synch carbs while on bike?

[roost]

So after a thorough carb cleaning, valve adjustment, o-rings, the bike starts and runs smooth.....at 3,000rpm!...and the idle screw is as low as possible. Thanks to all you GS folks for the tutorials, which were quite helpful.

I realize that I bench synced the carbs incorrectly, started with the sync screw between 2-3, then 1-2, then 4, but i left the butterfly just open a little, which is why I'm assuming it idles at 3,000 rpm.

After running, the number 3 header is cooler than 1,2,4. Obviously I need to re-sync these.

So my question is do I need to buy/build a manometer? Or can i adjust these without a manometer while the carbs are on the bike?

I'm assuming the answer is to vacuum sync. I wish you could rent these manometers...

[Larry D]

They stay on the bike, but, you'll need a manometer.

[BassCliff]

Hi,

For reference:

Synchronize Carburetors
(With the Morgan Carbtune)

Synchronize Carburetors
(bwringer's site)

There is lots of information available on the internet for putting together your own manometer. I like the "4 tubes into one reservoir" style better than the "4 bottle" style. But they can be bulky and messy.

If you put your location in your profile and your bike's model in your sig file, perhaps there's a member near you who can help out.


Thank you for your indulgence,

BassCliff

[d19407]

If you live in San Antonio, TX I would be happy to loan you mine.

I feel your pain my friend! $115 for what you think is a onetime use.

I had to bite the bullet and buy one (as per Mr BassCliffs advice) and I have to say it was well worth the cash.

Before and after my rebuild the bike was running really rough – once I rebuilt the carbs and balanced them – BOOM! It ran like it just rolled out of the showroom.

A few months later I also ended up using it to diagnose an air leak on carb #3.

And these older bikes always need something fixing – I foresee me using it again many times.

Either make it, buy it or loan it, but I highly recommend you get one.

Good Luck

[cowboyup3371]

You'll need to resynch them every time you adjust the valves (based on what I was told).

[81GS750]

They can be expensive, but manometers are worth it. Like d19407's offer, If your in San Antonio you can use my set. I'll even help ya do it.