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Author Topic: CB 750 - K7 running hotter on cylinder 4  (Read 962 times)

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Offline kvikgrip68

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CB 750 - K7 running hotter on cylinder 4
« on: June 09, 2021, 09:59:11 PM »
Hi

What to adjust if cyl 4 is running slightly hotter than the 3 other cylinders ? can see from colour on headers

regs C
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Offline 70CB750

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Re: CB 750 - K7 running hotter on cylinder 4
« Reply #1 on: June 10, 2021, 02:35:04 AM »
Lean mixture makes it run hotter, afaik
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Prokop
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I love it when parts come together.

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CB750K3F - The Red
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2006 KLR650

Offline ozpacman

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Re: CB 750 - K7 running hotter on cylinder 4
« Reply #2 on: June 10, 2021, 03:14:36 AM »
Have a good look at the rubber intake manifolds for any leaks.
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Offline kvikgrip68

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Re: CB 750 - K7 running hotter on cylinder 4
« Reply #3 on: June 10, 2021, 03:35:42 AM »
Quote from: ozpacman on June 10, 2021, 03:14:36 AM
Have a good look at the rubber intake manifolds for any leaks.
yes they are in good shape
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Offline kvikgrip68

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Re: CB 750 - K7 running hotter on cylinder 4
« Reply #4 on: June 10, 2021, 03:36:13 AM »
Quote from: 70CB750 on June 10, 2021, 02:35:04 AM
Lean mixture makes it run hotter, afaik
yeah youre right :)
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Offline PeWe

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Re: CB 750 - K7 running hotter on cylinder 4
« Reply #5 on: June 10, 2021, 05:06:19 AM »
Air/fuel screw properly adjusted?
Same as the other carbs.
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CB750 K6-76  970cc (Earlier 1005cc JMR Billet block on the shelf waiting for a comeback)
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
CB750 K2 -1975  build thread
http://forums.sohc4.net/index.php/topic,168243.msg1948381.html#msg1948381
K2 engine build thread. For a complete CB750 -75
http://forums.sohc4.net/index.php/topic,180088.msg2088008.html#msg2088008
Carb jetting, a long story Mikuni TMR32
http://forums.sohc4.net/index.php/topic,179479.msg2104967.html#msg2104967

Offline kvikgrip68

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Re: CB 750 - K7 running hotter on cylinder 4
« Reply #6 on: June 14, 2021, 01:28:31 AM »
Quote from: PeWe on June 10, 2021, 05:06:19 AM
Air/fuel screw properly adjusted?
Same as the other carbs.
air screws is only for slow running on k7 carbs
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Offline newday777

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Re: CB 750 - K7 running hotter on cylinder 4
« Reply #7 on: June 15, 2021, 02:56:31 AM »
Have the carbs been cleaned properly??
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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 kvikgrip68

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Re: CB 750 - K7 running hotter on cylinder 4
« Reply #8 on: June 15, 2021, 03:06:07 AM »
Quote from: newday777 on June 15, 2021, 02:56:31 AM
Have the carbs been cleaned properly??
yes
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Offline TwoTired

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Re: CB 750 - K7 running hotter on cylinder 4
« Reply #9 on: June 15, 2021, 06:22:31 AM »
The first thing to address is the routine 3000 mile tuneup checklist.  If something there is off, then whatever you do to cure the current complaint may have be addressed again when another tuneup is performed.

The check list includes a carb vacuum balance.  And while that doesn’t routinely drift, is can and may contribute to the symptoms you are trying to address.

Cheers!
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Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

Offline newday777

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Re: CB 750 - K7 running hotter on cylinder 4
« Reply #10 on: June 20, 2021, 04:47:44 AM »
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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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