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my dear old R100RS hasn't been run for 8 years,,but ive given it a spunk up and want to put it on red plate registration .was just thinking,,im about to start the sweet thing,,whats the thought on petrol filters,

I like to use the large clear plastic in line ones with paper element inside. Put one next to each petcock. Auto stores have them. You can see when they are dirty. Usually it tells what size particle it will filter. I like to get as small as possible. Bing carbs will overflow every time a tiny particle gets on the rubber float needle tip, so this has worked well for me.

They were on my bike when I bought it. My mechanic took them off and replaced the fuel line with the braided hose (as original) without filters. He recommended to once a year clean the tank and filters and not use the in-line aftermarket ones. Keep in mind that the bike did not originally come with in-line filters.

Never used them, loved cleaning out the tank every Winter after the last ride.

My '79 R65 had the straight 180° petcock. They have a small brass filter just above the hose attachment nipple.
AFAIK, the petcock that angles back at 90° does not have this secondary filter.

The primary filter is a large brass mesh that slides over the flow tubes.
So many of these bikes are out there without this filter. Really sad.

A clean tank is good. A clean tank and in line filters is better yet. The only reason I can think of why not to use them is if you dont like how they look.

I never found a need for them in the 35 years I rode that bike.

Oem fuel taps already have inline filters. They're part of the taps.

Karcoma taps..#4 & #12


Germa taps..#4


The small #4 lower filters are easy to remove and clean or replace. As they're out of sight and out of mind, I'm guessing they're forgotten about and rarely maintained. Cleaning them should be part of the tank flush I reckon.

I've also heard from several folks that in-line filters can restrict fuel flow enough to make the bike run lean at full throttle / high speed runs.

Bill Smith wrote: ↑Thu Jun 29, 2017 7:04 pm I've also heard from several folks that in-line filters can restrict fuel flow enough to make the bike run lean at full throttle / high speed runs.

That could only be from borderline too low fuel level in the bowls and would also be felt as an engine breakdown if the throttle was cracked just a little past the 'running lean' situation.
The fuel level in the fuel hose only needs to be just above the fuel level in the carb bowl (and remain there at least) to satisfy engine function.

The same lean situation would result from plain old too low fuel level in the bowl, which is most often experienced as an engine breakdown under load.

The filters could sure starve the engine of fuel, but I don't subscribe to the running lean as a result of filters restricting flow. I think the lean situation can only exist just prior to engine break down from fuel starvation.

'Course, I could be wrong.