900 series carb configuration for Atlas

Previously wrote:

Hi,

Does anyone know the main,pilot jet,slide sizes etc to be used for an Atlas running a single 900 series concentric carb?

Don't worry I'll just use the information as a starting point and fettle from there.

I know this may not be correct but I've got an unworn one,nothing else large enough and little cash.

Many thanks Keith Parsons

carbs when it was nearly standard. It had straight through reverse cone megas with minimal baffles. (The type readily available on Ebay etc).

HTH

Alan

Sounds about right - When I went from twin carb to single, I used the same jettings - didn't touch the carb and it runs absolutely fine. And I have a spare carb ready to fit when the current one wears out.

No. I know I should but there's not a lot of room to fit one. Anyway, up here in sunny Scotland, the biggest problem is ingesting rain, followed by midges... and of course carb icing. The joys...

No, not using air filters.

Cheers

Alan

Remember that there are a variety of choke sizes for this series of carb.

My Atlas originally had twin 928s and ran fine on 220 main jets, with no air filter.

I then converted to a single 930 carb, without an air filter, and was advised to use a 250 main jet.Again this seemed correct but I did frequent plug checks to make sure.

The only problem I really had was the pilot jet continually blocking and messing up the idling.

Eventually I fitted an inline fuel filter which turned out to be a smart move as it trapped huge amount of dirt in the petrol and rust from my tank.

Hi Phil, the inline fuel filter is a great idea, why didn't I think of it?!! I used one for years, with outboard motors. You can pick one up in any yacht chandlers, probably cheaper than from a bike shop.

That's the second good tip you have given me recently (the other re using alloy pushrods with an iron head). Keep it up please! John

Thanks .

I am a new member ( today ) and had the same question . Mine was fitted with a 190 main jet ( no filter ) . I had been trying larger sizes and am up to a 220at the moment , but think the 250 ( no air filter ) will work for me as well .

There is a picture in the October VMCC journal of a blazing Ariel - the in-line fuel filter had dissolved in our wonderful alcoholic petrol and leaked onto the magneto with predictable results. Not all fuel filters are safe to use. You have been warned! Gordon

This a very good point and yet another issue caused by Ethanol in the fuel we are often forced to use. Some of the better car accessory outlets sell filters that are supposed to be Ethanol resistant. It is probablya smart moveto test them off the bike.

Another irritating problem caused by this fuel additive is the effect it having on all the spray paints I use. The damn stuff is better than any paint stripper at destroying the finish on any bike parts I have recently sprayed. Is there a solution to this? My engine plates and primary chain cases keep changing colour overnight.