huge inlet valve clearance

[Ronajon]

did a valve clearance check today on my '79 bike.
the exhaust clearances are a little out of the specs, but the intake's are way off
the bike runs, and i didn't notice any ticking sounds when running.
these are the numbers
Ex (0.21 - 0.25)
0.15 0.20 0.20 0.15
0.50 0.70 0.50 0.45
In (0.16 - 0.20)
im wondering how it's possible that the ex clearances are below the specs and the inlets are far over spec?

[TopCatGr58]

Hey Ron,

The valve clearances on these bikes/engines NARROW with wear because the valves beat the seats into the heads, and so the valves end up getting closer to the cams=less clearance.

However, if a bike has sat for a long time, atmosphere, humidity and such from the intake side/carb side can get to the valve stem causing rust/corrosion to form especially if the valve was in the OPEN position, and that rust/corrosion can prevent the valve from closing as completely as it should.

Can you do a compression test, you may not hear any ticking, but you may also be only running on 3 cylinders instead of 4??? With that much clearance, you may have already burned that valve, and you will probably need to take the head off to properly evaluate their condition, and perform either a lapping or get them ground, as well as verify that they are not bent!?

T.C.

[Ronajon]

Hi TC

i did the compression test earlier, it had 170 psi on cylinder 1, 160 psi on the other three.

guess i'm going to pull the head to see if the valves are ok.
can it be done without breaking the camchain?

[CaptonZap]

Don't take it apart yet. With 170+/- psi compression, your valves are good.
If I were you, I would wonder if the previous mechanic made a mistake on figuring the correct shims, since they all have about the same margin of error.
Instead, I would shim them correctly, and ride it for a while. Check it again after a thousand miles, (clicks?), and see if they have changed appreciably.
If not, don't worry about it.

CZ