• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.

    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

Fast idle adjustment

ceedub

Senior Member
Country flag
Offline
The fast idle on my single Stromberg carb ('75 MGB) seems excessively high at about 2500 RPMs at startup. When I then kick it down, it seems too slow for satisfactory warmup but eventually works its way up as it warms up. How can I adjust the fast idle so that the initial RPMs are something around 1500 or so? Perhaps I should ask what the initial revs should be when the choke is first set. I think that 2500 too high on a cold engine. Other than the initial high revs the choke seems to work OK.
 
Yes, /ubbthreads/images/graemlins/eek.gif 2500rpms is way too high for a “stock” ZS setup.

BTW - Welcome to the forum! Lots of great folks here.

Anyway the first thing I’d do is try & reset the idle to 850RPMs Factory for a . But it sounds like you have a problem with the choke (automatic enrichment) settings are the reason for the high idle.

Try turning the idle screw down – if that doesn’t work you have other issues.

A safe bet would be to try to do a complete tuning - fuel mix, timing, plugs & wires if its been a long time too. If you don’t have one yet, get a good Manual for your MGB (Bentley 75-80 or Haynes) and a Moss catalog for their little tech tips. Next a timing light, tachometer, a Zenith Stromberg adjustment tool and a way measure your fuel mixture. Gas analyzer or a color tune will work but the analyzer is by far the more accurate and worth the money if you live in a state that requires smog testing on you B like mine (California) still does.

Good luck,
 
Back
Top