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iaccy
Samba Member
Joined: September 24, 2007
Posts: 1380
Location: CT
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 Posted: Sat May 17, 2025 5:18 am Post subject: Solex 28 PICT adjustment |
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Anxious to get some input regarding an issue I'm having with my 40hp 28 PICT carb. End of the season last year i had to regasket/clean it and I feel like the adjustment was a little off because it would sometimes pop while driving once warmed up. Fast forward to now, it starts right up, automatic choke works correctly and idle quality smoothes out. I followed the directions to CW turn the #14 volume screw until the engine speed starts to drop and then turn the screw CCW until it speeds back up. I'm mostly having the issue at higher rpms in 2nd gear, where it feels like it "skips" a little bit. It's fine at lower rpm's, and not an issue at higher rpms in 1st gear.
I checked my static timing at 10BTDC, set point gap at .016" and checked valve lash at .008".
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Eric&Barb
Samba Member
Joined: September 19, 2004
Posts: 25790
Location: Olympia Wash Rinse & Repeat
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| Posted: Sat May 17, 2025 8:51 am Post subject: Re: Solex 28 PICT adjustment |
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| iaccy wrote: |
I checked my static timing at 10BTDC, set point gap at .016" and checked valve lash at .008". |
Timing depends on the distributor used, but you do not list the distributor number.
Setting points gap at .016" is a good start, but you really need to adjust that to get proper dwell.
Are you using long or short rocker studs. If the latter should be .006" lash.
As for the engine being affected by higher RPMs, that could be due to jetting of the carb. Could be too small of main jet or more likely too big of air correction jet making the engine lean out too much. That would require a jetting gauge to measure each jet.
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glutamodo 
The Android
Joined: July 13, 2004
Posts: 26496
Location: Douglas, WY
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| Posted: Sat May 17, 2025 10:10 pm Post subject: Re: Solex 28 PICT adjustment |
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The mixture screw won't have any bearing on full throttle, by the way, at that point it's all a function of the main jet, the air correction jet and the power fuel system (extra nozzle with a gravity check ball trapped down inside the carburetor body)
You can see the full throttle fuel flow in this image that goes with a discussion of the power fuel system. Oh, and you can't change the size of the jet in the power fuel system discharge tube, it's permanent.
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"What is Glutamodo, Horror of Toyko, besides total, fiendish, quality-a-you brain!" |
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rcooled
Samba Member
Joined: September 20, 2008
Posts: 2724
Location: Santa Cruz, CA
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| Posted: Sun May 18, 2025 1:29 pm Post subject: Re: Solex 28 PICT adjustment |
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| iaccy wrote: |
| I'm mostly having the issue at higher rpms in 2nd gear, where it feels like it "skips" a little bit. |
This could be an issue with the ignition system, not the carburetor. You might try replacing the condenser. That 'skip' can be caused by not getting a strong enough spark at higher RPM when under load.
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Eric&Barb
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Joined: September 19, 2004
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Location: Olympia Wash Rinse & Repeat
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| Posted: Sun May 18, 2025 4:32 pm Post subject: Re: Solex 28 PICT adjustment |
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| rcooled wrote: |
This could be an issue with the ignition system, not the carburetor. You might try replacing the condenser. That 'skip' can be caused by not getting a strong enough spark at higher RPM when under load. |
True, but could be the coil instead.
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rcooled
Samba Member
Joined: September 20, 2008
Posts: 2724
Location: Santa Cruz, CA
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| Posted: Mon May 19, 2025 6:08 pm Post subject: Re: Solex 28 PICT adjustment |
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| Eric&Barb wrote: |
| True, but could be the coil instead. |
You're right, but condensers are cheaper than coils 
Both items can be tested before replacing.
Testing the condenser
Testing the coil
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Eric&Barb
Samba Member
Joined: September 19, 2004
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Location: Olympia Wash Rinse & Repeat
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| Posted: Mon May 19, 2025 6:58 pm Post subject: Re: Solex 28 PICT adjustment |
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| rcooled wrote: |
| Eric&Barb wrote: |
| True, but could be the coil instead. |
You're right, but condensers are cheaper than coils |
Sure, but the coil is easier to R&R, plus one should have a condenser and coil in the spare parts box to skip towing the VW as much as possible.
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iaccy
Samba Member
Joined: September 24, 2007
Posts: 1380
Location: CT
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| Posted: Thu May 29, 2025 8:13 pm Post subject: Re: Solex 28 PICT adjustment |
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I'm totally embarrassed to even share the answer to my problem. As many of you suggested, I checked several things with my ignition system. Checked static timing with a test light, set point gap, etc. When I went to replace the spark plugs, one of them was a little dirty/wet by the crush washer....turns out it must have backed off a bit and was just barely loose. I installed my newly gapped Bosch plugs and it ran like a top!!! Once it was running better, I adjusted the carb volume screw and did some testing, which went great. The following day I took it almost 400 miles round trip to an indoor show in Rhode Island. Didn't skip a beat. Thanks for all the input guys
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Eric&Barb
Samba Member
Joined: September 19, 2004
Posts: 25790
Location: Olympia Wash Rinse & Repeat
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| Posted: Thu May 29, 2025 8:49 pm Post subject: Re: Solex 28 PICT adjustment |
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| iaccy wrote: |
| I'm totally embarrassed to even share the answer to my problem. As many of you suggested, I checked several things with my ignition system. |
Main thing is that you found it!! We have all done that at one time or another. Always go thru the easy stuff like a tune up, before going into the deeper harder stuff.
Know a fellow who replaced gen, reg, and battery without any testing because he was so sure he knew what was wrong..... Only to turn out it was a faulty $8 battery ground cable.
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