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Butterfly location

Charlie J

Charlie J

Cruisin' Guzzisti
Joined
Jun 19, 2009
Messages
162
Location
Taree, Australia
Gday.With the Throttle Body assembly off the bike and looking through them to the light,you can see that both butterflys have a gap between them and the body at the bottom.Surely these should be central in there bores?The gap on the RHS is roughly twice that of the left side. This looks about 30 thou or so (0.75 mm). I had no suitable wire to measure with. I reckon this is why the bike runs like a busted ass if set up correctly using a manometer,yet will go not too bad using plug color.
What centralises the butterflys in their bodies? Bush length ? shoulders on the shaft? or is there springs or some such?
I was goin to look for some 2nd hand T/B's but thats no garantee they would not have the same issue,so now I will try to find a T/B doctor and have some butterflies made to fit my bodies ,and the bodies made concentric ,hopefully with a minimal diameter change.
Anybody had similar issues?
 
I think before I went into the throttle bodies, I'd look at new parts to see what they are like. If a dealer on importer had them in stock I'd get a peak at those before going drastic. Besides, if you take the left hand TB apart, how do your get it back to 4.6 degrees open?
 
Gday John. I was fortunate enough to be able to borrow a T/B assembly from Mario at Thunderbikes. These butterflies were centred in there bodies. I was asked to not alter any adjustments on them,which I complyed with. When fitted up to my bike it idled at about 1800 rpm so took them off and returned them. Mario has since sold them,but the point is they were concentric in there bodies.
As for finding 4.6 degrees open at idle,the W.O.T. stop as you know is on the RHS T/B,so using VDST set WOT between 84.2 and 84.5 degrees,a maximum travel of 79.9 degrees,if needed the sacred screw could be adjusted to suit in combination with a T/B balance to give an 1100 ish rpm idle,sweet gear change etc. A funny thing I have found is that if the stepper motor is isolated the bike is too rich and wont idle and the vacum on the manometer will swap sides and getting the bike to run ended up in a slight loss of engine brake at nearly shut throttle.
 
much better bet is to set th TPS to a baseline voltage using the sacred screw. I *think* that voltage should be 465mv but perhaps someone with an un-buggered about with set of TB's could measure it. The TPS setting never changes. it's how the signal is interpreted that changes things.

pete
 
pete roper said:
much better bet is to set th TPS to a baseline voltage using the sacred screw. I *think* that voltage should be 465mv but perhaps someone with an un-buggered about with set of TB's could measure it. The TPS setting never changes. it's how the signal is interpreted that changes things.

pete
Click to expand...

Pete,

I'm not so sure that is a valid technique. If the Guzzi TB is like the BMW TB they are set mechanically at the factory to the specified degree of opening. The ECU is then instructed to interpret what ever voltage the TPS delivers to be that specific degree of open. That is what a TPS reset with software performs to compensate for the eventual drift that will occur with a variable resistor. That voltage reading is dependant on too many variable to be considered accurate such as, condition of the TPS, supplied voltage to the TPS, accuracy of the DVM, resistance in the probes used to read the TPS voltage, and so on.
 
John I tried to use a cad program to work out how much distance is travelled when rotating a 45mm line through 4.6 degrees but couldnt get it (my brain) working properly,and the closest I could get was 1.8mm for 5 degrees. Is it feasable to put the butterfly at 90 degrees to the body,measuring from the mouth of T/B to butterfly with a depth gauge,and then moving it 1.8 mm or whatever the correct distance is? Of course the help of someone fluent in cad would be able to get an accurate distance.
 
Sorry I should have thought a bit more,you wouldnt need to put the butterfly at 90 degrees,measure from mouth to butterfly at 9 oclock and at 3 oclock and the difference should be twice 1.8 mm or whatever the correct distance is.
 
Charlie,

I believe your methodology is getting closer. Some type of fixture is needed to be able to accurately reset the LH TB to 4.6 degrees mechanically. The tricky part will be designing and making one. Once you do, you may have a very needed special tool to market.
 
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