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Where did my thread go?
Oddjob:
Seems pretty self explanatory to me Bryan, of course we’ll get the answer it’s not the same type of carbs etc. You can lead a horse to water but you can’t make it drink.
K2-K6:
Thanks Bryan, that's very clear to me.
In regard to carburettor type and relevance, this is not conditional to that but to the combustion characteristics of current fuel and the engine being worked on.
In very simple terms (it's using the hardware in place as method of measuring combustion air fuel ratio) uses known combustion effects of A/F ratio to determine complete mix point of burn THEN adds more fuel to that setting to bring down rpm by making the ratio richer. This the same for any carburettor that has a idle control circuit separated from main venturi in providing for accurate low level fueling demand.
That's all it does, nothing else. Its not responsible for part throttle opening response, nor any other characteristics. They have their own means of adjustment.
More involved detail, this is specifically to separate and set the off load /closed throttle air fuel ratio and NOT the initial opening part (under torque loading) of throttle mixture, which is controlled by the idle jet size.
Bryanj:
I just knew i had read it in a Honda manual and luckily tripped over the 750KDOHC one whilst looking for some thing else, as usual!
K2-K6:
--- Quote from: Bryanj on August 11, 2026, 04:11:55 PM ---I just knew i had read it in a Honda manual and luckily tripped over the 750KDOHC one whilst looking for some thing else, as usual!
--- End quote ---
It's interesting the point you made to me recently, that when these bikes were used in 1970s etc, they were and didn't need any real adjustment to this part, they just worked.
I agree with that as constant use, no ethanol, no sitting around for weeks/months etc, nothing changes and they work very well.
Many threads in this are on here are now because in part, or all of the above, along with stripping, clearing, worn components etc, that now needs untangling in chasing a fault in running response on these bikes. Many of these situations simply going further than original manuals could ever envision, making identification of real fault quite involved.
One area I can see, and learnt from forum contribution, is from Skoti in longer term with clear evidence of worn components in main jet and needle. This recently backed up by exvalvsetdabbler and his in depth assessment of this very aspect in his carburettor hardware during rebuild. Quantified assessment of this type are valuable to forum information, particularly in respect to understand whats happened to older components.
The function of that particular area, and seeming to show most wear too, is to all but close main jet flow at low throttle slide position, that in handing over metering to the low speed circuit. With wear there to compromise that function, it'll be all but impossible to set idle circuit accurately as in effect it has supply of un-metered fuel that distorts the fine resolution metering needed to run at that low level rpm.
Undoubtedly, the original manuals easily facilitated setup when these were ex factory bikes. They are not even complicated to adjust and set.
Given the conditions under which many currently operate though, then the manual can't really go deep enough into the topic to reveal much below that level.
Bryanj:
Very trus, in all the years i have been doing this i have only ever seen one VISIBLY worn needle and that was on a grey inport Suziki twin of about 400cc from memory and that was ridiculously worn to the point of nearly falling in half, about 1/3 down from top.
Same as in all the 500 i have done i oly ever found one worn crank and again that was so worn it didnt need a mic to say it was scrap!
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