FAQ: Carbie Sync & Cable Adjustment Procedure

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BevHevSteve
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FAQ: Carbie Sync & Cable Adjustment Procedure

Post by BevHevSteve » Sun Mar 14, 2004 9:28 am

Our bevel drives can be made to run extremely well with the stock dellorto carbs - especially if the carbs are in tune. If they are not adjusted correctly, your performance will be severly lacking... Here is what I do after a carb rebuild or dissassembly and cleaning etc;

First off, I disassemble, clean and properly lubricate the throttle assembly and throttle cables. I also make sure that the cable doesn't bind or have any sharp bends between throttle assembly and carbs when I reinstall [smooth bends!!!].

Check your exhaust gaskets [between the heads and the exhaust pipe] to make sure they are good [did you safety wire the nuts in place??]. Also make sure the intake manifold insulators are in good condition [the rubber spacer between head and intake manifold]. You can safely check to see if the intake manifold insulators are sealing well or are leaking by warming up your bike, going outside and spraying just a bit of carb cleaner around the rubber. If they are leaking then your idle will increase for a bit. Once I have checked the insulators and exhaust gaskets AND properly maintained the throttle and cables I turn my attention to the carbs.

Assuming you rebuild and setup the carbs correctly this is what I do to adjust them correctly and easily. Print this out, go to your bike and read this over a few times while you stare at things. Once you understand the bottom line, warm up your bike and go for it.

WHAT TO DO
*Back out slide screws so they are not touching slides
*seat [turn in] the mixture screw completely [closed] then back it out 1.5 turns
*loosen throttle cables so there is at least 1/8" freeplay at the adjusters on top of carbs
*warm up bike and hook up vacuum gauges [OK] or mercury tubes [great]
*adjust slide screws so you have an even idle tickover w/even vacuum readings, don;t worry about the rpm at this point, just same vacuum readings.
*turn throttle so tickover goes to 2-2500 RPM or therabouts and hold her steady [a friend here makes it easy]
*adjust for even vacuum at this RPM by the cable adjusters on top of carb[s] - adjustment starts by backing out whichever adjuster needs to be backed out [on whichever carb] to get constant vacuum between both carbs
*check idle vacuum again and re adjust as necessary. Adjust for proper tickover RPM now, using the slide screws only.
*adj cables so each has just a bit of freeplay, check 2500 PRM vacuum reading w/gauges again and readjust at the cable adjusters as req'd
*start playing with mixture screw for max idle [in = leaner or less gas]. I listen for sound change with my fingers over the muffler end while I turn the mixture screw on that cylinder's carb.

I go back and forth between the carbs sometimes several times making little adjustments, always listening for high tickover and feeling for a stronger exhaust pulse.

A dull BUH BUH BUH sound indicates you can make it better still. Keep adjusting until you hear and feel a louder and more authorative BAH! BAH! BAH!

WHAT IT MEANS
Adjusting the cables is an intregal part of carbie sync and verse visea. Start at the top of this list, go through it then repeat a couple or 4 times as neccessary...... You will get the hang of it soon enough and you will be surprised at how well your bike runs after this important step in the tune up game. You are making sure the slides are being pulled evenly causing equal vacuum through each carb from idle all the way through the range.

I also recommend that you pitch a single cable throttle - you know, the kind that has one cable going to a splitter then 2 cables one going to each carb in favour of a Tommaselli Daytona 2C throttle or the like. The DAYTONA throttle has some key adjustments - you can play with the throttle stop on it so that max pull doesn't pull the slides up against the top cap...... that will start ruining things for sure. Some of the stock throttles didn't have a stop so you would pull the slides up against the top cap and stretch the cables and wear the throttle assy, slides, etc etc.. The DAYTONA throttle also has a friction device so that you can give her partial throttle and tighten it up for a higher tickover during warmup.

Speaking of warmup..... make sure you do so. Running your bevel drive under load when cold will kill the bottom end. Blip the throttle until you feel some heat on the case on that first startup of the day then go ride taking it easy for a bit.

Tools & Materials You Will/May Need For The Job
Sync Pro http://shop.bevelheaven.com/detail.aspx?ID=923
Block-off Screw Set http://shop.bevelheaven.com/detail.aspx?ID=856
Adapter w/Cap http://shop.bevelheaven.com/detail.aspx?ID=1089
Exhaust Gaskets [currently on sale] http://shop.bevelheaven.com/detail.aspx?ID=90
Intake Insulators [you have options, see below]
*53mm rubber http://shop.bevelheaven.com/detail.aspx?ID=98
*58mm rubber http://shop.bevelheaven.com/detail.aspx?ID=97
*black aluminum http://shop.bevelheaven.com/detail.aspx?ID=599
*silver aluminum http://shop.bevelheaven.com/detail.aspx?ID=598
Last edited by BevHevSteve on Thu Sep 23, 2010 3:41 pm, edited 2 times in total.
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synch problem

Post by seddy » Sun Sep 25, 2005 3:13 pm

Steve,

I follow the instructions, can get a idle, can get the vacum the same at 2400, but the idle is inconsistant, it will hold for a while then drop real low and stall. IF I rev the bike it will stay at a high idle 2200 rpm for a couple of minutes, then drop to a regular idle (1500) or drop low and stall. Eventually if it does drop to a normal idle, it will eventually rop lower and stall. I Have malossi intakes, I replaced the orings, tightened everything up but it still is all over the place.

Any ideas.

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ideas........

Post by BevHevSteve » Sun Sep 25, 2005 4:32 pm

Hi Stephen, yes you simply [did I say SIMPLY???] need to continue doing the circle of steps. Start at the beginning and go through them all then repeat. Sometimes it is quick, somtimes it takes forever. I don;t know why. Remember, it is most important to get vacuum readings that are equal on both carbs at an idle, then also to twist the throttle to revv her to 1800 - 2200 or whatever and adjust the cable adjuster to get constant between the 2 readings there as well. Once that happens, then you start messing with the mixture [air] screws on each carb to get as high an idle as possible. Listen/feel for a BAP BAP BAP, you can always improve things a bit if one or both cylinders is going BUH BUH BUH. Don;t give up, make sure you get a fan to blow on the engine while you do this etc...
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Post by seddy » Sun Sep 25, 2005 6:01 pm

had ahorrible feeling you would say that, I seem to remember that you could tell if you had an intake leak by spraying carb cleaner around the intake area, is that true?.

Also if I had a leaky exhaust gasket would that give me any trouble?.

Thanks

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Post by BevHevSteve » Sun Sep 25, 2005 7:21 pm

you could tell if you had an intake leak by spraying carb cleaner around the intake area, is that true?.
yes, Do so outside wearing safety glasses etc, just a very brief spritz. The intake manifold insulators are most likely cracked and not sealing if you have a leak. Idle will increase for a brief moment then drop down if a leak is present.
Also if I had a leaky exhaust gasket would that give me any trouble?.
absolutely. It will burn your valves. If in doubt replace those gaskets. I always do when I get a new to me bike - intake manifold insulators and ex gaskets are the first thing to do...
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Going great

Post by Willemd » Wed May 10, 2006 3:27 am

:-D

Followed the procedure (with out vacuum meters for now, still to do). Just worked the slides by ear/eye and it's amazing how the bike's performence has improved already!
Before, doing 80KM or so then close the gas the bike would just hoover along like an old Trabant. Now: close the handle and the bike will slow down on compression with a slight BAP BAP every now and then.

It still starts and runs on the front cylinder for about 30 seconds or so, only then the rear joins in?? Will a proper BAP BAP BAP fix that too?

I suppose the vacuum meters can be hooked onto the connections on the intake manifold, screw into the holes?? Do the hoses to the dials have to be even lenght?

Willem
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hooking up vacuum meters

Post by Willemd » Fri May 12, 2006 12:33 am

Hi,

The bike was already running much better, today I had a change to "hook on the vacuum's", as per Steve's instructions.
:cry:
Took the screws out of the intake manifolds and hooked up the meters, one each. When I started the engine again, the meters were all over the place, can't read a thing!
Both meters came with plugs so I made adaptors to be able to use the 5 mm tread in the intake manifold and screw them in. I only used vacuum meters on cars before, with those you can simple plug the end of the hose on a connector.
What is wrong? What is the "normal procedure" the hook on the vacuum meter on a Darmah 900 SD?
Anyone?
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vacuum

Post by BevHevSteve » Fri May 12, 2006 8:13 am

The pulses on a big twin are large so the only way to make your vacuum gauges readable is the install some sort of baffle to slow down the pulses and put it in line. I have vacuum gauges as well, these made by HONDA for 4 cylinder bikes and they are worthless as well even with the so called baffle things in the lines. THat is why I recommend the CARB STIX which are mercury tubes. They bounce just a small amount and you can fine a good compromise setting no problem.
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baffle thingies

Post by Willemd » Sat May 13, 2006 2:12 am

Got the vacuum meters working! Like you said Steve, the twins have very big pulse, so the trick is to reduce the suction by squeezing the the tubes. Friend of mine had little screw type thingies, it takes a while to get it right but then it works. That was the good news, lolol.

The bad news for me is that my reading was very low, according to the meter late opening valves (just had them done, can't be that) or leaking intake (just put new rubbers on intake manifolds using yamabond and went very light on the nuts).
Although the motor run better again this time, it seems that I am not done yet. At least the procedure is clear to me now, thanks Steve ;)
Willem
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Post by machten » Sun Apr 27, 2008 5:50 am

I don't know if others have seen this, but as far as setting idle right, I ve found it easy to get good idle using vacuum readings. But getting a good idle to transition to a steady power pickup has not meant the same thing for me. My horizontal cylinder is about 15 psi lower than vertical, and this seems common on bevels I've seen. I tend to igonre the vacuum readings for idle and mixture, instead feeling the exhaust pressure by hands over the exhaust, and then using vacuum to sync the throttle movement. Where I've used vacuum measurements for idle and mixture, I seem to get lesser results.

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Post by conti-mental » Sun Aug 10, 2008 11:36 am

In addition to Steve's excellent advice (yup - works for me!), I'd like to throw in my ha'pennyworth (it's like 2 cents, but more imperial ;o) )

Older Ducati Elettrotecnica equipped twins 'enjoy' a step advance function which chimes from fully retarded to full advance at around 1500 rpm (check the footage with the sound up!)

http://uk.youtube.com/watch?v=X8rnFnd3Xdc

Bear this in mind when tweaking the mixture at a fast idle - to my mind at least, this explains why the engine can suddenly drop from a fast idle to a low....before it inevitably splutters to a halt!

Obviously the Bosch engines are not as badly affected, but the step function still applies, just less so...

Image

Hope this helps ;o)

Cheers,

Andy

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Post by welshmally » Thu Jun 30, 2011 2:22 pm

I know that I probably should start a new topic, but as this thread fits the bill, I felt that it would be appropriate to add to it .....

Followed your excellent instructions, up to the point where I needed to adjust the pilot screws. They were, I think, pretty much OK but did not seem to alter the state of tickover when I wound them in or out 1/2 a turn each way. Tickover is at a comfortable 1300pm, and anything lower treatens stalling. For the first time in a long time, I got the nice crisp BA-DA BA-DA from the Conti's. Columns level at tickover and at 2500 rpm

Starting from cold was 3 kicks. From hot, a few more :( but then, what's new?

Any tips? Not 100% sure what to look/listen for.
Cheers.

BTW using a Morgan Carbtune II - useful piece of kit.

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Re: FAQ: Carbie Sync & Cable Adjustment Procedure

Post by bobnorton » Mon Mar 04, 2013 9:40 pm

Not having any balancing kit at all, to set the throttle stops i start the motor and stop it after a few seconds, then i check the exhaust pipe temperatures with my very sensitive hands!!. As far away from the head as possible but equidistant on both cylinders. Health and safety rules say DO NOT DO THIS!!.

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