Synchronizing Carbs

[Bikesandfires]

Is there any Old Skool tips and tricks to synchronizing a pair of carbs? Are the synchronizing tools necessary? Is there something that can be home made to replace it? These are the Strombergs on a SV. I'v got it running pretty well, good throttle response, good idle quality, but I'v never messed with dual carbs for street use before. Do I even need to bother?

 

[Green67Alpine]

Having this set up myself, if their running like you said, I'd leave them alone, your more than likely going to need to do some work on them in the future.
Just my 2p worth.
Tom j

 

[Bikesandfires]

I can't believe I'm this good, or lucky...LOL...This car was a barn find, had been sitting 14 years going by the date on the liscense plate.

Buddy of mine bought it 2 years ago thinking we would clone a Tiger but decided not to after looking things over and seeing what a huge job it would be. It wasn't much trouble to get it running, had ot clean and coat the tanks, a normal points, plugs and wires tune-up got it started but it wasn't good. After reading bunches here...(Thank the Lord for this forum)....I pulled the carbs apart, cleaned and got the pistons unstuck, filled with oil and re-installed and adjusted. It runs pretty durn good, but my thought were, and are, that it just can't be right. Maybe I'm wrong.

Car is apart at the moment, just starting re-assembly after paint.

 

[todd reid]

Synchonizing Carbs

There are lots of fancy tools for this job, but I prefer to just use my eyes. Pull the air cleaners off, make sure you have oil in the pistons, and then watch the pistons rise as you open the throttle. Getting the pistons to rise together is what synchronising is all about.

 

[puff4]

I posted a couple of times in the past with some advice, and hopefully it's helpful to you:

http://www.sunbeamalpine.org/forum/showpost.php?p=105059&postcount=3

http://www.sunbeamalpine.org/forum/showpost.php?p=91320&postcount=3

I do use tools to get my carbs spot-on - I use the UniSyn and the Gunson Colortune. Both are very easy to use and highly accurate. The first tool makes sure the air flow is synchronized, and the second one makes sure the fuel mixture is optimal. Once set in this manner, you'll rarely have to fiddle with them. I actually use two Colortunes - one in #1 and one in #4 - so that I can tune both carbs at the same time which greatly increases the accuracy and ease of tuning. They're not cheap, but they're worth it.

Gunson Tuning Instructions: http://www.gunson.co.uk/items/pdf/Products/G4074_Chart.pdf

 

[Nickodell]

Instead of using eyes, like Todd, we old f*rts have used our ears for generations. Get a 3' length of 3/8" O.D. plastic tube and stick one end in your ear. Hold the other end near the air intake of each carb in turn and compare the rushing sound of the air flow at various throttle settings.

I refined this a bit back in the 1970s when the sound system on airliners was acoustic - they issued plastic head sets with twin tubes that you stuck into an outlet in the armrest. I "forgot" to give mine back on one flight (they must have cost British Airways all of 90c).

Not as scientific as flow meters etc., but saw me OK for 25 years until I switched to a Weber 32/36.

 

[puff4]

Nick, I *am* an old fart, and I used that method for years. But I gave up on the "listen using the tube" idea a long time ago. It's not bad for getting a quick setting if you just want to set them temporarily to get it running, but to get it spot-on you really do need to use a manometer.

Try this... set it using your ear-tube method, and then test it using a manometer... you'll be shocked how far off it is.

Same is true with listening to the exhaust note and lifting the piston 1/8" to adjust the mixture... it's not bad for a quick back-of-the-envelope setting, but using a clear spark plug (Colortune) or an CO / O2 meter is far better.

 

[Bikesandfires]

I posted a couple of times in the past with some advice, and hopefully it's helpful to you:

http://www.sunbeamalpine.org/forum/showpost.php?p=105059&postcount=3

http://www.sunbeamalpine.org/forum/...nson.co.uk/items/pdf/Products/G4074_Chart.pdf[/QUOTE

Yes...A BIG help.....I ran searches with every type of wording I could think of and came up with zilch. THANKS for the links, and the ideas. I'll update progress as soon as we get the motor back in and running.

 

[puff4]

Yes...A BIG help.....I ran searches with every type of wording I could think of and came up with zilch. THANKS for the links, and the ideas. I'll update progress as soon as we get the motor back in and running.

Glad I could help. We Sunbeamers (Rooters?) need to stick together!

BTW, both of those tools I mentioned are available via multiple online dealers. I know Moss Motors at least has the UniSyn - that one has been around since the 50's and is a tried-and-true tool that will last your lifetime (and probably your grandchildren's too). They were used in the 50's by hot-rodders to get their "trips" set up properly.

And here's a video of the Colortune in use, below. Note that in the beginning it is too rich (yellow/orange) and as the owner leans the mixture you can see it go to the proper shade of blue.

http://www.youtube.com/watch?v=6hFUvQ4gaPc

And here's another that gives you a complete 'how to' for using it...

http://www.youtube.com/watch?v=xEZ0-uN0NA4

 

[Nickodell]

but to get it spot-on you really do need to use a manometer.

Are we talking carbies here, or ED?

 

[puff4]

Are we talking carbies here, or ED?

No, I tried Viagra, but I ended up turning my H1 into an HS4.

(That's S.U. humour).

 

[Jay Laifman]

There are two things to consider here. The balance at idle and the balance at speed. Whenever I've spent the time to balance my carbs, I've always been so much more happy with just how wonderfully smooth the engine can run (or be off because of carbs).

Note that it is mandatory that you adjust all the valves and have the plugs, points and timing dialed in first.

Then be sure to adjust the linkage between the carbs with someone holding their foot on the gas pedal enough so that both carbs are off idle stops - I usually do it at about 2,700 rpm. As I recall, the Strombergs had a lot of twisting between the carbs.

 

[Bikesandfires]

Then be sure to adjust the linkage between the carbs with someone holding their foot on the gas pedal enough so that both carbs are off idle stops - I usually do it at about 2,700 rpm. As I recall, the Strombergs had a lot of twisting between the carbs.

I don't understand that part. I thought you used the idle speed screws to sync the carbs, then locked the shafts together before doing anything else. Am I missing something?

 

[65beam]

carbs

the photo of the carb is an emmision carb which is not syncronised in the manner you're talking about.

 

[chard]

There are two things to consider here. The balance at idle and the balance at speed. Whenever I've spent the time to balance my carbs, I've always been so much more happy with just how wonderfully smooth the engine can run (or be off because of carbs).

Note that it is mandatory that you adjust all the valves and have the plugs, points and timing dialed in first.

Then be sure to adjust the linkage between the carbs with someone holding their foot on the gas pedal enough so that both carbs are off idle stops - I usually do it at about 2,700 rpm. As I recall, the Strombergs had a lot of twisting between the carbs.

This makes sense, I've always done mine at idle and the linkages leave a lot to be desired. Anyone with tips for doing the job solo?

BTW I have tried color tune without success. I now just do it by ear using the lifting pin, followed by an 80mph run and check to plug colour.