Feeler Gauge for valve check

[skidxr]

Thanks for the input here guys. I left the valves alone this time even though the urge to take the cams out and mess with it was high. But I will save that till next time.

I'm looking at the shock now but will start a new thread.

[keener]

Its worth recording everything and what you have changed. It will be useful to refer to your record at the next valve check. You will know which valve is getting tighter or looser and will be able to make these decisions easier.

Having said that, once I changed several shims all the way to the other end of their specs depending on which way they were travailing. (if they showed they were getting tighter comparing to the last valve check, I shimmed them to max loose limit or the other way around)....that actually made a big difference in how the bike ran (not good), I had to change the jets on the carbs,....so I opened a can of worms.

My advise, don't change the clearances significantly.

Regarding the feelers, if you do not get a complete range, you can put two feeler on top of each other to make up of for the ones you don't have. I like the those sets that I can take apart, no handles, I can always pull them out with a set of pliers if I have to.

[Dustodust]

I have a mechanic/riding buddy who sands down the shims on a glass surface plate to a polish finish to get the valve clearance in spec .
Claims that because the shim is just solid metal billet and not hardfaced it works just fine

[markjenn]

Originally Posted by Dustodust

Claims that because the shim is just solid metal billet and not hardfaced it works just fine

I've heard differing opinions about this. And there is some risk that you won't get the shim perfectly flat but I'm sure this depends on technique and equipment.

Personally, I don't grind shims, but for shim-under-bucket, I would think the risk of a problem is slight. For shim-over-bucket, I wouldn't chance it.

- Mark

[Nailhead]

Originally Posted by keener

Its worth recording everything and what you have changed. It will be useful to refer to your record at the next valve check. You will know which valve is getting tighter or looser and will be able to make these decisions easier.

Another good idea. Thanks.

[Steveman]

Originally Posted by Dustodust

I have a mechanic/riding buddy who sands down the shims on a glass surface plate to a polish finish to get the valve clearance in spec .
Claims that because the shim is just solid metal billet and not hardfaced it works just fine

Being a mechanic myself I can tell you that this is a very bad idea due to the fact that most shims are just hardfaced. At least those used in KTM EXC models so I assume that this also applies for all other KTM shims.

But I am open to be teached better... Of course I am talking about a shim over bucket config.

[Dustodust]

Originally Posted by Steveman

Being a mechanic myself I can tell you that this is a very bad idea due to the fact that most shims are just hardfaced. At least those used in KTM EXC models so I assume that this also applies for all other KTM shims.

But I am open to be teached better... Of course I am talking about a shim over bucket config.

thanks for the info on hardfaced shims
yep , I would just put in the correct shim myself
saw them sanding shims and asked what are you doing
thats why I dont let anyone work on my bikes anymore
most of them are expert professionals who know everything
usually they just charge for the valve adjustment and do nothing

[KtmPedro220]

Try eBay UK?

[markjenn]

Originally Posted by Steveman

At least those used in KTM EXC models so I assume that this also applies for all other KTM shims....Of course I am talking about a shim over bucket config.

Are any new KTM's shim over bucket? Seems like almost all the recent designs are shim under bucket. The only sorta recent engine I recall using shim-over is the ZX11/ZRX motors and these have roots in the 1980's.

- Mark

[geometrician]

Originally Posted by Steveman

Being a mechanic myself I can tell you that this is a very bad idea due to the fact that most shims are just hardfaced. At least those used in KTM EXC models so I assume that this also applies for all other KTM shims.

But I am open to be teached better... Of course I am talking about a shim over bucket config.

+1. All shims are hardened. The only time you'd want to hand grind a shim is to gain operating clearance so you can get out of the wilds.

As for shim over vs. shim under it doesn't matter. The shim faces are still transferring the energy- were not JUST looking at the cam lobe/rocker sliding over the surface (shim over), the head of the valve stem/contact pad inside the bucket (shim under) are going to work/hammer the shim

Originally Posted by markjenn

Are any new KTM's shim over bucket? Seems like almost all the recent designs are shim under bucket. The only sorta recent engine I recall using shim-over is the ZX11/ZRX motors and these have roots in the 1980's.

- Mark

Shim over is very old (usually) air-cooled technology. These designs have their roots in the motorcyles of the 1960's and is some cases (KLR650 for one) continue to this day. Most shim-over are 22, 27 or 29mm diameter shims, the shim-under are 7, 8, 9mm by comparison. Most engine designs today stay away from shim-over as there is more reciprocating mass to be controlled which leads to heavier valve springs & more robust valve timing components to deal with the addtional loads

[Peanuts]

Originally Posted by markjenn

Are any new KTM's shim over bucket? Seems like almost all the recent designs are shim under bucket. The only sorta recent engine I recall using shim-over is the ZX11/ZRX motors and these have roots in the 1980's.- Mark

250, 350, 400, 450, 500, 530, 690 SX/EXC/SMR/SMC all have a shim sitting on the valve, with a rocker arm operating on the shim. No bucket. Some use same shim as the LC8, but not under a bucket.

[markjenn]

Originally Posted by Peanuts

250, 350, 400, 450, 500, 530, 690 SX/EXC/SMR/SMC all have a shim sitting on the valve, with a rocker arm operating on the shim. No bucket. Some use same shim as the LC8, but not under a bucket.

Thanks for clarification. I would think this wouldn't have any scrubbing loads like would occur with a cam lobe bearing directly on the shim.

Like I said earlier, I've heard conflicting views on whether grinding shims is a good idea or not. All over the map on this one, from "shims are completely homogenous and are ground to thickness anyway" to "shims are surface hardened and if you grind off the hardened layer, they'll rapidly wear and cause valve clearances to go way off in a short time". All a shim-under-bucket sees is compression loads and it doesn't seem like a very good application for surface hardening, but I'm not a metallurgist. In any event, I don't grind shims anyway. But I'm surprised there are such differing views.

- Mark

[geometrician]

Originally Posted by markjenn

Thanks for clarification. I would think this wouldn't have any scrubbing loads like would occur with a cam lobe bearing directly on the shim.

Like I said earlier, I've heard conflicting views on whether grinding shims is a good idea or not. All over the map on this one, from "shims are completely homogenous and are ground to thickness anyway" to "shims are surface hardened and if you grind off the hardened layer, they'll rapidly wear and cause valve clearances to go way off in a short time". All a shim-under-bucket sees is compression loads and it doesn't seem like a very good application for surface hardening, but I'm not a metallurgist. In any event, I don't grind shims anyway. But I'm surprised there are such differing views.

- Mark

ALL valve shims are centerless-ground to thickness and then chemically hardened which only penetrates the metal in tens of thousands of an inch- not throughout (which would be heat hardening)

The shims compression load includes taking the hit from (whatever) clearance being taken up as the cam opens the valve- at 6,000rpm that's 100 revs a second, divided by two (720 degrees of crank rotation in a 4-stroke) divided by the two cylinders equals 25 hits a second. Might not seem that the inertial loads of valve, top keeper, retainers & bucket is much but considering they are opening from a dead stop each time it adds up. FWIW most valve wear occurs in the top 15% of the RPM range, so road/drag/supermoto race engine speeds will see wear before someone who doesn't cane the shit out of their engine

I've taken out shims on customer bikes (esp the 250, 350, 400, 450, 500, 530, 690 engines metioned above) with such a depression hammered into them from the top of the valve stem they are unusable. They do, indeed, wear. Worse case is when the outer edge of the shim contact the spring keepers and the retainers get knocked out of their lock with the valve stem and the valve drops into the cylinder where it promptly makes contact with the piston which leads to bent valve if not valve head broken off stem which REALLY makes a mess! Rocker arms on these engines is required for SOHC (single over head cam) valve actuation, and the arms ("followers") themselves are hardened as well on the modern 250/350/500 KTM four strokes (pretty irridescent colors). The 690 uses rollers on the ends of the arms to reduce angular force acting on the valve/shim- not the perfect solution as they weigh more and the roller/retainer pin wears, which increases clearances/wear.

[markjenn]

Originally Posted by geometrician

ALL valve shims are centerless-ground to thickness and then chemically hardened which only penetrates the metal in tens of thousands of an inch- not throughout (which would be heat hardening)

Do you have any kind of reference from a mfg or other authority?

Thanks for your informative post, but again, I can tell you that there are lots of equally authoritative posts in other forums that say valve shims are not chemically hardened or case hardened but instead are through hardened, included a few folks who have done tests and concluded that the hardness is uniform throughout.

This shim kit says they are through hardened.

http://www.roseville-yamaha.com/esho...E_VALVE_SH.htm

I have no dog in this fight since I do not grind shims and am not advocating to do so. I'm just surprised by how little hard information there is on this subject.

- Mark

[MortimerSickle]

What I wonder about grinding shims by hand is, how do you keep the surface perfectly flat and aligned on the same plane as the other side?

I can see that it could be done with careful use of a surface grinder, but by hand I would think it would tend to be uneven.