Honda-SOHC
SOHC.co.uk Forums => CB750 => Topic started by: SumpMagnet on October 08, 2018, 05:02:02 PM
-
How???
The manual says 'undo the 4 countersunk screws. The bearing journal will come away with the housing'
Simple.....no
How in the name of sanity do you get thoise screws out. They appear to have been put in by Hercules himself, and glued downwith the strongest threadlock known to man. Is there a knack to this? Should I use heat ( I only have a small blowtorch and a hot air gun... ) and is there anything I could damage doing that? So far I have managed to shift none of them...not even a fraction. Screwdriver was not going to budge them, and hte impact driver won't shift them a mm either. Made me think they were left handed threads ...but the manual would have mentioned that....
It's the last barrier to splitting the cases for me and the only real issue getting it all apart ( well...that and the final drive sprocket being rust-welded on the splines...but once I get the thing out, I should be able to soak it some more and get a puller on it )
-
Drill the heads off with a sharp 6mm drill, start very slowly, and when all 4 heads have popped off (it's the countersink that is holding them so tight) pull the bearing holder off, and the remaining thread will probably unscrew with your fingers, but there will be plenty left to grip with pliers or mole grips if you prefer.
-
They do hold tight on that countersink don't they ;D
I use on countersink machine screws like this a multi stage routine. Use a drift or ball peen hammer to gently tap the cross grooves into shape if they've been chewed at all. Then get a really tight fit impact screwdriver bit that you can tap into the cross, and either using a power drill with screw torque to rattle them until they come out. Or impact driver on same bit with one sharp hit with a club hammer to release them.
-
impact driver on same bit with one sharp hit with a club hammer to release them
Worked for me....
-
Yes, you've got to hit it with a bit of commitment the first time, a club hammer properly activates the camming arrangement inside the impact driver to give a good drive while the screw head is intact.
The most important bit though is getting that piece of skin between your thumb and index finger properly out of the way before you swing the hammer ;)
-
Impact driver is not having any effect....and I know from personal experience how things can go if you are not 'accurate' with that blow.
If I can't shift it with a bit more impactiness....I will break out the drill. My M6 bit is blunt as a blunt thing..so I will get a nice fresh one before I go that route. I have soaked some penetrating oil into it in the hope that some will find it's way where I need it ...but.... brute force it is then!
I will brace the motor a bit so it doesn;t slip....then apply effort! I'll let you know how I get on
-
Yes you're right that you've got to support the motor so it doesn't go away from you. It's more so that the bit stays engaged than anything else.
As Hairy pointed out about the countersink, they are quite clever as the threads are not under much torque but the bite on the taper is what keeps it from undoing, and very effectively too.
It's not as brutal as it looks as a good impact driver doesn't transfer load straight into the structure, but the internal cam should give the maximum load in a rotary direction to get it moving. A club hammer just concentrates it in fewer blows.
I'm always wary of drilling these sort of fixings out as if you damage the taper in the bearing carrier, it could impair the effectiveness of the new screws.
Hope you get them out.
-
It is safe to use a 6mm drill bit as the thread is M6, therefore if you start slowly, and keep it fairly slow, you cannot damage the chamfer for the screw heads in the bearing holder. I have drilled them by choice successfully, as you will wonder why you bothered trying in impact driver as your hand throbs where you miss hit the driver and clout your hand! I have spent hours with impact drivrrs/heat etc, now it the screws don't move first attempt, easier to drill.
Sent from my X6pro using Tapatalk
-
Are these jis screws? Bought some bits from motion pro and they work well if that helps?
-
I must have upset a gypsy or three .... who placed a curse on me.
shifted 2 screws using impact driver and blunt force trauma. Then the impact driver buit shattered. Now I got to wait a few days while a replacement bit arrives. Can't get a driver bit locally...though I could buy a whole new cheap impact driver....just not the one bit I need.
Still...that's half the fun
-
Use a lefty drill. If you keep smacking them, then you run the risk of cracking the bearing housing ;) As Hairy said : If they don't move the first time, Drill, Drill, Drill ;)
-
I'm blaming a poor quality bit. I mean...I only got 30 years use out of the thing before it broke.....
-
You could take that back if you've still got the receipt :)