Author Topic: low speed jet length  (Read 803 times)

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Offline itsahonda4

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low speed jet length
« on: June 14, 2017, 12:27:29 pm »
Well Im finally getting everything sorted on my 71 CB750, that I really thinks an 836....but the idle hangup and other issues finally forced me to decide that it was lean off the bottom. This included the low speed adjustment being at 2.50 turns out..... so new 45 jets were acquired form the trusty Honda dealerman and without even looking at them, in they went and a series of odd issues caused me to pull them out and check them, and immediately its apparent that they are too long ...or not?
My simple mind says they are sucking fuel from almost the bottom of the bowl so it doesn't matter so long as they always have fuel. TRUE OR FALSE?
Or is my issue elsewhere and masked by the new jets? Adjustment is still at 1.75 turns out so the jets have definitely made a difference, just not as much as I would have expected.
Main is 130 and from mid throttle up it pulls like the proverbial steam train....

Offline itsahonda4

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Re: low speed jet length
« Reply #1 on: June 14, 2017, 12:28:34 pm »
old jet on the top, new jet on the bottom.....

Offline flybox1

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Re: low speed jet length
« Reply #2 on: June 14, 2017, 12:33:40 pm »
What are the brands of each?
Size DOES mater.  Just look at the emulsion holes. Hardly the same.
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Offline Bankerdanny

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Re: low speed jet length
« Reply #3 on: June 14, 2017, 01:00:33 pm »
A nice example of why we all advise newbies never to use the brass that comes with the aftermarket carb kits. Does the one that came out of the carb have the Keihin brand mark on it?
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Offline itsahonda4

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Re: low speed jet length
« Reply #4 on: June 14, 2017, 05:42:32 pm »
stamped Keihin......
The length of the jets is more critical to me at this time. I have the dealer looking for the correct length jets, and I insisted that they must be Keihin....

Offline scottly

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Re: low speed jet length
« Reply #5 on: June 14, 2017, 06:59:55 pm »
The extra length shouldn't be an issue.
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Offline TwoTired

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Re: low speed jet length
« Reply #6 on: June 14, 2017, 10:08:48 pm »
The extra length shouldn't be an issue.
I agree the length isn't of concern.  The hole sizes (if different) in the emulsion tubes could effect function, though.
Lloyd... (SOHC4 #11 Original Mail List)
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Offline 754

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Re: low speed jet length
« Reply #7 on: June 14, 2017, 10:15:54 pm »
Try 125 mains, just try and see what happens.
Just make on those low speed that all 4 are same type.
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Offline itsahonda4

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Re: low speed jet length
« Reply #8 on: June 15, 2017, 10:49:18 am »
I had the bike running this morning and its close to perfect.......no stumble off idle, mid range is strong and top end is like trying to capture lightning in a bottle  :)
This bike is off to my daughter in New Zealand  to be my runner when Im in town, so its all good...now to get the 69 no-number engine bike finished.......
Thanks ever yone for the input.

Offline Duanob

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Re: low speed jet length
« Reply #9 on: June 15, 2017, 12:50:39 pm »
The extra length shouldn't be an issue.
I agree the length isn't of concern.  The hole sizes (if different) in the emulsion tubes could effect function, though.

Unless it's too short, then it makes a huge difference :) Ask me how I know.  :o
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