Top end fuel starvation
Turbo Mini Forums

My problem is the engine will pull really well up to 4000 rpm and then it develops a huge flat spot, actually its more like a hole than a flat spot. Engine is 1380 twin hif 44 carbs, this set has worked perfectly in the past and was rolling roaded by Neil Slark @ 110 BHP. The issue started after the carbs were stripped to cure an over fueling issue caused by the choke seal failing. I fitted service kits in both carbs, when you drive the car and monitor the fuel air mixture with an oxygen sensor it shows good fueling up to 4000 rpm and then it suddenly shoots up to 20+ AFR. I have fitted richer needles changing BAM`s for BAP`s but made little difference. I feel that I am missing something obvious here but cannot put my finger on it.

I removed the carbs today and found that the float levels were about 1 to 1.5mm lower than spec so I have adjusted then; they are now set 1mm down on the carb body when measured across the float centre. I`m not sure how critical this measurement is and wether it would cause my issue.

Any thoughts would be appreciated.

Pump and hoses ok?

I run a supercharger and I don't care the TB is on the wrong side.
VEMS + 12 PSI + Liquid Intercooler = Small Bore FUN!

loose needle maybe ?