Settings for single carb with (unmuted) peashooters?

Yesterday, I replaced the original balanced exhaust & peashooter silencers which had the '74 Mk2 mute inserts. The R/H exhaust had cracked at the junction with the crossover section at the weld. In retrospect, I wish I had heeded the advice on here and gone with the non balanced set-up as fitting took me most of the day and was frankly a proper ball ache! On the plus side, the setup from Andover Norton is wonderful quality. I went with the Mk3 style flared ends with spherical seating washers.

I also run a single Amal Premier concentric with the RGM manifold, and it's has been running great (apart from the crack at the pipe weld) with the following settings:

Main jet: 260
Needle jet: 106
Throttle slide: 3-1/2
Needle position: Middle groove
Pilot screw: 1-1/2 turns out
Ham can filter.

Question. What carb settings should I anticipate with the change to the free'er flowing pipes without the mutes?
Although carb removal is a doddle with a single set-up, removing the top to change the clip setting becomes a pain due to its proximity to the centre frame tube, so I'd be delighted to get it right first time - yeah right

Simple - mute them again you hooligan!!

Just run with the same settings. Should be very similar. Graham.

A 260 is the right jet for an 850 with unmuted peashooters, I doubt 260 is right for a single carb setup, it would normally need to be larger. So you need to run at full throttle and see what issues you get and rejet accordingly, just don't come back and complain if it seizes before you get the main jet size right .

1st MAIN JET With throttle position 1 (fig 5). If at full throttle the engine runs “heavily” the main jet is too large. If at full throttle by slightly closing the throttle or air valve the engine seems to have better power, the main jet is too small. With a correct sized main jet the engine at full throttle should run evenly and regularly with maximum power. If testing for speed work, ensure the main jet size is sufficient for the mixture to be rich enough to keep the engine cool, and to verify this, examine the spark plug after taking the first run, declutching and stopping the engine quickly. If the plug body at its end has a cool appearance the mixture is correct: if sooty, the mixture is rich : if however there are signs of intense heat, the mixture is too weak and a larger main jet is necessary.

There was a 'set up guide' for single carb set up on the old RGM site, unfortunately that seems lost for now.

Don't know if anyone downloaded a copy?

Bonzo said:

There was a 'set up guide' for single carb set up on the old RGM site, unfortunately that seems lost for now.

Don't know if anyone downloaded a copy?

Click to expand...

Ooh. Found it!

From the RGM

As a guide when tuning Amal's the sequence is main jet, ie flat out for at least a mile preferably on a slight up hill gradient, pull in clutch, killmotor, cruise to a halt, look at plug colour, aim for a chocolate brown, any indication of a sooty colour go down, whiteness go up

Click to expand...

This sadly no longer works with modern petrol, the colours are no longer there. One way I did it on a tuned B44 was to get a series of main jets, stick the biggest one in and see if it 8 stroked, it did so I went 2 sizes down in steps until the 8 stroked stopped and then went up one size. I was using the peanut silencer with detachable mute, by running the same test with and without the mute I got a 3 size difference.