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I think I found my air leak

3K views 5 replies 4 participants last post by  Edwoo76 
#1 ·
my 86 450 has been running lean on both cylinders, so checking the air box, hit the cover seal with carb cleaner and rpms dropped 300 and ran rough, then it cleared and ran fine, did it again, same thing, new seal ordered, see what happens.
 
#2 ·
maybe I'm misunderstanding but this doesn't sound like an air leak. it sounds like you shot some carb cleaner through the air filter...... which seems like you'll get symptoms of shooting carb cleaner or starting fluid into the carb, which floods the mixture and kills the idle. I don't see where the leak is. the air filter won't filter out carb cleaner. isn't an air leak technically downstream of the carb/intake manifold boot?

change the seal. can't hurt anything. but shooting carb cleaner anywhere near the air filter would affect the idle on any bike.
 
#4 ·
The drop in RPMs is likely due to the fact that the carb cleaner doesn't burn as well as starter spray. It should run perfectly fine with the cover off the air filter box, and even run fine with the air filter removed (just don't do much of these). An easier test would be to remove the airbox cover while its idling and see what difference that makes without the spray.



Air leaks causing lean running would occur at or after the point of fuel+air=>mixture, vacuum piston cap, where the carb meets the intake manifold, vacuum ports around the throttle plate area of the carb and/or vacuum ports on the intake manifold, and where the intake manifold meets the cylinder head.
 
#5 ·
The drop in RPMs is likely due to the fact that the carb cleaner doesn't burn as well as starter spray. It should run perfectly fine with the cover off the air filter box, and even run fine with the air filter removed (just don't do much of these). An easier test would be to remove the airbox cover while its idling and see what difference that makes without the spray.



Air leaks causing lean running would occur at or after the point of fuel+air=>mixture, vacuum piston cap, where the carb meets the intake manifold, vacuum ports around the throttle plate area of the carb and/or vacuum ports on the intake manifold, and where the intake manifold meets the cylinder head.
both carbs are running lean, so I am assuming its from a common air leak and the air box is the only thing in common. I compare the problem to when you have to rejet carbs after installing pod filters. the engine runs great, just hot and lean. plugs are white, exhaust pipes blue.
 
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