CAN'T FIND NEUTRAL WHEN HOT

[Trigger]

Also stated on the decal on the side panel of the 750 SOHC 

[bobv7]

That maybe so but this is on the Castrol website.

https://applications.castrol.com/oilselector/en_gb/c/recommendation?vehicleType=motorcycles-scooters-mopeds-quads-(atv)&manufacturer=honda&model=cb-(1969-)&modelType=cb-750-four-(1969-1978)

[Nurse Julie]

And the W (as in 10w 40 for example) doesn't stand for 'weight' the W stands for 'Winter'

[gp_st3]

smooth steels - Lucas/TRW, made in Germany - bought on ebay.uk for about £40 (set of six) about a year ago ... why these work better for me is a mystery, so best try all other suggestions before shelling out for new plates that may not improve things for you.

[bobv7]

That's right. Alexander Duckham were the first UK oil blenders to produce a multigrade oil which meant there was no longer any need to use one oil weight for summer and another for winter. The 20w50 signified the oil would maintain a viscocity sufficient to provide engine protection for both summer and winter temperatures. Its introduction also reduced the constant need for engine decokes due to the use of various additives. A blue/green hue to oils signifies high quality and that is why Duckams used a green dye in their multigrade.

[StevieWonder]

I'm using 10W40 Rock oil, Gamma. It a mineral oil that are apparently better for 'running in' an engine after rebuild - as my top end was.

[pewe]

Finding neutral when engine is hot is one way for me to  verify the oil to be OK for the engine.

All 10W-40 oils I have used cause very hard an mechanical gear shifting. I used those for break in only.

CB750 should use 20W-50. I think that 10W-40 was for colder temperature, max 15C.

I have tested Motul 5100 15W-50 semi. Better than Motul 20W-50 mineral and much better gearbox feeling than Motul 10W-40 mineral. Castrol 10W-40 mineral also very hard gearbox.

Motul 7100 10W-50, even better.
Red Line 20W-50, best so far.
This in my K6.

Spectro Heavy Duty 20W-50 mineral caused sticky clutch. Out with 1L and in with Q8 SBK racing 10W-50 (cheap synth) made it really good. Gears shift very smooth!
In my K2.

Both Red Line and Spectro have high amounts of zinc and phosporous.

I have ordered Eurol Harley Davidson 20W-50 oil that is very cheap. It cannot be high quality synth as Motul 7100/300 or Red Line (esthers) but well worth to be tested. The gearbox when hit will tell!

I have done my own semi by mixing 2 Spectro 20W-50 mineral, 2 SBK racing and 1 Red Line 20W-60 to be used in My K2 stock spec.

The latter for my K6 summer 2018 where we had over 30C during a long period of time. I ordered a box of 20W-60 to my hotter running K6 with 1000cc Billet block.

I'm convinced that CB750 run well on V-Twin 20W-50 JASO MA oils.

[Nurse Julie]

In the UK 10w 40 or 15w 40 mineral or semi is perfectly adequate. We don't have the high temperatures you have Pewe so don't need anything ending in 50. 10W-40 is for Temps up to 40°. Thats plenty high enough for us in UK. Any 50 will be like treacle trying to go around the engine.

[pewe]

Then you'll get the harder gearbox, problems finding neutral while bike is standing still.
Check the other forum where Hondaman explains 10W-40 history for CB750, why it is mentioned on the sticker.

I'm sure you have higher temp than I have in Sweden
Yesterday was OK riding weather!

The old UK bikes runs with straight 50, right?

[Bryanj]

Only ever used 10 40 in dealerships never 20 50 and no problems except the known fact of neutral, even Honda said select neutral as stopping not when stopped

[Nurse Julie]

The old UK bikes runs with straight 50, right?

I do remember in the dim and distant past I may have use 50 on some of my pre unit Brit bikes but that was a totally different design and engineering tolerances. The thicker oil also helped it from pouring out of the all the joins in the cases.... But it didn't help much.

[bobv7]

"The old UK bikes runs with straight 50, right?"

Not since the 1950s! Interesting you should be experimenting with mixing the blends from various manufacturers. You must have a lot of free time on your hands as all motor lubricants whatever their SAE rating are basically formulated to the same standards. The only differences are the oil companies making minor changes to the additives to imply a USP that makes their product better than others. A 10W40 from  company "X" will not be substantially different to company "Y"s product for the simple reason they have to be compatable and not cause damage when mixed. Oil blends have to differ across the world simply due to the different climatic operating temperatures. What works in a tractor unit in Iceland probably wouldn't be much use in the Sahara.

[Green1]

Only ever used 10 40 in dealerships never 20 50 and no problems except the known fact of neutral, even Honda said select neutral as stopping not when stopped

Both my Hondas and Guzzi have to be rolling to select neutral. Both are air cooled the Hondas run on 10W 40  and the Guzzi on 10w 60

[MrDavo]

Oil threads in car and bike forums are to be avoided like religion and politics - they can go on forever and, being more faith based than scientific, no one ever changes their mind.

I ran both CB750s I have owned on 10-40, and however well I had my clutch adjusted, just like any other bike from that era I have ever ridden, neutral was something best found before you rolled to a stop. At lights that I knew were going to be ages, such as roadworks, if I hadn't pre-selected neutral I'd switch off for a second, get neutral and restart. At least we have luxuries like electric start and a neutral light - not so easy on a Brit twin.