SOHC.co.uk Forums > CB750
Warm up time
Erny:
Yes, that's correct, I was not precise enough
But still question remains, if somebody tried to change slow jets to improve this behaviour
I'm quite sure I've seen somewhere info (maybe SOHC us forum) about changing slowjets from 35 to 40, but cannot find it quickly
Attached specs of PD41A / PD41B
Bryanj:
Problem you have is getting the pressed in pilot jets in different sizes, only place i know of that produces any of them is Siriusonic in Canada and they do not do many sizes.
Erny:
Thanks for tip, yes they sell them, not very cheap, but I understand it
https://www.siriusconinc.com/pro-detail.php?pid=&product_id=1807
Note: link is accessible via PC only
Now, the question is if there is anyone who did that change, what is result and if something else has to be changed / replaced too?
K2-K6:
I've been mulling it over for a few days and feel that you can try to move it a little richer without having to change the jets.
Nearly all carbs have got some adjustment available to take into account temp and altitude variations, they are supplied to general markets like ours sitting more or less in the middle of that range.
To bring up the slow speed mixture using airscrews to adjust. If you turn them in a quarter turn it should bring that mixture toward more fuel through those low response rpm.
The main jets. You can drop the circlip/raising the needle to overall bring the mixture up across the whole range from about 1/4 throttle upwards.
If you try it with the idle set first to see if you get a discernable change, then you may want to add the mains to that. This should preserve the mixture parity across the whole rpm and avoid making significant steps in the fueling gradient (ie avoiding flat spots).
CR750:
--- Quote from: K2-K6 on December 14, 2018, 03:25:56 PM ---I've been mulling it over for a few days and feel that you can try to move it a little richer without having to change the jets.
Nearly all carbs have got some adjustment available to take into account temp and altitude variations, they are supplied to general markets like ours sitting more or less in the middle of that range.
To bring up the slow speed mixture using airscrews to adjust. If you turn them in a quarter turn it should bring that mixture toward more fuel through those low response rpm.
The main jets. You can drop the circlip/raising the needle to overall bring the mixture up across the whole range from about 1/4 throttle upwards.
If you try it with the idle set first to see if you get a discernable change, then you may want to add the mains to that. This should preserve the mixture parity across the whole rpm and avoid making significant steps in the fueling gradient (ie avoiding flat spots).
--- End quote ---
On the PD carbs to make the mixture richer [more fuel] you turn the screw out not in, turning the screws in weakens the mixture on the PD carbs.
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