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AQ131a with Solex carb (old style) just won't stay running unless at 2000 rom

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beeton

Member
Old info for some but I am having an issue with the Solex carb.
Details: Bought this Bayliner Capri (86) to clean up, our first boat.
Inboard Volvo engine.
Penta aq131A model with Solex carb, identified as "old" style

the boat started but idles roughly so we purchased and replaced:
Ignition wires, cap, rotor, plugs.
Cleaned carb and used new kit.
Cleaned up wiring at the coil.
Replaced all gaskets for the rad/exchanger, sea water O rings, etc.

Adjusted the screws out 2 turns as indicated.
When we start it, starts fine but revs around 2000-2500 rpm and we do get spray out of the top but it just will not idle if I try to turn down the idle screw.
This is cold or warm.

I see 4 points of adjustment, the 2 usual ones (idle and the mix screw, both at 2 turns out from soft seat), the pump arm and the throttle shaft.
I'm not sure, and can't find any info on setting those.
I say this because the position of the pump arm adjustment screw may or may not be an issue or it may. There is an indent on the threaded shaft showing where the nut was set but that may be a bit off.
the throttle shaft is bolted to the frame so no adjustment there except for the top, but, I don't know if I should turn the idle screw out 2 turns then adjust the shaft and attach it as having it high or low may affect the idle?
Not certain this makes sense so your patience is appreciated.

Thanks.
 
If you use ethanol laced gas... It can and does leave a hard deposit in small passages in carbs that no cleaner I've ever tried or air hose will clear... only mechanical removal, i.e. wire or small numbered drill. I've had this issue in both old Honda 4 stroke 7.5 hp outboards and 5.7L 260 HP carbed engines. The deposit, upon examination, is a hard clay colored brittle material and seems to like to form in the idle circuits/jets of carbs. The professionals, I hear, just dunk the whole carb in an ultrasonic cleaner to clear this deposit. No filter on the planet will prevent this as it the result of dissolved chemicals in the gas drying out as a solid in small passages.
 
sandkicker said:
If you use ethanol laced gas... It can and does leave a hard deposit in small passages in carbs that no cleaner I've ever tried or air hose will clear... only mechanical removal, i.e. wire or small numbered drill. I've had this issue in both old Honda 4 stroke 7.5 hp outboards and 5.7L 260 HP carbed engines. The deposit, upon examination, is a hard clay colored brittle material and seems to like to form in the idle circuits/jets of carbs. The professionals, I hear, just dunk the whole carb in an ultrasonic cleaner to clear this deposit. No filter on the planet will prevent this as it the result of dissolved chemicals in the gas drying out as a solid in small passages.
Click to expand...

Thanks for info. I used a new kit with new jets so may be an area that I did not look into but I did spray out everything and I rebuilt this 3 times. Frustrating as it is likely a simple issue. I am still not clear on the pump arm limiter adjustment as the manual has nothing on this.
 
Disconnect the throttle cable to make adjustments. I had no idea. I will try that. So, I used an ultrasonic cleaner and the carb runs much, much better but I still think it is idling high. I turned out the 2 turns as per the factory manuel but revs are around 3500 cold and although the temp reaches 175, the revs do not go down (I read that there is a bimetal valve in the carb that controls cold enriching circuit?). If I turn the idle down, the engine seems to struggle, although I am also trying to get the mix correct.
 
beeton said:
Disconnect the throttle cable to make adjustments. I had no idea. I will try that. So, I used an ultrasonic cleaner and the carb runs much, much better but I still think it is idling high. I turned out the 2 turns as per the factory manuel but revs are around 3500 cold and although the temp reaches 175, the revs do not go down (I read that there is a bimetal valve in the carb that controls cold enriching circuit?). If I turn the idle down, the engine seems to struggle, although I am also trying to get the mix correct.
Click to expand...

Make sure all ignition components are 100%, especially the dwell on the hopefully new points. I seem to remember some time ago discussions about replacing the less-than-user-friendly Solexes with other carbs. Do not forget to lube the cam surface on the distributor that the points run on. Preferable to set dwell with a dwell meter using a feeler gauge for initial start up dwell.
 
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