Sump Plug Problem

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Unfortunately, it is probably attached to the flywheel. I would try this: remove the big sump plug, bike on the center stand on enough wood to get your head under the bike (scary). Bike tied down somehow so it can't move or with a helper. Plugs out, in 4th gear. Get your head under the bike and using a light look in the big sump hole at the flywheel. Turn the rear wheel to make the crank turn and hope you see the magnet. If that's too scary, the scope might let you see it through the big sump hole.
I reckon you are on the money with this diagnosis
 
Unfortunately, it is probably attached to the flywheel. I would try this: remove the big sump plug, bike on the center stand on enough wood to get your head under the bike (scary). Bike tied down somehow so it can't move or with a helper. Plugs out, in 4th gear. Get your head under the bike and using a light look in the big sump hole at the flywheel. Turn the rear wheel to make the crank turn and hope you see the magnet. If that's too scary, the scope might let you see it through the big sump hole.
Greg,
I'll give that a try tonight!
 
When removing the sump plug on the Mk2 Commando, the bolt head snapped right off.
I was able to remove the other bolt half with an easy out, however as you can see from the photo the magnet is missing.
It is obliviously now in the sump. I tried fishing some wire through the hole hoping the magnet would stick to it, but no luck.
Any ideas? I'm not thrilled about having to remove the head and cylinder to get it



Sump Plug Problem
Sump Plug Problem
It puzzles me how a steel bolt, hollow or not, snaps off in an aluminum threaded case, especially while removing it. I have had one strip the threads in the crankcase, but never break the steel bolt. Possibly a defect in the bolt?
 
It puzzles me how a steel bolt, hollow or not, snaps off in an aluminum threaded case, especially while removing it. I have had one strip the threads in the crankcase, but never break the steel bolt. Possibly a defect in the bolt?
Magnet diameter too big , so the hole size and the root depth of the thread makes it too thin/weak .
 
Never heard of this problem before.
Though I have seen excessive torque applied to sump plugs and the like that have made it a right pita to undo to service etc.
 
I've had the same thing happen to one of the hollow rocker feed bolts into the head. The the protective zinc or cadmium coating only lasts so long.
 
I've had the same thing happen to one of the hollow rocker feed bolts into the head. The the protective zinc or cadmium coating only lasts so long.
I still struggle to see why a bolt that gets tightened to about 15lb snaps ? ..I know alot of parts are stainless and a tread treatment will help isolate electrolytic corrosion but these bolts are all low torque bolts with copper seal washers to stop oil leaks ...its got me beat
 
Please explain the relevance of the coating to strength of the banjo bolt.
I think the logic is that it may have seized into place.

Could also have been Loctited.

Either could cause high torque stress when removing, especially if over torqued when tightening.

I guess…
 
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I think the logic is good hat it may have seized into place.

Could also have been Loctited.

Either could cause high torque stress when removing, especially if over torqued when tightening.

I guess…
Unlikely to be seized imo because the thread in the crankcase would be bound to be oily
Unless a new build maybe
Even then with hot oil directly above the bolt and heat cycling going on I suspect the thread gets an oiling however slight all the way to the sealing washer in use
I doubt anyone would use loctite in that location?
I'm guessing overtightened when fitted and broke on attempted removal
 
Unlikely to be seized imo because the thread in the crankcase would be bound to be oily
Unless a new build maybe
Even then with hot oil directly above the bolt and heat cycling going on I suspect the thread gets an oiling however slight all the way to the sealing washer in use
I doubt anyone would use loctite in that location?
I'm guessing overtightened when fitted and broke on attempted removal
The worst thing I've snapped is a tap in the end of the camshaft years ago
Rebuilt motor with a new 4s cam ...had motor in and was about to fit ignition when I discovered the thread was crook ...grabbed correct tap.. pumped some oil in carfully wound the tap in and out a touch to clean thread up ...it bit and apon backing the tap out it broke !!
Had to pull motor out and in the end and set it up on a rotor spark machine to remove the bastard !!
Guess where the tap and die set was made....
 
The worst thing I've snapped is a tap in the end of the camshaft years ago
Rebuilt motor with a new 4s cam ...had motor in and was about to fit ignition when I discovered the thread was crook ...grabbed correct tap.. pumped some oil in carfully wound the tap in and out a touch to clean thread up ...it bit and apon backing the tap out it broke !!
Had to pull motor out and in the end and set it up on a rotor spark machine to remove the bastard !!
Guess where the tap and die set was made....
I wonder where it could have been made 🤔 🤔🤔
 
Please explain the relevance of the coating to strength of the banjo bolt.
The relevance is the OP said it snapped when removing. Bolt is iron steel. Sump (or, in my case, the cyl head) is aluminum. It is called dissimiliar metal corrosion.

In the OP's case, the corrision could have been accelerated by the interaction of the magnet and his specific oil chemistry, IMHO.
 
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I still struggle to see why a bolt that gets tightened to about 15lb snaps ? ..I know alot of parts are stainless and a tread treatment will help isolate electrolytic corrosion but these bolts are all low torque bolts with copper seal washers to stop oil leaks ...its got me beat

Original torque setting has nothing to do with it.
 
I still struggle to see why a bolt that gets tightened to about 15lb snaps ? ..I know alot of parts are stainless and a tread treatment will help isolate electrolytic corrosion but these bolts are all low torque bolts with copper seal washers to stop oil leaks ...its got me beat
If this was the AN plug and it was tightened to more than 10 ft lb, then maybe it was cracked when tightening and broke when loosening. AN warns not to tighten them more than 10 ft lb.
 
If this was the AN plug and it was tightened to more than 10 ft lb, then maybe it was cracked when tightening and broke when loosening. AN warns not to tighten them more than 10 ft lb.
Thanks Greg.....My torque figure of 15 ft ib I quoted was a stab in the dark....give or take 👍
 
If you make your own sump magnet don't let it protrude too far. I made one for my 4WD Willys truck tranny that broke off (maybe a gear tooth hit it). It got ground up and scattered everywhere in the gearbox transfer case. Lucky it stuck to the case shell and not the bearings and didn't cause much damage. I was able to clean things up at rebuild time.
 
If you make your own sump magnet don't let it protrude too far. I made one for my 4WD Willys truck tranny that broke off (maybe a gear tooth hit it). It got ground up and scattered everywhere in the gearbox transfer case. Lucky it stuck to the case shell and not the bearings and didn't cause much damage. I was able to clean things up at rebuild time.
Always a consideration. I also drill the bottom of my axle housing on my pickup trucks, tap 1/8 NPT, and use a below flush seated socket head pipe plug fitted with a magnet.

Sump Plug Problem
 
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