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Tickover question 1 year 3 weeks ago #31208

  • scotch
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It's good to hear that all your work and frustration has been paying-off ! 
After 43 years I have simply become profecient with these carbs and don't have to think twice. It's totally about familiarity, which is an accumulated learned thing !
In no particular order:
I came to the conclusion years ago that the manuals instruction for setting the Fast-Idle is incorrect, in my opinion. . Much like the recommended 1.5 turns for the Pilot-screws. The manual indicates a gap of 0.54mm - 0.55 mm between the Idle adjusting screw and "the Lever". Illustration "E21"/page 50 (in my manual).
I have NEVER been able to achieve this TINY gap. On every set I've rebuilt (all road tested) including my original carbs, the gap is in the range of 2.0mm. This also applies to the set I recently rebuilt and are currently on my bike.I'm at a loss for words for a detailed "Set-up" explanation because other variables directly affect the idle and it becomes a "Rubik's Cube" scenario. Synchronizing, Pilot-Screw setting and final adjustment to the fast idle screw (Cam and roller) all play into the equation and "turning" something one way or another affects the other adjustments.
Choke plungers: They should start to lift at the same time and must close completely with no interference from the lifting forks. When fully closed the "Spools" must "Float". This ensures the plungers are fully closed and seated.
A vacuum leak anywhere will adversely affect the idle and will create idle consistency issues but generally not a choke applied "runaway" scenario.
I don't know if you've done the Choke Air mod. The original restriction size was an arbitrary decision .I had to start somewhere ! Those (few) that have reported on their own choke-air mod. indicate starting is much easier but the choke is "Finicky" until the engine warms. It works but is not perfect.Never walk away from the bike when it's warming-up on ANY amount of choke. The runaway can be SCARY! I think of this as the "Lazy Carb. Syndrome". Some idle circuits take their time to fully draw fuel equally and until they do the choke-applied idle will be rough but as each cylinder "comes on line" the RPM's will increase dramaticly !
The second set I am currently running allowed me to experiment with the Choke-Air restrictor size. I went from the initial restrictor size of 3/32" up to 1/8". I simply drilled them out. This has made the application of choke much more manageable and to some degree predictable, but I still will not walk away until the idle smooth's-out and the application of choke is minimal.
There are two "Gaps" that are critical. The aforementioned "2mm" between the Idle-screw and the lever AND the fast-Idle "Cam and Roller". With the Choke OFF, the "Roller" can not be touching the Cam ! The setting for this is easy. Simply back off the Adjusting screw "C" (per diagram) . There should be a few thou. gap between the roller and cam. This ensures that the idle is actually being maintained with the Idle Adjusting Screw. ( # 109 in the break-down diagram.)Throttle cable. I prefer to have the cable adjusted so that a few degress of rotation is required before the the throttles actually start to open. I like to see the "slightly" slack cable tighten as I roll the throttle those couple of degrees. This ensures the actuall idle setting is being controlled by the idle knob and not a tight cable.
Ignition timing (if applicable) will have a very noticeable affect on the idle. Several degrees either way can make the difference between an "acceptable" idle and an Idle that will make you weep with joy !
If you've suffered through all this blah, blah I hope you got something from it and this in turn helps you with some of these points of concern.
I'm sure that after I submit this there will be something I have forgotten but in the meantime if questions arise - just ask !
1980 KZ 1300 sr# KZT30A-009997
Always High - Know Fear !
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Last edit: by scotch.

Tickover question 1 year 3 weeks ago #31210

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Yes I’ve done the choke mod, I used a pop rivet with the center removed which left a 1/8” hole the bike starts instantly from cold where before it took a fair bit of cranking to get it to fire so I’m happy with that. I’ve also removed the over run diaphragm which seems to have improved the mpg. All I’ve done with the fast idle mechanism is move the cam up the choke rod so it doesn’t touch the roller. I just jiggle the throttle until she warms up. The choke plungers are fully seated when the choke is in the off position. What I usually do is get her running around 2000rpm then lock the cruise control lever until I’m ready to ride off like you I wouldn’t dare walk away from the bike wit the choke on for fear of a runaway. When she’s warm she ticks over at 1000rpm as smooth as you like. I’ve got a spare set of carbs so I’ll fiddle around with the fast idle mechanism until I’m confident I fully understand it. 
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Last edit: by PaulD.

Tickover question 11 months 4 weeks ago #31280

  • beertad
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Great assumption Kawboy. The UK is sadly in the position of unless it's water ,clean air, or lettuce, everything else in the world bar none is dangerous and you should stay clear of it.
you cannot purchase lacquer thinner here at all, only cellulose thinner.
There are supplies from modeling shops , you know like airfix, but tiny bottles like 100ml.
It is a pain and other than importing some I don't know the answer
I went in a auto paint shop and they had never heard of it!!
Tad
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Tickover question 11 months 3 weeks ago #31282

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Great assumption Kawboy. The UK is sadly in the position of unless it's water ,clean air, or lettuce, everything else in the world bar none is dangerous and you should stay clear of it.
you cannot purchase lacquer thinner here at all, only cellulose thinner.
There are supplies from modeling shops , you know like airfix, but tiny bottles like 100ml.
It is a pain and other than importing some I don't know the answer
I went in a auto paint shop and they had never heard of it!!

I can’t remember the name of it but my local car paint shop sold me 2K lacquer thinners. It worked where normal cellulose thinners didn’t. I’ll see if I can find the name 
 

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