Feeler gauges and valve clearances - how tight is right (ooh er missus)

[Martin#30]

Doing the valve clearances on my 10R at the moment, and I am not sure how much force/friction gives you the right clearance value. For example, an exhaust clearance should be 0.17mm-0.25mm.

My 0.152mm feeler blade will go in, but it needs a bit of force. My 0.14 blade goes in with less force, but still far from easy. My 0.127 blade goes in easily and slides with almost no friction.

So, what do I call the clearance? 0.135 maybe?

Martin.

.... and yes, it has not been running perfectly recently 

[big gav]

Have you smeared clean engine oil on the feeler gauge before checking each clearance ?

[Green_Ninja]

basically you should feel a slight resistance ( not forced) and to get an accurate measurement the feelr guage should be clean and dry not oiled.

[Jonesy]

Have you smeared clean engine oil on the feeler gauge before checking each clearance ?

the feelr guage should be clean and dry not oiled.

Eek, couldnt be 2 different opinions in the first 2 replies 

[big gav]

The moving parts in the engine will have oiled surfaces when running. All you are doing is mimicking that.

It also helps stop the feeler gauge binding in the gap.

the first net search i did brought this up := http://www.triumph675.net/forum/showthread.php?p=2349777

[Green_Ninja]

Good find that Gav, I was always told that when measuring, be it feeler gauges micrometer or slip gauges they should be clean and dry otherwise you can get a false reading. Sorry engineering training kicking even though I haven't been 'on the tools' since the late 80's 

[big gav]

To be fair to you mate, when machining they should defo be as you say.

as for how 'tight' ooer, they should be. Try dragging a feeler gauge over quite a weak magnet . It should move freely with sone resistance, albeit light resistance.

[Martin#30]

Thanks all. Clean oil on the feeler blades makes sense to me.

Now comes the complete fun and games that is removing the cams and getting new shims.

Martin.

[big gav]

Remember not to buy shims until you've done your maths to see if you can swap the existing ones around mate.

[zxrob]

I work on the basis, if the correct guage size goes under and is a bit tight it is ok, if if dont go under then it aint

Rob

[Martin#30]

Measured all the clearances now, every single exhaust clearance is too small - 0.14/0.15 instead of the 0.17-0.22 range it should be in.

Strangely, a number of the inlets are too small also. I had always thought that the inlets tended to get bigger as they wear.

I think it may be time for a bit of refresh work on the valve seats. 100 or so trackdays has got to be hard on an engine.

Martin.

[Green_Ninja]

Measured all the clearances now, every single exhaust clearance is too small - 0.14/0.15 instead of the 0.17-0.22 range it should be in.

Strangely, a number of the inlets are too small also. I had always thought that the inlets tended to get bigger as they wear.

I think it may be time for a bit of refresh work on the valve seats. 100 or so trackdays has got to be hard on an engine.

Martin.

modern high revving motocycle engines do tend to close up the valve gap as the seat 'recedes' after 100 trackdays I'm not surprised as you will be running the engine at clsoe to peak revs all the time. Don't 'they say' a trackday is like 1000 road miles.

[big gav]

Aye the gaps decrease as the valves recess into the seats. Hence why you now need smaller shims so that
the valves are opened later and closed sooner throughout the cycle.

[ash]

Got all of mine custom ground in work to make top tolerance. It does make a difference to performance, so well worth doing...as well as reducing the risk of scorching a valve seat when the gaps close up.

[Coxy]

I wish I knew what the fuck you boys were talking about, I feel like Danoir in a tech thread!