US Spec Camel 501 Carburetion

[michaelt]

I'm having carburetion issues with my American spec Camel 501. It came with pod filters but have put the original airbox back in minus the shroud that wraps around the actual filter and part of the tube that goes inside the filter. All designed it seems to impede airflow!
The bike just dies under full or even three quarter throttle at around 5000 rpm. If you use slightly less throttle it will rev right through cleanly up to the red line.
It has the PHBH 30 ES "pumper" carbs. It is still running the jets that were fitted with the pod filters.

Namely

Main 110
Pilot 50
Atomiser 263

Standard jetting from the Morini NL website apparently is

Main 80
Pilot 47
Atomiser 261 or 263

I assume jetting should maybe be somewhere between the two given airflow should be greater than standard. Before I start switching jets around does anyone have some advice?

Cheers
Michael

[EVguru]

This is a known problem.

In order to meet US emissions requirements, they had to jet leaner. To counteract the extra leaning out you get from rapid throttle opening, they then had to use 'pumper' carbs that squirt in an extra dose of fuel on a rising throttle.

Original 500s were on 26mm carbs, with 501s using 28mm. Unfortunately, the smallest carbs available with accelerator pumps are 30mm, which is really too big for the state of tune. They're notoriously hard to get set up right.

A set of 26-28mm non pumper carbs might be the best solution in this case.