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Offline Vintageguy

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Oil Recommendations
« on: June 28, 2020, 04:37:45 AM »
I know this is a rabbit hole, but what do y'all think is best oil for a 1978 CB750F with 9,000 miles? I live in Florida and obviously it gets real hot here. I do get some false neutrals at times. Currently running Valvolene synthetic 10-40 as per factory handbook. I know some other references state 10-50, others 20-50. Any responses are appreciated. Thanks.
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Offline bryanj

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Re: Oil Recommendations
« Reply #1 on: June 28, 2020, 05:32:57 AM »
10w40, 15w40 but mineral not synthetic, synthetic isn't worth the extra cost as you cant leave it in any longer
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Semi Geriatric ex-Honda mechanic and MOT tester (UK version of annual inspection). Garage full of "projects" mostly 500/4 from pre 73 (no road tax in UK).

Remember "Its always in the last place you look" COURSE IT IS YOU STOP LOOKIN THEN!

Offline American Locomotive

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Re: Oil Recommendations
« Reply #2 on: June 28, 2020, 05:44:27 AM »
There are a billion different opinions. Some people run 10w40, some 15w40, others 20w50. I used to run Rotella 15w40, but I switched to 20w50 this last oil change and the shifting seems a little better. I'll probably go back to Rotella next oil change to see if the shifting is actually noticeably different or if its just in my mind.

Basically anything between 10w40 and 20w50 will be fine. Look for the "JASO MA" rating on the back of the container, which means it suitable for wet clutches. If it doesn't have the JASO MA rating, make sure it doesn't say "Energy Conserving" otherwise your clutch will slip.
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Offline PeWe

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Re: Oil Recommendations
« Reply #3 on: June 28, 2020, 06:13:00 AM »
Search with Google:
Sohc forums + cb750 + motor oil
Motorcycle oil semi synth 20W-50 is my tips.
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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 jlh3rd

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Re: Oil Recommendations
« Reply #4 on: June 28, 2020, 07:03:45 AM »
manual says 10w-40...or 20w-50. If oil says energy conserving,as stated previously, don't use it. Synthetic oil offers a higher degree of protection against viscosity breakdown, excellent for aircooled engines. It did cause my 550 to seep oil from the head gasket...so I went back to conventional...others seem to have good luck.....
     I use the rotella for diesel engines because zinc has been reduced in automobile oil..my understanding...( google it)....I'm not sure if there is a synthetic diesel...
   
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Offline beemerbum

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Re: Oil Recommendations
« Reply #5 on: June 28, 2020, 07:57:56 AM »
Quote from: Vintageguy on June 28, 2020, 04:37:45 AM
I know this is a rabbit hole, but what do y'all think is best oil for a 1978 CB750F with 9,000 miles? I live in Florida and obviously it gets real hot here. I do get some false neutrals at times. Currently running Valvolene synthetic 10-40 as per factory handbook. I know some other references state 10-50, others 20-50. Any responses are appreciated. Thanks.
For what its worth, when I switched from 20-50 Maxima to 20-50 Spectro in my K7, the shifting improved noticeably.
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Offline Vintageguy

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Re: Oil Recommendations
« Reply #6 on: June 28, 2020, 11:15:28 AM »
hecked and bottle says JASO MA, and not engergy conserving, so I guess I got that part right (by accident). Also says specifically for wet clutches. Guess I'll go with what I put in there this time, and try 20-50 just for grins next time and see what (if anything) happens. Thanks, all.
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Offline newday777

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Re: Oil Recommendations
« Reply #7 on: June 28, 2020, 11:34:48 AM »
Quote from: Vintageguy on June 28, 2020, 11:15:28 AM
hecked and bottle says JASO MA, and not engergy conserving, so I guess I got that part right (by accident). Also says specifically for wet clutches. Guess I'll go with what I put in there this time, and try 20-50 just for grins next time and see what (if anything) happens. Thanks, all.

That'll work. 20w-50 is good for high heat. But hard starting in the winter temps.
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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 Vintageguy

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Re: Oil Recommendations
« Reply #8 on: June 28, 2020, 01:45:27 PM »
Thankfully no real winter temps in Florida.
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Offline bryanj

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Re: Oil Recommendations
« Reply #9 on: June 28, 2020, 09:49:05 PM »
not just hard starting it takes longer to get to the cam
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Semi Geriatric ex-Honda mechanic and MOT tester (UK version of annual inspection). Garage full of "projects" mostly 500/4 from pre 73 (no road tax in UK).

Remember "Its always in the last place you look" COURSE IT IS YOU STOP LOOKIN THEN!

Offline grcamna2

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Re: Oil Recommendations
« Reply #10 on: June 28, 2020, 10:39:30 PM »
I regularly use Rotella T4 15/40 and the bike starts,runs and shifts very well,I've been running it for years and a gallon is less than $15.My clutch basket 'fingers' are 'notched' from hard powershifts on my bike and I need to remove my clutch basket and file those notches smooth:that really causes me hard shifting.
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75' CB400F/'bunch o' parts' & 81' CB125S modded to a 'CB200S'
  I love the small ones too !
Do your BEST...nobody can take that away from you.
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