Solex 40 needle and seat sticking

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James Watters
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Solex 40 needle and seat sticking

#1 Post by James Watters » Mon Jul 08, 2019 2:11 pm

Do I need to pull off the top of the carb to remove the needle and seat assembly? What gaskets will I need? Any tips for un sticking?
Thank you
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Geoff Fleming
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Re: Solex 40 needle and seat sticking

#2 Post by Geoff Fleming » Mon Jul 08, 2019 4:10 pm

Yes, the top must be removed in order to access the valve. You should not have to replace the large gasket which covers the openings unless it is in very bad shape. The needle valve is then easily unscrewed and can be blown out or replaced with another . When replacing the carb top, be sure that the two small springs that are on the under side go into the carb , in order to hold down the float pivot.
Compressed air will suffice for blowing out the valve of any debris or let it sit in solvent for a while, then blow it through.
With the carb top off, it is a good time to see if both accelerator nozzles are spraying fuel when you depress the throttle.

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Re: Solex 40 needle and seat sticking

#3 Post by James Watters » Tue Jul 09, 2019 9:19 am

Thanks Geoff.
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Dick Weiss
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Re: Solex 40 needle and seat sticking

#4 Post by Dick Weiss » Tue Jul 09, 2019 11:55 am

Also, if the float is 'floating freely' and not sunk.

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Re: Solex 40 needle and seat sticking

#5 Post by James Watters » Tue Jul 09, 2019 11:58 am

Thanks. Looking at the diagrams and the spring issue, should I remove the carbs or can I do this while leaving them on the motor?
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Geoff Fleming
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Re: Solex 40 needle and seat sticking

#6 Post by Geoff Fleming » Tue Jul 09, 2019 3:12 pm

Pretty easy to do with the carb still mounted on the engine...just spread some cloths in order to catch any bits that may drop into the engine bay. Turn the gas lever to OFF, so you don't have a steady stream of raw fuel running into the bay from the open fuel line. I tie the end of the fuel line up with a bit of cord in order to keep it clear of the work.

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Re: Solex 40 needle and seat sticking

#7 Post by David Jones » Tue Jul 09, 2019 3:36 pm

While Geoff is correct in saying it is possible to do this service with the carb mounted I would personally feel you would be better off removing the carb and work on the bench as you have not performed this task before. After all there are only the 4 nuts to remove plus washers and the fuel line and then you can be sure you will nor lose any parts in the engine compartment.
If I had known I would live this long I would have pushed the envelope a little harder.
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Doug McDonnell
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Re: Solex 40 needle and seat sticking

#8 Post by Doug McDonnell » Tue Jul 09, 2019 3:52 pm

It might be overkill but I soak them overnight in Yamalube Carb cleaner then blow them out.
1965 356C There is never enough time to do it right, but always enough time to do it over.

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Re: Solex 40 needle and seat sticking

#9 Post by DaveErickson » Tue Jul 09, 2019 4:39 pm

It probably goes without saying, but if you are going to remove the carbs and clean them, you will also need to remove all the jets and clean and check them as well. An ultrasonic cleaner helps to loosen deposits. Pine Sol is a good cleaning fluid in the ultrasonic cleaner (the acidity helps to dissolve the inorganic deposits inside the carburetor). Bruce Smith wrote a good article for the Registry a few years ago about checking the jets, and if you can't find it, visit his website, a pdf is available (http://sparkingplugs.com/resources/BSmi ... etting.pdf).

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Re: Solex 40 needle and seat sticking

#10 Post by Robert Vaughan » Wed Jul 10, 2019 6:54 am

and...
don't bend the feet when you reinstall the carburetor and tighten its four mounting nuts
don't loose the grain of rice sized little air vent brass "jets" that poke through the side of the float bowl
don't interchange the air correction jets
don't leave the intake manifolds un-covered so that things can fall in

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Vic Skirmants
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Re: Solex 40 needle and seat sticking

#11 Post by Vic Skirmants » Wed Jul 10, 2019 8:05 am

Robert Vaughan wrote:
Wed Jul 10, 2019 6:54 am
and...
don't bend the feet when you reinstall the carburetor and tighten its four mounting nuts
don't loose the grain of rice sized little air vent brass "jets" that poke through the side of the float bowl
don't interchange the air correction jets
don't leave the intake manifolds un-covered so that things can fall in
"brass jets"; I think you are referring to the over-pressure relief plugs found only in split-shaft Solexes; right?
Don't interchange the idle air jets and fuel enrichment jets. Same thread, way different holes.

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Re: Solex 40 needle and seat sticking

#12 Post by Tim Berardelli » Wed Jul 10, 2019 9:11 am

You might want to verify that you have the correct needle and seat-1.75mm with the spring loaded ball in the tip. Most common replacements are 2.00mm,w/o the spring loaded tip. The replacements are very prone to sticking. Stoddards and Partsklassic have correct replacements.

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Re: Solex 40 needle and seat sticking

#13 Post by James Watters » Wed Jul 10, 2019 9:21 am

I bought these carbs from from 356 Carb Rescue about 4-5 years ago. At that time they were totally rebuilt non split shafts.
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Robert Vaughan
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Re: Solex 40 needle and seat sticking

#14 Post by Robert Vaughan » Wed Jul 10, 2019 12:47 pm

" over-pressure relief plugs " they have the tinyest little orfices in them. They blow streams of tiny bubbles.

" found only in split-shaft Solexes " yes.

Is your float valve Stuck open? Or stuck closed?

Since those carbs are 356 Carb Rescue product I wouldn't take them all apart. It is quite possible that your upper fuel lines have released granules of rust into the float valve preventing them from sealing. Thus stuck open. (It happened to me.) Flush the float valves out with a water hose over a white plastic bucket and see what you find in the bucket. Look in the threaded boss into which the banjo fitting flows. See if you find a little sand bar of rust. If you find rust in the bucket then flush and bake dry the upper fuel supply lines as well. Drive some bee bees through them with a water hose over the white plastic debris-catching bucket.

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Re: Solex 40 needle and seat sticking

#15 Post by James Watters » Thu Jul 11, 2019 8:28 am

Car has an electric fuel pump. I replaced the inline filter, cleaned the idle and main jets and checked for fuel flow. All ok. I let the fuel pump stay on for about 20-30 seconds give the throttle a few pumps and it turns over but no start. If I turn it over without umping the throttle, after 6-8 times the motor will catch and slowly keep running at about 2-3 00 rpm's and after about a minute I can slowly increase the throttle until it runs fine. Once the motor is running it's great. If I try and start it and pump the throttle multiple times over the course of a minute or two, there's gas in the drip pan under the car.
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