Is it safe to use a hit with a mallet type of impact driver to undo stubborn case screws......or do I risk bending the casings ?
Trying to take B40F outer timing case off. Screws are a mix of slotted, some with shallow slots, a couple a bit mashed. 4 not keen on moving.
advice/tips welcome
It's an alloy case so impact driver every time. Never fails.
FOR CLARITY: I don't have a electric/pneumatic impact driver......only an old style whack it with a mallet manual one........hence my question.
A lot of the times just hitting a normal screwdriver will free the screw.
Hi,
Before any brute force is used apply some penetrating oil and allow it to soak in. If possible lean the bike right over so it pools around the screws and leave it over night. Also a good fit 'T' handle screwdriver gripped with mole grips enable maximum pressure and torque to be allied without the screw driver twisting out of the slot.
Dave.
Quote from: hoogerbooger on 26 Feb, 2025, 18:50 FOR CLARITY: I don't have a electric/pneumatic impact driver......only an old style whack it with a mallet manual one........hence my question.
Nor me, but an impact driver is good enough. Don't know about whacking a screwdriver though... :o
this may sound stoopid but...
a drizzle of coca cola and left a couple of hours (maybe another drizzle after a while) then GENTLE use of an impact driver.
OR...
sowing machine oil... i laughed too until i tried it
Just put the screwdriver in the screw. Just a sharp tap with the hammer will very often break the bond between screw thread and case. Better than force and ramping the screwdriver out of the screw causing damage.
1 drop of coke or sowing machine oil will be beneficial . trust me i'm a haberdasher
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.
I guess the action of a " whack-it" impact driver is potentially better than an electric as I presume the impact from those is only rotational and on the very shallow screw heads it's down to you to press against the screw hard enough that the bit doesn't jump out.....whereas the whack a mole version is driven inwards at the same time.
I did use it on 3 that did come out but pretty lightly....then thought is it sensible to whack the remaining stubborn ones harder. Will get back to this after weekend.
2 more out after plusgas and switching to lump hammer from rubber mallet. Light short sharp blows only.
Mmm. ....reticent to strike harder on the last 2. .
Might be able to borrow an electric impact driver....but that might pose more risk of jumping out and gouging the casing?
Does anyone use an electric and have knowledge/ advice
Correct me if I'm wrong. I think they are Phillips 3. Met a few people using #2 and destroyed screws.
My very old impact driver which only has #3 does a decent job. If used with a Triumph sized hammer.
I've usually had success with a hammered impact driver. Hold and twist then whack!
As said above the bits are a good fit on BSA cross head screws.
It's only when the screws are damaged that crested drilling the head off; I don't understand why but with the head off and the cover raved the stub usually comes out easily with mole grips.
All the screws on this case are slotted. Two different sizes.
The impact driver bits fit pretty well. One screw head fairly mashed but bit not jumping out....just haven't budged them at my level of whack.
Well electric impact driver was no help and dangerous. Not enough whack and jumps out.
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
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.
Quote from: hoogerbooger on 27 Feb, 2025, 21:20 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
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)
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.
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?
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.
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)
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.
Quote from: Mike40M on 01 Mar, 2025, 11:52 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.
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
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.
Quote from: scifi on 02 Mar, 2025, 14:48 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)
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}
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.
You can get aerosol shock freeze spray.
ive just had a close up look at that bolt. it does look a bit like threadlock doesnt it.
if it is then heat heat heat as dump the trump would say.
many moons ago when i was a greenhorn i had to change a worn out front disc on my older sporty. i broke 2 allen keys attempting it.i then went for a socket. i spoke to the guy in the tool shop and he said a snapon would do it. it cost an arm and a leg butit was sale or return if it didnt...it didnt turned out it must have been a snapoff not a snapon part. he was amazed,
any way.. an old guy i new said 'heat heat heat but not too much'. 5 minutes later the new disc was on
Hi,
Even if it is not thread lock it could just be detritus that accumulates over the years. Bits of sealant and gasket get pushed in to the hole and can easily act like a thread locker.
Once you have all the screws out give the threaded hole a really good clean and run a tap down to ensure all muck is removed.
Dave.
thats absolutely right. the mess in those threads is insidious. even to this day my missus is amazed how muck from the shed gets on the bed sheets
A handheld electric battery impact driver might work - they have a torque release ratchet that rotates after max torque but still produced some force at the drive head. Unlike mains impact drills that usually just stop (dangerous!) if they can't turn.
Yes, and do get it hot before hand.
Quote from: MadPete on 06 Mar, 2025, 12:39 A handheld electric battery impact driver might work
.........
Yes, and do get it hot before hand.
Was a battery impact driver I borrowed....without success.
I don't have a blow torch, but did try a hot air gun focused on the head for 5 mins. No luck and head a bit more mashed
So I've given up for now and have changed the kick start seal and LT lead grommet/boot. Will get it back together and running.
When it's running and hot I can have another go on the top of the 2 ( exhaust might hide bottom one). If it does shift then I will know heat was the missing ingredient. To drill off the heads I think I'd need a local guru to work with ( or there's a garage not too far away that does old bikes)
Hot air gun is unlikely to get it hot enough - and you need to point whatever heat source you're using at the alloy surrounding the screw rather than the screw itself. The hope is that the alloy will expand faster and further than the steel screw hence releasing it.
Quote from: iansoady on 07 Mar, 2025, 10:23 Hot air gun is unlikely to get it hot enough - and you need to point whatever heat source you're using at the alloy surrounding the screw rather than the screw itself. The hope is that the alloy will expand faster and further than the steel screw hence releasing it.
Thanks for the clarification.
I can't see it working for these two screws as it looks like the thread they engage with is distant. With the head drilled off and case cover removed then it would seem easier to heat the necessary area.
The problem with drilling the head off the screw is that the drill bit will bind in the screwdriver slot and snap a 1/8th. or 1/4 inch drill. Maybe the only safe way would be to gouge the head flat, then centre punch, and then drill.
I suppose you will be looking to replace all these screws with Alan Key screws, maybe stainless..? I think there is a firm in Cornwall that stocks a good selection of stainless bolts.
if i'm reading this right you're trying to heat the bolt?
surely you should be heating the area of the crankcase where the bolt thread is. its that metal that needs warmth.
i have a b&q propane blow torch thats infinately adjustable. i've removed many stuck bolts . its easy to me.