Topic: '82 CB650SC Leaking Oil from Cylinder Head-Cover

[tykenfitz]

Hey all, thanks in advance for any light you can shed on this situation!

So after repairing all the damage to my Nighthawk from an accident in the summer of '20 (brake lines, handlebar, clutch lever, etc.) I decided to take a crack at the thing which has been bugging me since I got this bike. The whole time I've owned it, it has leaked a moderate amount of oil from the spot circled in the image below.



Thinking the problem was the gasket between the cylinder head and head-cover, I took the head cover off and replaced the gasket. When this did not fix the problem I realized that the bolt where the oil leak was could not be torqued down, it would go in and then just keep spinning, never getting any tighter. So I took the headcover off again, drilled that bolt hole out and tapped it to take an M8-1.0 hex socket bolt. I was able to torque it to spec and oil no longer leaked out at that spot.

However at some point during this whole back-n-forth I must have over-torqued a bunch of the other head-cover bolts because there are about 6 or 7 of them now that will not torque to spec and now when the engine runs the head cover leaks more oil than before, just out of the other side now   

I am sort of at a loss as for how to proceed with this. I have a helicoil set so I was thinking of trying to repair those bolt holes in the cylinder head with M6-1.0 helicoils. I figure helicoils oughta be fine since the bolts only need to be torqued to 6ft-lbs and if they don't then I still have the option of drilling and re-tapping to a bigger bolt. The only issue I immediately see with this is that some of the bolt holes are inaccessible due to the frame rail, so I'll need to pull the head off to work on them.

So my questions are as follows:
1) Does this sound like a solid solution for the problem or is there a better way of going about this that I'm not thinking of? And,
2) Is it possible to remove the cylinder head without pulling the whole engine? I'd rather not if it can be avoided but if not I can probably rope in a buddy to help

Please let me know whatcha think, and thanks again for any advice you can provide!

All the best,
Fitz

[bryanj]

Helicoils done correctly are fine

[fizzlebottom]

Yes to helicoils. And you can get all the way down to removing pistons without removing the engine from the bike. It is a real bummer that you'll need to do it, but this does give you an opportunity to replace the cylinder head bolt pucks and all other rubber bits.

Read and follow the FSM, take your time, and use the right tools. Don't rush anything and you'll do just fine.

[kerryb]

Reading this because I have one of those and want to find out more about it.  If you do this thread repair in the frame,  won't the frame rails be in the way for some of it?  I took my engine out to replace the starter clutch (thru the oil pan) which wasn't difficult because I made a "hook" described by members on this forum and have a hoist to use it with.  Not expensive or difficult, you might want to consider this.  That and a hf engine stand with bedframe mods make doing engine work much easier.

[bryanj]

You can remove down to base gasket with engine in frame

[tykenfitz]

Awesome, then I'll remove the head and give it a go! Probably between Xmas and NYE as I have some time off, thanks for the advice, everyone!