Just changed the oil and filter in my 01 400EX. It sounds fine for about 5-6 seconds after starting it. Then I get a slight squealing noise that *sounds* like it's originating from the right side of the engine. Possibly from the filter section.

I followed these instructions:

Honda 400EX ATV Oil Change Instructions

The filter is installed as pictured. I drained both the crank-case and the tank and refilled with 1.75 qts of Rotella 15w40. It did this on the first startup. I pulled the clutch lever and the sound doesn't change. I shut it off, let it sit, then restarted. The noise starts up after about 4-5 seconds.

Is it air in the oil line? Maybe the delay in the sound is the oil pressure coming online. When I re-checked the filter I did notice a lot of tiny bubbles in the oil suspended in the oil in bottom of the housing.

I've only run it about 15 seconds or so. I've changed the oil before and never encountered this sound. Very weird.

Has anyone else experienced this?

 

You might want to pull the filter and check if it is installed properly. Those filters are directional. IIRC the metal ring on the filter is stamped with the proper orientation for the filter.

 

You can open up the oil line thats has an banjo bolt thru it at the crankcase cover were the oil filter is an see if pressure is there...just open bolt about an 1/4 turn while engine running.... if oil pump is working okay oil will get pumpped out under the bolt.

 

Yes the oil filter is directional... the oil seal on filter goes to the outside toward cover

 

Hey thanks for all the replies!

I let it sit for over a week and didn't touch it. When I started it up the squeal was gone. So it must have been a bubble being forced through the filter.

Thanks again!

 

Hey, thats great news. Thanks for the follow up!