Airbox Questions

[imported_n/a]

POG, I haven't had an opportunity to peer under many Penton seats at the top of the airboxes but have noticed some varied applications in pictures I've seen. As is apparantly common the airbox on my 74 Six Day has a triangular modification around the top. I assume that's to adapt to the high breather frame. Lately I've noticed some airboxes with metal lids for sale here and there. Or I've seen just the metal lid that appears to fit the triangular opening in the high breather airboxes. My questions are - when did the lid come into the airbox picture? And, are they for pre-high breather frames?

Still learning:D Thanks and Seasons Greetings!!

Chris Heeter

[rob w]

Chris, That's correct, the metal air intake scoop is made for the pre-high breather's, or the '72/73 seat breather frame airboxes.
Also still learning, Bob

[slvrbrdfxr]

Chris,
The early CMF frame bikes area little different looking when it comes to the frame design under the gas tank and seat. The early CMF bikes have a non-perforated round tubular backbone and is mostly open between the frame rails under the seat. They draw air into the airbox from under the seat through the triangular lid you described. This triangular lid is attached directly to the top of the airbox. The high breather frame like your 74 has a perforated square tube backbone which transitions into a steel air chamber welded between the frame rails under the seat. The airbox on the high breather mates up to the the air chamber under the seat using a foam weatherstrip seal. Once the airbox is installed with the weatherstrip seal, no air should be able to enter the airbox unless drawn through the frame backbone. I hope this helps but if not I can send you some pics of my 100 Berkshire which is not a high breather. Just let me know and I'll be glad to send the pics. Talk to you later.
Dave McCullough

[Dennis Jones]

Chris,To add to what the other guys said I can go out to the garage and lay my hands on four (4) different versions of CMF air boxs.
The early ones with the lid, 2 different high breathers for the late 73 early 74 bikes (maybe due to using Sachs and KTM engines) and the 74 1/2 on bikes. How do I know this? From being dumb enough to buy air box's off ebay that the seller didn't know or wouldn't say what year bike they were on. I must have the worlds biggest Penton airbox collection. When you lay them out side by side it is pretty easy to see the difference but not so easy from a picture. You can make some retrofit others but they are just not quite right.

Dennis Jones

[imported_n/a]

Thanks guys! Yup, that answers my questions! The other day though I had a little concern when looking at the square backbone that crud could get in up under the tank, through the air intake holes, and run down into the airbox. Has this ever been a concern? I wonder if there's anything that can be done about it in heavy mud or dust conditions....

Thanks, Chris H.

[slvrbrdfxr]

Chris,
I guess its possible that water and debris could enter the airbox as you described but highly unlikely unless you get into some really deep water. I'd say as long as the air filter element is in good condition, properly serviced and properly installed it should be able to catch any dust or debris encountered under normal circumstances. When you install your airbox, be sure to get a good tight seal where the airbox mates to the steel air chamber. You can buy a roll of good quality foam weather stripping at most any hardware or home improvement stores like Lowes/Home Depot that works just fine for this application. Happy Holidays !
Dave McCullough

[john durrill]

Chris,
 Like Dave said. It is a very good system for clean air. You should have a drain ( little steel tube braised on the rear underside of the back bone just where the tube changes from a square shape to a flattened rectangle ). It should have some clear tubing  attached their and running down as a drain for any small amount of moisture that might get in.  
 If the air box is sealed you can take water up as almost as high as the top of the cylinder head fins. If you are moving and making a wake the bottom of the tank. Just don't stop for any reason chuckle chuckle.
 It is the best air intake set up made for trail , enduro's or 6 day trials events. We use the weather stripping that Dave mentioned  to seal the side cover to the air box also. If you have trouble with the glue that is on the weather strip sticking , contact cement will work and resist oil and fuel.
 John D.

[Paul Danik]

I am sure that a lot of you are aware of where the frame breather idea for the Penton came from, but for those who don't know and who have an interest in such information here goes.

   It came from the German NSU motorcycles that Penton Brothers were a dealer for and that JP used in enduros in the late fifties and early sixties.  I don't recall if NSU developed this system for air flow management or just to provide clean air, but either way JP really liked the way this system kept his air clean. It is interesting to note that NSU was also a maker of sewing machines, although I have never seen one, Husqvarna also was a maker sewing machines, an interesting thread that connects these two motorcycle manufactures.

   They say that most ideas have been used before, but I have never heard of any other motorcycle that used the high breather system before the NSU, anyone know of any?

Paul

[paul]

Hey, I have a question about the 72/73 cmf airbox. My 72 6 days did not have an air cleaner when I bought I. So, I took the one out of my 175 which is a 73 to see if it fit which it does but the 175 had a metal cover with two tabs that evidently push against the # plate. When I tried to put the lid on the 125 it acted like there was not room. Is the number plate on the built differently to take the place of this metal lid? They look identical but I may be missing something besides my brain. My 125 engine is now brand new so I really need to get this right before any dust enters. Thanks y'all,TTP

[thrownchain]

If anyone is interested, I've got a full size template for a "plate" that is form fit under the tank on pre 74 frames. Looks to be a upgrade that someone came up with to at least stem the problem of water entering around the tank and seat. Looks to be rider fabricate and install, make out of stiff plastic or like material. interesting if nothing else.

[tofriedel]

Paul,

If you are using a No Toil 2 Stage or similar filter which covers the entire filter gage except where it mounts onto the airbox, you do not need the metal plate.  The pressure from the number plate will keep the filter in position.

If I am not mistaken, 72 & 73's came with a paper filter that was open on both sides, therefore the need for the metal plate.

Tony

[paul]

Thank you Tony. The one I have is foam and that explains why it acts like there is not enough room for the metal plate as the foam is about an inch longer than the cage. I thought about using the "dollar bill" trick (with out the metal plate installed)as I do on auto door seals to see if they seal and if not where. If the bill or paper pulls thru easily or has no resistance you know you are not getting a seal. Take care and Happy Holidays,TTP