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Author Topic: CB 750 K0 running a tad rich - Questions  (Read 600 times)

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Offline Scootch

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CB 750 K0 running a tad rich - Questions
« on: May 21, 2022, 10:57:10 AM »
I think it might be running a tad rich but would like input. Please see the attached pic for specs regarding jetting. I don't know what position the circlip is at on the jet needles tho. Looking for some opinions on the jetting that is used. From the info I found those are the jets called for for a 1970 K0. I forgot to take a pic of the plugs. They are indicating just a little on the rich side...  TIA
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Offline 69cb750

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Re: CB 750 K0 running a tad rich - Questions
« Reply #1 on: May 21, 2022, 11:13:38 AM »
#120 and #40 are fine, be aware previous owners have drilled jets so you need to measure or compare with new jets and check air filter is clean.
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Offline newday777

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Re: CB 750 K0 running a tad rich - Questions
« Reply #2 on: May 21, 2022, 11:36:59 AM »
Quote from: Scootch on May 21, 2022, 10:57:10 AM
I think it might be running a tad rich but would like input. Please see the attached pic for specs regarding jetting. I don't know what position the circlip is at on the jet needles tho. Looking for some opinions on the jetting that is used. From the info I found those are the jets called for for a 1970 K0. I forgot to take a pic of the plugs. They are indicating just a little on the rich side...  TIA

Are you running  the Stock 300 exhaust and stock air cleaner?? Those play into the factors.
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Stu
Honda Parts manager in the mid 1970s Nashua Honda
My current rides
1975 K5 Planet Blue my summer ride, it was a friend's bike I worked with at the Honda shop in 76, lots of fun to be on it again
1976 K6 Anteres Red rebuilding project, was originally my brother's that I set up from the crate, it'll breath again soon!
Project 750s, 2 K4, 2 K6, 1 K8
2008 GL1800 my daily ride and cross country runner

Prior bikes....
1972 Suzuki GT380 I had charge of it for a year in 1973 while my friend was deployed and learned to love street riding....
New CB450 K7 after my friend returned...
New CB750 K5 Planet Blue, demise by ex cousin in law at 9,000 miles...
New CB750 K6 Anteres Red, to replace the totaled K5, I sold this K6 at 45k in 1983, I had heavily modified it, many great memories on it and have missed it greatly.....
1983 GL1100A, 1999 GL1500 SE, 1999 GL1500A

Offline Scootch

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Re: CB 750 K0 running a tad rich - Questions
« Reply #3 on: May 21, 2022, 11:44:43 AM »
Quote from: newday777 on May 21, 2022, 11:36:59 AM

Are you running  the Stock 300 exhaust and stock air cleaner?? Those play into the factors.
[/quote]
Yes running the stock 4 into 4 HM300 exhaust. Stock air cleaner.
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Offline Scootch

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Re: CB 750 K0 running a tad rich - Questions
« Reply #4 on: May 21, 2022, 11:49:16 AM »
Quote from: 69cb750 on May 21, 2022, 11:13:38 AM
#120 and #40 are fine, be aware previous owners have drilled jets so you need to measure or compare with new jets and check air filter is clean.
Thank you for the reminder. That is a good point. The carbs are said to have been rebuilt but I do not have info regarding origin of kits/parts...
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Offline newday777

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Re: CB 750 K0 running a tad rich - Questions
« Reply #5 on: May 21, 2022, 01:24:33 PM »
Quote from: Scootch on May 21, 2022, 11:44:43 AM
Quote from: newday777 on May 21, 2022, 11:36:59 AM

Are you running  the Stock 300 exhaust and stock air cleaner?? Those play into the factors.
Yes running the stock 4 into 4 HM300 exhaust. Stock air cleaner.
[/quote]

Well this new phone is driving me batty.  I can't get my pictures..... ugh
« Last Edit: May 21, 2022, 01:28:15 PM by newday777 »
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Stu
Honda Parts manager in the mid 1970s Nashua Honda
My current rides
1975 K5 Planet Blue my summer ride, it was a friend's bike I worked with at the Honda shop in 76, lots of fun to be on it again
1976 K6 Anteres Red rebuilding project, was originally my brother's that I set up from the crate, it'll breath again soon!
Project 750s, 2 K4, 2 K6, 1 K8
2008 GL1800 my daily ride and cross country runner

Prior bikes....
1972 Suzuki GT380 I had charge of it for a year in 1973 while my friend was deployed and learned to love street riding....
New CB450 K7 after my friend returned...
New CB750 K5 Planet Blue, demise by ex cousin in law at 9,000 miles...
New CB750 K6 Anteres Red, to replace the totaled K5, I sold this K6 at 45k in 1983, I had heavily modified it, many great memories on it and have missed it greatly.....
1983 GL1100A, 1999 GL1500 SE, 1999 GL1500A

Offline Scootch

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Re: CB 750 K0 running a tad rich - Questions
« Reply #6 on: May 21, 2022, 01:38:46 PM »
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Offline ekpent

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Re: CB 750 K0 running a tad rich - Questions
« Reply #7 on: May 21, 2022, 06:25:29 PM »
Would be nice to know from a baseline tuning aspect someday for you in the future to know if you still have stock factory jets or questionable size aftermarket. Stock will have a stylized 'K' mark on them and usually can tell from the number stamping. Clean air filter is good and not an old dirty broken down old one. Can do some adjustments with the air screw but if its running well and not fouling plugs I wouldn't tear into it to deep. Those original airbox's are fragile and some of the early bikes ran a little rich anyways. I think Hondaman would suggest a Nippon Denso spark plug but not sure on the exact number off the top of my head. Its a 24 with some letters.  :D
« Last Edit: May 21, 2022, 06:27:21 PM by ekpent »
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Offline Scootch

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Re: CB 750 K0 running a tad rich - Questions
« Reply #8 on: May 21, 2022, 06:36:07 PM »
Thank you for the info. I agree with leaving well enough alone at the moment. It is running well. There is something to be said for if it ain't broke don't fix it...
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Offline newday777

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Re: CB 750 K0 running a tad rich - Questions
« Reply #9 on: May 21, 2022, 07:29:15 PM »
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Stu
Honda Parts manager in the mid 1970s Nashua Honda
My current rides
1975 K5 Planet Blue my summer ride, it was a friend's bike I worked with at the Honda shop in 76, lots of fun to be on it again
1976 K6 Anteres Red rebuilding project, was originally my brother's that I set up from the crate, it'll breath again soon!
Project 750s, 2 K4, 2 K6, 1 K8
2008 GL1800 my daily ride and cross country runner

Prior bikes....
1972 Suzuki GT380 I had charge of it for a year in 1973 while my friend was deployed and learned to love street riding....
New CB450 K7 after my friend returned...
New CB750 K5 Planet Blue, demise by ex cousin in law at 9,000 miles...
New CB750 K6 Anteres Red, to replace the totaled K5, I sold this K6 at 45k in 1983, I had heavily modified it, many great memories on it and have missed it greatly.....
1983 GL1100A, 1999 GL1500 SE, 1999 GL1500A

Offline Scootch

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Re: CB 750 K0 running a tad rich - Questions
« Reply #10 on: May 22, 2022, 03:39:25 AM »
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Offline ekpent

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Re: CB 750 K0 running a tad rich - Questions
« Reply #11 on: May 22, 2022, 05:37:21 AM »
Dead link here also.
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Offline newday777

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Re: CB 750 K0 running a tad rich - Questions
« Reply #12 on: May 22, 2022, 09:14:49 AM »
Well I'm guessing this new phone didn't copy the whole link address 🤔
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Stu
Honda Parts manager in the mid 1970s Nashua Honda
My current rides
1975 K5 Planet Blue my summer ride, it was a friend's bike I worked with at the Honda shop in 76, lots of fun to be on it again
1976 K6 Anteres Red rebuilding project, was originally my brother's that I set up from the crate, it'll breath again soon!
Project 750s, 2 K4, 2 K6, 1 K8
2008 GL1800 my daily ride and cross country runner

Prior bikes....
1972 Suzuki GT380 I had charge of it for a year in 1973 while my friend was deployed and learned to love street riding....
New CB450 K7 after my friend returned...
New CB750 K5 Planet Blue, demise by ex cousin in law at 9,000 miles...
New CB750 K6 Anteres Red, to replace the totaled K5, I sold this K6 at 45k in 1983, I had heavily modified it, many great memories on it and have missed it greatly.....
1983 GL1100A, 1999 GL1500 SE, 1999 GL1500A
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