- Sat Jul 13, 2019 9:14 pm
#84088
The 26mm Wassell carb is now on the bike.
Thankfully it fitted straight onto the existing studs (lateral spacing on the inlet flange is 50mm). The existing throttle cable (Minda controls for the Mikcarb 24mm) also went straight on, with the adjusters at both ends wound right in.
The carb came supplied with a choke mechanism. I don't have a choke cable or a handlebar lever as per the Mikcarb so I decided to remove this and rely on the "tickler" for now. I found a suitably sized screw, washer and locking nut to block the aperture in the top cover, where the cable adjuster was fitted and used a little silicone sealer paste on the threads to ensure it was completely airtight.
The carb came with a 160 main jet and the fuel needle "out of the box" was on its lower (weaker) position on the clip (only two needle positions on this carb). I left everything as it came for the initial setup.
I never like running an engine on an open intake. I had a washable "cone" filter on the Mikcarb but this proved too small in diameter to fit over the short "bellmouth" type intake adapter on the Wassell and too big without it. I fitted a suitable foam one I already had, from another project, keeping the bellmouth in place.
The initial run proved that the mixture was too weak, with a lot of spitting back and poor power. The spark plug's centre electrode insulation after a full throttle "plug chop" was very white in colour, which confirmed it.
To remedy this, I fitted a 170 main jet. I just knew those old AMAL jets I'd saved from my old BSA C15 tuning days would come in handy one day - albeit it's now 46 years later...my wife was amazed I'd got them to hand, some fourteen house moves (and two country moves) later but a man needs to prioritise such things.
I also raised the needle to it's richer position.
The float level seemed quite low, it was at the lowest position mentioned in the included instructions, so I tweaked the tab a little to raise it a couple of mm.
The bike then ran really well, it pulled noticeably stronger than with the Mikcarb at full throttle. There was absolutely no sign of the initial problem of the carb running out of fuel - BINGO!
However, another plug chop proved that the top end was now too rich, confirmed by a rather sooty exhaust. The original 160 main jet is now back in. Yet another test shows this is OK (I think it could really do with a 165).
The bike now pulls really nicely and idles well. I suspect for colder weather I might need to refit the choke mechanism so I intend to source a cable and air lever from Mr H. But for now, the bike starts first kick.
Although this Wassell "Concentric" carb isn't actually an AMAL, it's a relatively cheap pattern copy, I can certainly recommend this type of carb as an upgrade modification for a 350, as per the "OE" ones sold by our host.
Built like a gun... could go BANG!