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Can I swap Solex carbs on my aq131a?

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beeton

Member
1986 Capri Volvo aq131a, Penta outdrive, older Solex carb.
After wasting hours (spread across weeks) trying to get the boat to idle, I decided to pay for a mobile boat mechanic to come by and set things right. So, after adjustments, swapping the old gas with some new stuff, checking things over, the boat started properly and all good UNTIL, either during testing or when replacing the top plate (of the carb, not cover), the goosneck injector, for lack of a better name, went missing. I looked everywhere: around engine, in bilge, in bucket full of water (for outdrive), around boat, in all visible cracks and nooks and no luck. The boat will not run without this as fuel spills all over. I made it clear that I am not paying the 2nd half of the service fee until this part is found or replaced on their dime. I case it gets down to it, I am looking for a replacement carb to either swap (after another rebuild) or cannibalize the part but the only one I see locally seems to be the newer version.
So, can I simply swap carbs or do I have to change other parts as well (throttle cable, etc.)?
 
You know, I did just that. Pulled it, nothing in or against valve stems. I was hoping it would be in one of the intake tube. It's a mystery.
 
O.K. maybe now the question is getting silly... still no luck finding the brass tube. Now, I did take off the intake manifold and found a part of a crass washer. No connection to the missing tube but thought I should mention it. The valves also seemed clean (no chipped or bent edges). I took out the plugs and used my small borescope to look inside. The 2 rear cylinders and front cylinder seemed clean and although plugs were a bit fouled, nothing unusual. The 2nd (from the front) seemed to have some marks on the crown and, if my eyes do not deceive me, small brass residue? It's difficult to get a clean image but I am including one. So, in the unlikely event that this tube did get sucked into the chamber, being thin brass, what should I expect? I used a syringe to pump in some clean oil and sucked it immediately out and there seemed not to be anything but oil in the tube, and small flakes of carbon, which are probably normal being it's a combustion chamber. I'm doing a compression check tomorrow.

WIN_20230702_10_55_02_Pro.jpg

WIN_20230702_11_14_19_Pro.jpg
 
Compression tests (cold) showed 155 psi average. warm showed 160 average. The missing part is the Pump injector jet. I mocked one from a metal pen insert and it squirts fine but obviously not an ideal setup. Anyone having this elusive part or a rebuildable carb for cheap, please let me know.
 
Looks like I will have to buy some brass tubing and make one of these. As info is sparse, can anyone confirm the jet size (if indicated anywhere)? I see a "40" on another version. I'm not sure how I will translate that to i/d but at least it is a starting point.
 
I have made a new goosneck tube and it works well. I still can't get it down to idle properly. The boat starts up immediately (changed plugs just i case the aftermarket ones in the "upgrade" kit were also an issue; they were 3 electrode types. Switched to NGK)
Here's a possibly dumb question:
If I have the air screw set properly and idle set properly, and I remove the throttle cable, I should be able to prime the pump manually by pushing in the pump lever a few times and the engine should idle (so the cable position and adjustment should not affect idle)?
If so, I still have a carb issue or adjustment issue and if not, I may have a cable adjustment issue. I have scoured for info on adjusting the cable properly and can't find anything on cable adjustment.
Your patience is appreciated.
 
Disconnect throttle cable at carb.... Adjust idle when warmed up. Adjust the fitting on the end of the throttle cable so that it's end just slides into the hole on the carb lever with slight pressure holding the carb lever against the idle screw stop. Reinstall cotter pin. If there is excessive slop at the carb lever, sometimes installing a thin metal washer will tame the slop. There are several different types of throttle end fittings, common among them is a means of adjustment by screwing it more or less onto the end of the threaded cable end
.
 
Took another look at things today. I have made a new jet pump out of brass tubing and the accell pump squirts fine. I give it a few pumps and it starts right away and will throttle up but dies at idle. When I remove the emulsion/jet (see image please) idle is fine and consistent but I can't throttle up. So, at idle, fuel does not seem to be making it up through the emulsion jet (as it is called in the parts list... this is the jet in the center of the carb, over the throttle plate). The fuel pump is strong. I am at a loss of what to do next.... another rebuild but is this symptomatic of a clogged passage in a specific area that I should look into? One note. The exploded views I find show a 2 piece emulsion jet and I only see a one-piece version in my carb.

carb 2.jpg

carb 1.jpg
 
Interestingly though, I could not find any info on float adjustment in the forums, I did find this video on just that this morning. I will give it a try.https://www.youtube.com/watch?v=HemkOIKe3nk
 
Just following up on this constant idle issue. I did manufacture a new tube and fuel squirts just fine. The problem I was having before and still having after the mobile mechanic showed up is inability to idle properly.

So, frustration basically caused me to ignore this for the last month but I thought I had better get to it so I can at least have one small victory before winterizing.

I changed the washer/spacer for the float needle to a slightly thinner one (.8mm vs .9mm) as I wondered if the float was closing a bit too soon.
I may be way off base here.

I put it all back together and starting is not an issue and I can throttle to 2000 + but idle is a no-go.
I did increase and decrease idle setting a bit and also played with the mix but no changes.

What I find odd, and may be helpful, is that when I remove the emulsion tube, idle seems fine but when I install it, fuel does not get to the top to spray. I had the fuel pump checked and that was rated good.

One other note, as it was idling without the emulsion tube, I adjusted the mix screw out and soft bottomed and there seemed to be no change in engine speed.

So, if this is a float-level issue, and you are not supposed to bend the tang (tab?), should I increase or decrease the spacer for the float shutoff valve? I hope I have all of the terminology correct.

A video is attached.

Thanks and safe boating to you all.
 
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