Does anyone have a crank and flywheel for a 241?

[hero]

The flywheel was jammed on my 241 engine after shearing the woodruff key. I finally got it off and split the cases to see what was required for a full rebuild. Unfortunately, after 20 years in storage, there has been water ingress. This is only on the magneto side and the Crank is badly pitted on the bearing shoulder and where the oil seal fits. It would be a shame not to be able to save another 241 from the heap. Has anyone got anything to help or ideas?

[kurtas]

You could investigate getting the damaged areas chrome plated.
They would grind the part down and then chrome plate back to size, hopefully removing the damage in the process.
The seal area is the key, I don't think it would matter if there were a few surface defects like what you've got where the bearing sits.

If the depth of the defects are less than 0.25mm than it should be acceptable to chrome plate.

[hero]

Interesting, presumably the shaft would have to be removed from the crank web to do this. The problem might be the cost of such work and where to find someone who could do it. It might even be more cost effective to have a new shaft turned down.

[kurtas]

Another thought, you could see if a sleeve was available for the seal area.
Then just give the bearing area a light cleanup with emery.
https://www.skf.com/au/products/industrial-seals/power-transmission-seals/wear-sleeves/skf-speedi-sleeve

[hero]

Thanks Kurtas, I did come across the Speedi-sleeve and considered using one in each area. The downside to that is that I / someone, will have to split the crank in order to put the shaft in a lathe to have the areas trimmed down the 2mm required. It would make a nice repair but possibly expensive by the time it was all pressed back together (plus the cost of a flywheel). I was hoping someone would have a crank somewhere lurking in the back of their shed but it appears not.

[konrad]

I was going to stay out of this one because I expect any proper repair would cost as much as the bike is worth.  Beside the aforementioned sleeve, plasma spraying or welding followed by grinding is what would be done for industrial equipment.   

A lower-cost option may be to build a working crank from two scrap cranks with different problems.

The most critical area is the seal running surface.  Depending on severity, an air leak there will make the bike difficult to carburate or prone to seizure.

As for a ghetto repair, I may be tempted to try a metal epoxy (JB Weld comes to mind).  This would last long enough to evaluate whether a more permanent fix would be worthwhile.

Fitting a different seal, or altering the location of the standard seal, is another possibility.

[konrad]

One more thought.  Replace the OE crank bearing with one from a more modern 2T engine that uses sealed packed-in-grease main bearings.

[hero]

Thanks for getting involved Konrad, I had not considered a sealed bearing. The original bearing on the flywheel side is definitely shot for the same reason the crank is, water ingress, and so a new bearing is necessary anyway. JB Weld has served me well on fairings in the past but did not work well on pitted forks ( between the triple trees, not on the lower legs ). The rest of the engine seems ok so, if low cost or used spares were available, then it would be worth the effort. I’ve come this far it’s worth a bit more thought yet. The overall condition of the bike is scruffy but I hate sending anything to the scrapyard, it’s my age I guess. The crank is still contained in the L/H case as it would appear that the bearing on that side needs to come out with the crank before it can be removed from the crank itself. Do you know if that is correct?

[konrad]

  On 4/15/2025 at 4:31 PM, hero said:

The crank is still contained in the L/H case as it would appear that the bearing on that side needs to come out with the crank before it can be removed from the crank itself. Do you know if that is correct?

Expand  

Yes, that would not be uncommon.  But I have zero knowledge about Fantic engines, and the bearing could well be difficult to remove due to corrosion.

[hero]

I think the bearing face on the crank is more important than normal because it’s not where a contained inner part of a race fits but is where the rollers contact directly. A sealed, normal type, enclosed bearing might be the answer if I can find a 62x25x17. Whilst this type of bearing is usually used in wheels, I’m not sure if it’s suitable in mains situations.

[konrad]

Well, that is not at all what I expected.  I had assumed a ball bearing with an inner race.  That is quite possibly a special bearing manufactured for Fantic.  I'd suggest taking everything to a local bearing supply company and having a chat with a specialist.

[hero]

I can get a 25x62x17 sealed bearing with inner and outer flanges from lots of suppliers, even SKF. The main advantage of the original is that it allows end float because the L/H side is pressed onto the crank and casing so any end play there is not possible. I would need to ensure that there would be some sideways movement in the inner flange of the new bearing against the slightly damaged crank. The original NU305E bearing is also readily available. Sorry Konrad, I know you intended to stay out of this one.

[paulc76]

The crank has a inner bearing race on it you will get a new one when you buy a new bearing so that will not be an issue they can be tricky to get off though and i'm not sure if a standard 241 had that type of bearing from the factory maybe been added by a previous owner, as for the seal face it can be sleeved fairly easily where are you located?

[hero]

Thanks Paulc. I did see adverts for the bearing that seemed to offer the sleeve as part of the package. However, in the description it said there was an outer flange but no inner. I presume that the sleeve is therefore heated and shrunk in place. I need to take a closer look. I am near Salisbury in Southern UK.

[hero]

Paulc you’re right. The original sleeve is still on the crank and it doesn’t want to come off. I thought it was part of the crank. The bearing is supposed to have an inner flange of 25mm but the face I have on the crank is 33mm. I feeling a bit daft now!