Very tight JIS screws

I'll try and be as careful as I can and do the right thing. 

Just to give an idea about this engine, I got a lot of good miles out of it and it never missed a beat, and previous owners had clearly decided the wiser move was to use it and do basic maintenance, and so nobody ever opened the cases. That's my best guess. The last guy (the one I bought it from) put in a new primary chain (probably just because he could get to it without splitting the cases). The cam chain isn't a split rivet type and may be original, for all I know. The oil filter bolt was so seized nothing would get it out. I had to weld a piece of 12mm square section steel rod to it, and wind it out with a huge extension bar on my breaker bar. The total extension was about 1.5 metres long. Crazy amount of torque just to remove that oil filter bolt. 
The bolts and screw heads that have been covered in oil (i.e. engine internals) won't have much galvanic corrosion but there will still be some, along with whatever high torque and threadlock from the factory. I'm expecting this whole thing to play hard-to-get. 
 

Michi wrote:

All good points, thanks. 

I've had a handheld impact driver for years. It will move anything, but I've only used it a couple of times. I just don't like the idea of transmitting direct lateral impacts into the engine case.
 

What do you think is going to happen?

Impact drivers are typically used with small sledge hammers in the 2lb-4lb range, and the operator is not supposed to pretend he's Thor. The parts of the cases that house the fasteners are very robust. A few taps from an impact driver won't hurt anything.

OTOH if you're swinging a 12lb sledge like you're trying to hit a home run, then yes, you might cause some damage.

Nothing like the sinking feeling when the head comes off and the BOLT IS STILL THERE. 
Steve

SWest wrote:

Nothing like the sinking feeling when the head comes off and the BOLT IS STILL THERE. 

Steve

 

The advantage is, you can slip off the part that the screw was holding. I'm actually expecting that, in the case of the 4 screws holding on the oil screen under the engine. When the lower half comes off, I'm not even going to waste my time with an impact driver because nothing normal will work on those. I can predict that. So I'm grinding them off to expose stubs to weld nuts onto them to get the remains out, and replace the little cover. 

All these are reasons why people don't touch bike engines. Old cars, lawnmowers, etc. all make good Youtube content. They get it roughly running, give a little chuckle of triumph, then onto the next video. But old bike engines are considered by normies to be scrap metal. Good thing we're not normies, eh.

I

Hate to admit it, but I've had some experiences with an impact gun (on the jis screws that hold some jap car brake rotors in place on the hub, never on a motorcycle) - it's never ended well.  As Wookie said, it will rotate the bit out of the slot and chew up the head. As stated earlier, a sharp rap with a 2 - 4 lb hammer (mine is a 36 oz dead blow) will usually break it free. 

Scotty

Michi wrote:

SWest wrote:

Nothing like the sinking feeling when the head comes off and the BOLT IS STILL THERE. 

Steve


 

The advantage is, you can slip off the part that the screw was holding. I'm actually expecting that, in the case of the 4 screws holding on the oil screen under the engine. When the lower half comes off, I'm not even going to waste my time with an impact driver because nothing normal will work on those. I can predict that. So I'm grinding them off to expose stubs to weld nuts onto them to get the remains out, and replace the little cover. 

All these are reasons why people don't touch bike engines. Old cars, lawnmowers, etc. all make good Youtube content. They get it roughly running, give a little chuckle of triumph, then onto the next video. But old bike engines are considered by normies to be scrap metal. Good thing we're not normies, eh.

That is unless it breaks at the threads flush with the case. Then you're in trouble. Had that happen not long ago with the cam tower cap bolt. It just broke off below the surface where I couldn't get a straight in shot with my reverse drill bits. 

Steve

 

In my experience (and I'm very good at breaking off screws) the screw usually breaks flush where it threads into the part, not at the head.  So as Steve said, you now have a new problem.  

Scotty

 

A few lateral shocks to the head of a fastener are a great way to help the fastener release cleanly & without drama.  The shocks tend to relieve the stress at the threads, and break any microscopic corrosion that might be present.  We use a brass drift as a punch to not crush or otherwise damage the cross heads of JIS screws.  Heat helps too, as the aluminum expands slightly more than the steel of the fastener.  We use a small 1,500 watt ceramic heater directed point-blank at the problem area for 20 ~ 30 minutes to get it too hot to handle without gloves. The same technique also works to remove iron liners from Z1/KZ1000 cylinders; heating for 20 ~ 30 min. allows the liners to just drop out.

As many mentioned above, we'd strongly suggest not using a simple rotary impact tool, such as a simple rotary impact wrench, that doesn't use a lateral hammer strike to set the bit firmly within a cross head fastener concurrent with the loosening torque being applied.  Impact wrenches are useful for hex head bolts & nuts, Torx-type heads and such, but not cross heads on fasteners where the bit can rotate & lift out.

Good Ridin'
slmjim & Z1BEBE

Over on GS Resources, I can't tell you how many times I've read about some newbie breaking off the header screws while trying to remove the exhaust.  Corrosion seizes the threads into the head, then some hamfisted person puts a 3/8" ratchet on the screws and promptly breaks them off.  Some PB Blaster, and heat from a torch, followed by a CAREFUL hand, can remove the screws safely at least 90% of the time.  I always tell guys to use a 1/4" ratchet, with a short handle.  This way you won't have enough leverage to break off the screws.  

Engine case cross-point screws...straight to the Impact Driver.  Carburetor screws on the ganging bars, I use the Vessel Impacta.  The only reason not to use one of these is when the screws are threading into a piece of unsupported metal, such as an engine frame tab, for example.  

If I come across a screw that has been messed up and cant get a JIS driver on it and if I can grab it with a tight vise grip pliers and rotate in the proper direction that works well. If I cant grab it with a pliers I can use a sharp chisel held at a slight angle and with a couple of sharp hits with a hammer in the proper direction they normally break loose. Last resort is to drill off the head.

I'm not touching it until my tools arrive. 

Messing with bike engines isn't a hobby I'd choose, tbh. I couldn't even give the thing away on Ebay with its blown pistons and rings, so my thinking was, might as well make it work again. I don't like the bike and I don't like the task at hand. 

As I've decided it's going to be my last ever old bike, and I'm only going to get new or nearly new bikes in the future, I'll get this done one way or the other. All comments are noted, and thanks. I'll use the impact driver as a first-resort then.

Don't forget corrosion isn't "ageist" even much newer machines suffer from corrosion and seized bolts