Balanced Throttle Bodies?

[willowstreetguzziguy]

In early June this year, my 1200 Sport needed a major service at 11,000 miles.  A local master mechanic who has worked on Guzzis for many years performed the service.

He called me when it was completed. He wasn't home when I picked it up (mistake) but he had told me the throttle bodies were out of balance and that it should be running better. He made a drawing on my service statement how the bubbles were misaligned on his device.

Upon leaving his driveway, I wasn't out of second gear before I realized "this bike is running rough!" I couldn't go back because he wasn't home. It was a long 70 minute ride home with the 1200 Sport vibrating more than normal and with a worse throttle response. My thinking was "Something's out of balance... probably the throttle bodies."

I called him the next day and took it back a few days later  He attached the throttle body device and showed me the bubbles were dead even.  I said "I see that but it running terrible!" I'm not a mechanic but the problem solver in me said "Here's the drawing of where the bubbles were before you adjusted it.  Adjust them so the bubbles are in this same (misaligned) position" He adjusted them like his drawing showed.  Immediately the idle sounded smoother. When I took it for a test ride, I wasn't out of FIRST gear and the engine felt smooth like it was before.  "First time I've ever seen the factory settings wrong", he said.

My bike was back to running smooth again with great throttle response. I had a fantastic and smooth ride to the NH rally.  I now have 14,000 miles on the bike (got it in 11/13 with 3,8000 miles) and the engine fantastic and it continues to smooth out as the miles add up.

Has anyone ever had this happen to them where the throttle bodies appear out of balance on the gauge but are in actually in sync?

[Madtownguzzi]

I wonder if your mechanics throttle sync balance gauge needs to be recalibrated? Find someone else with a gauge and compare readings.

[willowstreetguzziguy]

Good point. I'll do that and inform him if his was wrong. Thanks

[rodekyll]

Yes, but not without something like a vacuum leak causing the imbalance.

[Bisbonian]

Did he reset the TPS after balancing?

[Vasco DG]

Did he reset the TPS after balancing?

This.

[Wayne Orwig]

There are (sort of) two balances. You need to balance at high speed, and then balance at idle. Did he do both?

[Kev m]

Another "Master Mechanic" who doesn't do something as basic as TEST RIDE IT to verify the work he's just performed? 

[lucian]

I would say it best to learn  do the basic tuning and valve adjustments yourself. It really isn't that difficult thank's to Pete and others who know and are willing to provide guidance. A little research on this forum and you will be off to the races with a much better understanding of the nuances of the 8v motor. A lot of well meaning mechanics out there that will assume it is just another FI twin and no harm can be had by f***ing with this or that. Not the case with the 8v as you just learned. A couple of cheap cables,guzzi diag, and a balancing tool, a feeler gauge and a metric wrench and allen set and your in business. The rest is all right here. I know not everyone is interested in all this, but at least learn the basic tuning premise so you know what should be done if you choose to have someone else do the work. There is nothing sweeter than a properly set up 8v that I have discovered in an air cooled twin. Thank you to Pete and Mark for making it all possible for all of us want to be's.     Dave

[dl.allen]

You need to calibrate the tubes every time then balance the bike
I have played with the motion pro balancer and it can be off just sitting for a while

[redrider]

I use and prefer the vacuum gauge set. I use the ones from JC Whitney and set the balance at 3000 rpm on the V11. Not exactly the same engine but similar characteristics. Very helpful to have some type of valve to dampen the needle movement. Metal, not plastic, aquarium air supply valves work well.

[Vasco DG]

I use and prefer the vacuum gauge set. I use the ones from JC Whitney and set the balance at 3000 rpm on the V11. Not exactly the same engine but similar characteristics. Very helpful to have some type of valve to dampen the needle movement. Metal, not plastic, aquarium air supply valves work well.

And herein lies a lot of the problem. The set-up of Guzzis with the W5AM controller, (With the exception of the Bellagio which is slightly different.) is NOTHING like the set up of a 15M or 15MRC machine.

The TPS setting is an interpretive value. Because the adjustment for throttle body high-speed balance is on the left hand throttle body but the TPS is on the right hand side when you perform the high speed balance you alter the position of the TPS so it's value changes. After the high speed balance has been performed you must re-calibrate the TPS otherwise it's signal value will be incorrect.

The W5AM bikes do not have an air flow sensor. The ability of the ECU to deliver the correct amount of fuel is dependent on correct set up because the only way the ECU knows how much air is passing through the TB's is by *Knowing* how much goes through at any given TPS setting. This is why the TB's are set up on a flow bench by MM and why you should NEVER mess with the throttle stop screws.

YOU CANNOT TUNE A W5AM WITHOUT SOME FORM OF INTERFACE TO RECALIBRATE THE TPS AND CLEAR THE TRIMS.

Pete