stuck case screws

[Bigsingle]

If you get "stuck" , and all else fails drill the head off it , then you can slide the cover off and get some vise grips on it , warm it with propane and spray some WD40 on it .after that , drill it out.cheers

[iansoady]

I find the old style impact driver that you whack with a hammer work well for this type of screw. Otherwise try to drill the heads off. I find this easiest by starting with a centre drill as used on lathes as it's easier to accurately drill the centre.

[cornishbob]

Is that diet or full fat coke?

Not that it matters as I have neither...but I do have Singer sewing machine oil. I may give it a go if plusgas fails.


[/quote/]

its not the coke its the mild acid reaction on the oxidation (chemical reactions to do with aluminium). the coke/lemonade/lucozade/sprite/tizer/etc has a reaction with the oxide and weakens it making it easier to remove.

but then what do i know

[hoogerbooger]

Thanks all. Rather than get a drill out and risk a real stuff- up I may give up and try to replacing the kick- start seal and LT lead grommet without removing  the case....

(but this will unfortunately leave an oil leak from the outer case below the kick start requiring regular checking and topping up of the gearbox. Ho Hum)

[DAVE BRADY]

Hi,

Sometimes striking an arc can break the bond between the stuck screw and the case.  I have achieved this a couple of times.
It may be a bit tricky if the screw is a bit recessed but it may be worth giving it a go.

Dave.

[V500]

This is steel screw into a nice oily alloy casting, so it's only problematic as someone's done the screws up too tightly and/or mullered the heads. There shouldn't be any need for release oil or magic potions of any sort.
Have you thumped the head of the screw straight on, to shock the threads? Then some application of an impact driver with whatever bit you think fits the best, or even a tap with a centre pop on the edge of the screw in an anti clock direction to start movement?

[Mike40M]

Galvanic corrosion occur between parts of different materials. So not unusual after decades. I'm told that it happens faster if stainless screws in aluminium than ordinary steel screws. Zinc plated screws slower.
One thing that might help is to try when when the engine is hot. Aluminium expands more than steel when warmed. Norton exhaust roses shall always be tightened warm, not to come loose.
An impact driver shall be used with a fairly heavy steel hammer.
There is different fluids for sale that is said to prevent galling. For use when refitting.

[hoogerbooger]

Thanks again.

Have tried using a flat headed punch of matching OD to the screw heads and a standard hammer( 1lb?) To shock them.

They are not stainless. Zinc plated may be...heads fairly soft and I can see the impact driver has impacted the slot to make the slots a little more hour glass shape....than when I started.

I can try when hot when back together....but for now only option seems to be look for a snugger fit bit ( the one used is not bad though)

[Stubaker58]

One other things is to use a screwdriver bit from a docket set so as to get more torque. Even a small ratchet bar will be more effective than trying to twist a screwdriver handle.
I've got a great little Proxon set but Lidl does something very similar for not a lot of cash.

[V500]

Galvanic corrosion occur between parts of different materials. So not unusual after decades.

Possibly, if the engine was stored with no oil or oil residue present and in a damp lock-up or similar. Shouldn't be an issue on our old bikes though.

[cornishbob]

that isnt how galvanic corrosion occurs. in this instance it would because of vibration. no matter how little that vibration may be it will happen in a way described by our mate alice volta. think its called a 'dilectric' effect but it was a long long time ago i did my 'O' levels.

the vibration causes a titchy electric current that can weld and oxidise the 2 metals. hence my suggestion of applying a weak acid before the sledgehammer becomes involved. because as we all remberber from our school chemestry lessons  metal+acid gives?... hands up and stop talking at the back

sowing machine oil is also slightly acidic on the pH scale and does the same thing but is more gentler than coke

[scifi]

If you use a rotary impact drill, then put all your weight on the drill, to stop it jumping out of the slot.
As a last ditch attempt, use a centre punch on the outer edge of one side of the slot, and hit the centre punch with a heavy sharp blow from a steel hammer.   You could also use a cold chisel on half the slot, as a final attempt before drilling the screw out.

[hoogerbooger]

If you use a rotary impact drill, then put all your weight on the drill, to stop it jumping out of the slot.

I did put weight on it.....but I confess my head was thinking when it jumps out with my weight on it I'll gouge more of the case off. The electric rotary impact drill I borrowed was as far as I can see providing less "whack" , than the manual one. As you can't just set it to do one whack, it's done a few before you let go of the trigger...by which time it could do some damage having jumped out. Maybe with extra weight it might not jump out.....but it's a lottery I think.

I have been feeding the last screws sewing machine oil and will have one last go tomorrow...but do not hold out much hope. Based on Screw No2 only the last half inch or so is actually engaged.....with most just sitting in the outer chaincase void ( it seems) ....so any penetrating oil needs to be Indiana Jones to actually get to where it's needed.

FWIW I attach  a couple of pictures. Based on the ones freed up there is a mixture of short and long screws. The 2 stubborn ones remaining are 3 & 7 in the photo which I suspect are both long ones ( like No 2 screw attached)

[cornishbob]

dont know when you applied the oil or how much. i'd suggest a bit of masktape aroundthe blighter to form a bit of a well. no need to slaver it on but enough to give indie a fighting chance and a modicum of heat just before you do the twist

oh and by the way i dont drink wife beater (hint hint}

[scifi]

That screw looks a bit dark on the threaded side.  I hope the previous owner did not put Loctite red on it, as that needs to be heated to loosen it.  The blue is slightly less permanent.
Best of luck with the lubrication.