This is a discussion on 450 Head Gasket? within the Yamaha Big Bear/Bruin/Wolverine ATV Discussion forums, part of the Other Yamaha Forums category; Hi Folks,
Finally finished work on my 03 - 04 450 kodiak and fired her up on the driveway this week, I noticed a small ...
Finally finished work on my 03 - 04 450 kodiak and fired her up on the driveway this week, I noticed a small amount of frothy coolant leaking from the lower radiator hose connection where it enters the rad on the left hand side of the bike so I grabbed the hose to see how hard it was and it was really hard - there doesnt appear to be any oil in the coolant or vice versa and it isn't blowing white smoke but I guess it could be due to pressurized combustion gases getting into the water system?
Will check the thermostat and see if its opening and also see if the fan comes on but I suspect it might be the head gasket so what I want to know is can the head gasket, piston rings and timing chain be changed with the motor in the frame or am I going to have to pull it all out onto the bench.
Did you do any work to the motor where most of the coolant ran out? If so you may have a air pocket in the system. Run the motor to temp with the rad cap off to ''burp'' the the system. If bubbles still come up after a while it my be pumping CO into the cooling system.You usually can smell something(co is oderless) wrong in the vapor coming off of the top of the rad, but in some cases you need a co tester. After the test if the blue fluid does not change color(blue to green then yellow) its ok with no combustion leaks.
I believe you can do the piston/rings or head in the frame.
I have a snap-on co tester but it cost about 60 bucks. Lisle makes one (#75500) that you can buy for under $30. Lisle 75500 Combustion Leak Detector
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Well last night I pulled the top end apart in the frame (no need to pull the motor plenty of room) and the head gasket has definitely gone.
Timing chain was badly stretched too it had run out of adjustment on the auto tensioner and looked like the stretch was bad enough to put the timing about 5-7 degrees out if you line up the t mark on flywheel and the groove on the cam drive sprocket with their marks on the engine castings.
thanks for the help and advice guys