cb750 79 s plate kinds of oil ??

[mark73]

would i be able to use 5w/40 synthetic oil ? or semi synthetic ? or will ir be too thin and do damage ?

or can you only use the 10w/40.

[Re-run]

I currently use rotella T synthetic in my 78. It is 5-40 for diesel engines and it works great! You should be able to use it with no problems unless you have sludge in your engine. In that case, it would cause issues and maybe plug oil lines. That is not a fault of the synthetic but of the other oil that was used that the synth cleaned off.

[LukeM]

Would it be helpful to put in a compound like Rislone Engine treatment in the oil, prior to switching over to synthetic oil?  This would de-sludge the engine and gearbox pretty well.  I've used it before, and this and similar treatments seem to work well.

Luke M