1986 Capri AQ131 won(39)t idle below 2000?-gctid816590

[Ibdeadeye]

My 1986 Capri 1950. AQ131 with solex carb won't idle below 2000 rpm. I noticed this the first time out this year. I rebuilt the carb, changed the points. plugs and set timing. Pulled the distributor and cleaned and oiled the weights. Checked compression all are equal and good. I did these things one at a time. But it still doesn't want to idle. Runs fine 2000 rpm to full throttle. I have tried adjusting per the owner's manual. I'm not new to tuneups with points and timing lights so I have done the obvious. Has anyone else run into this problem and fixed it?

ps I stored it last winter with a half tank of gas and Sta-Bil added I topped off the tank before first outing.

[builderdude]

It idled fine prior to the rebuilding of the carb? Turning the idle set screw does nothing?

[Ibdeadeye]

No it didn't. So I figured it was time to rebuild the carb and do a tune up. Turning the idle screw will increase RPM's just won't bring it down below 2000. Well it does drop 2000 RPM's but will stall out. I'm thinking a vacuum leak but haven't found it. I think I will check the intake manifold for leaks next and ordered 2 new gaskets for the base I didn't like the ones that came with the kit.

[mister_larry]

If messing with the idle set screw won't bring the idle speed down it seems logical that there is something wrong with that system. Assuming you have spark, it's only a matter of some fuel and some air to get her to idle. does a Solex have an idle mixture screw? Adjusted either fully rich, or lean, could result in inoperable air/fuel ratio.

Could the choke be completely closed? Pull if off manually and see if that helps.

Could the carb rebuild kit gasket have covered an idle air or fuel passage? If you have the old gasket you might compare it with the replacement. While it's apart again really clean (blow out) those narrow passages.

Just some thoughts on the "charge air" side of the equation.

[Ibdeadeye]

I compared gaskets and all holes match up. While looking at things I examining the carb cover. I noticed the 4 fastener holes show the cover has been over torqued. Then while looking at the mating surfaces I could see a definite void between the fastener holes. The gasket shows areas where there is no contact.. So I believe I found my Vacuum leak. I'm not sure if I can post photos on here but if I can I will. I also noticed on the old cover gasket i can definitely see a difference in colors. Where the gasket is sealing good it's a light color and where the void is the gasket material is definitely darkened.

[Chief_Alen]

That's why g-d made gasket maker the black stuff.

Fills the void.

Gasket still good smear a good coat on the gasket both sides,

I use aviation form a gasket, like the commercial says if i can drink that chit i would.

[Ibdeadeye]

The old gasket


Attached files

[Ibdeadeye]

Another view.


Attached files

[Chief_Alen]

I reused worse.

[Ibdeadeye]

No that is the original gasket.

[soulhunter]

I had the same problem. Removed the out drive and it would idle fine. Turned out it was being caused by a misaligned engine. I did not know that the alignment needed to be checked every 100 hours or 3 years so I have been told.

[Ibdeadeye]

I've never heard of that one.

[mister_larry]

Just a quick thought if you still have issues. You can resurface the carb faces and put it back together without any "goop" and without too much torque.

I have a dedicated piece of glass and a fairly flat surface on the workbench. With some fine sandpaper (at least #400) I place the paper on the glass and gently sand the mating surfaces flat. When all areas are shiny you can quit sanding and start cleaning. Blow out all orifices, wipe the surfaces with a moist rag, and put it back together.

In the absence of more scientific input, I only torque the screws a quarter turn past finger tight. There's no pressure in this component, only vacuum.

You should be good to go.

[Ibdeadeye]

The good news, problem solved. It was the carb lid being warped. I took a bolt, washers, nut and a socket. Stacked them up and basically pulled out the depressions ( like pulling a dent) that were caused by someone over torquing in the first place.. Then I gently tapped out some other areas then filed. Put it all back together and started her up, she purrs like a kitten. Quite satisfying. Now it's time to enjoy the boating season. Thanks for reading and any advice that was given. Happy boating everyone.