Home-tuning a Breva V1100 etc

[GrahamNZ]

Unless you are fortunate enough to have access to a mechanic with the equipment and knowledge to tune these bikes, or want to be as self-sufficient as possible as far as tuning goes, these notes may be of help. They have been posted a number of times on GuzziTech but the chequered history of this generally great forum has caused a lot of the older technical guide-notes to be lost. Anyway, here we go.

As well as the common hand tools you need a vacuum balancing tool and a VDSTS diagnostic/tuning kit and a PC laptop to tune these bikes. Going by “feel and ear” just won’t do it.

At every scheduled maintenance interval, tuning is necessary. While new bikes should be properly tuned ex-factory, some are not so should be tuned at the first service, or before that if throttle response is poor. The tuning covered here includes setting the tappet clearances, synchronising the throttles and resetting the throttle position sensor (TPS).

Tappet clearance adjustment

This is the first tuning step because it can alter the volumetric efficiency of the cylinders. Although the Workshop Manual calls for the petrol tank to be removed that isn't necessary, which is good because disconnecting the rather fragile "quick release" fuel line is tricky unless you know what you're doing.

However it is necessary to raise the front of the tank for access to the top rocker cover screws. To do this just remove the rear tank retaining bolt and the front-of-tank air duct then move the tank back a bit, raise the front and move the tank forward again so it rests on top of the front locating rubbers each side. For even more access, raise the rear of the tank onto a block of wood about 40mm thick.

• Remove the outer spark plug lead covers, rocker covers and outer spark plugs.
• Remove the round plug over the crankshaft front nut and turn the engine, always forwards (clockwise when viewed from the front), with a 24mm socket and ratchet.
• Check the clearances on each cold cylinder separately with a feeler gauge with the piston at TDC on the firing stroke and both valves closed. To find this position, turn the engine until the inlet valve has just closed then check the rise of the piston to TDC by shining a torch into the spark plug hole. It's easy and near enough is good enough.
• Use an 11mm ring spanner and small adjustable spanner to set the tappet clearance between the rocker foot and valve stem top. Inlet 0.10mm and exhaust 0.15mm. There seems to be a tendency for the clearances to increase slightly, which is better than the opposite.
• If the cover gasket has been damaged or leaking, fit a new one. They're cheap, so it's wise to have a spare pair available before you start.
• At the same time (10,000km intervals) the handbook calls for new NGK BPR6ES outer spark plugs, gapped to 0.6mm, to be fitted.

Synchronising the throttles and resetting the TPS

These bikes like to have the throttles very well synchronised and for that reason a very sensitive vacuum balancing tool is desirable. An oil-filled manometer is probably the best tool for this because it’s more sensitive than a mercury manometer and much more reliable than a gauge-type vacuum balancer. It’s important to understand how the throttle system works in order to avoid making unwise adjustments.

General arrangement
• The left throttle body carries the throttle-stop screw, which is factory set and must not be altered. It sets the left throttle butterfly mechanically at a base position of 4.5º to 4.9º with the throttle closed.
• The right throttle spindle carries the TPS which must be zeroed electronically whenever throttle vacuum balance is adjusted. The TPS should also read 4.5º to 4.9º with the throttle closed and the engine stopped.
• TechnoResearch VDSTS specific to the bike model is needed for the ECU type IAW5AM to set the TPS zero position of the adjustable right throttle to agree electronically (but not physically) with the pre-set position of the non-adjustable left throttle.
• Idling speed and mixture are dealt with automatically by an ECU-controlled stepper-motor and cannot be adjusted manually.
• Both throttle bodies have air bleed screws which act independently of the ECU and are used only to perfect idling vacuum. Both screws should be closed or just one slightly open.

Using VDSTS on a laptop
The standard cable supplied with VDSTS is for connection to a laptop old style 9-pin serial port but VDSTS can be purchased to include a Keyspan serial to USB adaptor for connection to a USB port. That adaptor needs the software driver supplied on a CD with the unit to be installed on the laptop in order to function.

• Install VDSTS from the VDSTS CD. Open the progression of relevant VDSTS folders and subfolders and then the one for XP or whatever operating system your PC has. Open it and click the setup icon to install VDSTS.
• Once installed, use the desktop icon to launch VDSTS.
• On the first window to appear press the English language button.
• On the next screen to appear click on the Communication tab at the screen top and from the drop-down menu click Port Setting. A window will appear and at the top of it a panel labelled VDST with up/down arrows beside it. Move through to choose the appropriate Com port on your laptop which you are to connect through and click OK. Unless you know the Com port number you may need to re-visit this to get connection to the bike.
• With the cables connected to the bike and laptop and the kill switch on Run, turn on the ignition and click the bike icon button (Brand/Ecu/Model) and then VDSTS will automatically search for and identify the Ecu type and show the type on the screen bottom. For Breva V1100 this is MM IAW5AM. A window will appear indicating the Ecu type found and asking you to confirm if that is correct.
• Now press the HotSync button to connect VDSTS to the Ecu. Once connection is confirmed, all the buttons along the top of the screen will become active.
• Press the dials button (Gauges/Meters) to display data including the TPS reading. Open the throttle progressively and the TPS reading should respond accordingly. For Breva 4.5ºto 4.9º with closed throttle and 84.2º to 84.5º fully open.
• NB The Breva V1100 has the left throttle plate factory set at 4.7º + or – 0.2°and the idle stop screw on the left throttle body must not be touched at all.
• To reset the TPS, press the screwdriver icon (Active Settings) and then select TPS from the tabs towards the screen top. That will take VDSTS to two windows where resetting the TPS are dealt with but only the left window is active. Press the TPS/screwdriver button and a warning will come up that resetting the TPS will affect the engine operation. Press OK and to the right of the screwdriver icon a seconds count down will appear and when finished Pass should appear together with an ECU Reset window. This window will invite you to turn the ignition off for a minimum of 13 seconds and then to turn the ignition on again. When done, press OK.
• Return to the Gauges/Meters screen and the reset TPS reading will show. At this stage the TPS resetting is done but you can go on to check the function of many components by going to the icon which looks like a fuel injector (Active Test) and then activating the various options presented to you. All quite fun really.

Throttle synchronisation
This is done by balancing the vacuum readings.
• Start the engine and warm to 60 degrees C and then stop it.
• Remove the M6 blanking screws on the outer sides of both throttle bodies and fit vacuum hose nipples. Connect vacuum gauge hoses to the nipples and close both throttle-body air-bleed screws so any vacuum balancing won’t be influenced by the air bleeds.
• Start the engine and gradually increase the speed to a steady 3,000 RPM. If the vacuum readings at 3,000 RPM are not very close to each other the balance will need to be adjusted and the TPS reset again.
• Vacuum balance is adjusted using the adjusting screw on the left end of the link rod. Moving the screw is best done when the engine is just idling, before returning to 3,000 RPM to view the result. The rod length should not be altered by moving the ball joint ends because that can affect the parallel movement of the throttle levers and give unequal opening as the throttles are opened further.
• Stop the engine and re-run the VDSTS TPS resetting procedure. This is essential because any adjustment of the link rod will have moved the TPS position at the same time. VDSTS then tells the ECU to treat the TPS physical position as matching the mechanically-stopped left throttle.
• Start the engine and at idle fine-tune the vacuum balance by opening only the air bleed on the side with the lower vacuum reading.

What to do if the throttle stop screw has been tampered with
You can tell if the in-hex headless screw (the “sacred screw”) has been tampered with if its head is no longer filled with yellow paint. Here is a method of resetting the "sacred screw".
• Using VDSTS reset the TPS as described earlier.
• Close both air bypass screws.
• Using a vacuum gauge set, balance the throttle vacuum as described earlier.
• Reset the TPS again.
• Use the air bypass screws to balance the idling vacuum. At this point you know that the throttles are balanced mechanically and electronically.
• The idling speed now is likely to be too high or too low but otherwise the engine should throttle well. To set the idling speed to the correct 1100 to 1150 RPM adjust the sacred screw as necessary.
• Reset the TPS again. This is necessary because the TPS will have moved relative to the left throttle position as set by the sacred screw.
• Fine tune the idling vacuum again using the air bypass screws.
END

[john zibell]

Graham,

Thanks for re-posting. I'm sure many will find it useful.

[dimitris]

This is a great and very useful post! Thank you Graham!

[2Laner]

Thanks again Graham. It is such well written and concise "how to's" that enable me and others, with limited mechanical background, to still be able to enjoy and be somewhat confident on basic servicing.

[GrahamNZ]

As posted elsewhere, for really perfect idling vacuum balance, the stepper-motor should be isolated when adjusting the relevant airbleed screw. It can be isolated using one of Todd's isolator kits, or in the case of a Breva at least, by temporarily slipping the airline which leads to the stepper-motor off the airbox nipple - readily accessible from the right hand side inboard of the injector body - without any dismantling being required - and plugging the hose end with an 8mm bolt etc.

[rguzz]

Just read your tuning article. Excellent reference for those of us who wish to dabble.
A question Graham, can I use this method exactly same on 8v Griso, or are there any differences?

[Zapa]

Printed!

[3ackok]

What kind of a vacuum gauges are suitable for balancing? I remember that Graham built a differential device with tubes and oil, but I'd like something smaller and leak proof. I checked out automotive gauges, and their range is 30"/ 70cm Hg. Service manual calls fir difference between the cylinders of less than 1cm Hg, which can't be reliably measured on 70cm gauges.

[pete roper]

The system for all the CARC bikes apart from the Bellagio is essentially the same. The only difference with the Bellagio being it uses the throttle linkage ystem as used on the Californias rather than the linkage rod used on Brevas/Grisos/Norges/Stelvios etc.

FWIW although Graham says that things like the TB ballance and TPS should be adjusted every service in my experience once they have been set up right once at the first service they will rarely need adjusting again unless something is replaced or the whole set-up is subjected to a large shock, (Like a crash of some sort.).

While I was particularly anal about my 8VG when I first got it what with it being an almost completely new design etc. I found that not only was the TPS set accurately ex-factory but the TB's were pretty much spot on as well. In fact the whole thing was pretty good, as have been the other 8V models I've dealt with. I checked and double checked stuff repeatedly over the first 2-3,000Km to see what, if anything, changed and all the FI stuff remained obstinately spot-on. The older pushrod bikes all seemed to come from the factory with their TPS's set wrong and sometimes their TB ballance was a bit 'How's yer father?' but overall they seem to be set up pretty well. Most of the 'Problem' bikes I've seen have been the result of mechanics at other shops doing stuff wrong or touching things that they had no need to touch. Once set up correctly what is going to cause stuff to change? I mean, when was the last time you gave the EFI on your care ven a second thought?

Check stuff by all means, but don't be at all surprised if it is exactly like you left it the last time you looked and if the bike is running fine don't feel *obliged* to change stuff just 'cos you've got the tooling hooked up. That road leads to madness!!!!

Pete

[3ackok]

Pete, you are probably right about TB stability, however it would be helpful to check it from time to time. If it slowly drifts away it will be hard to notice until it gets seriously off.