CB750 and leak from head gasket area is standard and have always been. Oil from one place will spread all over the head and more when driving, the wind and heat will make the oil to float, impregnate everything.
Thanks to this forum and all combined knowledge from all members and bike experts that worked with the bikes from the very beginning we know what to do and not. The CB750 can be bone dry.
-Oil leak under rubber coins under the cam holders. Make sure that the rubber coins are fresh and seal them with non hardening sealer.
- cam studs: They must not be removed or coming loose. If they have, new thread inserts like time-sert that are glued with loctite 272, stud sealed with teflon high temp thread sealer.
- Gasket under valve cover OK, no oil leak thru bolts keeping the cover.. EDIT: forgot the breather cover on valve cover. All 3 bolts need to be tightened and good o-ring. oil will leak from here otherwise. I had one leak when driving , front bolt not tightened at all
- Tacho connection to valve cover, typical place from where oil is weeping. Remove cover and replace the oil seal, do not press it in too hard. Do not use a screwdriver from outside when removing the old one. The cover can crack and alu parts falling in beside cam and rocker arms between 3-4. (How do I know?
)
Head gasket: MLS, Multi layer steel (mounted dry) does not require another tightening after 500km. The rivets must be hammered flat to not interfere with the mating surfaces. I drilled small dents on my head and cyl block where rivets are located with 8-10mm drill. That gasket need only 2 o-rings for oil feed around the inner 2 studs on inlet side.
MLS need a good surface. I made my blick and head good on the kitchen table. First grit 240 paper, later 400 when all scratches were gone.
I'll fine tune my head again to remove some small scratches happened the last 2 seasons head liftings. Case surface to cyl block too.
Photos when I fixed head and block 2012 when repairing/restoring the engine. later the entire bike..project never stops...
