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Hi All,

I have a LD Mk3 (57 / 58) that I need to remove a Mag Flange. The engine is out and striped as much as I can at the moment. I have heard that Mk3's are difficult to get off. So far I have:

Removed magneto cover and spring,
Removed the 19mm nut and washer,
Used the tool to remove / pop the flywheel off
Remove stator (x3 screws) and placed into the flywheel to aid me in not loosing magnetism on the flywheel unit.
Remove mag flange bolts (x6 small bolts)
Bent the locking washer down and removed the large nut, washer and circlip, so that I can now see the oil seal
Using a Stanley blade, cut into the mag flange gasket as much as I could around the edge of the outside of the casing
Placed my mag flange removal tool over the crankshaft end (GP / SX / LI fitted good and I just needed difference bolts!) and using three bolts, slightly bigger than the original ones used on the stator, screwed the tool on over the crankshaft and into the stator holes as far as they would go, to prevent thread damage on the stator holes when applying pressure to pop off.
Attempted to tighten to no avail. I have also used heat for 20 minutes around the mag housing area and tapping the side with a mallet to no avail. I have also used a long pipe for additional leverage on the tool to tighten it up and pop it off and ended up bending the very big bolt slightly with the force I used.

My thoughts now are perseverance and time. Over several days, leaving the tool on with pressure applied and on and off over the next week or two, continue heating up the mag flange area and using a mallet, taping at the mag flange around the side.

Any further thoughts would be greatly received.

Two images are attached to the post for viewing of the current state. Note: The holes used to secure the tool onto the mag flange ARE the stator ones!

Much obliged.......

It's not just the Mk3 mag flanges which are a pig to remove, the earlier ones are much the same! The problem is that the grey (asbestos-based?) mag flange gasket seems to stick to the crankcase and the mag flange, and with a bit of corrosion, the whole lot seems to seize solid. I've had some success in the past by getting the mag flange to rotate back and forth very slightly, just enough to persuade the gasket to part company with the alloy. I've done this my tapping the mag flange with a medium size hammer, using a drift (brass or alloy bar) between hammer and flange. The place to tap is the raised section on the mag flange casting, where the wires from the stator plate exit the flange. Unlike the Li mag flange, using long screws in place of the stator plate retaining screws as extractors doesn't work too well, as the ends of the screws won't have a solid piece of crankcase to press against. If you can get the mag flange to rotate slightly, it's possible to move it to a position where there is solid metal for the stator plate retaining screws to press against. You will probably mark the gasket seating area on the crankcase, but it's easy enough to clean up afterwards. If you can get the flange to move at all, it might help to use penetrating oil or similar to assist in getting the gasket to release its grip. Don't use excessive force - I've seen lots of badly damaged mag flanges with the outer rim broken, through trying to directly tap the flange out of the crankcase. Heat may also help, as would the correct extractor, once you've persuaded the gasket to let go!

Steve J wrote:It's not just the Mk3 mag flanges which are a pig to remove, the earlier ones are much the same! The problem is that the grey (asbestos-based?) mag flange gasket seems to stick to the crankcase and the mag flange, and with a bit of corrosion, the whole lot seems to seize solid. I've had some success in the past by getting the mag flange to rotate back and forth very slightly, just enough to persuade the gasket to part company with the alloy. I've done this my tapping the mag flange with a medium size hammer, using a drift (brass or alloy bar) between hammer and flange. The place to tap is the raised section on the mag flange casting, where the wires from the stator plate exit the flange. Unlike the Li mag flange, using long screws in place of the stator plate retaining screws as extractors doesn't work too well, as the ends of the screws won't have a solid piece of crankcase to press against. If you can get the mag flange to rotate slightly, it's possible to move it to a position where there is solid metal for the stator plate retaining screws to press against. You will probably mark the gasket seating area on the crankcase, but it's easy enough to clean up afterwards. If you can get the flange to move at all, it might help to use penetrating oil or similar to assist in getting the gasket to release its grip. Don't use excessive force - I've seen lots of badly damaged mag flanges with the outer rim broken, through trying to directly tap the flange out of the crankcase. Heat may also help, as would the correct extractor, once you've persuaded the gasket to let go!

Hi Steve J - Thanks for the detailed reply. It's good to read about your experiences with LD mag flanges and suggested solutions. There good ideas to try next. I will remove the tool and persevere with heat and take my time over the next few weeks with trying to rotate it left or right a little, with some "tapping" on the case. Currently, with heat and the tool loaded on, I am trying to tap it off, rather than tap it to the left or right to loosen it. I will also see if I can get a Stanley blade around the areas of the gasket I can't get to with ease, to try to separate the gasket further.

Looks like a good plan! Just avoid excessive force whatever you do. I'm sure I've seen a product in the past designed to soften old gaskets, which might be worth a try - provided it's still available. I think it was some kind of aerosol, but I can't be certain. Possibly I was thinking of something like this:- https://uk.rs-online.com/web/p/chemical ... s/0293489/
The other problem in removing the mag flange is that the flywheel side double row ball bearing is a tight fit on the crank, and also a tight fit within the flange, so it's worth using heat to expand the alloy, allowing the bearing to slide a millimetre or two within the mag flange. If the clutch bevel gear, shaft and bearings have been removed, it's possible to remove the nut on the drive end of the crank (left hand thread) to allow the crank to slide sideways, which may help in getting the mag flange free. It's no wonder that the French Mk4 Ld replaced the double row ball bearing with two separate roller bearings - the flange on those is no more difficult to remove that on an Li series motor!

Steve J wrote:Looks like a good plan! Just avoid excessive force whatever you do. I'm sure I've seen a product in the past designed to soften old gaskets, which might be worth a try - provided it's still available. I think it was some kind of aerosol, but I can't be certain. Possibly I was thinking of something like this:- https://uk.rs-online.com/web/p/chemical ... s/0293489/
The other problem in removing the mag flange is that the flywheel side double row ball bearing is a tight fit on the crank, and also a tight fit within the flange, so it's worth using heat to expand the alloy, allowing the bearing to slide a millimetre or two within the mag flange. If the clutch bevel gear, shaft and bearings have been removed, it's possible to remove the nut on the drive end of the crank (left hand thread) to allow the crank to slide sideways, which may help in getting the mag flange free. It's no wonder that the French Mk4 Ld replaced the double row ball bearing with two separate roller bearings - the flange on those is no more difficult to remove that on an Li series motor!

Hi Steve J - Thanks for the additional comments which I will review as well. I've not come across a product yet that eats into the gasket seal like a rust or acid type perpetrator. Hence the Stanley blade approach, which has worked on the transmission and barrel separation. I think the spray solution mentioned at RS is used after the unit has been separated and you then spray it on to remove the gasket that is stuck down. I've also thought about the seal and bearing impact that may be keeping the flange securely in place and thought about digging this seal out and heating the bearing to aid in the flange removal. I may try this approach as well after spending some more time heating it and tapping left to right. This beast had a seized piston which has taken me over three weeks to finally get the barrel off. After removal, I found the drive shaft rather stuck. After resting most of the engine in diesel and using rust penetrating fluid, I now have good free movement of the crank, so this seems salvageable. Since I replied to your first post, a further 1.2 hours have been spent heating the flange and engine casing and taping left to right, to no avail. It's an interesting challenge and one I need to repeat on a few LD's I have. Once I have resolved, I will update this post on my final resolution - whether it's successful, or if I have damaged or cracked it........ Watch this space........

It all sounds very typical of an Ld engine which hasn't run for decades! Before you go to the trouble and expense of getting the barrel rebored, I'd carefully check the spigot area of the barrel for hairline cracks. I once had a seized Ld engine where the buildup of carbon and crud at the back of the rings was pushing the rings hard against the barrel wall. When I finally got the piston to move, I'm convinced that the pressure of the rings on the cylinder wall was too much for the thin spigot, which cracked vertically. I've also seen a couple of NSU Prima D 150 barrels in exactly the same state - these also have a 57mm bore and a spigot diameter of 62mm, meaning the spigot walls are only 2.5mm thick as standard. Probably because both engine types were originally 125cc, and minimal changes were made to squeeze a 150 cylinder into the existing design of crankcase.

A quick update.

I have left the entire mag flange and part of the engine in soak in diesel for at least three weeks now, taking it out every so often for a review and attempted removal. I have a few LD's and am therefore working on two others while I sort this beast out and leave it in soak, coming back to it in between jobs.

For attempted removal, I have removed my mag flange tool you see in the images and placed some long bolts into the x3 stator plate holes, not too tight, but tight enough to aid in applying some pressure, while I use heat on the top and side of the mag flange.

I have used heat (Blow torch - two and a half canisters) for at least 2 hours on and off over the last few weeks and continued to use Stanley blades to cut into the gasket as much as I can. When the engine is very hot, holding it with a cloth, I have also used a rubber mallet and tapped the mag flange to try to get it to move a little. In all honesty, I am probably using more force than I should with the rubber mallet.

As well as using heat around the side of the mag flange and on the top, when applying heat on top and through the bolt holes, I can now see a flame come out the side of the mag flange. The other way, if applying heat from the side, I can now see a flame coming out of most of the mag flange bolt holes. The Stanley blades helped with this. I think I have managed to get around 35% of the gasket released looking at the amount of flame that seems to be coming out of the side.

I am also using plenty of a rust penetrating fluid on it and down the holes to aid, which of course gets set on fire when reapplying the heat.

I have heard a few positive whispers of a crack with the heat, implying the flange expanding with the heat thus aiding with the releasing it from the casing.

After waiting a long time for it to cool down, I put it back into the diesel to continue to soak.

With all the heat I am applying and tapping of the mag flange, I am realistic and do understand that I may end up causing some damage to something and am happy to take this risk based on how stubborn it is to get off. I'm also as careful as I can be under the circumstances.

I think that once I have 100% flame coming out of the sides, it will indicate that the gasket is release as much as it can be and I may be able to use the mag flange tool to aid in it's removal (Or continue with trying to tap it off with a mallet!).

I'm hoping a few more weeks should do the trick and will report back, hopefully with some positive news and not about damage caused!