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1973 Suzuki TM250K

I picked up this very sad TM250K to be my first vintage MX bike project.  Considering the condition, many would say it isn't worth it, but I like a challenge and hate to see any classics go down.  Besides, if I can get this thing back in race condition, I should be able to handle anything, right?

She's not much to look at.  Plastics and seat are toast, the tank I suspect is from a '78 RM, but usable.  The forks are shot, bent and badly pitted.  And there's not much left of the exhaust.  None the less I'm excided to have her.




Hopefully, at some point, she will resemble the brochure.

1973 Suzuki TM250K
1973 Suzuki TM250K
1973 Suzuki TM250K
1973 Suzuki TM250K
1973 Suzuki TM250K
1973 Suzuki TM250K

Well for this teardown everything will come apart, and I mean everything.

1973 Suzuki TM250K

Like the rest of the bike the engine was in pretty bad shape.  While it turned over and had decent compression, disassembly showed a lot of issues:

  • The main bearings and lower connecting rod bearing were shot. 
  • The frame mounts had worn a hole in the top of the cases allowing mud in; a result of poor maintenance – loose mounts – no doubt.
  • Cylinder and piston were border line.

I had the cylinder bored and ordered a new Wiseco kit.  I found a NOS crank and ordered new bearings.  One of the head studs was sticking out a little further than the rest.  Investigation showed the stud was stripped in the cylinder.  I had a Time-Sert thread repair kit from another project, so I used it to repair the threads and then ordered all new studs.

To repair the cases, I built up the mount points with a TIG welder, and then machined them.  It wasn’t necessarily the prettiest repair but it worked.

The oil slinger was cracked.  I originally repaired it with some welds, but then found a NOS one on eBay.

The reassembly went well and I think she looks pretty good.

The frame had several issues that needed to be addressed.  It had worn and broken motor mounts, some rust pitting and a crack under in one of the top subframe bars.


I cleaned up the frame with sandblasting, wire wheels and an angle grinder.  I welded the cracks, pits and broken motor mounts.  I also brazed on some washers to improve the strength of the mounts.


The subframe also has a slight bend upward, likely from a hard rear ditching.  I haven't determined the best method to straighten this yet.

Rusty spokes, pitted and cracked rims, rotten tires - basically shot.  The rear rim could be salvaged but the front rim had several cracks and some bad corrosion pitting.  I decided to replace them and ordered new Tusk rims.  Unfortunately, I prematurely ordered spokes and they turned out to be the incorrect length for the new rims.  It turned out the rear spoke kit was missing a spoke anyway, so I was able to return it.  I'm waiting on a used set of forks from a '74 model which will include the front hub.  I suspect the front spokes will be incorrect as well.

I contacted Buchanan's spokes via email, but didn't recieve a reply.  Once I get the new front hub, I call them to see if they can supply the spokes I need.


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Project | by Dr. Radut