1. Husqvarna Motorcycles Made In Sweden - About 1988 and older

main bearing re-boring

Discussion in 'Vintage/Left Kickers' started by Tom Dowell, Nov 20, 2021.

  1. Tom Dowell Husqvarna
    C Class

    Husqvarna Motorcycle:
    1972 250WR
    Other Motorcycles:
    1976 Bultaco Alpina DT 400 Yamaha
    I am in the process of restoring a 1972 250wr. split the engine cases and found a previous owner had installed one of the main bearings with copious amounts of red loctite. I have a small machine shop and am contemplating reboring the cases for liners and then reboring the liners for new, on size, main bearings. Anyone else been down this road and if so how did it turn out?
  2. Picklito Husqvarna
    Pro Class

    Location:
    Washington
    Husqvarna Motorcycle:
    430, 430, 430, ,400, 175
    Other Motorcycles:
    KTM250xc, KTM500mx, KTM440exc
    I just had this done by a friend/machinist. Worked very well. It's a different motor than yours, but the principle should be the same. We did it on an 80's 430 (magnesium cases) at the large bearings on both transmission shafts. That's the large one behind the clutch, and the output bearing at the C/S sprocket. The bores had lost their heat-fit and the bearings were loose and moving in the bores. Something to consider:

    On those 430's, the main bearings are already steel sleeved from the factory. If yours are, perhaps you can remove the originals and start over. You'd still have to make your own new inserts but it might at least save you some time finding the original center to work from.

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    moto_surfer and Tom Dowell like this.
  3. Tom Dowell Husqvarna
    C Class

    Husqvarna Motorcycle:
    1972 250WR
    Other Motorcycles:
    1976 Bultaco Alpina DT 400 Yamaha
    Thanks for the reply. I am fortunate in the fact that one bearing bore is still good, so I plan on squaring the one case up using the dowels, assemble the other case on top, zero off the good bore, reach through and bore the bad bore to a cleanup. This should give me good locations for future operations when I separate the cases.
    Picklito likes this.
  4. Picklito Husqvarna
    Pro Class

    Location:
    Washington
    Husqvarna Motorcycle:
    430, 430, 430, ,400, 175
    Other Motorcycles:
    KTM250xc, KTM500mx, KTM440exc
    Even better. In fact, it will probably be straighter than it was originally.
  5. motomwo Husqvarna
    AA Class

    Location:
    Imbler Oregon
    Husqvarna Motorcycle:
    Many vintage big bore and automatics
    Husky should have done this from the beginning!
    Marty
    Picklito likes this.
  6. Picklito Husqvarna
    Pro Class

    Location:
    Washington
    Husqvarna Motorcycle:
    430, 430, 430, ,400, 175
    Other Motorcycles:
    KTM250xc, KTM500mx, KTM440exc
    Steel sleeves for everyone!
  7. Tom Dowell Husqvarna
    C Class

    Husqvarna Motorcycle:
    1972 250WR
    Other Motorcycles:
    1976 Bultaco Alpina DT 400 Yamaha
    I was planning on turning press fit, 4140 steel liners for each side and then do a finish bore after installation.
  8. Picklito Husqvarna
    Pro Class

    Location:
    Washington
    Husqvarna Motorcycle:
    430, 430, 430, ,400, 175
    Other Motorcycles:
    KTM250xc, KTM500mx, KTM440exc
    I don't know the material 'my guy' used... that's why I need... "my guy!" But that's what he did. Finish bore in place. It's assembled, but not fired yet. Assembly was beautiful. Very good heat-fit, once again.
  9. Tom Dowell Husqvarna
    C Class

    Husqvarna Motorcycle:
    1972 250WR
    Other Motorcycles:
    1976 Bultaco Alpina DT 400 Yamaha
    That's what I wanted to hear!
  10. Picklito Husqvarna
    Pro Class

    Location:
    Washington
    Husqvarna Motorcycle:
    430, 430, 430, ,400, 175
    Other Motorcycles:
    KTM250xc, KTM500mx, KTM440exc
    I sent him an email asking for materials info and pearls of wisdom. I'll post it here.
  11. Picklito Husqvarna
    Pro Class

    Location:
    Washington
    Husqvarna Motorcycle:
    430, 430, 430, ,400, 175
    Other Motorcycles:
    KTM250xc, KTM500mx, KTM440exc
    So, he used aluminum for the new inserts, but remember it's for trans bearings, not mains. I don't know, but would expect, that we'd need to stick with a steel insert for the mains. At least, that's what Husky did.