Are you able to check the progression holes just behind the throttle plate?

If these holes are blocked or partly blocked, then this would effect the transition from idle cct to main cct. But with the larger pilot [idle] jets currently installed, it may be disguising the blockage as the idle jet also would be feeding fuel to the pump cct. Also with the increase of the fuel delivery duration on the pump cct [as you mentioned you modified the accelerator arm] It may be now be over fuelling the mixture via the pump cct.

So many variables in these little animals...

Sounds like the pump nozzle is a fixed size [40] so I guess you will have to tune around it. Are you able to adjust the accelerator arm somewhere in between where it is now and where it was set before? [say 4mm travel]

Be sure to keep track of the changes and the effects you have trialled so far.

cheers
benny

I've just had a browse for the last hour or so on other peoples jetting lists. Your dead right in saying my jetting is on the big side Benny.

What confuses me is the pilot system, at first with the 60 pilot jets I had the pilot screws out almost four turns to get a decent idle and remove the lean pops. So I put bigger pilots in (which are huge in comparison to typical Datsun A12 with twin webers people are running on here)and I don't have to screw out the pilot screw as much.

If anyone else has any comment on the jetting size of my setup compared to their own, please don't hesitate to make comment.

So yeah, flipped venturi, upped the accelerator arm adjustment so it were to actuate within the range that the manual said. Facet arm on accelerator pump now moves 6mm up and down as opposed to the 2mm or so that it was.

Maybe my jets are all too big except the pilots. The pilot air jets are machined into the body, perhaps I should double check that those are clear?

Hey Benny (@ your first post!),

Yeah if I wind in the pilot screws I get major carb backfiring (even on the PJ70's) and it's hard to keep the engine running unless I'm throttling it. On the 60 pilot jets I had to screw the pilot screws out almost 4 turns to get a decent idle. When I went to 70 I they're around 2 1/2 to 3 turns out and the engine runs smoother on idle when around this range of pilot screw turns.

Manuals insist 2 turns. So I assume the fewer screws (i should say turns) the bigger the feed from the jets.

When I put the big pilots in (unknown size because of the #OOPS# drill bit) but maybe .9mm I got lots of backfires- like exhaust backfires.

When I took the carbs off today I gave them a throttle on their own and they squirted from the nozzles just fine but it did look like a lot (not that I know what to look for). I'm confident that upping the delivery from the accelerator pump has improved the running of the engine but of course I flipped the back to front inner venturi as well so perhaps there's a variable that I should have changed separately.

venturi in the wrong way will get you every time. basically the main cct is blocked on one cylinder. Is this what was happening Chris?

@ ssskiwi

Yeah quite possible Dean. I had a venturi round the wrong way that I found today. Basically it runs like a dog until I throttle the F out of it then it rips into life. Sounds pretty damn good too. Gopt some pretty disapproving looks from neighbors but what the hell they're noise bastards on the weekend nights anyway.

The throttle plates have angular edges but do not incorporate a cutout little cutouts like Webers do. But I suspect they're handed somehow so I'll check them.

I am balancing first body against the last body, skipping 2 & 3. Using an oldschool SU balancer.

Looks like your slowly getting there Chris. Those jet sizes you have currently installed, still seem rather on the large side. I run 145 main and 45 idle/pilot and a 30 pump jet on a 1434cc A-series.

If you engine is bogging down, sounds like its over fuelling...

edit: Are you able to tune it with the jets you currently have to run lean [popping backfires through the carbs] if so, what jet sizes are they?

cheers
benny

@ Greendog

Yeah I got some POS cheapy eBay bits. I'm not sure how well it would drill though, I mean how do you ensure that the bit stays central as you drill? or does it not matter?

I opened up the pilots with one bit but I obviously opened them up too much, so when the throttle valves were opened (minimally) and as they incorporated or activated the bypass (to go from supplying the pilot screw to supplying the cylinder itself) all the engine did was run but not really respond, too much fuel.

So I'm hoping that maybe 75 - 80 pilots will help things along.

Not sure about cheaper. If you think about it, with those tiny drill bits you'd need a micro/mini chuck to accommodate them so I'm not sure that that is cheaper. Either way the bits I had would work well if I had a decent chuck.

Normally you should only need to balance one carb body against the other and then balance shouldn't change regardless of jetting changes.
So to me it is all a jetting issue (guess you already knew that tho!). Backfiring or spitting under accel usually indicates leanness, a rich mix will normally feel "heavy" as it revs.
Just throwing it out there but are the throttle plates around the right way? Some have a groove on the edge that should pass across the progression holes as they crack open, I have seen them inserted backwards before..

EDIT: Wurzel has my carb book which gives basic starting points for weber/dellorto carbs but I can't see them being that different for a Solex, I mean you are still trying to put the same amount of fuel in per cylinder regardless of carb type? Anyway I don't have it on me so can't tell you what it would be for your motor sorry, maybe contact Wurzel?

soldering iron and a set of machinist drill bits is wat you need then you can resize any jet to any size.trust me saves time and money.