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

1978 390 porting

Discussion in 'Vintage/Left Kickers' started by cntymnty, Jul 10, 2018.

  1. cntymnty Husqvarna
    AA Class

    Location:
    Mayberry, USA
    Husqvarna Motorcycle:
    1974 250CR Mag, 1978 390 OR
    Other Motorcycles:
    KTM 350 XC-F, Harley Ultra Classic
    I'm curious as to the intake ports on a 390. Mine is a 78 OR. When I had the motor rebuilt, I noticed the intake ports were large rectangular. Now I've seen a couple pics posted of a CR and now a WR cylinder showing the intake ports that are L shaped, mirroring each other. Unless the OR intake ports were unique, I guess mine has been ported. The bike runs great, no complaints there. Thoughts? Reasons for opening up the intake ports like that? Reliability decrease?

    Attached Files:

  2. Crashaholic Husqvarna
    Pro Class

    Location:
    Antelope Valley, CA.
    Husqvarna Motorcycle:
    73 450WR 6spd motor in a 75 MK frame
    These ports are stock. I don't remember seeing L shaped intakes on a vintage Husky. Maybe you could post one of those photos you saw.
  3. cntymnty Husqvarna
    AA Class

    Location:
    Mayberry, USA
    Husqvarna Motorcycle:
    1974 250CR Mag, 1978 390 OR
    Other Motorcycles:
    KTM 350 XC-F, Harley Ultra Classic
    Check the pic in “390 WR rebuild questions “ a couple threads down
  4. Crashaholic Husqvarna
    Pro Class

    Location:
    Antelope Valley, CA.
    Husqvarna Motorcycle:
    73 450WR 6spd motor in a 75 MK frame
    Okay, I'm confused, which comes as no surprise. Are the L shape ports somewhere in the above pics? They look stock to me.
  5. cntymnty Husqvarna
    AA Class

    Location:
    Mayberry, USA
    Husqvarna Motorcycle:
    1974 250CR Mag, 1978 390 OR
    Other Motorcycles:
    KTM 350 XC-F, Harley Ultra Classic
    The two pics I posted in my original post are my intake ports. Large and rectangular. There’s two pictures in the thread that I mentioned that have the L-shaped ports.
  6. cntymnty Husqvarna
    AA Class

    Location:
    Mayberry, USA
    Husqvarna Motorcycle:
    1974 250CR Mag, 1978 390 OR
    Other Motorcycles:
    KTM 350 XC-F, Harley Ultra Classic
    Also, Here’s a pic of the 78 390 CR cylinder from The Cycle Guide review of the bike in 1978

    Attached Files:

  7. Crashaholic Husqvarna
    Pro Class

    Location:
    Antelope Valley, CA.
    Husqvarna Motorcycle:
    73 450WR 6spd motor in a 75 MK frame
    Oh, on the inside of the cylinder. Yeah those booster ports are factory. So you're saying your cyl doesn't have those?
  8. cntymnty Husqvarna
    AA Class

    Location:
    Mayberry, USA
    Husqvarna Motorcycle:
    1974 250CR Mag, 1978 390 OR
    Other Motorcycles:
    KTM 350 XC-F, Harley Ultra Classic
    Now I’m getting confused. Lol... I didn’t take a pic of the inside of the cylinder, only the outside after was together. I’m fairly positive mine are rectangular inside and out of the cylinder .
  9. cntymnty Husqvarna
    AA Class

    Location:
    Mayberry, USA
    Husqvarna Motorcycle:
    1974 250CR Mag, 1978 390 OR
    Other Motorcycles:
    KTM 350 XC-F, Harley Ultra Classic
    Hell, now Im beginning to wonder myself. Wouldn't you be able to see the L shape booster port looking from the outside in like the pic I took of my cyl? If not, maybe Im :confused: loosing it and they are stock.
  10. Crashaholic Husqvarna
    Pro Class

    Location:
    Antelope Valley, CA.
    Husqvarna Motorcycle:
    73 450WR 6spd motor in a 75 MK frame
    Yeah you should be able to see the very bottom of the booster ports, or with the piston at bottom dead center you should be able to feel them inside. Your pics show the booster slots in the piston so I would think the cyl ports are there.
  11. jimspac Husqvarna
    Pro Class

    Location:
    Connecticut
    Husqvarna Motorcycle:
    82 250WR, 82 430WR, 84 250WR, 85 400
    Other Motorcycles:
    86 400WR, 82 Montesa Cota 349
    I have never seen L shaped intake ports and such in my opinion an L shaped intake port would be an obstruction to optimum flow through the reed valves into the cylinder. The ports in the liner are quite often L shaped so I think you were confused.
  12. Crashaholic Husqvarna
    Pro Class

    Location:
    Antelope Valley, CA.
    Husqvarna Motorcycle:
    73 450WR 6spd motor in a 75 MK frame
    He's referring to the booster ports on the inside.

    [IMG]
  13. cntymnty Husqvarna
    AA Class

    Location:
    Mayberry, USA
    Husqvarna Motorcycle:
    1974 250CR Mag, 1978 390 OR
    Other Motorcycles:
    KTM 350 XC-F, Harley Ultra Classic
    I think I was confused guys. I assumed you would see the same L shaped configuration from the outside of the ports looking in as you see looking at the inside of a removed cylinder. So when I started seeing the L shaped ports on inside of cylinder pics, I started trippin’. Sorry for the confusion and thanks guys for the responses.
  14. Crashaholic Husqvarna
    Pro Class

    Location:
    Antelope Valley, CA.
    Husqvarna Motorcycle:
    73 450WR 6spd motor in a 75 MK frame
    No worries, I've created my share of confusion on this site and its always been politely ignored. Good folks here. :)
    oldbikedude likes this.
  15. Bigbill Husqvarna
    Pro Class

    Husqvarna Motorcycle:
    '83 250wr
    Other Motorcycles:
    0 right now
    It gets confusing even more if we look at a 360 exhaust port.
    DeathFromAbove likes this.