Having had problems getting my bike carbs to fuel properly and thinking they were clean, I stripped all the jets and soaked them in carb cleaner over night - the difference is amazing!

I've been setting up the carbs today in anticipation of te IVA test. I have a lambda in the exhaust and a gunson gastester. I left the gunson running for 10 minutes, set it to 2% and then left it for another 10 minutes to make sure it was stable. Got the car hot until the fan ran then started adjusting my ZX6R carbs, on my 1.8 Pinto (1987)

What I have found is that at an idle of 950rpm, and an AFR of 13.3, I get a CO of 2.5% BUT, I can hear occasional small pops from the exhaust. (Advance is 14 degrees)

If I richen the mixture up to below an AFR of 13 (normally around 12.7) then the popping disappears, but the CO goes up to 3-3.1%

At 2500RPM, I have an AFR of 13.1 and a CO of 2.9%

Out of interest what have other people achieved with their Pinto setups? The popping would seem to be a lean misfire so will this give me problems with the HC at the IVA?

Cheers

Dave

I've had exactly the same problem with my Pinto, only I'm fuel injected / megasquirt. I tried increasing the ignition advance to see if that would enable me to run leaner at idle without the popping in the exhaust, but didn't make much difference. Basically I've come to the conclusion that on zero / light throttle settings below about 2000 rpm you need to be around 12:5/1 to get it to run well. With my set-up I can make small changes easily via the tuning programme to see what the effect is. Fortunately my car went though SVA years ago and at MOT time the tester I use just gives it a visual without checking CO.

Have you balanced the carbs? Bike carbs are sensitive to balance and blocked jets.

On a pinto it has to be 3.5 co and 1200hc the popping could be a exhaust leak sucking air in
Jacko

Another thought, what fuel are you using? If you use super unleaded / high octane, it burns slower to avoid detonation. If you use ordinary unleaded which burns more easily and faster, you will get better combustion and a lower CO at idle. My Pinto certainly runs better at light loads when I have had to fill up with it, but I'm careful to avoid det. until its used up. So after your IVA, switch back to Super before you give the beans!

Thanks guys

Timbo, interesting that you've had the same experience as me.I'm running normal unleaded at the moment.

I've setup the balance on the carbs very carefully as I found it was very sensitive to being well balanced.