LCGB Forums

Hi folks

Does anyone have experience with the high flow air filters through the standard airbox, any feedback please?

Good or bad

I one with a Mugello 225 with a standard 22 carb with an airbox with a 50mm opening set up. It seemed to work ok but obviously the carb was jetted to suit.

I had a spare one that I put on my SX200 and it made it run lean as the revs and road speed increased, it would pink on the hills. I went back to a standard filter and the pinking stopped. That is with a standard pipe and 20mm carb with standard jetting.

I fitted one to a newly built TV175 which was standard other than electronic ignition and a GP200 exhaust. I increased the main jet by one to compensate for the exhaust I had a soft seize when the tank ran low on a long stretch of double carriageway. With hindsight, I think there was a small element of pinking. I filled up and carried on my way at lower speeds.

A few weeks later, I checked for an air leak and I also checked the 17 degree static timing. No air leak and the timing was fine.

Since then, the scooter has done precious few miles but that will be rectified soon. Your post has got me thinking that the MB filter may well have allowed too much air in. As it is hard to make appropriate adjustments to SH carburettors, I am going to put the standard paper filter back on too.

Thanks for posting this question and thanks for the answer too.

Perhaps my input may be more theoretical than practical via experience, but I believe that any OEM type of air-filter box is going to have it’s limitations due to it’s design. The surface area - laid flat - of the filter is probably adequate, but the way that the cartridge is encompassed provides some restriction. The proof of that is Innocenti re-designed the later ‘boxes & Servetta did away with that type completely. Why would either company have spent money/resources unless it was necessary, though in Servetta’s case, it may have been due to supply problems

However, I believe that a good, clean, cold, plentiful air supply is necessary for any engine that has the potential to provide a good increase in performance, not only for a good, complete burn but also to augment the top end cooling.

I reason that the frame hole being 50 mm shouldn’t be a problem, but the OEM filtration system is restrictive. That’s why I believe that adding holes to the box can increase air flow but in so doing introduces warm air. It would never be my choice

Gradually we are all evolving with our machines & an evolution of the air filter system is long overdue, with the potential to fit on machines with intake either side & with the OEM battery & tray location. Of course - & I have considered this - the OEM air scoop, even as fitted to the later machines, may then be restrictive, but it shouldn’t prove too difficult to replicate a slightly larger scoop that looks ‘factory’ especially nowadays with 3D printing.

Getting back to the OP, then it seems fairly obvious that an increase in the supply of filtered air will necessitate up-jetting & on a Lambretta large frame machine utilising SH carburettors, that is not difficult to do. Personally, if I were to fit a better flowing cartridge type filter, I’d be disappointed if I didn’t have to increase the main jet size to compensate……

a breathe sweet filter, airbox drilled out, Armadillo air hose, I have used a sh2/22 bored out to 25mm thru this system on my TV, up jetted to suit on a Mick Abbey tuned 175 & on a Gori 200, now I use a 26mm PHBH thru' this system with a RT200 & have done numerous rallies with this set up, uncluding Euros & 4 Nations

hullygully wrote:a breathe sweet filter, airbox drilled out, Armadillo air hose, I have used a sh2/22 bored out to 25mm thru this system on my TV, up jetted to suit on a Mick Abbey tuned 175 & on a Gori 200, now I use a 26mm PHBH thru' this system with a RT200 & have done numerous rallies with this set up, uncluding Euros & 4 Nations

If I understand this properly, you have a Breathesweet filter sitting in place of the OEM cartridge in an OEM air-filter box - albeit ‘drilled out’

So, is the filter somehow ‘sealed’ in the air-filter box to only take in fresh - body scoop - air & additional under-panel-air via the holes added?

Warkton Tornado No.1 wrote:

hullygully wrote:a breathe sweet filter, airbox drilled out, Armadillo air hose, I have used a sh2/22 bored out to 25mm thru this system on my TV, up jetted to suit on a Mick Abbey tuned 175 & on a Gori 200, now I use a 26mm PHBH thru' this system with a RT200 & have done numerous rallies with this set up, uncluding Euros & 4 Nations

If I understand this properly, you have a Breathesweet filter sitting in place of the OEM cartridge in an OEM air-filter box - albeit ‘drilled out’

So, is the filter somehow ‘sealed’ in the air-filter box to only take in fresh - body scoop - air & additional under-panel-air via the holes added?

Dunno but it had me puzzled too. Why would you have a breathe sweet filter AND a drilled airbox?

I'm presuming mines a 'breathe sweet' as I bought & fitted it 14yrs ago, same shape as std one but wire framed & different filter material

hullygully wrote:I'm presuming mines a 'breathe sweet' as I bought & fitted it 14yrs ago, same shape as std one but wire framed & different filter material

That sounds like a BGM one. A Breathe Sweet is a foam remote filter which goes on top of a bellows.

^... as Rich has said, the Breathe Sweet is a foam filter, like a RAM AIR but with higher flow rate (single skinned and coarser grain).

oops found the filters box, correct it is a BGM Pro

Cheers folks.