880SFC Dyno results

After all this time trialing and erroring I myself would swap left for right carb, easy on a twin, so that you are certain you are chasing the correct rabbit.
 
chrisk said:
Here is the conundrum though.
Both O rings good, both springs same length. To get even mixtures at idle, dyno guy had to set mixture screws ...... wait for it....... l/h 3/4 turn from closed. R/h at 2.5 from closed.

WTF is wrong here?
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Both idle adjusters of the same type?  Chased this for the best part of an afternoon before I found it.  From a box of approx 150 new adjuster screws, I picked the one and only rogue screw and didn't notice.  The tip is slightly different, but enough to throw the adjustments out of whack.

piet
 
SimonR501 said:
Could be a partial blockage on RH pilot?
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Took carbs off, 6:00am tinkering in the garage had the family scratching their heads, I?ll check for blockages at work.

Idle adjusters look the same by eye, but I?ll mic them up.

Slides are 60/3, will order 5?s. Was a bit of a shock, but still doesn?t explain the mixture variation. Unsure what ramp value I need though.

Thanks for all your suggestions and advise



 
Chris,

I meant to write "idle mixture adjuster".  Hope you're not mixing them up with the throttle stop screws.

The type used by Laverda have a taper about 2.5-3mm long.  There are however, screws with different tapers available.  I had one correct screw, and one with a thinner tip.  Idle was lumpy and pick-up lousy.  Took the suckers apart about 4 times before I stumbled over the fucking screw...

piet
 
sfcpiet said:
Chris,

I meant to write "idle mixture adjuster".  Hope you're not mixing them up with the throttle stop screws.

The type used by Laverda have a taper about 2.5-3mm long.  There are however, screws with different tapers available.  I had one correct screw, and one with a thinner tip.  Idle was lumpy and pick-up lousy.  Took the suckers apart about 4 times before I stumbled over the fucking screw...

piet
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Piet
You could well be in the running for a Noddy Badge.
Just measured the length of the IDLE mixture screws: length of taper is 5mm on both. But taper goes: L/H carb 1.00 - 1.27mm  R/H carb 0.91 - 1.16mm.
Clearly this explains the variance in turns to get the mixtures even. Remembering, "dyno guy had to set mixture screws ...... wait for it....... l/h 3/4 turn from closed. R/h at 2.5 from closed"
 
I have heard that its possible to snap the tip of the screw off and it stays there if you bottom them too hard.
 
Vince said:
I have heard that its possible to snap the tip of the screw off and it stays there if you bottom them too hard.
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is mainly an issue with the Mikuni RS Flatslides, not seen many Dellorto mixture screws suffer that fate

 
OK, found out a couple of things from Gowanlochs.
My choke plungers have no rubber ring at the bottom, and rely on a domed brass plunger tip to seal off the seat.
New rubber tipped plungers on their way.

The 5mm needles on the mixture screws are anti-pollution needles, the 3mm long ones are for earlier 'I don't give a fuck about pollution' bikes.
I don't give a fuck about pollution mixture screws are on their way.

 
I'm guessing something like this? 
markQLD said:
to suit Dellorto PHF 32  ??

most (99%) of the mixture screws, i've unscrewed, have had the short tip (~2.4 mm)
but once in a while, i've unscrewed mixture screws with a long tip (~5.0 mm)

Dello-mixture-03.jpg

so, i just 'assume' the long tips are incorrect and have been swapped by a dpo.
but, when and for what are the long tips required?
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Went a searching, as I thought this had been discussed earlier  :-\
http://www.laverdaforum.com/forum/index.php/topic,91906.msg307936.html#msg307936

Paddy said:
Long tip are exclusive Guzzi
Short tip are Lav and Duc.
:)
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I've never seen a choke plunger without a rubber tip. Never knew such a thing existed.


Not sure what you have in mind for your nice new set of jet drills. Dellorto jets come in a wide range of sizes so you should be able to find what you need from the standard selection.

All you can do with a drill is make the jet bigger, so you can only go richer with that approach. I suppose if you drill a jet out and whatever problem you're trying to fix gets worse, then you know you've gone the wrong way and you need a leaner mixture. Bit of a crude way to do things though, because you've just buggered a perfectly good jet.

Personally, I'd leave the drills in their box. Once you start drilling jets, the size number stamped on the jet will be meaningless, rendering the jet useless for any further tuning work.

 
Have a look at where the needle drops into the carb and check both carbs look the same, Guzzis came with a shrowd there as an anti-pollution thing.If one mix screw is wrong maybe its a carb off a Guzzi, I thought you said they were new carbs?
 
Vince said:
Have a look at where the needle drops into the carb and check both carbs look the same, Guzzis came with a shrowd there as an anti-pollution thing.If one mix screw is wrong maybe its a carb off a Guzzi, I thought you said they were new carbs?
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They are, but what they were set up for I don?t know. Mr Muir reckons it sounds like they are set up for Guzzi too.
 
Dellortoman said:
I've never seen a choke plunger without a rubber tip. Never knew such a thing existed.


Not sure what you have in mind for your nice new set of jet drills. Dellorto jets come in a wide range of sizes so you should be able to find what you need from the standard selection.

All you can do with a drill is make the jet bigger, so you can only go richer with that approach. I suppose if you drill a jet out and whatever problem you're trying to fix gets worse, then you know you've gone the wrong way and you need a leaner mixture. Bit of a crude way to do things though, because you've just buggered a perfectly good jet.

Personally, I'd leave the drills in their box. Once you start drilling jets, the size number stamped on the jet will be meaningless, rendering the jet useless for any further tuning work.
Click to expand...

I have jets without markings on them from Red. The only jets I can get are from Sydney, and waiting a day and paying Express Post for 2 jets is a pain in the arse. So, crude trial and error will do until we find optimum, then order in correct new jets.
 
chrisk said:
Piet
You could well be in the running for a Noddy Badge.
Just measured the length of the IDLE mixture screws: length of taper is 5mm on both. But taper goes: L/H carb 1.00 - 1.27mm  R/H carb 0.91 - 1.16mm.

Clearly this explains the variance in turns to get the mixtures even. Remembering, "dyno guy had to set mixture screws ...... wait for it....... l/h 3/4 turn from closed. R/h at 2.5 from closed"
Click to expand...

Back it up a bit CK ! I'm not gunna be dudded out of a Noddy badge by an ex pat Aussie named Piet  :P Ya best send it down to good ole Vic  ;)
Hooksey.
 
hooksey said:
My twin the same Chris..... although not as big a discrepancy, only 3/4 turn diff !

Quite possibly carb orifices/mixture screw taper a little different who knows.  :-\
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You need a Noddy Badge for that! You can get them on EBay
 
chrisk said:
You need a Noddy Badge for that! You can get them on EBay
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Yep  :D

Tried the bay..... and bugger me supplier is out ! Seems some knob nth of the border has bought all his remaining stock  :o
Seems you will be handing a few out during the tuning process of your 880  :-*
 
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