Throttle Body balancing

Hello Grisoligists
After reading and absorbing as much as I can from this and other forums, I have a question.

How do you balance the throttle bodies on the GRiSO?
I have had cars with triple Webbers and multiple S.Us etc  but nothing I currently have will do the job on this bike?

Do I need a manometer, flow gage or are we talking old school stethoscope ?

Feed back on procedure and where to get the required equipment is always appreciated.

Mike

I use a Carbtune - u know the 'manometer' with the steel rods instead of liquid? Pete has a fancy electronic gizmo.

Pete will likely be along shortly to write up the procedure, otherwise I can cut & paste one of his from another site...

Short answer is yes, 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

Thanks for another great write-up Pete.  One question, is this part at idle?

Pete Roper wrote:

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.Pete

TIA, Dave in NYC

Pics I stole from Pete to assist.

RH Cylinder air-bleed screw:

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LH Cylinder air-bleed screw:

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Bell-crank screw:

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That's for the 8V. The position of the air bleeds is a bit different on the bikes with the smaller TB's

Yes, the operation performed with the air bleed screw after re-start is the idle balance. Note that sometimes there is no need for an air bleed screw to be open to achieve optimal idle balance but there should never be BOTH open as this will confuse the stepper motor. Or rather the ECU and the signals it sends the stepper.

Pete

rear tube on the G11 as described
and you may have to make an adapter to attach the vac gauges

OK - a bump for the maintenance-challenged, such as myself. The SF-based Guzzi shop wants 1.5 hours [~$150] to perform this, and my better/more reasonable local shop is backed up and seems leery of working on anything Italian.

The Aussies seem pretty well set up with all the necessary equipment, but over here....I, at least, need to set myself up as an entry-level hobbyist n00b.

For a 2010 GRiSO: what manometer, from where?

I can probably use Pete's instructions [above] to noodle things out, but is there an NBG-proof set of instructions that includes pictures and small words?   

Honestly, I'd really rather do it myself. For something like this, spending $$ on repair/maintenance equipment is, to my mind [such as it is] easier to justify than paying someone and hoping they get it right.

Like Beetle, I also have the Morgan Carbtune which is a very nice piece of kit.  Rather than a mercury manometer (or whatever the EPA allows) the Carbtune uses stainless steel rods.  Durable, reliable, no muss, and no fuss.

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You can buy it directly from Morgan Carbtune in the UK

~$90 for 2-column Carbtune w/tool pouch shipped to USA (this is what I have - great if all your bikes are twins)
~$112 for 4-column Carbtune w/tool pouch shipped to USA (get this if you have 4 cyl. bikes as well)

Another option is the CarbMate which has gotten good reviews from other Guzzi sites, but I have neither seen nor tried one.

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They are available on Amazon for $95.00

Or you could also just buy a Motion Pro manometer at Cyclegear or probably any auto parts store for $80-$110, but don't break the tubes...

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The sync procedure is easy as pie and takes no more than a half hour where most of that time involves getting the engine temp above 60℃. OK, the first time might take you a bit longer, but once you get the procedure down, it's easy as pie.

As for the procedure, there is a member on Guzzitech who wrote up a nice step by step protocol.  Here is a link.  It was written for the Stelvio 8V, but it also applies (obviously) to the GRiSO.

You can also find an abbreviated protocol in the Guzzi service manuals ([You must be registered and logged in to see this link.], but it is not as comprehensive as the procedure linked above.

Just remember that you have to reset the TPS (simple with GuzziDiag) every time you sync your TBs.

As for fitting to attach the tubes to the gauges? Simply buy a pair of 6mm thread, (8mm hex.) Brembo brake nipples and grind the pointy end off. Voila! Instant adaptor!

Another thing to be aware of is that they generally hold their tune very well. While especially the 8V's are very sensitive to throttle body balance once it has been set up accurately once it will generally remain calibrated for a long time unless the bike has some sort of mishap. I mean? When was the last time you played with the set-up of the fuel injection system on your car? Probably never would be my guess! While with a twin throttle body system there I more potential for thing to get out of adjustment than there I on a 'Conventional' single TB car set-up everything is pretty rigidly mounted and hard to upset.

Pete

Yeah. I was looking through my maintenance paperwork, and while I just passed through 9000 on the oddo, I'm virtually certain the throttle bodies haven't been touched; they certainly weren't during the 6k service.

It I quite common for bikes to leave the factory with both air bleeds open. Why such a basic bit of tuning int carried out I have no idea but getting it right will result in a much smoother and more even idle, consistent behaviour during warm up and better off idle pick-up.

Pete

Well, this was a big success. My CarbMate and I took it to my GRiSO 8V, and by all objective measures it was a success. The CarbMate vacuum cables required no adapters.

Read Pete's post [above] and hit the above-referenced GuzziTech post prior to doing this procedure.

The air bleed screws are harder to get to than may be imagined; with the crash bars that came with my bike, the left one was goddamned tough to access.

But I was victorious. The bell-crank adjuster needed some, er, adjustment with a 7mm box wrench and as Pete mentioned above, both air bleed screws were open [left much more so than right, but still...].

As I had no helper, I used a 3mm hex wrench jammed in between the throttle and cable housing to hold the throttle at 4000 RPMs for the first set of adjustments.

Necessity is the mother of invention. Good work NBG!

BTW this is a twin a manometer for this is like $7 and is more accurate than any on the market tool just get about 10ft of clear plastic hose 1/4" and tape it to a yard stick, then put about 36" of two stroke oil in the tube bend it into a u and tape it to the piece of anything yardsticks are free at home store. you have then 18" of oil on each side then hook each tube to the ports with a 6mm adapter (buy from motion pro) or use the factory banjo fittings you are going to plug them any way later.

balance till the oil is at the same level

use smoker oil then if you fuck up and suck it into the motor no harm done just refill.

two stroke oil is lighter than any of the carb tuners fluid, and this set up is way more sensitive and reliable than the electronic pressure sensors.

Pete Roper wrote:

....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...
Pete

I have a (perhaps stupid) question about that.
Balance should be obtained at a specific RPM (for example 3.8k) OR in a range of RPM (for example between 3 and 4k)?

I am seeing Ahdammit's carbtune results and he's getting an averagly good balance in wide range of RPM
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Not sure of I can get it like this on my bike...

Some people claim to have increased the overall accuracy by repeating the proceedure a few times and re-setting the TPS in between adjustments. I can't personally see how this works but I have seen improvements myself.

Really though it is highly unlikely you will be able to achieve 'Perfection'. I just aim to get the high speed balance *Right* in the 3,500-4,500 range as when under load this sort of throttle opening is most likely what you'll be using on the cruise where you want things smoothest. When that's right I sort out the idle.

Pete

Ok, got it.

Just for curiosity, a local guzzi mechanic told me he plays with the linkage rod to get the bodies perfectly balanced between 2 and 3k.
Why should one play with the rod when you ca use the screw? Aren't they both moving the RH butterfly?

Is this something that even has to be done? Well, I guess it is, but on "modern" bikes, this should be a set and forget thing?

That being said, I overfilled my oil once and should probably remove and clean the TB's. Which will of course lead to me having to balancing them. Ugh.

voulga77 wrote:

Ok, got it.

Just for curiosity, a local guzzi mechanic told me he plays with the linkage rod to get the bodies perfectly balanced between 2 and 3k.
Why should one play with the rod when you ca use the screw? Aren't they both moving the RH butterfly?  

Well I'd avoid taking my bike to him then! The whole point of the bell crank arrangement on the linkage is to ensure that the butterflies open in synch. If you adjust the rod they will open differentially as the throttle angle increases. The system doesn't use a mass flow sensor, it depends on the ECU *Knowing* how much air is being passed by the throttle angle and air density. Screw with the linkage rod and that's stuffed.

Pete

That's what I thought...

What I like about Pete is that his answers are documented

so i just recently picked up a new 2013 GRiSO with 0 miles. factory leftover.
from what im reading it seems that a lot of bikes seem to miss this service somehow. should i be concerned that mine need to be synced also? i've never ridden a MG before and only have experience with inline japanese 4's. how would i be able to tell if my bike needs to have this done?

Very easy preliminary check is to grab a 5mm Allen key and see if one, both or neither of the air bleeds are open. If both are open, and they usually are on new bikes, then the TB's have never been balanced correctly.

Before you touch anything I suggest you do some research on the proceedure. It is very simple but if you galavant in and start messing with stuff you can end up in a world of pain.

Under NO CIRCUMSTANCES touch the throttle stop screws on either throttle body.

You also need to have a tool, (Guzzidiag or equivalent.) for re-setting the TPS after the high speed balance is done.

Pete

How to tell? Generally speaking, poor idle, hunting, vibes. You may get one jug hotter than the other and even pinging if it's really bad.