Pesky twin carburettors

lawrence · Post by **lawrence** » Sun Jun 11, 2006 11:29 pm

On my er......... 'Ajay special' the twin carbs are a pain. Once balanced the bike runs beautifully but within a few hundred miles they have wandered out of balance and stutter like crazy when the throttle is opened. Has anyone found a way to stop them going out of balance?

ps. never buy a bike with twin carbs (unless it is me trying to sell it, in which case they are great!)

Biscuit · Post by **Biscuit** » Mon Jun 12, 2006 12:38 am

That will be something to look at!

Don Madden · Post by **Don Madden** » Mon Jun 12, 2006 4:13 am

I have owned many Triumph's with the dual carbs & serviced countless others over the years. Also have not a few Japanese machines with dual or quad carbs but have had good experiences.
First, obviously, the carbs must be in good order.
Next, the ignition must be spot on.
The cables & throttle must operate freely. It is easy to miss a frayed or pinched cable.

Don Madden · Post by **Don Madden** » Mon Jun 12, 2006 4:21 am

Addendum to above post: The ---- computer posted before I was finished.
All cables must have freeplay at rest. I adjust for about 1/16".
Finally?, no matter what some manuals suggest, synchronise them when lifting from idle not full throttle. I place a finger in one, touching the slide, & peer into the 2nd while slowly turning the throttle & adjust until both lift together.
See if this helps. Cheers, Don.

paul knapp · Post by **paul knapp** » Mon Jun 12, 2006 5:02 am

Lawrence, you could try fitting a balance pipe. We fitted a balance pipe to a '49 Beesa Star Twin to improve idle and Commando's have balance pipes fitted, ex works..... Pop over and I'll turn up a pair of brass manifold nipples for you..
Cheers Paul..Edited by - paul knapp on 12 Jun 2006 04:06:46 AM

Don Madden · Post by **Don Madden** » Mon Jun 12, 2006 5:15 pm

Ask Paul if he is subsidising the trip to the Antipodes. I'll come, too! (=->)
Cheers, Don.

itma · Post by **itma** » Mon Jun 12, 2006 5:45 pm

if your carbs are going out of tune that quickly Lawrence you must have elastic cables.
The best carb balencer is a very special tool we used to use on Triumphs, they are known as lollipop sticks.
one in each bell mouth and squint along them from the side and you will immediately see which slide is out of line with t`other, also which one lifts first, or late as the case may be.

Biscuit · Post by **Biscuit** » Tue Jun 13, 2006 12:08 am

I'm assuming here that you have the cylindrical cable divider, ie one in two out. Firstly DO NOT have the divider hanging in the air, clamp it securely to a suitable location, ie, the top frame tube or any where that permits an easy run of the cables. Closely inspect the nipples of the two cables to the carbs., make sure that the inner ends of the nipples are free from solder blobs, scrape any excess off with a sharp scraper, ensuring not a vestige of solder remains at this point. Inspect the recesses in both the carburettor slides and the divider, ensure the recessess are clean, with flat bottoms with no burrs, bulges, buckles, breaks or bends. Check, as best you can that the outer bowden spirals have not opened up at some point and are acting as a spring. Sling the whole caboodle together and set the balance by your normal method, I used to use a length of radiator hose and list to the hiss until I got a super-dooper four column super sucker. Stop the engine, if it hasn't stopped all ready, and wind the twist grip hard against the stop, recheck the balance, if it has moved, start from the top. I discovered all this c..p as a very young lad struggling with a recalcitrant Rapide.

Course, if you want to do the job properly, study Jap. bikes - one cable operating a cross shaft above the carburettors.

lawrence · Post by **lawrence** » Tue Jun 13, 2006 1:00 am

Its a 1970 export model and has two cables all the way from the carbs to the twistgrip. I think it may be the pilot screw vibrating off setting. I think I will try marking its position to see. I will check everything else mentioned as well.

The lolly stick tip sounds good.