A local friend. He had just freshened up his high mileage motor. He'd replaced cams, camplate, cam bearing, lifters, oil pump, rocker arms and shafts, umbrella valves and filters, chain tensioners - and had a valve job done and valve guides replaced, cylinders honed and new rings. He did all the assembly labor himself.
He fired up the bike this morning - and after a few minutes of idling, blew the dipstick across the garage. After much head scratching and troubleshooting, he'd found nothing wrong. 75000 miles on the bike and he'd never had this problem before.
So I drove over to his place and had him talk me thru everything that had been done. Then we fired up the motor, and sure enough, the dipstick popped out. I had two thoughts...oil pump or umbrella valves. Umbrella valves were easiest to check, so we removed the gas tank and rocker box covers - and sure enough the umbrella valves were the culprit. With the new stamped umbrella valve breathers, it is incredibly easy to install the "center" section of the stamped assembly upside down. This puts the umbrella valve on the bottom, and the mist filter on the top - rendering the valve useless. This causes rather immediate crankcase pressure to build up. The fix was as simple as assembling the breather assembly correctly and putting it all together. I didn't have a camera with me, or I'd have taken a couple of photos. As easy as it is to put this together wrong, I'm surprised it hasn't come up before...
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Topic: Got a call from a friend today... (Read 1136 times)