Cylinder/head nuts and studs

[CBX1000chris]

Hello all,
Having got the parts to sort out my clutch (clutch animal thread) I decided to start on the top end, compression has been low for a while and I couldn't ignore it any longer.
The first curios thing was the two 8mm domed head nuts on right-hand side of the engine were damaged, the stud had pushed through the dome. I hadn't noticed this on the two occasions I'd checked and adjusted valve clearance. The head and cylinder took some separating but I got there in the end, however the second curious thing was as the cylinder lifted from the crankcase oil pooled out on the right-hand side of the engine.
When it was all apart, and after I'd checked the parts list, I realised the 8mm studs on the right-hand side of the engine look to have been swapped with the 8mm studs on the left-hand side of the engine, they are different part numbers and therefore length I guess? The left-hand studs currently sit about 5mm lower than the 10mm studs and right-hand studs sit about 5mm higher than the 10mm studs. I think the clutch animal has been at it again.
It looks to me as though the design is such that when parked on the side stand oil drains from 4,5 and 6 down the cam chain gully and cylinders 1,2 and 3 drain down the stud holes in the cylinder and head, there is a notch in the head and the crankcase to facilitate this.
The oil that pooled out from the cylinder / crankcase joint had found it's way past the damaged domed nuts but there was nowhere for it to drain to at the crankcase.

Does all of the above make sense?

So I plan to swap the studs to their correct position. I've not removed studs like this before so unless someone shouts NO!!! I'll grip the studs as close to the crankcase as possible to avoid them twisting then after a few minutes with a heat gun on the crankcase give them a twist. I've already been at the studs with WD40.

Incidentally the pistons all measured 64.46 - 64.47mm and groove clearance was <0.038mm. There was no signs of damage so they should be OK to reuse. Ring gaps were well out of specification. I'll get the bores measured later but hopefully I just be replacing the rings and with a light hone and I should be good to go.

Any feedback / advice on the studs would be appreciated.

Thank you in advance and regards,
Chris.

[jnnngs]

Chris,

Sounds like the outside studs have been switched around as you say.

The outer left pair of studs are longer as they screw into a recess in the crankcases - where oil drains down the stud holes from the head into the crankcases.

I think what has happened by switching them is the extra length on the right side has caused them to burst thro' the dome nut. This will then mean oil will trickle down the threads down the studs and fill up the stud holes - no drainage to crank cases on right side.

So, swapping the studs over will fix everything. Getting the studs out should be OK - given they have been out before to swap them over! They can be tight, and I use a stud extractor that grips the studs at the bottom.

Paul.

[CBX1000chris]

Hi Paul,
Thank you for confirming my thoughts about what had happened.
Chris.

[Jeff Bennetts]

Chris,

Sounds like the outside studs have been switched around as you say.

The outer left pair of studs are longer as they screw into a recess in the crankcases - where oil drains down the stud holes from the head into the crankcases.

I think what has happened by switching them is the extra length on the right side has caused them to burst thro' the dome nut. This will then mean oil will trickle down the threads down the studs and fill up the stud holes - no drainage to crank cases on right side.

So, swapping the studs over will fix everything. Getting the studs out should be OK - given they have been out before to swap them over! They can be tight, and I use a stud extractor that grips the studs at the bottom.

Paul.

Nice explanation Paul!
Chris the nice thing about the stud extractor is that it only applys more clamping force on the stud as you turn the extractor counterclockwise, much more manageable and less destructive to the studs!