Mk 2 Solex jetting

[David K]

I have purchased a "restored" 1956 Mk 2. Great cosmetic restoration, but he didn't ride it. I put 30 miles on, blew the head gasket. Purchased and installed the Otto head gaskets fron Draganfly- wonderful people to work with- but now have some other issues.
The bike is running very rich- black very sooty spark plugs. Can I get a leaner main jet? Any other suggestions?
Also, have about 90 miles on the rebuild. Getting ready to retorque heads- per Roger's specs from Draganfly. Have noticed plenty of power at start of ride, gets hard to pull 4th gear after 20 miles or so. Will this abate after break in miles?
Thanks for any help!! Looking forward to riding this wonderful machine
David K

[paul_turner]

Hi David
Firstly if your bike is a 1956 mk2 it should be fitted with an SU carburettor not Solex as SU were fitted from 54 on. You can purchase a rebuild kit for the SU from Burlen fuel systems Ltd in Salisbury. I would retorque the heads not forgetting to reset the tappets.

[will_curry]

The Solex was fitted to the very first Mk2 and had a 120 main jet with a 170
air correction jet. Rich running with a Solex can be something of a trouble
to diagnose - there are a number of threads on this forum so a search will
be informative.

[chris.shearwood]

Hello David,
Welcome to the Forum.
When you did your rebuild did you check that the sludge traps of the crankshafts were clean?
Regards, Chris

[paul.jameson]

Hello David and welcome to Square Four ownership. Having had many Squares over the past 35 years or so, my experience of them is that they cause all kinds of problems to begin with, but once you get them right they are absolutely unbeatable.
To assist you with your current problem we do need to know whether the carb is a Solex or an SU. As Paul T says, it should be an SU and they are easier to tune than the Solex - but also correspondingly easier to get out of tune. The Solex has a knob you pull out for the choke. The SU has a lever you lift up for the choke.

[David K]

My bad. It is a SU... too used to working on Amals. Sludge traps are clean. Tappets were set on 1st torque of heads, will recheck this weekend on retorque. Have heard that the nut on the bottom of the carb can adjust the richness... any truth to that? Thanks

[Roger Gwynn]

I think you need to get yourself a manual, the Waller book contains good instructions on tuning the SU, copies available from Draganfly and elsewhere. I don't think the manuals are on the club's website, just the owner's guides, which are useful as well.

[Simon.Gardiner]

.... I don't think the manuals are on the club's website, just the owner's guides, which are useful as well.

Shame on you Rog - there are at least 2 Waller manuals (5th ed. and 6th ed.) in the Club doc repository!!

SG

[David K]

Can I access/ print the relevent pages of the waller manual on this site? How do I get there? Not very computer savvy, LOL.
Thanks again
Dave

[paul.jameson]

Now that we know it is an SU, it is easy to adjust. Look at the operation of the choke lever and you will see that when you take the choke off, the part on the end of the lever comes to rest on the brass nut at the base of the carb. Screw this nut upwards a couple of flats - so that the choke lever will go that bit further up when you take the choke off and see how it goes with the mixture. You may well need to do this operation several times to get the mixture right but if you go a couple of flats each time you will not risk damage by getting the mixture too lean.

The part on the inner end of the choke lever is in fact the main jet itself, so the action of adjusting the nut effectively moves the main jet up and down in relation to the needle.