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carb sync tools


jp02ti
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Guys,

I'm having a beast of a time getting my carbs to sync. The ti has dual 40 phh solexes and the '70 has dual weber 40 dcoes. I have a Unisyn tool, which is really annoying me, so I'm looking into getting something else. I see a couple available, in 2 formats. this first:

http://www.amazon.com/Deluxe-DELUXE-CARBURETOR-SYNCHORNIZER/dp/B0007D20MQ/ref=sr_1_6?ie=UTF8&qid=1285955202&sr=8-6

I've seen this used with good results. not overly pricy, and is fairly simple.

second:

http://cgi.ebay.com/ebaymotors/CARBURETOR-SYNCHRONIZER-2-4-CARBURETORS-NEW-/160486110827?pt=Motors_Automotive_Tools&hash=item255db7b66b

somewhat more complicated, but I expect it to give a much better readings. I like that I can set this up and then make adjustments without having to stick the device into each port individually. what I'm not sure of is whether there is a good port on the solex (or weber for that matter) to attach the vac lines. I'm wondering if it would be worth taping the intake stacks with a vac port or if I can just drop then end of the vac line into the stack?

thoughts?

Jon

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A Uni-syn is a worthless piece of junk. It is very inaccurate and nearly impossible to duplicate results.

The second tool is the equivalent of a manometer and also pretty much worthless on a Weber because the Weber lacks the vacuum ports with which to hook it up and take readings. These ports must be below the butterfly or you don't get accurate readings.

This is why I preferred the Dellorto DHLA carbs I had on my Esprit. These are essentially Weber DCOE clones, but much more tunable. They also have vacuum takeoffs built-in. We kept the test ports connected and sealed them with vacuum caps, making a carb tune/sync a less than 10 min. job. But, if you want a much better manometer, go with the Morgan Carbtune II . It is much easier to use and more accurate.

Realize that there are 2 functions to perform, synchronizing the carbs and tuning them. So, you really need 2 tools to do the job right.

The carb-sync is one of them, with this, you can adjust the airflow of each carb barrel and synchronize it's 'twin' and with the other carb. First, close down one carb and take a reading with the carb-sync from each barrel - these will be different. Since you cannot strengthen the weaker barrel, you must weaken the stronger one to match. Do this for both carbs. Take readings for each carb, again realizing that you need to weaken the stronger of the two. Then, using the synchronizing screw on the linkage between the carbs, adjust the linkage between the carbs until the airflow matches.

Now, you need to tune the carbs. The best tool for this is a Gunson Colortune . This is essentially a clear spark plug which lets you see the actual combustion inside the cylinder. It turns out that a proper stoichiometric mixture (14.7:1) burns a bright 'Bunson Blue' color. Using the Colrtune, with the car off idle (+850RPM), adjust the dedicated carb barrel for that cylinder until you get the proper color. Then move on to all the other cylinders.

If this procedure doesn't get it right, you either have a dirty carb which needs cleaning, vacuum leaks, or your floats and jetting are incorrect.

Cheers!

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The uni-syn is a pain in the ass to use. It can be accurate if you use it correctly. Usually.

It is a royal pain in the ass.

The Synchrometer (your first link) is much easier, and works well enough for me.

You do have to have a little patience.

And a good throttle linkage. Which is uncommon.

And (stepping onto the soapbox) the best way us mere mortals to tune a

set of sidedrafts is a wideband oxygen sensor.

Or 2. Or 4.

That, c0mbined with common sense and your preferences,

will most likely either make you happy or drive you to fix whatever

part of your setup isn't working. Or sell teh whole mess and megasquirt it.

But you'll get answers.

They may be more complicated than you ever imagined...

(done with soapbox)

t

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Jon,

I have one similar to that in the first link. Purchased from Pierce Manifolds when I bought the DCOEs, I probably paid more than the price quoted in your link.

One thing to consider is that if the bushings are bad or if there are any air leaks, sych will be very tough. The Solex DDHEs I purchased used from Dave NEVER stayed in tune because they were very worn. Something to consider.

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The first one you posted works good enough for my DCOEs. If you want to spend more money and time on precision, then you can I'm sure. But mine has a fairly smooth idle after borrowing that synch tool from a friend. No, the Weber DCOEs do not have a vacuum port. If you did have vacuum ports, you could compare two cylinders at a time by using a long piece of clear tubing with fluid in it (ATF for the cool red color), tape it around a yard stick, and adjust until the fluid balances out on each side of the yard stick. That's how I synch the carbs on my bike. For more than 2 cylinders, I've heard of more complicated ways of doing it with a plastic bottle and tubes running into it thru a rubber stopper. But, I've never tried that, since I don't have 4 vacuum ports on a vehicle....

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