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Discussion Starter #1
Any one played with the jet kits on monsters?

I know there's a hundred and one threads on this out in the tech folder, but was wondering more from a Oz perspective.

I've got basically open mufflers and Uni-filters, and while I'm still missing brake lines inital indications from running in the shed is it's so badly lean just off ideal I probably wont be going anywhere till I do something about it.

So, the Oz type questions:
-How's the standard kit in oz whether (0-40c)
-where'd you get it from?
-Any experience with our different fuels?
-is it worth it?
etc.

(surely someone in oz has used these things?)

cheers all :)

P.S. the sooner these nigling problems are fixed the sooner I can be drinking coffee with you all!
 

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DWH said:
Any one played with the jet kits on monsters?
I spent a fair amount of time tweaking a FactoryPro kit on my 750 a few years back. My settings won't be of much use to your 600 though... (42.5 pilots, 132.5 mains FactoryPro needles with the clip in the top groove, 3 turns out on the idle screws)

I found the FactoryPro reccommendations a little ambiguous regarding which of the jet selections I should use with my stock headers with Staintunes and a choppped airbox lid with a K&N, I started out with the middle of the 3 jet choices in the kit (the 137.5) and the middle needle groove. I ended up after a few dyno runs with the stock 132.5 mains and the cli in the top needle groove, and an almost perfect air/fuel ratio right across the rev range at both full and partial throttle openings (a little rich through the midrange at 50% throttle).

big
 

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Best thing to do is go and get the bike dynoed!

There is thousands of variables to muck with, in the end the bike will not run right.

This is one area I don`t touch and I play with most parts of any bike!
 

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DUCMONROB said:
Best thing to do is go and get the bike dynoed!

There is thousands of variables to muck with, in the end the bike will not run right.

This is one area I don`t touch and I play with most parts of any bike!
Well, not _thousands_...

For adjustments in the stock CV carbs you've got: main jets, needle jets, needles, needle springs, pilot jets, float height, and idle mixture screws. Thats it.

Thats only seven "variables", some of which (like float height) have a "right" setting (14mm), most of which have only a few possible options. Main jets come in increments of 2.5, you'd start down near 125 for a stock 600 up to maybe 142.5 for a heavily tuned 900 so there's only 7 or 8 sizes that make any sense at all, and its easy enough to narrow that down to 3 or 4 sizes by "guessing" based on the motor and mods. Needles only have 3 or 4 adjustment grooves to put the clips in (though some people do shim the clips when they're wanting to tweak further) and there are only 4 or 5 different needle tapers available. Even the mixture screws, which in theory have continuous adjustment, end up pretty much being adjusted in increments of half a turn, giving a full range of only 8 or 9 steps, and a real world useful range of maybe 2-4 turns or only 5 steps.


If I were to narrow down all my possible settings to their most likely guesses, I get (assuming I go for the 14mm float height):

4 main jet sizes * 2 needle choices * 4 clip positions * 2 spring choices * 4 pilot jet sizes * 4 mixture screw settings

which is 6 variables with only 1024 possible configurations.

The problem is, they are all quite inter-related, so changing one may mean all the others need changing to suit. You _do_ need to know what order to start fiddling, you don't try setting the idle mixture until you're sure everything else is as close to right as you can get it. You also need to know which adjustment changes which part of the engine speed/throttle opening area. Main jets affect full throttle mixture, needles tune the partial throttle midrange rpm area, pilots and mixture screws adjust idle and near idle low rpm mixtures. Needle tapers and springs change the way transitions happen.

It _is_ fiddly, but its not a "black art", and there's not quite as many ways to get it wrong as most people seem to think. (Having said that, I'm not quite "old school" enough to have ever learnt to tune by "feel", I get dyno runs done with af ratios plotted at several throttle openings so I can see where and when its running rich or lean, then make the estimated changes and dyno it again...)

big
 
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