Is there anything special about the crank grub screw?

[HMBAtrail]

I have a 450 crank sitting here and as I look at it the M8x1.25 grub screw isn't there. Is there anything so special about the grub screw to prevent me from simply taking an m8 bolt, lopping off the bolt head and then slotting it for a screwdriver? Or do I try and source an actual grub screw?

[Jordan]

I don't remember thinking there was anything special about that grub screw the last time I took it out - to check ignition timing.
It should be OK to use a socket head grubscrew, if that's easier to find than a slotted type.
Size specs should be in factory parts list.

[blethermaskite]

The grub screw just restricts the oil flow in the crankshaft redirecting it through the primary drive gear, otherwise the oil would just flow into the crankshaft out rigger bearing in the primary drive cover and pretty much starve the primary gear, any m8 slug you would make will do the job, I think it would only need to be about 9/10 mm long max. if I'm wrong on the length somebody will correct me
Cheers,
George

[Eldert]

yes there is something special about the grub screw .

total lenght is 10 mm but the first 4 mm is turned down to 6 mm .
so the threaded part is 6 mm long

Eldert

grub screw 002.JPG

[Duccout]

Thanks Eldert!

[HMBAtrail]

yes there is something special about the grub screw .

total lenght is 10 mm but the first 4 mm is turned down to 6 mm .
so the threaded part is 6 mm long

Eldert

grub screw 002.JPG

Thanks! That's the info I was looking for. A few minutes on the lathe and I now have a grub screw.

[Jordan]

yes there is something special about the grub screw .

Sorry.

[LaceyDucati]

As long as the grub screw blocks the hole it will fulfil it's function.

It is of course debatable how much oil will find it's way to the primaries anyway. Any oil that doesn't exit to the bigend has to fight it's way against centrifugal force to reach the other side of the crank. Maybe that's some of the reasoning why some aftermarket cranks didn't bother with the drive side oil feed.

Nigel