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

78 390 Auto Exhaust Question

Discussion in 'Vintage Restoration Projects' started by nick2412, Feb 24, 2019.

  1. nick2412 Husqvarna
    B Class

    Husqvarna Motorcycle:
    1978 390 auto
    I am looking for a more modern exhaust pipe and silencer to reduce how loud the bike is. Do i need to bend a different models pipe. I know this effects the power but im riding it to work and the neighborhood wants to pull me by my neck behind their prius's. I am a super novice and so any help is good help. Also any other tips for noise . I herd about rubber between the fins but i cant find a resource to buy them. Thanks
  2. 390wr Jon Husqvarna
    AA Class

    Location:
    New England
    Husqvarna Motorcycle:
    1980 Husqvarna 390WR
    Other Motorcycles:
    1979 BMW R100RS
    Comet Kart Sales have rubber fin inserts. Here is the link: https://cometkartsales.com/Yamaha-Head-and-Cylinder-Parts/

    I used them on my 1980 390 WR and they fit fine (I bought my 390 WR new and they came with them from the factory). The Comet Kart rubber insert width and fin spacing was the same as my original rubbers.

    The only thing is the Comet Kart rubber inserts are not as deep as the originals (in other words, they don't go it the cyclinder fins as deep as the originals). They would probably not come out, but to be safe I put a couple of dots of 3M black 5200 to make sure they didn't go anywhere.

    I do believe the rubber inserts cut down on cyclinder noise/ ring.

    Also , I had a 1974 400WR back in the day and if my memory serves me right it did not have the rubber inserts. However, I cut legths of black rubber fuel line and inserted it between the fins. It worked well, but did not look as nice a the rubber inserts.

    Hope this helps.
  3. nick2412 Husqvarna
    B Class

    Husqvarna Motorcycle:
    1978 390 auto
    will a 80 400 model expansion chamber fit a 78? or any other later years with little modification?
  4. Crashaholic Husqvarna
    Pro Class

    Location:
    Antelope Valley, CA.
    Husqvarna Motorcycle:
    73 450WR 6spd motor in a 75 MK frame
    I'm not very knowledgeable with Huskys later than 75 so I can't help with your exhaust questions but something else comes to mind. How many miles (hours) has it been since its last re-bore? Piston slap can be very noisy.
  5. grouty Auto Lover ...

    Location:
    South West UK
    Husqvarna Motorcycle:
    78 390WR, 78 390 AMX, 500 Humph
    Other Motorcycles:
    works 73 CCM 520, another 73 CCM520
    The factory pipe on the 390 Auto was noisy. A 1978 6 speed 390 WR pipe will quieten it down a fair bit. Failing that, you could cut the silencer off from a WR pipe and fit an alloy one from HVA Factory for a later 79/80 390. If you don't mind a bit of fabrication and welding you could use the complete system from a 79 390WR. The WR's had a more effective silencer and a twin walled front pipe.
    I have the 390CR one piece system on my auto, and yes, it's still a bit loud.
  6. DeathFromAbove My Cat Says AREAR!

    Location:
    North New Jersey
    Husqvarna Motorcycle:
    70,71 360 8s 72,74 450 73 360 73 250
    Other Motorcycles:
    66 Triumph Trophy 99 ZRX1100
    I like them loud, the pecker in the prius can't hear you unless it's loud. They are made to be quiet to the occupant. Drop a 6 pack on the neighbors porches and call it good. You gotta make a living, and using a 41 year old Husqvarna Auto as transpo is way cool, the men on the street wished they could be so trust worthy to a machine (they sold their dreams a long time ago) There lives are over! Their women wish you weren't so reckless (they married a man with dreams and a motorcycle). I say let it hang out!! You only get one chance to ride this life, I hope you never say never!! Just not to the fuzz!