Three options-new keyway, new bottom end or new 4 stroke

Discussion in '2-Stroke Engines' started by haoleboy, Aug 12, 2014.

  1. haoleboy

    haoleboy New Member

    Hello all;
    I am at a dilemma. I have a 2 stroke F-80 from Dax, and have a broken crankshaft woodruff keyway. I am a novice at disassembling the motor. 1) Shall I remove the crankshaft and put in a new keyway and reassemble, 2) buy a new bottom end, 3) or buy a good new 4 stroke where I might have better luck without a breakdown. The present f-80 is about a year old, and may have less than 1500 miles on it.
    Any suggestions or advice? Thank you in advance.

  2. crassius

    crassius Well-Known Member

    when you say "keyway" do you mean the slot in the shaft or just the key that goes into it?

    the key is easy to find or make and easy to replace - the slot could be a real problem
  3. haoleboy

    haoleboy New Member

    Yes it is the slot in the shaft. The woodruff key was forced out of the "slot" and caused damage to the crankshaft. By that I mean, the new woodruff key does not stay in the slot, because part of the crankshaft is broken away. I had the new woodruff key welded in, but it broke away, and I surmize there is a lot of force between the clutch and the 20 tooth gear. I am hesitant to re-weld the woodruff key back into the slot. I am now thinking to disassemble the motor, take the crankshaft to a machinist and have a new keyway made 180 from the bad keyway.
  4. HeadSmess

    HeadSmess Well-Known Member

    thats about the best option but its going to cost as much as the new shaft would... unless its a very helpful machinist you happen to know? like, a model/hobby machinist would do it for some beer.

    up to engine, learn nothing.

    fix/replace crankshaft...learn how to tear the things apart :) and get them back together again!
  5. haoleboy

    haoleboy New Member

    Good point.... thank you for your reply.....
  6. haoleboy

    haoleboy New Member

    Done deal.... I have ordered a bottom end put the cylinders and pistons on and away I go.... case closed...tnx for reading this....
  7. HeadSmess

    HeadSmess Well-Known Member

    when swapping over the top end...dont remove the rings from the piston, or...if you do, make sure to note which is top and which is bottom ;)

    though if you lose track of that, you can usually line em up from the scuff marks, look at the pins in the piston grooves, and work out which goes where.

    they wear in to the cylinder, and youll never get good sealing if they go in wrong.

    also, its best to get new circlips for the wrist pin. ie, NEVER use 2nd hand circlips... and line the tag up so its vertical otherwise they vibrate and eventually snap off, ruining the bore.

    last tip is to install piston into cylinder first, THEN insert wrist pin into conrod, tis fiddly getting the rings in with piston attached to the rod! not impossible, just fiddly.
  8. haoleboy

    haoleboy New Member

    Thank you very much for the tips. The rings are still on the piston, and will take your advice on putting the piston in the cylinder first. Thank you!