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 overcarbed 998

 Created by: VG30JT1N
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 Posted: Oct 19, 2023 07:38AM
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All SU needles of a particular class (90 thou for HS2s) are almost identical at idle.

I would be looking at the float bowl jet that could be causing flooding at very low revs…

Cheers, Ian

 Posted: Oct 15, 2023 03:52AM
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Get it tuned on a dyno (rolling road)

 Posted: Oct 13, 2023 09:36AM
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What pulgs and what gap ?

GY needles with the jets two turns down should be about right.

 Posted: Oct 13, 2023 05:40AM
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1968 Mk2 998 with dual 1 1/4" SU's. Plugs are fouling at idle, black sooty exhaust. If the vehicle is driven right after start the plugs clear and driveability is excellent. Plug check if shut off at speed indicates a light tan color and good plug temperature. The needles were originally AN which would indicate that this setup probably came from a 1275. I have changed the needles to GY with little effect. My assumption is that at idle the air drawn into the engine isn't sufficient to atomise the fuel mixture correctly and keep the plugs hot enough to keep them clean. 
What does the forum say? Thanks