I have recently bought a Pantah 500SL. Actually I swapped it for my 906 Paso. Even as the Paso is the much better bike I think I made a good deal. The bike is fitted with an open 2-1 Conti and carburator bell mouths with a gauze. As I live at the end of a gravel road I decided that its better for the bike to reconnect the rubber hoses going to the airbox and fit a filter element in there. The air intake system is now completely standard. I feel however that the bike breathes a bit less easy now. Obviousely the filterbox creates a restriction over the open bell mouths. Is there a way to modify the air filter box (basically a plastic tube with a cylindrical filter element in it) to get more air in? I have a spare box so I will not destroy original parts.
Have you thought about replacing the open bell mouths with a K & N type bell mouth filter. They will be less restrictive than the standard intake still provide protection. Also they may well suit the open pipe without requiring any rejetting.
I did actually thought about those but think the original airbox, sitting up high under the tank, is better shrouded from dust than separate K&N pods. I feel like I have to blow them out with compressed air after every ride. So I prefer to use the OEM intake system.
It's true that the original airbox and filter strangles the engine considerably, especially at the top end. But it is effective at protecting the Nikasil cylinder bores. Still, those of us who choose to ride 40 year old 500 twins accept limited top end speed as the price.
Remember K&Ns require oiling periodically and this does help them filter out dust particles. I fitted them to my Darmah and the only issue I've had is what to do with the engine breather that is normally fed into the front air boxes. Another smaller K&N fixed that:
Oiling the filter will add to even more dust sticking to it. I agree with Pete1950. Some consessions have to be made when riding vintage. As most roads around our mid italian countryhouse are 95% corners and 5% straights its difficult to go over 90kmph anyways.
In 1980 a 500SL with airbox was timed at 116 mph, without airbox at 120.8 mph. Electronic timing at MIRA, I saw with my own eyes.
But that was with stock 2-2 exhausts. I believe the 2-1 Conti is less restrictive and could flow more air than the stock set-up.
Exactly. If mopre air can get in it will be a more efficient exhaust. I made a small improvement in the size of the airintake by carefully modifying the lid of the airbox. I fitted two new plugs so i can see what the mixture is and will report back after a few testmiles.
