Carburettor jet sizes with air filter

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Whiskey98
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Joined: Wed Oct 26, 2022 1:56 pm
Location: West Yorkshire UK

Carburettor jet sizes with air filter

Post by Whiskey98 »

Hi all!

I'm looking at installing a threaded cone type air filter from Amal to the 389 monobloc for my G12. I have CSR pistons fitted so according to the owners manual, the main jet size is 450 for an unfiltered carburettor and 390 with an air filter. The manual was written in the early 60s and I'm confidently assuming since then air filter material technology has progressed and filters today allow a greater amount of airflow. So I'm wondering if I should change the main jet to 390 as per the 60 year old manual or is there a larger size I can go towards based on similar peoples experience?

Thanks
Peter
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jackstringer
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Location: Somerset UK
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Re: Carburettor jet sizes with air filter

Post by jackstringer »

Might be worth asking Amal as they may offer some advice, even if it just confirms what someone else here will say.
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