SOHC.co.uk Forums > CB750

What engine oil

(1/3) > >>

Craizeehair:
I’m sorry to do this again as I’m sure nobody wants another what oil thread but I have searched and haven’t found anything recent on this. My CB750K0 seemed to have a bit of clutch drag at the end of last season, I do intend to replace the cable and springs as I inherited what’s on the bike and suspect it’s been some time since it was replaced, I found that the clutch was getting very stiff to operate, so that will be my starting point.

I have also tried to do some reading around the correct oil for these bikes / clutches and a mineral oil, 10w40 JASO with zinc if possible seems to cover most bases.

I did find an old post by HondaMan on the subject stating that these bikes should in fact use 20w50 and the 10w40 that was actually listed by Honda was a mistake, does anyone know if this is correct, could he be talking about when using in warmer climates than ours, I am having trouble getting out of this particular rabbit hole.

Any suggestions for a tried and tested oil that suits these bikes and helps with clutch drag would be very much appreciated!

Yetanotherbike:
I'm not qualified to give you any advice on the correct oil for your bike, obviously there will be people on here who will be, based on knowledge & experience. However I stumbled across this site when I was looking for oil advice for one of my Laverda's. Hope it helps or is of interest to you.
 https://bobistheoilguy.com/forums/

TrickyMicky:
I have no technical qualifications on this subject, only my memories. When I ran a 750 K2 in the 70's I used 20/50 oil. All the comics were singing the praises of the wonderful Duckhams "Q" multigrade, so, in it went.  My personal experience was "What a load of crap".  unless the bike was used on extremely long journeys, every time I took the dipstick out of the tank, the top of it was covered in white frothy sludge. I finished up using Shell Super Multigrade 20/50, and never had any problems at all regardless of type of usage. It also helped that my father worked in a Shell garage, say no more!!!  I carried on using this oil even when I got the 400, but then it changed to becoming Super Helix, also suitable for diesels. I then started using Motul 10/40 mineral oil, and have done ever since.  It's interesting to try to remember that there was life before the multigrade revolution, just over a year ago I did a cosmetic restoration on a 1966 CL160, and cast into the upper crankcase were the oil specifications, winter - straight 30, and summer - straight 40, and still they lasted!!   

Craizeehair:
Thanks for the input, I think I would normally be less concerned about a specific oil but my main concern is the clutch / gear change. I noticed towards the end of last years riding that the gear changing was quite clunky / grinding when being ridden, I think it was worse when hot?

As a relative beginner to all things related, I tried to research and find the causes and as I came across HondaMans post, stating the very first thing to do is check you have the correct oil and 10w40 was a mistake my Honda, that was enough to start the rabbit hole.

I also found that he states that the clutch assembly diagrams from the Honda fiches in their books are incorrect as well.

Now I’m so confused I don’t know where to start

The clutch itself is very stiff and hard to pull, so that will need some sorting. I hope to get this issue sorted and ready for the years riding but feel a little lost.

Hence the question about the oil from the UK members, just to satisfy myself before moving on to the potential clutch issues.

TrickyMicky:
Engine oil in gearboxes is not the ideal solution, they perform much better on EP gear oils, that's why the older British bikes with seperate boxes had a superior gearchange, and it's not just us either, my mates in the 70's ran original type BMC Mini's and suffered from the same effects, cold engine:- nice smooth gearchange, but crap when hot.
  Regarding the clutch, 1st place to look is the cable, they are normally routed very close to the hot engine and suffer, I normally replace the cable about every 18 months/2 years, plus check if the handlebar lever is free in its mounting.

Navigation

[0] Message Index

[#] Next page