Valve Check - 1 Valve Way Loose?

Just checked the valves on 82 XJ750, clearances were as follows:
Intake - .006, .004, .004, .006
Exhaust - .015, .006, .006, .008.
To have one valve that far out seems a little strange to me. Bike has 4900 miles, and is coming out of a 20+year sleep. As Fitz has pointed out to me, with that little mileage, it may have never had a valve check/adjustment. Could it have come from Japan with one valve that far out of whack? Or could it be something more sinister?

 

Very likely you have a valve not fully closing (although not by much.)

How much have you run it, and have you done a compression test yet?

With that few miles, unless something horrible happened (we had a member picked up a sweet 550 with 2 holed pistons and only 5500 miles on the bike) I'm more inclined to think you've got a slightly rusty valve, or it's getting hung on a piece of carbon.

I'd spin the motor over a few times, and check again. DON'T try to start it, just spin it over.

By the way, .004" is actually out of spec, if they're truly at .004" then they are at .1016 millimeters. Drop the ".0016" and you're at .10mm. Spec is .11mm.

Likewise .006" on exhaust valves; that's .1524mm. Drop the .0024mm and you're out of spec at .15mm.

Understand, .0024mm (the dropped part) equals .00009". If you do the math on .0016mm, it's .00006". That's why it's ok to "drop" it.

This is why I prefer true metric feelers. K-D 2274, widely available for under $10.

Good catch, but don't panic. It's probably more a case of old motor that sat than it is a sign of something horrible.

This is why we check them. You did have the cam lobe pointing away from the face of the shim at 90* (180* to the centerline of the valve) right?

 

how did you determine the lobe was perpendicular to the shim ?
if you don't use a degree wheel, your just guessing

 

No, no degree wheel... but of course I didn't guess. I used my eyes (after calibrating them of course).

 

Fitz, your assessment sounds plausible, as I am pretty confident the bike was in good working order when it was put to sleep. I have not yet tried to start it, nor have I done a compression check.

I am still sorting out carbs. Ordered some "magic stainless bowl screws" from Len. Once they show up I will be ready to set the levels and hopefully get the bike started. Although if that valve doesn't tighten itself up, guess I'll need to figure it out.

As for the std vs metric feeler gauges, saw from a previous post that you may scold me; note to self: pick up some metric gauges... And as for .004 (in) and .006 (ex) being technically out of spec, maybe, maybe not. I don't really know the "exact" clearance on any of the valves as I used the "go-no go" technique. For example, for an intake if .004 fits, but .006 doesn't, all I really know is that the clearance is somewhere in between. Not good enough?

 

Hey Polock, you don't have to be spot on when you move your lobes into position, a few degrees won't matter if you eye ball it.

 

On my SECA 750 I found an exhaust lobe where the heel (the round part) was not ground perfectly, and went from about 0.0035 with the toe pointing away from the valve, to 0.0015 at another location, but before the cam lobe.

This two thousanths imperfection was only found by going further than "by the book" proceedures. The engine was dropping a cylinder and I was on the verge of burning an exhaust valve.

Back to RickB 's motor -
Hope it's just a hunk of carbon.