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Engine Idle Question

Chris01

Just got it firing!
Joined
Jul 30, 2012
Messages
5
My Griso 1200 8V idles at 1100 RPM bang on. When the clutch is pulled in, the RPMs increase to 1500. It seems like 1500 RPMs is a little high when stopped at a light. I know that there is a sensor on the clutch to tell the engine to do this, but what is the purpose of this?

Thanks
 
Hi
I have a Norge 1200 (2006) and when I got her the idle was all over the place, mainly way too high. My problem turned out to be the base throttle position setting now she idles great at 1100 rpm but just like yours if the clutch is held in the engine speed rises slightly, It does this all the time and if when riding I pull the clutch and coast the revs dont drop to idle speed but remain high the revs never increase from what they were before pulling the clutch though.

In my day job as a motor mechanic I drive a lot of different vehicles and have noticed many cars have similar behaviour programmed into the e.c.u's not only to prevent stalling when stopping but to aid smooth gear shifting, some very early cars had dampers on the carb linkages to do the same thing. (showing my age now) although none of the cars I have driven have increased their idle speed when stationary and just pressing the clutch only as I said when stopping and pressing the clutch to disengage the drive, then the revs stay elevated for a few moments and slowly settle to the programmed idle speed.

I had always thought Moto Guzzi had also programmed this feature to do the same thing, i.e. stop the engine stalling and help with the gear change.(just not quite as sophisticated as the cars)

Perhaps someone else will confirm if this is normal or not but either way I am very happy with mine as she is.
 
As explained elsewhere.

Idle is stepper controlled.

A target idle speed of 1200rpm is programmed into the ECU. If the idle drops below this point the ECU instructs the stepper to allow more air in which will lean the mixture and cause the engine speed to rise. If the idle rises above 1200 the ECU instructs the stepper to reduce air,enrich ending the mixture and causing the engine speed to fall.

Thing is the amounts of air are very small. For the stepper to be able to perform it function properly the engine has to be tuned properly. If both of the air bleeds on the throttle bodies are open the mixture may well already be critically lean and the stepper's ability to control air flow may be marginalized. The way this usually manifests itself is by a high or variable idle.

Why, on your bike, the engine speed is rising when the clutch is pulled in is probably down to simple mechanical factors. The gearbox is new and the sealed bearings, when new, impose a fair bit of drag on the shafts. When you engage the clutch this drag, or at least a substantial part of it, is removed. When this happens the work the engine is producing is freed up to do something else. Namely spin the crank faster.

When the bike goes in for it's first service the valves should be re-gapped, the TB's synced and the TPS re-set. After this is done, providing there are no other problems, the issue should vanish. I always perform these steps on a new vehicle as part of pre-delivery. I have yet to find a pre-2013 bike that came from the factory with only one bleed open. Quite frankly, they aren't set up very well on the production line and if this stuff isn't checked these sorts of niggling issues will rear their ugly heads from time to time.

Pete
 
Thanks for the reply Pete! I see you found my post on both GuzziTech and Wild Guzzi.

Looks like Omnione and I have a similar issue with our bikes. It's my understanding the the Norge and Griso have similar engines (if not the same engine).

At least now, I have a much better understanding of what's going on. The issue doesn't trouble me much, and like you said, after it's next service, it will most likely disappear. Now I just need to put on enough mileage to warrant another service!

Thanks once again.
 
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