Strange Shim problem - at least strange to me

I just restored a badly rusted 1981 Maxim. After rebuilding most items on the bike I had it running great. Since the valves probably hadn't been adjusted in a very long time, I went ahead and took the measurements and replaced the shims as needed. I took all readings twice before ordering my shims. The 1st and 4th cylinder intakes were in spec. One measured at .127 with a 280 shim. .127 is at the tighter end of the range but the chart showed to keep that shim. The other cylinder was .152 with a 275 shim. Also in spec by the chart but at the loose end of the range. I'm comfortable with that. The four exhausts and 2 other intakes were replaced and then checked after I had finished all the shims. The 6 valves where I replaced the shims were all exactly where they should be. The 2 intakes that were not adjusted are now tight and outside the acceptable range. I removed those shims again just to make sure there was no debris in the bucket. Used air compressor to blow oil out of bucket to clean. Still tight. Now I can get shims for those two intakes but I'm confused as to why they are now tight. Remember, I double checked the readings on all valves before deciding which valve needed shims. Thoughts? Oil that hasn't squeezed out yet?

 

That sucks.

Speculation, but if the camshaft caps weren't torqued down to spec (loose), and now they are, that could in theory close up tolerance and make things tight.

 

You took measurements on a motor that had not been run in a long time. Rust and debris can build up on valve seats giving false readings. It will prevent them from fully closing then you tale a measurement and replace the shim. When the motor finally runs the valve seat is cleaned off and the readings change.
As a personal rule I never adjust valves on a motor that has been sitting unused for awhile. I always run the motor for at lest 10 minutes before any attempt to check valves is done. Running it longer is even better.

 

But then you let the engine completely cool before rechecking.....correct?

 

always roll the motor over the way it runs when taking measurements. (the motor spins the same way the wheels do)
you wouldn't be the first guy to have two feeler gauges stuck together.....b.t.d.t.
how tight did they get? could they be in crooked ? a lot of times i get a snap as they seat in the bucket

 

+1 on making sure the engine is cold (under 90 degrees internal temp)
+1 on checking for feelers stuck together
+1 on checking for dirt build-up

Now, ALSO make dang sure the lobe is exactly perpendicular to the shim, not perpendicular to the ground.

Also, it makes no difference if the shim is closer to the tighter end or the looser end of the spec range. IN SPEC IS IN SPEC. THIS IS SIIMPLY A SHIM CLEARANCE CHECK. If it is out of spec, then you change it. If it is in spec, you leave it til the next time to check.

Keep us posted----

 

the cams don't need to be removed to change shims on his machine. Of the XJ series, only the Maxim-X is shim under bucket.

 

Plus, if the cams were loose, they'd be pushed up farther away from the shim being measured, and thereby creating a clearance that would be too GREAT.

 

Thanks for all the replies guys! You're not going to believe what the problem was. Optical illusion caused by a halogen shop light I turned on. I checked the clearances of the 6 I replaced first. It started to get dark so I setup a very bright light behind the bike and it was casting shadows. The cam lobe looked like it was 180 from the shim which is where I took the measurements. When I held a flashlight to the area, the shadows being created were gone and all of the sudden the cam lobe didn't look to be 180 from the shim. It was off by a bit. Using the flashlight I rotated the lobe to 180 and took the measurement and I got the correct clearance. I turned the flashlight off and I swear the cam lobe looked like it moved from the 180 position. It was the angle of the bucket/shim that seemed to change angles. Strange. Anyway it's back together and running just fine.

Just to clarify a couple of posts. The cams were not removed. The engine had been run for 300 miles since I restored so checking the valves wouldn't be an issue. Bike actually ran good and I was able to sync the carbs so I knew the valves were not off by a great margin of error. They were checked cold. Engine always turned counterclockwise except when using bucket tool on intakes but would turn a tiny bit back counterclockwise to take measurements.

Great site. Thanks for the input.

 

See why I said that now? the last time someone was told that, they went on a tirade of 'what exactly is ''perpendicular to the shim" '. Thank you for just simply checking that. Glad you found it.

Dave F

 

Yep, realized this after I posted.

 

Nobody wants to use a degree wheel.
Oh well.

 

I like that idea, it removes the parallax out of the situation of aligning 8 different lobes.