How to perform a carb sync

discussions specific to the 750 Paso

Moderators: paso750, jcslocum

Post Reply
regan

How to perform a carb sync

Post by regan »

Does anyone have or know where to go to get information on how to perform a carb sync? How about how to perform a valve adjustment?? I ride a 88' 750 Paso with twin del' Orto carbs.

Thanks.

regan
User avatar
mike
paso grand pooh-bah
Posts: 581
Joined: Thu May 06, 2004 12:00 am
model: 750 Paso
year: 1988
Location: NorCal
Contact:

Post by mike »

Pro Italia sells a valve adjustment video that applies more or less to the Paso. Carb syncing (if you have 2 carbs) is best accomplished with one of those mercury carb sync tools. If you have a weber you can use one of those doohickeys that slips into the venturi.
User avatar
Skins
paso grand pooh-bah
Posts: 1304
Joined: Tue Oct 26, 2004 12:00 am
model: 750 Paso
year: 1988
Location: Kapiti, New Zealand

Post by Skins »

This is what I do, and my bike goes like a rocket:
1. Take the tank off . Adjust the throttle cables so that there is at least 4mm of play in them. Make sure the choke control is working properly and the choke pistons are seating and sealing well. Often a bit of grit will stop the choke piston seating well, giving a rich mixture.
2. Look down the mouth of each carb while you move the handlebars and check that the throttle slides aren't moved by too-short cables.
3. Take the throttle slides out of the carbs and make sure the throttle-stop screw is seating onto clean metal where it contacts the slide. Often a wear mark, which will prevent proper adjustment, will have to be removed. Throttle-stop adjustment will compensate for any metal you remove.
4. Take out the idle mixture screws, which control fuel flow at idle, and also influence fuel at higher revs. Make sure the ends are clean. Blow air into the screw holes just in case there's bit of grit there.
5. Put the screws back, gently screw them right in, then screw each one one-and-a-half turns out. Put the throttle slides back and screw the throttle-stop screws out till the slides are down as far as they'll go. Then screw the throttle-stop screws in again so each slide is just lifted. Put the air cleaners back on, put the tank back on, and see if the bike will start.
6. If the bike doesn't start, turn each throttle-stop screw in a quarter turn and try again. Do this till the bike starts. At some stage the bike will start, and you will then find that turning one throttle-stop screw has more effect on revs than the other. Start turning the ineffective screw till it begins to effect revs. Then turn both screws in sequence till each one seems to have a similar effect on revs. Then make the same kind of adjustments with the idle mixture screws. The idea is to have both slides as low in the carbs as possible, and the idle mixture screws at about one to one-and-a-half turns out, with the bike idling at about 1000rpm. (SEE Post Script below). The exhaust sound should be a kind of sharp, irregular, fizzy burble. It will sound like the bike wants to go, and if you leave it for a while it won't speed up or slow down.
7. Take the tank and the air cleaners off again. Stand on the right side of the bike, grab the twist grip with one hand, and with the other reach over the motor and poke a finger into the front carb (coming off the back cylinder) till you can feel the bottom front edge of the slide. Look into the back carb (coming off the front cylinder - you'll be down on one knee at this stage) and while you?re cuddling that Ducati, watch the slide closely and ease the twist grip open. You should feel the front slide move at exactly the same time as you see the back slide lift. If not, adjust the cables till you do.
8. Once you have achieved the above, your bike should run better. The next stage is plug colour and changing jets etc if required.
Last edited by Skins on Thu Oct 27, 2005 2:31 am, edited 3 times in total.
User avatar
jcslocum
paso grand pooh-bah
Posts: 1714
Joined: Mon Jul 19, 2004 12:00 am
model: 750 Paso
year: 1988
Location: Eastern Shore, MD
Contact:

Post by jcslocum »

My Dell's don't have a tap for the mercury sync tool to connect to. I will rememdy that this winter when I do a bit of work on the engine.
User avatar
Skins
paso grand pooh-bah
Posts: 1304
Joined: Tue Oct 26, 2004 12:00 am
model: 750 Paso
year: 1988
Location: Kapiti, New Zealand

Post by Skins »

POST SCRIPT to second above:

DON'T remove one plug lead to compare cylinders. You'll damage your ignition control modules (black boxes) as I did before I learnt about electronic ignition. :toofar: Taking out a cylinder doesn't really tell you much anyway - they work differently together than singly. It's better to learn to use and trust you ears.
Post Reply