When I used to service my Kawasaki I followed the service manual and used this handy tool to check and balance vacuum (manifold absolute pressure (MAP)) across the 4 inlet manifolds: Morgan Carbtune - carburetor synchronizer for balancing motorcycle carbs I could not find any similar procedure in the Multistrada manual nor much about Ducati throttle body balancing on line. I have found out that the Ducati throttle pairs have a mechanical linkage which can be adjusted and that each inlet manifold has a bypass screw for fine adjustment. So balancing is technically possible, but seems to not be done very widely. There are is a MAP sensor for each inlet manifold which the ECU uses to decide how much fuel to inject at low RPM. I was thinking of inserting a "T" in the hoses joining the sensor to the manifold and connecting the Carbtune to try to get a manual vacuum comparison. Will this work? Is there any other connection point that I could use to measure vacuum?
Tim, one of the guys here I know well (but rarely frequents the forum) was doing some research on throttle body balancing last year and as you said found there was little/no information available anywhere and nothing in the workshop manual. I'll drop him a line and see if he can be persuaded to pop in and let us know how he got on.
Yes you can balance the throttle bodies. Ducati say you shouldn't so you do need a fairly clear reason for doing so. In my case, after some head work I could feel a two-stage response to opening the throttle, just like a bike with un-balanced carbs. After checking with my dealer that twiddling the adjusting screw wasn't going to void my warranty I used my Carbtune just as I would have on any other bike. The awkward part is getting the reading off the rear throttle body. Both of them have access ports with blanking screws in them. It you have a Scottoiler V-system, the instructions show you to use the front port for the vacuum takeoff and supply a ferrule to screw in. It has an M5 thread. For my throttle body work, I removed all the bodywork and petrol tank to get to the rear port and moved my Scottoiler ferrule to the rear port. After that I could refit the tank and plug the Carbtune pipe onto the rear ferrule through the frame. The front port is out in the breeze so it's easy to screw in one of the Carbtune M5 ferrules. I started the engine and found quite a difference in vacuum. You cannot reach the adjuster while the engine is running at tickover so I stopped the engine and rotated the stub shaft with the adjuster on it until the screw faced the back of the bike. In this position I could feed a screwdriver through the frame to the adjuster and give it a tweak. Then I started the engine again to see what effect it had. It's quite a fine adjustment, I ended up about 1/3 of a turn before I was happy with the balance. There is a yellow paint mark on the screw from the factory setting in case you get lost. I checked my bike again this year after it's second cam-belt replacement service (30,000 miles) and gave it another small tweak. I can feel the difference or else my imagination is telling me so. Sorry I didn't take many pictures. I'll keep watching the site in case I can help at all.
Thanks for sharing your experience and all that good info, Longwayhome. I know on my old bike balancing made a very noticable difference to smooth running just off idle. If I understand you correctly, you inserted ferrules into the throttle bodies replacing screws 4 (blue arrow). I actually thought that these screws could be used as bypass screws to do fine balance adjustments i.e. one screwed all the way in and the other screwed out slightly. What did you use to block off the front ferrule or do you just replace the ferrule with the original screw when you are finished balancing? Did you use the screw indicated by the red arrow to adjust the balancing? The Scottoiler doc here: http://www.scottoiler.com/images/stories/general_guides/Vacuum_connections_general.pdf says that an alternative is to insert a 'T' into existing vacuum hose (green arrow). The rear MAP sensor hose may be easier to get to than the screw - I will see. Do you think the connection location would make any difference to the vacuum measurement?
I had a look at my bike this morning and have a small correction to the post above. I think the screw that will take a ferrule is marked by the blue arrow below (4 in the drawing above). I thought the brass or plastic bronze coloured screw marked by the red arrow below is the bypass screw for fine adjustments? It is not called out in the schematic above, but you can see it near where 11 points to.
The screw marked with the red arrow in the top picture is the throttle stop and if the MTS is like the other Ducatis since the 999 shouldn't be adjusted. The butterfly linkage rod has no adjustment so the mechanical balance must be fixed at manufacture. The screw with the red arrow in the bottom picture is the air bypass screw. There is one on each throttle body and they are the only balance adjustment available. They will also affect the CO at small throttle openings but that may be compensated by the Lamda sensors.
The screw you have marked in blue is the place to fit the ferrules. I put the scottoiler ferrule in the rear and one from the carbtune in the front, connect the carbtune to both ferrules, start the engine warm it up and take a reading. Now stop the engine. The adjustment is made by adjusting the screw on the quadrant between the butterflies, you have a red arrow pointing at it on the diagram above. This DOES adjust the linkage between the butterflies. You have to stop the engine because you can't reach this screw in the bike unless you rotate it by hand against the return spring until it faces to the rear. Then you can reach it with a horizontal screwdriver. Make a small adjustment, release the quadrant start the engine and see what difference you have made. Repeat until balance is achieved. (Don't ever touch the screw you have marked in red on the photo). I put the allen screw back in the front pot and pushed the Scottoiler pipe onto the rear ferrule where it carries on providing the vacuum for it.
Thanks guys for your posts. I am now very clear on the process you followed, Longwayhome. I believe that there are actually 2 ways to adjust throttle balance by using either of the screws that I have marked in red above. The red screw in the schematic will adjust the actual position of the butterflies relative to each other and the screw marked in red in the photo will allow a small amount of air to bypass the butterfly. What I propose to do is fit the ferrules (or insert "T"s) and measure relative vacuum in each manifold. If it needs adjusting I will start with the bypass screws and if I run out of adjustment on them I will turn them both all the way in and try to adjust the linkage screw. I'll document the process and post results here.
Longwayhome, after reading your post above and looking at the diagram again I realise I was wrong now appreciate how the balance linkage works and your procedure makes perfect sense.
Tim.....it would be great if you could take some photos as and when you go for it and make a note of any details and/or tips for doing the job that could be added to Robin's notes to make a full on 'how to' - thanks
Right - It was a rainy Sunday today so here it is: Longwayhome's posts above are spot on and I used exactly the same technique he did, but took a few more pics along the way. In summary all you need to do is to screw an adaptor into each of the inlet manifolds, measure the vacuum and then adjust either the throttle linkage or the bypass screws, but access is an issue. Firstly the tank does have to come off to get access to to the vertical inlet manifold. Lots of screws, but you all know that! I left the whole beak section in one piece and did not take it right off the bike, just left it resting on a towel on the front mudguard. I then made up 2 hose adaptors like so: The M6 thread adaptors and rubber blanking caps I got from Carbtune: Morgan Carbtune - carburetor synchronizer for balancing motorcycle carbs 5mm vacuum hose connector from ebay: Double barbed 5mm hose connector, fuel/vacuum pipes | eBay 7.3 -8.3mm spring hose clip from ebay: 10x Double Wire Band Clamp Spring Hose Petrol Fuel Pipe Clip Size 7.3mm 8.3mm | eBay 120mm hose cut from two of my carbtune hoses they are plenty long enough. The front cylinder does not really need the extra hose as access is easy, but I wanted to make the measurement as similar as possible. Then I took out the rear screw using a flex shaft screwdriver: and fitted the hose adaptor with the o-ring removed and with Loctite on the thread: Also fitted the other hose adaptor to the front temporarily, leaving the o-ring on and without thread lock. Put the tank back on and connected fuel and electrics, but not screwed on for better access. Connected the Carbtune and run the engine until it warmed up. Vacuum was a little out with the rear (left) showing less: After marking the position of each by-pass screw (Red arrow below) I turned both bypass screws fully in: Front bypass screw: rear bypass screw: Then with the engine off I made small adjustments the throttle linkage screw as Longwayhome describes above, you have to rotate it back into a position that you can get a screw driver to it from the rear underneath the airbox. This means opening the throttles so that's why the engine needs to be off. I ended up tightening the screw about 1/4 turn to get the balance right: finished measurement: Looks much better. I will see if I can feel the difference commuting tomorrow...
Many thanks Tim (and Robin)........Tim maybe you can email me the original full size images and I'll add them to my MTS1200 photo galleries ;-) Cheers Andy
All pics here: MTS TB Balancing - a set on Flickr And yes the balancing did make a difference. Idle and pull off from stationary are noticeably smoother. It pays off to balance those big cylinders!
Thanks it was a good way to while away a rainy afternoon! I did rev the bike a little when checking the balance but what happens is that manifold pressure drops away very rapidly as the throttles open. On compression after releasing the twist grip it rises very high. There seemed to be a small lag in pressure drop as the throttle is opened with one cylinder slightly behind the other (can't remember which). The advice that I have read is to set balance at idle and on bikes where you can adjust the idle to keep setting idle back to spec as you adjust balance. As you open the bypass screws on the MTS the idle RPM climbs, which is why I prefered to close both bypass screws and adjust the linkage instead to keep idle speed down. I also believe that mechanical balancing of the linkage would have better results at higher RPM and low MAP over bypass balancing.
Ive just balanced my throttle bodies using the method described in previous posts. Had to adjust 3/4 c/w to bring them into sync. The motor now sounds a lot smoother at idle. Never touched the air bleed screws though, I here what your saying but a little reluctant to mess with them. I did notice the the idle rise after sync then it cam back to 1100ish shortly afterwards. During this process I found one of the Air Pressure Sensors without its hose connected! I believe this is for low RPM. Not had time for a ride yet but im hoping both these are going to make a noticeable difference after years of low rpm surging making the bike near unrideable. I have just ordered Tuneboy kit to enhance her even further...fingers crossed. Many thanks for the informative posts above with regards to throttle body sync, helped a bunch!
Guys, many, many thanks for this explanations . I did the throttle sync without touching the by pass screws. Mine was out of sync also resulting in bad driving at approx. 3000 rpm. I already installed a rexxer kit, but this was not the solution. I see also something else, normal my temp was 73 degrees, now it stucks at 64 degrees? Strange! I have a new ducati!
balancing of the throttle bodies for high speeds 3000+ by using linkagescrew, with closed bypass screws. Adjust idle afterwards by using bypass screws, which is what they are for.
Hi aero, for what I now know the riding of this bike is 100% better then it was, specially when driving beween traffic at low speed. So I assume the the balancing must be good. Running at idle the bike runs much smoother. Are you telling me that this can be better? Can you please explain me how to adjust the by pass screws after I have fully closed them for balancing? Thanks!
