First time balancing throttle bodies - well that was easy!

During the last month I'd noticed that the bike was smelling a bit 'fuelly' while waiting at lights and pulling up to a stop so the other weekend I pulled the plugs.
The right hand one didn't look great.
(I replaced them both).


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Checked the valve gaps -
Right hand side inlets had closed up a little. Exhausts were still correct.
Left hand side inlets and exhaust were still correct.

TPS was reading 4.6.

I had ordered a Carbtune a little while ago but whilst I understand the process, sometimes I like to see something done once before diving in myself.
So I'd dithered and never done them.

Now I just got on with it.


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Followed Pete's instructions below and it really couldn't have been easier.
Bell crank adjuster needed a quarter turn clockwise.
Right throttle air bleed needed to be opened slightly.
TPS back to 4.8.

Went for a ride and all seems good.
Didn't notice any smells.
Need to do more miles but the heavens have opened this week.

Thanks for the easy to follow instructions Pete.

Pete Roper wrote:

you need a manometer of some sort. You'll also need some form of diagnostic device, (ie Guzzidiag.) to recalibrate the TPS after doing it.

Apart from this the procedure for all the W5AM equipped CARC bikes is identical and incredibly simple.

Firstly close both of the air bleeds on the throttle bodies. These are, in the 1100's in the outside of the throttle body underneath in one of the 'Tubes' cast into the body itself, I think its the rearward one but I don't have a bike handy right now. It needs a small, flat bladed screwdriver. On the 1200's it is a 5mm Allen key 'Tube' right on the inside of the TB facing down as well. Its a bit of bugger to get to but its not really a big deal.

Once these are closed  and you've removed the screws from the inlet manifolds or disconnected the suck hoses for the charcoal can on US bikes start the bike and warm it up. You can connect your scan tool/Guzzidiag while its warming up.

Once its above 60*C you can hold the throttle open so that the engine is spinning about 3,500-4,000 RPM and check the balance with your manometer. If the depression is unequal on both sides use the screw on the bell-crank adjuster on the LH TB, NOT the linkage rod to adjust the balance at that engine speed. Once it is balanced at 3.5-4.0K let it off the throttle and kill the engine.

Fire up Guzzidiag and connect. Go to the 'Measurements' page and check the TPS setting. If you have had to use the bell crank screw to balance at high speed the chances are the TPS will be out.

Choose 'Actors', follow the prompts and do a TPS re-set, then go back to 'Measurements' and the TPS reading should flick to 4.6 for an 1100/1200 2VPC bike and 4.8 for a 4VPC machine.

Re-start your engine and look at the manometer. Whichever side has the highest manifold depression use the air bleed on that side to lower it until both sides are running identically.

Disconnect everything and re-install the manifold plugs or reconnect the charcoal canister suck tubes.

Job done. It really is a delightfully simple procedure. Much, much easier than most carburettors!

Pete

Did the same as you Clancy a few months back. First time too. Had to get Guzzi diag going and then bought the Carbtune a well. With help from Pete and Beetle it all came together. It’s good because there is no shop near me. This site and ghetto members are invaluable.

JohnA wrote:

Did the same as you Clancy a few months back. First time too. Had to get Guzzi diag going and then bought the Carbtune a well. With help from Pete and Beetle it all came together. It’s good because there is no shop near me. This site and ghetto members are invaluable.

Sorry, I know this is an old old post, but does the type of manometer matter? All I can seem to find is digital, but everyone seems to have these water looking ones. I don't want to get the wrong one, they're a tad expensive..

Not really. Digital is fine. I've got a 4-cylinder Carbtune that I've had since ..well, since I rode 4 cylinder carbed bikes, so back in the cryptozoic era...

Carbtune is now available in 2-cylinder version. I recommend them.

I was replying to your other post which you must of removed but since it might be helpful this is what I wrote.


Basically a manometer is a device that will measure the change and or difference in pressure between two places. In our case you are measuring the difference in pressure from ambient air pressure and the pressure in each of the inlet manifolds. The aim of balancing the pressure differential between the two inlet manifolds is to ensure that the same amount of air is passing into each cylinder so that, assuming they air/fuel mixture is correct, both cylinders work the same as each other rather than one working harder than the other which will cause rough running and vibration and may upset the air/fuel mixture of one or other cylinder.

An engine is simply a self propelling air pump. It uses fuel it burns to expand gas which is then turned into mechanical work. By balancing the throttlebodies you get each cylinder to produce the same amount of work at any given throttle opening.

There are a variety of options for manometers for our purposes as you have found. These range from simple tubes filled with fluid through to more sophisticated electronic devices but for the home mechanic who doesn't want the inconvenience of the former or the expense of the latter the commonest types are either vacuum dial gauges, something like this....

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Or, much favoured by many here, the Morgan Carbtune.....

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The disadvantage of dial gauges is that many nowadays are cheap and inaccurate. If you get a decent set? They're fine. But an inaccurate set is worse than useless.

The Morgan set-up uses chromed rods in close fitting tubes and is hardy, robust and accurate.

For the professional you can't go past

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Which is what I have and it is a useful diagnostic tool as well as being super accurate for TB balancing but the price will make you swoon and it's complete overkill for the home mechanic.

With the W5AM system used on the CARC Guzzis both a manometer and some form of diagnostic tooling like the excellent Guzzidiag is required to perform the task. It simply cannot be done by guesswork or fiddling.

I took down the other one since I got my main answer and didn't seem like it contributed much else. I appreciate you taking the time for a further in depth explanation! I'm hopefully going to be going to attempt this next week. Went with the carb tune pro 4. Hopefully if I do this properly I can actually get the bike to run properly and decent. If it still doesn't I have more ripping apart to do by the time I get this thing running good enough to not need to tear it up every week, I'll be a full fledged mechanic hahaha

If it still doesn't my guess is that the TB's have probably been irretrievably buggered by some previous owner. If that's the case you can start searching for a second hand set from any of the 2V CARC bikes, Breva, Norge or GRiSO but make absolutely sure that the paint is intact on the throttle stop screws and the linkage ball joints.