aboard and took off like a kid on a new bike, he was actually gone long enough that my buddy started to get concerned. He returned smiling ear to ear, jumped off the bike, thanked him for the chance to ride his Penton and put that elusive little "passed" sticker on the headlight........
When I asked my buddy about the inspection, he smiled and said it passed :D He then told us the stroy.
I don't recall having had any trouble with sound tests back in the day, at the ISDT while running the timed speed test with a sound meter aimed at the bike part ways thru the test, I would muffle the exhaust with my right foot and put my hand on the engine fins. I don't know if it helped but it was always fun to do:)
Paul
We would ride from Avon Lake to the "Old Lorain dump" without our silencers on the stinger ends of our 72's. Just to see how many rookie cops would give it a try in catching us....the RR Track bridge over the Black River was usually a choke point !
Those were the days.
My Mom had to come get me at the police station a few times.
Victor
I got yanked outta the woods on time in 1974 for excessive noise. Cop handcuffed me because I had the "nerve" to actually complain about leaving my new sixdays laying in the wood! Can you believe that! He actually made me Leave it there! Anyway, my mom had to come to the station and get me. She has an Irish temper and "went off" on the cops. No ticket and when I got back to the weeds where I left my Penton, It was still there.
Jeff
Jeff,I guess it's time to come clean.I called the cops,yes I'm ashamed to admit it but after chasing you around every track in nw Ohio and so. Michigan I figured they'd keep you in long enough to get me some 1st place iron.All those first and second loser ones were gettin old!
Dave
I learned a little trick from LR one year. Italy ?
Take one of those old style muffler tips that had the little
rubber flap on it.
Weld up a bolt and nut in the center of the muffler,
With this rubber flap covering the end.
Grab the outer ring, tighten up and "wala" Super quiet"
Then reach back and loosen up and instant full power again.
Made my KTM 350 super quiet.. And could still do 5th gear wheelies.
Maybe NETRA needs a "Grandfather" clause in thier rules for air cooled bikes.
Pete Petrick
175 Jackpiner
Slow but Good
They need something, the Husky I just picked up will shatter my Coleen collection. The flap selection sounds like a plan, I have a good selection in te shop.
1973 Penton Six Day
1973 Penton Jackpiner
1982 Yamaha XT200
1982 Yamaha XJ650J Maxim
1984 Husqvarna 400WR
1987 Yamaha YZ490
2005 Honda CRF450R
Got a picture of that. Interesting but I can't quite visualize it.
Lew Mayer
Lew,
dont have any pictures of it.
Dont know if I can explain it well enough for you to visulize it, but will try.
Think in terms of a regular muffler with a large opening at the exit.
there were 3 metal bars across the opening with a small hole in the center where the metal bars met in the center.
There was a round metal circle of metal with a round rubber flap rivited to this 3 bars in the metal. With just a slight tension against the back side of the muffler. The exhaust would push the flap away from the back of the muffler.
What we did was drill out the rivet in the center of the metal/rubber flap. Then we welded a 8mm nut in the center of the 3 bars. Then we took a 8mm bolt about hmmm oh, 60mm long ran it thru the nut that we had welded to the tri-bars. From the inside out. Then we welded the round metal/rubber flap to the end of the threaded part of the bolt sticking out of the back of the muffler.
By turning the round metal/rubber flap in to the muffler, it tightened the rubber flap up against the back of the muffler restricting the exhaust flow and making it very quiet.
Then you could reach back, turn the metal/rubber flap counter clockwise out and it would have a big gap away from the end of the muffler, letting the exhaust flow freely... It could not fall out of the muffler because the end of the bolt would only let it come out so far....
Hope this helps you visulize it...
Otherwise I will have to get out the crayons and try drawing pictures. ;)
Bob
Lew,
If memory serves me right, I think it was old Huskys that had this rubber flap on the end of the muffler....Dont remember what year/model
Bob
Thanks, Bob. I think I got it. I failed crayons in school anyway.[:o)]
Lew Mayer
While reviewing a French magazine from 1975 I noticed this Sachs powered BPS. Obviously there was great emphasis on eliminating any vibration noise from the cylinder.
(http://i957.photobucket.com/albums/ae59/CheneySachs/BPS.jpg)
There you go, used heater hose, 1001 uses! Noise was a concern even back in 1975 in many parts of the World. Nicely made bike, notice the continuous weld on the frame gusset beneath the fuel tank.
1973 Penton Six Day
1973 Penton Jackpiner
1982 Yamaha XT200
1982 Yamaha XJ650J Maxim
1984 Husqvarna 400WR
1987 Yamaha YZ490
2005 Honda CRF450R
Oh my, look at those horrid foot pegs!
Brian
'72 Berkshire
Here are a couple of overall pictures. Note this is advertised in two models 125/175 both in these pictures (same lower end). Look at the ultra-quiet exhaust must have been the ultimate for river crossings :D
(http://i957.photobucket.com/albums/ae59/CheneySachs/BPS-2.jpg)
(http://i957.photobucket.com/albums/ae59/CheneySachs/BPS-3-1.jpg)