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

Piston Deck Height ?

Discussion in 'Vintage/Left Kickers' started by 1982 XC 430, Oct 14, 2018.

  1. 1982 XC 430 Husqvarna
    AA Class

    Location:
    Seattle Wa
    I have one of the 1984 250 WR Cylinders with the extra Ports. The Liner Cracked and pretty much took out the bottom end. I have since replaced the Crank and Rod, Piston and Liner. The Liner was hand made by a gentleman who hade been making Liners for 40 years or more. Since the Liner didn't fit tight in the Aluminum Cylinder we bored the Cylinder over size and put a larger diameter Liner in it. I have ported the Liner to the recommended factory specs found else ware. I measured the Top of the Ports from top of the Liner as per the factory drawings. When I assembled it I checked the piston to Head clearance and all was well, Breaking it in went well for 10 minutes until it died and had little compression. Disassembly is showing that the Head is not sealing. Looking closer the Head is bottoming out on the Cylinder, and not the Liner. My concussion is that the Liner must not of been completely pressed into the Cylinder and when it heated up for the first time it sunk until the Head bottomed out on the Cylinder. So now I have a mess to figure out.
    My plan is to start out setting to correct top of liner to Piston at TDC. By adding subtracting base Gaskets. My Maico manual shows how this is done but I don't have the Specs for the Husqvarna. Once this is set I can Machine the Head and or make a Head Gasket to get the right Head to Piston Clearance and seal. I assume that putting a straight edge across the top of the liner and measuring the clearance between it and the center of the Piston is the way to do it. So what is the Clearance ?
  2. ct cr430 Husqvarna
    AA Class

    Location:
    Connecticut , litchfield county
    Husqvarna Motorcycle:
    1981 cr 430
    Other Motorcycles:
    2007 honda crf450
    Seems to me the first thing to solve is why it moved in the first place , does the liner have a lip or step on the outside to prevent it from moving past a certain point ?
  3. suprize Husqvarna
    Pro Class

    Location:
    Bendigo, Australia
    Husqvarna Motorcycle:
    WR 400, bike in a box Moto Villa 350
    Other Motorcycles:
    ktm 300
    that lip is your deck height with the head being lapped on to it
  4. auto Husqvarna
    AA Class

    Location:
    NJ,USA
    Husqvarna Motorcycle:
    too many
    Rough guess .040 to .060
  5. 1982 XC 430 Husqvarna
    AA Class

    Location:
    Seattle Wa
    OK so I answered my own question. I remembered that I has acquired another Cylinder with the stock liner. Well it turns out that the Piston is higher than the Top of the Liner. I guess I'm used to V8 Engines. My Maico manual didn't make any sense it measured from the top of the Ring to the Top of the Liner and now that I see that a 2 Strokes Piston Crown is above the Liner it makes perfect sense.
    More importantly I see that the original Liner has a grove machined into the Top at the Sealing surface. My Liner did not. But its all for not I started to machine a grove in my Liner and just broke it so its time to start over. I see somebody is selling an LA Sleeve Liner on e-bay. I might get to learn how to Drill the extra Exhaust Ports in the Cylinder to make a 82 into an 84.