Why can't they just leave it the fuck alone?

Ralf bought his bike up yesterday and we spent a good four hours frig-arseing about with it. Ever since it had shat it's ECU it had been running like a munter. I went through all the usual things, then the unusual, (ECU, phase sensor, blah blah.) it was still not running worth a shit.

I realized I was chasing my tail so I gave up for the day, lent Ralf my bike to get home and went down the pub. Ralf rode my bike down and even on that short trip said "Mine's never run like that!".

Ah-Ha! Thinks I. I wonder if someone has fucked with the sacred screw. It appeared that the paint was intact but the screw was suspiciously positioned. So this morning I get to work and get my magnifying glass out and my close-seeing front-of-heads, (Reading glasses.) and have a bit of an poke about. What do I find but under the paint on the screw there is more, slightly different coloured yellow paint! Yes, it seems that the clowns at a motorbike shop that won't be named who are no longer a dealer had fucked with the screw, realized they'd buggered something but being unable to work out what had simply gone and got a pot of yellow paint and re-sealed the screw .

Anyway, about 3/4 of an hour of playing about, adjusting, measuring and re-setting coupled with a bit of guesswork, a multimeter, a couple of bent paperclips and a lot of cursing and it's back as close as dammit to perfect! I've even reloaded a map that will allow him to continue to be a noisy moron

Why it originally, with the old ECU, ran acceptably, (Although now he's ridden a GRiSO that runs well I don't think he'd be happy going back to how it was!) I don't know? Perhaps I forgot to re-set the self learners after the upload? I really can't say. What does piss me off is that the other shop flagrantly misled and mis served the original owner of the bike. In retrospect it's not hard to see why he sold it! When it got hot it really was running like a munter. Anyway, it's a different bike now. Thank god!

Pete

All hail Saint Pete, Saviour of the Guzzi Name.

Good work

Nice find! It makes me wonder how many other 8V's out there have been diddled with?

Wasn't the shop that I bought my Breva from was Pete?

Ex dealer in Sydney whose name resembles a small mountain or humock.

Pete

beetle wrote:

Nice find! It makes me wonder how many other 8V's out there have been diddled with?

Unfortunately I think quite a few. Just took it for a blat around 'Test Track B' in 37*C heat. Runs good. Idle is a a bit high at 1400 so I messed with the CO trim but it doesn't seem to respond majorly so I've left it in the low negatives, (-5 or some such.) and it's fine.

Pete

This place is a wealth of information - I had never heard of the "Sacred Screw" - A quick google search of various forums has given me some idea. It should be marked "burny!! don't touch".

It reminds me of the time I was trying to set up and adjust tension on a Tennis Racquet Stringing Machine, having never owned or used one before. I misunderstood one of the instructions and ended up adjusting a single wrong screw - kaput!! I tried for weeks to do the micrometer style infinitely small adjustments to no avail. I ended up giving up, swallowing my pride and sending it back to the manufacturer to be reset

I should point out that using your work computer to look up the words "Sacred Screw" is probably not a good idea.

Whatever you do, before you start playing with ANYTHING, ask here. It is very, very easy to fuck stuff up if you just work on assumption rather than knowledge. There are plenty of people here who do their own maintenance, Guzzis remain a very simple and easy machine to work on. But the modern ones are NOT your father's Panther Sloper from 1955.

Ask and information will be forthcoming. Obviously we can't gaurantee that we can fix everything over the Internet but we can give it a good nudge if you don't have a local dealer worth a pinch of shit.

Pete

Pete Roper wrote:

Unfortunately I think quite a few. Just took it for a blat around 'Test Track B' in 37*C heat. Runs good. Idle is a a bit high at 1400 so I messed with the CO trim but it doesn't seem to respond majorly so I've left it in the low negatives, (-5 or some such.) and it's fine.

Which map, out of curiosity? Might be the lack of dB killer messing with it.

The hi-pipe no dBk map. He's thinking of buying the same pipe as us anyway because he's been starching his shorts over how mine behaves. As it is I know it isn't perfect but it will basically be a bit rich and the delta will maybe a bit off if I read what you've told me right. It certainly isn't in any way dangerous, (Believe me, I *Tested* it this arvo in the heat! If it was going to do anything weird it would of done.).

Generally I'm using the 'Universal' CC+dBk in almost anything but if people really want noise I start off with the Hi-Pipe w.dBk map and if it runs OK and doesn't show any obvious signs of misbehaviour or dangerous underfueling I send 'em on their way with the caveat that it hasn't been log developed for that pipe. No complaints or damage so far.

Pete

Well, as long as they understand it ain't gonna be perfect and there's no dire consequences...

Well there you go, I click on the forum and there's all this talk about my bike.
As Pete said there was my bike in his workshop pulled apart.
A lot of head scratching, butt scratching, me asking a lot of dumb questions and passing tools and doing as I'm told...
After hours of poking tools and electric testing kinda stuff and then it gets weird when Pete goes out the back and faces East and chants to the " guzzi God"
He declares enough and let's go to the pub.

So after the two minute ride on petes bike to the " office"
I asks, why the fuck don't my bike go like that..

Does now, or at least reasonably close. We can make it better with a Mistral. That being said Don from Qld's bike had the same problem as mine with the Hi-Pipe with no dbK. It only idled on one unless you put it slightly out of balance at idle. My guess is that because the no dBk was log built for Mar's bike there is enough of a difference when gas flow is low, (No idea why. Well I do bUT i won't bore you with it.) means that one cylinder in some bikes, like mine and Don's, go incombustibly lean. Put it slightly out of balance and re-set the TPS. Golden.

Pete

Pete Roper wrote:

Whatever you do, before you start playing with ANYTHING, ask here. It is very, very easy to fuck stuff up if you just work on assumption rather than knowledge. There are plenty of people here who do their own maintenance, Guzzis remain a very simple and easy machine to work on. But the modern ones are NOT your father's Panther Sloper from 1955.

Ask and information will be forthcoming. Obviously we can't gaurantee that we can fix everything over the Internet but we can give it a good nudge if you don't have a local dealer worth a pinch of shit.

Pete

Pete is quite right here. I consider my self a fairly experienced mechanic, but when I venture into the unknown I still ask stupid questions. Here is one, Pete, what is this holy grail screw? Do you mind posting a picture? Thanks matey.

I make my self feel better by saying "it's better to ask stupid questions than making stupid mistakes ".

Really no need for a picture. It's the throttle stop screw on the LH throttle body. Get down on the LH side of the bike and you'll see when you open and close the throttle that a bar on the bell crank mechanism hits a stop that is threaded through a welded on nut. It should have a dab of yellow paint on it that shouldn't be disturbed.

The problem stems from people who are used to more basic technology think that if you close the throttle plate it will behave in a similar fashion to lowering the slide in a carburetor. Thing is in the system used on modern big block Guzzis and many other vehicles the idle speed is controlled by a system where a device controlled by the ECU determines if the idle speed is correct by adding or subtracting air. Leaner the mixture? Higher the engine speed at idle. It's ability to do this properly is dependent on the position of the throttle plate remaining at a known constant. This is set using a flow bench at manufacture.

If someone messes with this setting it completely screws the ability of the ECU to tell the stepper motor how much air to deliver to achieve the target idle speed. The wider the throttle opening the less relevance and effect this will have but at, and just above, idle on small throttle openings it is vital that this signal to the ECU be correct or things go fucking very quickly.

I don't mind people doing dumb shit. Good lord! I do enough dumb shit of my own but if you do screw up at least have the testiculosity to man up and admit you've fucked up! You don't hide it by re-painting a screw you don't know the function of! I'll admit that the factory manuals may not explain this well but they also say in their preamble that a certain amount of mechanical aptitude is assumed. That's why they are known as 'Workshop Manuals' rather than 'Dumbfuck uncle Kevin's instructions for making your bike go faster!'.

Pete

Tassiedevil71 wrote:

I should point out that using your work computer to look up the words "Sacred Screw" is probably not a good idea.

...

If you do a search on "throttle body balance" or somesuch, there's pics in other threads....

The red arrow points to the sacred screw...

[You must be registered and logged in to see this image.]

Since we're on the topic... There was a dissertation written over on GuzziTech about the Sacred Screw. What it does, how it does it, and what "4.7" TPS really means. I believe it's pinned in the tech forum. Anyone know if it's accurate?

Dunno, haven't been there for ages.

Pete

Link?

Here --> Sacred Screw

He doesn't purport to be an expert, just what he thinks he learned working on his B11.

Actually this article seems to make sense when I read it some time back...

If it worked? All well and good.

Pete