RentAGuzzi Motorcycle Rentals & Tours – Los Angeles CA
  1. Ciao Guest, We've completed the split of this website from our custom bike builds and products to our sister site; GTMotoCycles.com. You may need a new username and password to get into the new GTM Store system - pending and past order info is available there. GuzziTech.com is now a secure site (https), and may require you to sign in again using your same password. We are back to our origins here with the Forum and Resources only. As always, zero tolerance on personal attacks and off-site links to other Forums or competing products. Note there's decades of Guzzi hands-on experienced help on this site, all whom give endless amounts of their time for free - be courteous. For those who are new here, the owner of this site (Todd - GT-Rx) has been immersed in Guzzis since 1999. He's raced and wrenched for two-thirds of his life, both Pro dirt-track and road-race, and contributed to Cycle World Magazine 2000-2007. He began Guzzi dyno performance modifying and fuel tuning in 2001, and has been wrenching them full time since 2007. His GT MotoCycles Performance and Service workshop has been open for ~4 years in Orange, CA. We do not have a phone number for this site or GTM, we're online only... do not ask us to call you. Click on the Service tab above for more info or to book an appointment -- it is not a retail shop to visit. If you're in L.A., you can come sample our work with our rental fleet - click the image link above. In a few short years GuzziTech.com will hit the 20 year mark of providing advice and tech tips for free. Understand that this is a privately paid for website, not a free social media platform littered with ads to help pay for it. Donations appreciated via the Account upgrade (see Site Support section below) or the Donate tab above, which unlocks all of the content here along with the Classifieds, Ask the Wrench sections and our seasonal discount notices. Thank you for all of the continued support and contributions.

The Sacred Screw, the elusive 4.8, my story

Discussion in 'CARC' started by Nordicnorm, Aug 11, 2014.

  1. vincedeguzzi

    vincedeguzzi Just got it firing! GT Famiglia

    Joined:
    May 31, 2012
    Messages:
    18
    Likes Received:
    1
    Location:
    Zurich, Switzerland
    Hello Scott

    I donated 50US some time ago, I remember that Todd replied me, that this was too much :))
    Your forum is for us Guzziisti in europe also "sacred", like the famous "Guzzi-sacred screw"

    Ciao
    Vince
     
  2. scottmastrocinque

    scottmastrocinque High Miler GT Famiglia

    Joined:
    Jun 26, 2011
    Messages:
    536
    Likes Received:
    196
    Location:
    Findlay, Ohio
    Awesome. Ciao!

    Scott
     
  3. Nordicnorm

    Nordicnorm Cruisin' Guzzisti GT Contributor

    Joined:
    May 12, 2011
    Messages:
    122
    Likes Received:
    17
    Location:
    Vancouver Island BC
    Vince!
    You are brilliant! Not only were you able to decipher all my mumbo-jumbo and make sense of it and make it work for you, you have also added the drawings that were so badly needed to make it easier to understand. When I posted the original, I had never added a picture to a post, and because I could understand my own explanation, I never thought of taking it that step further. Thank you!
    You should have seen some of the things I rigged up in my shop at the time, to determine what that number 4.8 really meant!
    With the stepper motor and the TPS all referring back to that throttle valve setting, it can be a mess when you do not know where the valve is at.
    I did not have the luxury of re-setting my TPS at home. As the bike warmed up, and the stepper motor went to the minimum air position, it would no longer idle. At this point I had no doubt I was on the right track, so I nursed the Breva 35 km out of town to a shop that did the re-set for me, and BINGO!
    My bike had a similar story of sitting for more than 2 years (startus interruptus issue)before my time. Removing and cleaning the injectors also made a very noticeable difference in running at the time. Give your stepper motor some love while you are at it, and you will (like me) love the Breva.
    Your donation is incredibly generous. This site has been invaluable to me, and we are all better off for it's existence. So thank you....we are all in this together.
    And thank you Scott for getting involved and encouraging Vince on his quest.
     
    scottmastrocinque likes this.
  4. tris

    tris Tuned and Synch'ed

    Joined:
    May 30, 2012
    Messages:
    33
    Likes Received:
    7
    Morning Chaps!

    Sorry to resurrect an old thread but I've only just found it!!

    My 2005 B11 also came to me with a molested sacred screw but I didn't know such a thing was a problem until it was too late. Hey ho you live and learn.

    ANYWAY.
    Can you measure the dimension with the throttle bodies on the bike or do they need removing as Vince did?

    Cheers

    Tris
     
  5. vincedeguzzi

    vincedeguzzi Just got it firing! GT Famiglia

    Joined:
    May 31, 2012
    Messages:
    18
    Likes Received:
    1
    Location:
    Zurich, Switzerland
    Hello Tris

    I would strongly recommend to take out the throttlebody. Its also a good chance then to clean it.
    I fixed it in a vice and the with a calliper you can make it very exactely. A digital calliper is in that case better, because you can set it in any position to zero and then turn up or down to 2.40mm.

    You can also check aproximately the second throttle (synchronise) it with the connection link. In my case it was almost perfect, but you can change this then later when you synchronise and set the idle at warm engine.

    I wish you good luck
    regards from switzerland
    Vince
     
  6. tris

    tris Tuned and Synch'ed

    Joined:
    May 30, 2012
    Messages:
    33
    Likes Received:
    7
    Cheers Vince

    The bike has got to work for the next 2 weekends so I wont touch it for a little while, but I have one more question

    Is the position of the butterfly very sensitive to the adjusting sacred screw? ie does a small change to the screw result in a large change in the distance to the edge of the butterfly

    Anyway the "job list" is building up:-
    • Dash to Carmo - LCD keeps going black
    • Clutch thrust rod
    • Reaction rod bush change
    • Sacred screw fondling back into position
    I might call the riding season to an early conclusion this year so I can get this lot nailed down!

    Thanks again

    Tris
     
  7. Nordicnorm

    Nordicnorm Cruisin' Guzzisti GT Contributor

    Joined:
    May 12, 2011
    Messages:
    122
    Likes Received:
    17
    Location:
    Vancouver Island BC
    You will love the result of the reaction rod silent bush.
    Measuring the throttle valve with the T/B in place can be a tad awkward, but if you move a couple of the relays (starter etc.) out of the way so they do not interfere with your calipers, you should be able to get a good measurement, at least to get you to the end of the season, if you need to clean your throttle bodies.
    It has been some time since I did this. I went back and re-measured a year or so later, still with the t/b in place. Everything in order, and I have not had an issue since.
    An Allen key has six sides, each representing 60 degrees, either one flat to the next, or corner to corner. Once you have the throttle set, take a picture of the position of the Allen key "hanging" in the throttle screw, or commit it to memory. Set your TPS here. If you find the idle a little high for your liking (in traffic on a hot day it can climb over 1200 rpm, which seems a little frantic), a roughly 30-40 degree turn will lower the idle speed about 100 rpm. The original Power Point presentation gives you a window of 4.5-4.9 inclusive. If you are in this range, they say a re-set is not required. So there is a bit of wiggle room at the end of the assembly line.
    If you lower the idle speed a tad (as I have done, to good effect), I suggest going back to that original idle screw setting for your next tune up (t/b balance) and TPS re-set.
    Not very scientific. I call it "Fumbling towards ecstasy".
     
  8. tris

    tris Tuned and Synch'ed

    Joined:
    May 30, 2012
    Messages:
    33
    Likes Received:
    7
    Cheers!

    Things have moved on since I last wrote

    a) Reaction rod fitted and .... all is good!
    b) After a ride in the rain last Saturday the bike decided to disconnect its ECU and had to come home in a breakdown van :(

    I find its quite tricky to adjust the idle speed when the engine wont run :D

    Hey-ho - these are the joys of Guzzi motorcycle riding!!
     
    Nordicnorm likes this.
  9. Nordicnorm

    Nordicnorm Cruisin' Guzzisti GT Contributor

    Joined:
    May 12, 2011
    Messages:
    122
    Likes Received:
    17
    Location:
    Vancouver Island BC
    When I started this journey in 2013, I did not have much to go on. The actual idle speed did not seem important, and my 3 sources of information all said 1100 +/- 100 rpm. In an exchange with Todd E back then, he told me "The system is designed to idle at 1,250 rpm".
    I filed this info in the back of my mind, thinking it seemed a tad high.

    To make it short, this is the key to the whole issue (Thank you Todd). You can only buy the complete throttle body assembly (part # 05112530, same for G11 and B11), with the two TBs assembled on the mounting plate that will also hold the stepper motor in the end. Weber sets up the assembly at 4.8 mm fully syncronized on a flow bench (this is my own theory).
    At the end of the assembly line, it is hooked up to diagnostics, TPS and learning parameters set, then started, the idle set to 1250. Shut down, re set TPS and parameters, good to go. The stepper motor set-up is proven and reliable, so no need to go to full operating temperature.

    Your stepper motor MUST be in order.
    Fully warmed up, set the idle at 1250 (the tack is accurate, but hard to read, diagnostics is best). Your stepper valve is in the min. air position. Your next cold start should see the following: Idle settling @ 1250 within just a few seconds, and staying there through the entire warm up. On a hot start (gas station), it will rise briefly to 18-2000 rpm, while the stepper valve goes from max air to min air , settling at 1250 in maybe 5 seconds.
    If it struggles a bit on a cold start, the airbox orifice that feeds air from the airbox to the stepper motor may be too restrictive. I will open mine up with a 15/64th (6mm) drill to match the intake pipe on the stepper motor. More on this below.

    In the zone:
    Best power ever, with flawless low speed fueling (stock w/K@N and O2 optimizer).
    Fuel consumption computer extremely close to fuel metered into the tank.
    Less Carc rattle @ idle.

    There is a G-11 in my life for the last year. It is set up the same way, and acts exactly the same.
    It had other issues; a severe restriction in the airbox feed to the stepper, significant enough that I will make a separate post in the Griso/Bella section. Horrific when you look back at the history of the early models.(Griso only)

    Why is the screw "sacred"? Why the dire warnings from MG?
    If you alter the screw to somewhere outside the parameters, then re-set the TPS, your bike may no longer meet Euro-3/ CARB emission standards.
    In the past I had to over-think all this to assure myself I was doing it right.
    In the end it seems so simple.
    I am now looking forward to a few years of uncomplicated riding!
     
  10. tris

    tris Tuned and Synch'ed

    Joined:
    May 30, 2012
    Messages:
    33
    Likes Received:
    7
    An interesting insight Nordi

    I purchased my B11 with a futzed sacred screw before I knew of such things and have been slowly trying various things to get it back where it belongs

    Its not far off now, and I shall see if mine reacts as you describe above.

    However, I found this from GrahamNZ which I found interesting as allows you to remove one of the variables when trying to get things correct https://www.guzzitech.com/forums/threads/stepper-motor-on-off-kit.3025/page-4#post-28926

    I'd be very interested to know if you plug the stepper feed on your sorted bike whether it now idles at 1k RPM as Graham suggests

    Cheers
     
  11. Nordicnorm

    Nordicnorm Cruisin' Guzzisti GT Contributor

    Joined:
    May 12, 2011
    Messages:
    122
    Likes Received:
    17
    Location:
    Vancouver Island BC
    Thanks for the link, I have red the whole thing.
    On your Breva, you can reach the air pipe from the right side under the tank. It is the size of your pinky, and comes down vertically from the bottom of the air-box, then loops around to the stepper motor.
    If you reach in with a pair of long nosed pliers and pinch the tube shut, the idle rpm should drop about 200 rpm, as the stepper is always passing air, even in the minimum air position when idling a full operating temp.

    An interesting aside re. B-11: the owners hand book boasts about a cold starting function programmed into the system, that will be activated below freezing temperatures. During a late October overnight cruise with minus 3 deg.C (frost on everything), this was nowhere to be found, so throttle was needed to light the fire. It added to my suspicion that the air supply is somewhat restricted, and may not being able to keep up with what the ECU requires to make this function work.
     
  12. tris

    tris Tuned and Synch'ed

    Joined:
    May 30, 2012
    Messages:
    33
    Likes Received:
    7
    Cheers Nordi - I really think you're onto something here.

    Its interesting that you observe that blocking the feed drops the revs by 200 RPM and right into Grahams target range.

    After setting mine up using Grahams methodology, I've found that mine struggles a touch from cold and I think that I'll disconnect the feed from the air box as an experiment

    If there is a restriction is in the connection on the air box, I should ;) see an improvement in cold starting

    When I get time to play with the bike I shall experiment some more!

    Thanks again
     
    Last edited: Nov 13, 2018
  13. Nordicnorm

    Nordicnorm Cruisin' Guzzisti GT Contributor

    Joined:
    May 12, 2011
    Messages:
    122
    Likes Received:
    17
    Location:
    Vancouver Island BC
    Just checked the air supply orifice in my Breva airbox. It is the correct size (6mm or 15/64") to match the intake of the stepper motor, so there is no restriction there. Just to make sure, I reamed it slightly with a 1/4" drill bit, making sure to dis-connect the hose first to keep the stepper motor clean.
     

Share This Page