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Why is the exhaust so hot?

Discussion in '40- & 55-Series Tech' started by tetradymite, Mar 3, 2003.

  1. tetradymite

    tetradymite

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    Need some help diagnosing this problem:

    Just bought an FJ60, fired the engine up, sounded good. As we check everything out (vaccuum leads, hoses, etc.), notice that the exhaust gas pressure is strong. Continue to play with things as the motor warms up. It revs up good, no noticeable hesitation, sounds strong. After about 15 minutes, my other buddy checks the exhaust and yelps as the gases burned all of the hair off the top of his hand. It was really hot. The exhaust manifold looked normal (was not glowing red), and the engine temperature was normal. Looking under the vehicle-also no glowing.

    Our first thought was that the catalytic converter was bad. However, it has a thermosensor and no idiot light (or other signal) was going off. Also, I was told that if the cat was bad, I would not be able to rev the motor up. Any thoughts there?

    Another mechanic suggested that I might be running lean. I live in Colorado at 9000 feet elevation. It should be running rich, if anything. Is there any way it could be running lean (faulty emissions equipment? there's lots of 'em)?

    Final note, I bought it with no clutch (great price), So, It's sat at the previous owners for almost a year. It has not been out on the road and opened up-driven. I don't know if this could have any bearing . . .

    Any insights would be really appreciated. Thanks,
     
  2. woody

    woody Internet Fireman Staff Member

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    might check for an exhaust restriction, forcing the motor to work harder and create more heat....I know my 350 TBI motor was on the engine stand for about 2 months in my garage, and the mice filled the exhaust manifolds with dog food. (caught 5 mice in 3 days after that...heh heh)
     
  3. Gumby

    Gumby Supamod Staff Member s-Moderator

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    Lean causes hot exhaust, but so does way over rich. If the cat is not glowing from excess fuel being burned in there, then I would lean toward lean. I've melted heat resistant exhaust hoses from way over lean exhaust. The would suggest a vaccuum leak or bad carb.
    It's also possible that the cat is bad, but not plugged so it won't run. Open cats usually happen if the material brakes up and is blown out, or much more frequently, the owner takes it off and busts all the stuff out to get "performance". Then a way over rich condition could have fuel unburned in the combustion that is burning in the exhaust.
    If you had a lot of material in the exhaust from sitting that started to burn, you might have caused a one time only kind of condition as well
    Could be the PO pulled the 2F and dropped a turbine in too. :D
    I think I would go with the first thing as the most plausible.
     
  4. lead4yourhead

    lead4yourhead

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    :dunno:I might be a Dumb @$% for doing this to my 85 J60, but i unbolted the Cat Converter, cut the flanges off, welded them to a straight pipe, then bolted the straight pipe back into place where the Cat once was.

    My cruiser does the same thing still (back fires in the morning, hot exhaust) , so I will be looking for the same advice as you. I shall check on the carb situation for now.


    Toodles
     
  5. CruisinGA

    CruisinGA

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    Just to reinforce your lean=hot exhaust-
    I know that a dirtbike and a FJ60 are quite different but-
    A friend of mine has a fairly new but hard ridden Yamaha TTR 225, it became very difficult to start, and took forever to warm up. My friend (who is not very mechanically inclined) couldn't figure it out. I was over there one night kickin tires on my 40 and such and we pulled out the dirtbike. Cranked it after some work, and then were letting it warm up when I noticed the titanium exhaust was GLOWING! It was so bright it threw illumination on the ground and on everyhting around it. Turned out it was mud in the carb cloggin stuff up and a too heavily saturated air filter. Just something to check out. &nbsp:Doesn't sound like yours is as bad.
    Also, after I reinstalled my exhaust header on my 40 after a new gasket got installed, I cranked it up and after it had only been running for maybe a minute i reached in to tighten a bolt, didn't even touch the exhaust pipe but could feel hair curling up and lots of heat. And my engine is running normally, so maybe it is normal. I don't know for sure. :dunno: Maybe some of the resident cruiser gods will enlighten us?