piston porting, widening ports

Discussion in 'Performance Mods' started by Fast Shag, Nov 29, 2014.

  1. Fast Shag

    Fast Shag Member

    I just finished porting out my piston because I noticed that @ BDC my transfer ports and exhaust port were covered up a little by piston. I widened up the exhaust port a little as well.
    I put everything back together correctly and it fired right up and ran for about 1/4 mile and it died! Didn't get to WOT Checked spark, good, fuel, good, air, I thought it was good. While inspecting magneto, fuel was in case. Checked seal, toasted! Time to change! Not impressed at 250 miles!:shout: Maybe that's why it always ran rough... Got one in the mail and a new magneto as well. PB270074.jpg PB270078.jpg
     

  2. butre

    butre Well-Known Member

    crank seals are one of those things that you just need spares on hand
     
  3. Slogger

    Slogger Member

    Can those crankshaft seals be installed without splitting the cases?
     
  4. Fast Shag

    Fast Shag Member

    I hope so! I plan on pressing them in carefully. Never done it....
     
  5. HeadSmess

    HeadSmess Well-Known Member

    Slogger likes this.
  6. Fast Shag

    Fast Shag Member

  7. Fast Shag

    Fast Shag Member

    So I ordered a new magneto and HD CDI. While waiting, I widened up the exhaust and intake ports, raised the exhaust 1mm and lowered intake .5mm. I can't wait to fire this thing up! When I took the pipe off, gas POURED out!!! Supper flooded!
     
  8. HeadSmess

    HeadSmess Well-Known Member

  9. Fabian

    Fabian Well-Known Member

    Yes they can, but it is a very difficult process; requiring an extremely steady hand and a specially designed tool (such as a dentists pick) to carefully pry out the seal without either damaging the aluminium of the engine case halves or the crankshaft surface where the seal rubs up against.

    All you need is the slightest scratch on the crankshaft surface, and it will act as a rough edged scraper; chewing out the crankshaft seal in a very short time.

    From past experience, i no longer bother trying to pick out a crankshaft seal, for if it is leaking, i strip the thing down and reassemble it; replacing any parts as necessary.
     
  10. Fast Shag

    Fast Shag Member

    Installing, not removing. I have the same question. Will they just press in around shaft?
     
  11. Fabian

    Fabian Well-Known Member

    If the engine is assembled, you need to lubricate the crankshaft and the seals, then carefully press them over the shaft and drive them home approx 0.5mm below the outside face of the engine case.
     
  12. HeadSmess

    HeadSmess Well-Known Member

    using a socket ideally. small plug sockets about the right size.
     
  13. Fabian

    Fabian Well-Known Member

    but preferably have someone turn up a piece of plastic with a centre hole that fits snugly over the crankshaft, and with a centre section that is machined 0.5mm proud of the the larger outside diameter, to press the crankshaft seals into place; ensuring they sit in place perfectly true and with consistent recess.

    I have had a tube socket/plug socket leave scratch marks/dent marks in the crankshaft, so this method is no longer used in my assembly process.
     
  14. Fast Shag

    Fast Shag Member

    I was able to get everything back together...Seal went on really nice and even, all lubed up. HD Lighting hooked up, new mag...She fired right up and the low end was insane! Much better throttle response, top end pulled 2mph faster. Hill climbing gave me 2.5mph better as well. By widening ports, I could tell a slight increase in RPM. Very impressed with this!

    ported piston at transfers and exhaust, sharpened transfer points at crankcase, widened intake and exhaust ports by 2mm each. New crankcase seal on mag side, new mag, new CDI. STOKED!
     
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