Dirty Motor

Discussion in 'Motorized Bicycle General Discussion' started by Toothy, Aug 22, 2014.

  1. Toothy

    Toothy New Member

    Joined:
    Mar 25, 2014
    Messages:
    181
    Likes Received:
    0
    Hey guys,
    I was wondering if black build-up on the engine around the exhaust port is just normal or do I have a leak. I’m guessing I have a small leak but it doesn’t seem to affect my ride. I’ve tightened it down but it still fouls after a little while.
     
  2. a.graham52

    a.graham52 New Member

    Joined:
    Nov 22, 2013
    Messages:
    232
    Likes Received:
    0
    sounds like a leak. get yourself anohter gasket and swap it out.
     
  3. 2door

    2door Moderator
    Staff Member

    Joined:
    Sep 15, 2008
    Messages:
    16,304
    Likes Received:
    29
    Ditto.
    If the gasket isn't sealing you'll get what you're having. Here's a hint. The exhaust flange where the gasket sits is usually warped from the welding process at the factory. You need to sand/grind the flange flat to make a good gasket surface.

    Remove the pipe from the engine. Clean the gasket surface so there is no old gasket material then 'paint' that surface with magic marker, or machinist dye, even a light coat of paint will work. Now run that surface over sandpaper placed on a known flat surface such as glass. Just a few swipes will do. You'll quickly see where the high and low spots are. Eliminate them. They are what cause a bad sealing surface. You can tighten the fasteners all you want but if the gasket surfaces aren't flush it will eventually leak.

    Make a new gasket from gasket material made for exhaust applications. I like 1/8" minimum thickness. Tighten the fasteners then check them again after a couple of heat/cool cycles. Torque is about 60 inch pounds. Good luck.

    Tom
     
  4. Davezilla

    Davezilla New Member

    Joined:
    Mar 15, 2014
    Messages:
    2,708
    Likes Received:
    3
    I agree... the exhaust flanges are usually the culprit here and making sure teh flange is flat and true as well as properly torqued will stop any leaks once a new gasket is installed. If you can get the flange perfectly flat you could even use just a very thin layer of high temp rtv and it'll seal just fine
     
  5. Toothy

    Toothy New Member

    Joined:
    Mar 25, 2014
    Messages:
    181
    Likes Received:
    0
    Ok thanks guys....I'll let you know how I get on.
     
  6. crassius

    crassius Well-Known Member

    Joined:
    Sep 30, 2012
    Messages:
    3,565
    Likes Received:
    58
    yep, flat mating surface & a good muffler gasket & hanger will fix that
     

Share This Page