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Discussion Starter #1
Hi all,
I have a 75 spider with Solex's was u.s spec but now has been rebuilt with slightly higher lift cams.
It seems to be running quite rich from the sound and looking at the plugs. I have fitted a color tune and tried some leaner than spec idle jets. What I am finding is I can adjust a nice "blue" flame in the colortune from 1000 -1500 rpm but beyond that it suddenly goes very yellow indicating rich.
It seems a bit early to me for the main jets to come in to play and the mains are standard so just wondering if you had any other ideas?
I am going to re-check float level, ignition timing and carb balance to be sure but would be great to know if I should be looking anywhere else in particular.
All help much appreciated!
 

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Tuning carbs is a compromise. You are unlikely to get the mixture close to perfect for all driving conditions. You will always be a bit rich or a bit lean somewhere. I like to run my Weber idle circuits lean to normal. It keeps things clean. I just don't want it so lean that it hesitates. I use a mixture analyzer from an Oz company - Jaycar, I think. It is cheap and lets you know whether your flat spot is due to rich or lean running.

Regarding your question about timing. I would get a variable delay timing light and just use the P mark - TDC. Adjust your distributor for the maximum advance that you want. I suggest 36 - 38 degrees BTDC is a good starting point. Retard it a little if you experience pinging. I did my tests with slightly lower grade gasoline than I usually use, to give a little safety margin. My plan was to advance it until I could make it ping, then back it off a little. I got to 40 degrees with no pinging and decided to stop there. I now run at 38 degrees.
 

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Discussion Starter #3
Many Thanks for that. My concern is that the mixture suddenly becomes super rich, as in sooty plug rich when just off idle as opposed to a little more rich. I appreciate that my description is not the best. If you dont mind I might make a youtube video of the plug in action and get you to comment at a future date.
With regard to the Jaycar mixture analyser, those are exactly the kits I was looking at, just waiting for the Mrs's approval for the purchase! It would be great to know if you are using their cheaper kit with the l.e.d. lights or their more expensive one with the digital readout. I was going to go with the dearer option and wide band O2 sensor but if you are doing O.K with the cheaper one it would be great to save the money. Many Thanks foryour help!
 

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I am using the cheap one with LEDs and a narrow band sensor. Some purists will say that narrow band is worthless but it is fine for setting up carbs.

I don't know anything specifically about Solex carbs. I am a Weber guy.

Good luck,
Ed
 

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A narrow band sensor is at its best when detecting rich vs. lean. Unfortunately, you are looking at rich (idle) vs. richer (off-idle), so the narrow band won't help much.

Don't know anything about sidedraft Solex carbs. If they have multiple progression holes, like Webers, I expect you are still on the progression circuit. So, did leaner idle jets help?
 
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