74 250 Mag restoration

After finding out the bike I bought was in fact a Mag, I decided I need to restore it.

This is what it looked like when I bought it. Can't blame me and the previous 2 owners for not seeing what it was But the engine is a 2033 and the part of the frame number that's readable also matches a Mag serial. It has the wrong plastics, tank, exhaust, wheels, and probably a bunch more stuff. But it's a start..


The engine was stuck, which is why I got it cheap. So first thing on the todo list was inspect the damage. After getting the cylinder off the crank is still stuck, there has been water in the engine. The cylinder might be okay after a hone but as it's still 69.5 I figure after almost 40 years and with a bike that has obviously been around, the bore is probably not gonna be too good anyway so I'll have it bored to 70.0, I just ordered a new Wiseco piston.
The cylinder has had some porting done to it and it didn't look like a complete hackjob so this bike might just have been raced back in the day.

I want to get the engine running first before starting on the frame, so I'm in the process of collecting parts. Luckily the gears are all moving freely and from what I can see, hear and feel it all looks to be in good shape in there.

A restored bike can't have a clutch cover that looks like this, so the hunt was on for a replacement. Thank god for ebay, I found an in tact one of the correct year there which is on its way over to Sweden now


As the engine will have to come apart I've also ordered a complete gasket kit, so hopefully all I need now are bearings, seals and a bunch of new bolts. I have no idea if the ignition system works but I'll deal with that later.

I do have a question. Can anyone tell me the correct inner diameter of the exhaust flange for a 74 engine? My exhaust is not correct and I'm wondering if the flange is too small.

To be continued!

Your exhaust is not "correct" but I meant to tell you it looked like it was fabbed from the original.

The part after the first bends does look very similar to the 74 exhaust, but it doesn't look modified unless someone did a very good job welding it together. The problem I have with it is that it seems to have a way longer tuned length than the correct exhaust, so I'll be losing out on top end power

This is the same exhaust as is on mine. This one of those MC258 military bikes, recognize the rear fender?

To find an unknown mag is very cool. I'll be watching your thread. thx.

I have never seen a picture of an MC258 before, but I was not saying it was a bad fabrication. I thought the crossover was not what I am used to seeing with Husqvarna pipes

Here's a pic of a complete MC258. The engine is a 250 4 speed automatic with 18 HP. Those 18 HP are why I don't like this exhaust. It's probably got a lot of low end power though but I don't need that. One of the army's requirements for this bike were that it had to carry 2 soldiers with full packing and do 70 mph with a load like that. It's more of a workhorse than a racer. A lot of it is probably in the porting but I'm sure this exhaust won't help much. When I bought this bike, I thought it was one of these with the wrong engine. I know the 2 previous owners and they were under the impression it was one of these too. You can probably see why But it didn't take long before I found out the frame didn't match. It's pretty clear that it has received a bunch of parts from a 258 though. Looks like it's got the ignition coil from one too, it had army green paint on it.


Next question then.. Is there any way to identify exactly what year a cylinder is from? My cylinder has a split exhaust port, 1 transfer port on each side, and of course reed intake. 4 long studs with 2 extra for the head. From what I can tell it all looks correct for a 74, but is there any way to tell for sure?

You want to be carefull about assuming the cylinder will clean up at 1st oversize. My 84 250WR had standard piston when I got it and about .008" clearance. 100psi compression had it sent out for overbore. I sent it to the shop with the 1st over piston. They called me to look at it. It did not clean up mid stroke and egg shape in the front to back plane. Check the cylinder completely with dial bore gage or at least inside micrometer to check size and roundness through out the bore. You may be surprised to find you may need to go right to 2nd over like I did

.008'' clearance is quite a lot though, it's hard to tell because it is a bit rusty but I don't think my bore is anywhere near that. I already ordered the piston so it's too late now anyway If it turns out it needs to be bored more than first over I'll simply have to get another one.

Progress is pretty slow otherwise. I've started stripping the frame a bit, getting rid of that rear fender made it look a lot more like the bike it's supposed to be! The seat also looked good underneath, will have to get a new cover but very usable otherwise. I'm a bit torn about the extra shock brackets. The welds look so good they could be factory and I think it kind of adds to the history of the bike (not that I have any).
The Swedish Husqvarna factory museum can look up info they have on the bike with just the engine number or frame number. So I'm kind of tempted to spend the $30 it costs to get the frame number for it, or at least get the frame number for my engine. Altho I'm pretty convinced the engine and frame belong together. In some cases they can also see who the bike was delivered to, that could potentially be very interesting. Not that I have high hopes of it having belonged to someone famous or anything, but I won't know until I find out

The main reason progress is slow is because I've just sold my workshop a couple of weeks ago so at the moment I don't have anywhere to do my stuff other than out in one of the sheds as you can see on the pics. My only workbench atm is outdoors, which is why the engine hasn't come apart yet. I'm in the process of restoring one of the barns and turning it into a shop, which should be finished in a month or 2. Gonna be big change from a ~3500 sqr ft shop to a 450 sqr ft one, but having a shop right outside the front door instead of 15 miles away should help a lot with the productivity!

Bah, the clutch cover I bought on ebay turns out to be a 74 WR cover, so it doesn't fit If anyone has a correct cover for sale I'm interested!

You should have been able to determine that visually as the older big engine cover has a distinctly different size and profile. If there was not a good picture to look at it is understandable. You can return it to the seller for full refund if he listed it for a 1974 250CR. It will fit a 74 400CR but you do not seem to have one.

I have a cover from a 75 or 76 250 CR. Aren't they the same as the 74 Mag cover? I'd be happy to sell it, but shipping to Sweden could be expensive??? Let me know.

Yea it was my own stupid fault for getting too enthusiastic and not staring at the picture long enough and compare it properly to what I had The auction said 74 250, but didn't specify CR or WR. Looking at the parts manual it will fit a 250 WR so there's not much I can say or do about it. I could probably return it and get a refund but shipping costs would be almost as much as what it's worth. Shipping from USA to Sweden is a lot cheaper than the other way around. Oh well, I'm sure there's someone out there in need of this cover, and if not I'll have to get a bike I can put it on

Picklito thanks for the offer! I have been offered a 75- cover from a member in Sweden but if that falls through I'll shoot you a PM!

A guy somewhat local to me wanted me to restore his 74 MAG but of course that is contingent on him being able to sell off his Lechien Kawasaki ex works bikes. His biggest obstacle to that is that he sold off the works motors for pocket change a few years ago. Now if he puts together the parts into bikes, he only has stock engines to put in them.

The cover you bought is used on all the big engine models so you will not have a difficult time selling it

There's seems to be some kind of spell on this bike.. Things are really not going my way!
So I ordered a 70.00 piston.. What I got was a 70.00 box, 70.00 rings, and a 70.50 piston!

Obviously this time it's actually the seller's fault (or maybe Wisecos) so I'm sure it'll be resolved, but it's gonna take more time.
I suggested they send me a matching ring set in order to have this resolved quickly, instead of me having to return the piston and what not, then it would take another 3-4 weeks before I can get the cylinder bored. The cylinder needs to be bored anyway and boring it an extra 0.5 mm is not the end of the world.

This will be a great bike.. anything causing this much trouble will be worth it

you should have the cylinder cleaned up first, and then the machine shop can tell you what piston it would need

I know that would be the proper way to do it, but it'd take even more time. And if I get sent the wrong parts anyway, getting it cleaned up first wouldn't have helped much
Pistons (and most other parts) are about twice as expensive over here as they are over there so I'm doing most of my shopping from the US. Even with high shipping costs it's a lot cheaper than buying locally. The drawback is that I have to wait about 2 weeks for my parts. I was hoping to get it running this season and start on the frame in the spring so it'd be ready by summer, but with only a month of riding left up here it's not looking too good.

Anyway, the piston issue has been resolved. The store was more than helpful and a 70.5 ring kit is on its way. They talked to Wiseco and the other option was for me to send the piston back, and Wiseco would've sent me a correct kit. A new ring kit was the fastest and easiest way so I went for that.