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The Sacred Screw, the elusive 4.8, my story

The bikes came out acceptable but could be better with a flow bench set up. Same bikes had issues with stepper, that's how they got messed with instead of changing stepper.
Later plastic stepper is way up in price from when they came out at least 10yrs ago.
 
Mines running better than ever just from fixing some small vacuum leaks and valve adjustment and cat removal .I’ve had it about a year and don’t know much of its history since po was deceased when I bought it from his wife. I know from the mileage it hadn’t been ridden much and aside from a few hand written notes in service manual that’s about it. I’m going to do the sync and reset this week sometime. I wonder if some of the language about the tb being unusable is to some degree is lawyer talk to keep big brother content as far as tampering and emissions go.
 
Although that method might be a crude band-aid, it is not very accurate. If it were that simple, the factory would have said so. They said the exact opposite.

The screw is set at the factory flow bench, then fixed with solder and/or paint.

You have to consciously screw with it to muck it up. Not recommended.

Caveat emptor.
 
... I wonder if some of the language about the tb being unusable is to some degree is lawyer talk to keep big brother content as far as tampering and emissions go.
I'm not sure why you're persisting... do you have some reason to disbelieve the situation as described? what seems unlikely to you about the flow bench answer?
 
I’m just curious and find it strange and quite frankly unbelievable that there’s no practical way way to readjust if necessary. It’s just my nature to try to understand things that seem out of the ordinary.
 
I’m just curious and find it strange and quite frankly unbelievable that there’s no practical way way to readjust if necessary. It’s just my nature to try to understand things that seem out of the ordinary.

Curiosity is one thing but you seem unprepared to accept the fact that some things just don’t tolerate tinkering with.

All throttle-bodies are calibrated on flow benches and so were carburetors. That’s why the manufacturers put plugs over the idle mixture screws.

When I was a young man, I thought the same way about VW Kombi Fuel infection air mass meters. The service manual tells you not to touch the wire but of course I did.

It was a one-time-only very expensive mistake but I learned.
 
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I’m not wanting to tinker with anything I’m mostly curious as to why whatever the process is can’t be repeated. When I was young carburetors didn’t have the caps on the adjusters and fuel injection was for the most diesel only. Adjusting the idle speed and a/f mixture setting was part of regular maintenance. If it requires a flow bench that’s something not too awfully uncommon so it would make more sense to me to have a service procedure and specs rather than throwing a 1600.00 part away and buying a new one. Whether it’s been tampered with or not eventually it’s going to need some attention like all things mechanical.
 
I’m not wanting to tinker with anything I’m mostly curious as to why whatever the process is can’t be repeated. When I was young carburetors didn’t have the caps on the adjusters and fuel injection was for the most diesel only. Adjusting the idle speed and a/f mixture setting was part of regular maintenance. If it requires a flow bench that’s something not too awfully uncommon so it would make more sense to me to have a service procedure and specs rather than throwing a 1600.00 part away and buying a new one. Whether it’s been tampered with or not eventually it’s going to need some attention like all things mechanical.

A quality flow bench at a dealer would be cost prohibitive considering if you don't mess with the screw it isn't needed. If you mess with it you pay the price for a new part. It is a matter of economics. It is expensive enough to be a dealer. Overhead just for the required software is very high as not only is there the initial cost, but the annual fee to use it.
 
Square One: the TB valve is set on a flow bench to a specific CFM value. The air output of the stepper motor is calibrated to match that value for hot or cold starting and running. So is the fuel supplied by the ECU for hot or cold starting and running. This set-up meets Euro 3 emission standards. If you alter the throttle valve setting, the harmony in the system is gone. You will have more ore less air entering the throttle than what the design criteria specified. That is why MG says the throttle body must be replaced. To tell you anything else would leave them in a situation where they encourage tampering with emissions. Not likely.
Your bike should start from cold or hot with no use of throttle whatsoever. A cold start should give you a 1250 rpm idle and stay there till the bike is fully warmed up. Once at operating temperature it will often idle lower than that. A hot start (gas station) should give you a short burst of 1750-1800 rpm before the stepper motor finds it's proper position for the engine temperature, and returns to the 1200 rpm area. After that half hour coffee break, it burbles contently up to 1200-1250 rpm area.
I have "recued" 3 TB set-ups. If you are "out to lunch", you can use my early measurements to get started, but the key is in the idle speed, where the goal is to come close to the flow-bench target. Baby steps! If the idle is low, raise the TPS from 4.6 (if that is the reference on your diagnostic system), to 4.7, then re-set to 4.6. Go ride, and watch your idle. One decimal at a time with riding time in between. And I mean a full day in the saddle so you are sure you have a clear picture. Any idle above 1250rpm during the day is too high, so back it down one decimal step at a time.
You should end up with hands-off starting and your fuel consumption computer in full agreement with what you meter into the tank.
It can be done with patience and persistence (and access to diagnostics). When working as it is designed to do, it is a great system.
 
This is tedious and I for one am completely over it.

I don’t care what you do. Have at it. I’m tired of this.

[Imagine the fun this will become when he discovers the stepper motor]

It never ceases to amaze me when newbies to Moto Guzzi motorcycles want to have an impetuous fit at why things don’t bend to their will, rather than take at face value, the information that numerous people who have owned, ridden, and wrenched on Moto Guzzi, some their whole lives, generously share with them as well as what the factory even says.

Do whatever the hell you want but please…

Give it a damn rest. :banghead:
 
Hello all.
One question. Is it possible to use TPS sensor PF3C and set 150 mV at zero TPS position and after it set the 4.7 TPS position by corresponding voltage?
 
OK. And does anyone know exactly the flow that needs to be set?
 
OK. And does anyone know exactly the flow that needs to be set?

You are not understanding the concept here.

There is no set 4.8 value. There is a range and the reason there is a range is because no 2 throttle-bodies will breath exactly the same.

The initial setup is done on a flow bench. (You cannot home-build an accurate one.)

Air flows through the flow-bench ducts on both sides of the cabinet.

On intake, the air blows out the vents; on exhaust, air is sucked in.

The test device (whatever it is being tested) is mounted on top of the cabinet over the baseplate opening.

A test pressure meter (pressure transducer) measures the pressure or vacuum at the base of the test device (just under the baseplate).

Test pressure is the differential pressure as measured between atmosphere and a point just under the baseplate of the flow bench. This is essentially the total pressure drop across whatever is being tested or bolted to the flow bench. The test pressure is set to a standard value, for instance, 25.0" (60.0 cm) of water, by entering the value on the bench control panel. The flow meter (another pressure transducer) measures the pressure difference across an adjustable flow orifice inside the flowbench.

The amount of flow then displays in cubic feet per minute, liters per second, or cubic meters per hour (cfm, lps, or cmh) on the display panel.

By selecting different ranges for testing, the flow meter can maintain high accuracy over a wide range of flows.

Most flow-benches have twenty unique flow ranges, 10 for intake and 10 for exhaust. This insures the highest accuracy flow measurements from near 0 to 1000 cfm (0 to 470 lpm).

All of these other measurements or sideways methods of trying to back into a correct TPS value for a throttle-body which has been messed with, are rough approximations at best.

Without a flow-bench, there is no accuracy. You are just guessing.

In answer to your final question, NO. The factory publishes no values for the throttle-body dynamic flow settings because without a calibrated flow-bench, the values are of no use.
 
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Norge or all guzzi with ECU IAW 5AM using the PF1C TPS senrsor. TPS sensor PF1C is linear TPS sensor, in this case we are able to set 4.7° as difference value.

In this case should work the process:
- For the reset, find the absolute closed position (point where it stops moving closed) hit reset TPS button.
- turn screw till software says 9.4*, hit reset TPS button. (9.4/2=4.7)
- It is set to 4.7° now
 
Norge or all guzzi with ECU IAW 5AM using the PF1C TPS senrsor. TPS sensor PF1C is linear TPS sensor, in this case we are able to set 4.7° as difference value.

In this case should work the process:
- For the reset, find the absolute closed position (point where it stops moving closed) hit reset TPS button.
- turn screw till software says 9.4*, hit reset TPS button. (9.4/2=4.7)
- It is set to 4.7° now

Oh my God. Are we going to reopen this can of worms?

Please.

People who have disregarded Moto Guzzi’s warning, and they mess with the throttle stop plate “sacred” screw, have destroyed their own motorcycles and ruined their running condition.

THERE IS A REASON WHY MOTO GUZZI GOES TO SUCH GREAT LENGTHS TO KEEP YOU FROM FIDDLING WITH THIS NON-ADJUSTABLE COMPONENT!

This is not how you use a TPS reset.

What you are suggesting here is tantamount to madness.
 
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Norge or all guzzi with ECU IAW 5AM using the PF1C TPS senrsor. TPS sensor PF1C is linear TPS sensor, in this case we are able to set 4.7° as difference value.

In this case should work the process:
- For the reset, find the absolute closed position (point where it stops moving closed) hit reset TPS button.
- turn screw till software says 9.4*, hit reset TPS button. (9.4/2=4.7)
- It is set to 4.7° now
You are wrong, and it has been discussed earlier in this thread. The throttle plate edges are beveled at 85 degrees. This information is stamped into the throttle plate. When you back the throttle stop screw all the way out, the throttle plate will be fully closed at 5 degrees from perpendicular (90 degrees to the bore).
This converts to a 3.75 mm throttle valve "angle" in a 45 mm bore.
If you double the TPS re-set from there, like you suggest, you will end up with a much larger valve angle than desired, with the TPS set to 4.8 mm, which is all it knows when re-set. With a linear TPS you will run extremely lean from bottom to top of the throttle range.
In the words of Joe Minton: "The bike is already caught between running too lean, and being too lean to run". Don't make it worse!
But by all means arci, fill your boots.

A recent operation on my right hand has kept me off the key-board for a while. What is posted here is workable if you have the patience and understanding, and it beats the $1500 alternative.
Like Scott, I think we have beaten this subject to death.
 
A recent operation on my right hand has kept me off the key-board for a while. What is posted here is workable if you have the patience and understanding, and it beats the $1500 alternative.
Like Scott, I think we have beaten this subject to death.

Welcome back! You have been missed. 😀

Yes, truly beaten to death.

Sometimes, I feel like I’m preaching to Lemmings, who are charging full blast off the cliff overlooking the rocks 1000 feet below.
 
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