air filter or not

[tonydevon]

ok so whats the consensus on running an air filter

all the jetting guides I read are for open carbs

BUT I live right by the beach, Im really concerned about the damage that could occur to my engine

Im currently building it, and thought that now would be the best time to decide, so that I can play with jetting etc from the start as I think I understand that non filter jetting will be too rich for an air filter setup

I have seen the elbow setups on ebay with a Ramir filter sat atop

I have used Ramair filters on bikes with no problems in the past, are there any problems with running this setup as opposed to a different one or open carbs

whats the trade offs??

[Timbo]

The only problem you may get is flooding when starting the engine when its hot

Interesting, why is this?

[nelson pk]

I'm guessing if you have a tuned piston port motor (rather than reed) and the inlet timing is higher than say 150 degrees you will get spit back which will be held in the filter elbow so when you switch off and then restart after a short time it will draw that fuel in the air filter elbow through with the normal charge of fuel and flood a little.
If you left it overnight the fuel in the elbow will evaporate so if you start from cold it will be easier.
I guess if your barrel had an inlet port timing of say, below 150 degrees the spitback will be greatly reduced and therefore the scoot will not flood half as much when restarting after a short period of time.

[Adam_Winstone]

I'm a big advocate of filters but have found that many of the filters available from scooter dealers are far too small and too restrictive, limiting performance. Indeed, the RamAir filter that I was initially supplied for remote use proved too restrictive on a Rapido 200 ant then too restrictive on the iron 175 that I ran it on (this was not a result of poor jetting). I substituted this small RamAir for a bigger RamAir and performance (on 175 and 200) improved. However, changing again to a remotely mounted Breathe Sweet filter from Cambridge improved performance again.

I've recently run these Breathe Sweet remote filters on PHBH carbs (actually off standard GP airhoses, rather than the bigger hose supplied with the filter) on an Avanti TT3 motor and Mugello 260, with no loss in performance over the same carb run open mouthed. I do also run a BIG RamAir filter directly off the mouth of a 34mm VHSB and am happy that it doesn't limit the performance for road use.

The point of me bothering to write the above is to highlight that small filters will limit performance as they simply cannot supply enough air fast enough. I noted that Tino ran VERY BIG Polini filters when crossing Australia, where dust would have quickly choked smaller filters.

Others may have a different opinion but the above reflects my personal experience.

Adam

[tonydevon]

Breathe sweet.

do you have any more info on them? uk supplier?

many thanks.

[Adam_Winstone]

http://lambretta.co.uk/catalog/product_ ... ts_id=3178

I note that they have a large range of other filters too, incl. what appears to be a decent size RamAir that is made to their size requirement. These may be worth considering as the hose that somes with the Breathe Sweet filter may not fit your carb. Best thing would be to give them a call and talk through your specific requirements (carb, otor, etc.)

[Timbo]

If its not a daft or obvious question is it the size of the filter that makes the difference as in bigger the better, or shape/material?

[Adam_Winstone]

Both, size and material. The Breath Sweet are big and are not quite as dense a foam as the inner layer of the RamAir filters. You could say that the RamAir's finer foam gives bigger filtration but it comes down to air-flow trade offs again, size vs material.

Surface area for travel from one side of filter material to the other is what matters, which is why paper filters (greater restriction) need to be concertinaed back on itself to give the area required.

[joey]

...been messing about tuning a vega..tried loads of different carbs/filters on 80cc ali barrel...running 25m dello and best result with breath sweet...it went up three jet sizes from running open mouth!!!

[CANbus]

http://lambretta.co.uk/catalog/product_ ... ts_id=3178

I note that they have a large range of other filters too, incl. what appears to be a decent size RamAir that is made to their size requirement. These may be worth considering as the hose that somes with the Breathe Sweet filter may not fit your carb. Best thing would be to give them a call and talk through your specific requirements (carb, otor, etc.)

Is that filter element tapered?
I have found most filter elements are parallel and contact the inner side panel when mounted.
Thus loosing this effective area for air intake. I always glue a rubber grommet on my hose to ensure the element is lifted off the inner panel when fitted.