When valve clearance cannot be arrived at with thinnest shim ....

[ukjules]

The bottom line is you need to grind the valve top ! I wouldnt go messing with buckets.
I myself am testing reducing shims (stock Suzuki ones) to less than 2.15 down to 1.8.

It has worked OK for me , but check on this thread just in case iI have iissues
600 miles so far and bike perfect still ...

Pull buckets straight up !

[chuck hahn]

BUT you can only take off so much before the keepers start getting above the top of the valve stem. If that happens its new valve time.

[ukjules]

Agreed ! Def thing to watch.
On mine I am fine at 1.85. Trust me I religiously checked out that possibility !

But grind the valve !!!!!!!!!!!!! If it iis needed. There is no need to do what I did unless you like testing and taking risks.

[1948man]

Thanks for the info.

[Grimly]

I'd be inclined to suspect valve stretch. In the event of that happening, I'd replace - wouldn't be the first engine to have stretchy valves, especially if you don't know how hard it's been run by POs. If the valve stem stretches enough, it will snap and the engine is lunched.

[qcktvr]

Hi there,
I have worked around motors for many years and "stretchy valves" is a new one for me; maybe that was a joke?
Air cooled motors, when pushed for max power, will typically fail in the area of the exhaust valves, and yes, they could drop their head. BUT you said this is on an intake valve, where heat is not usually an issue, unless maybe if the valve is held open / no clearance.
If the head was off / on the bench then the valve could be removed and an amount ground from the end of the stem to get things back in spec;
Good luck

[Grimly]

Hi there,
I have worked around motors for many years and "stretchy valves" is a new one for me; maybe that was a joke?
Air cooled motors, when pushed for max power, will typically fail in the area of the exhaust valves, and yes, they could drop their head. BUT you said this is on an intake valve, where heat is not usually an issue, unless maybe if the valve is held open / no clearance.
If the head was off / on the bench then the valve could be removed and an amount ground from the end of the stem to get things back in spec;
Good luck

No joke. You've never heard of stretched valve stems?

[2BRacing]

......BUT you said this is on an intake valve, where heat is not usually an issue, ......

Don't know where you read that it was an intake valve? He clearly says in post # 7 that ..."mine is the exhaust on cyl 4."

[tkent02]

No joke. You've never heard of stretched valve stems?

I have always heard it as a joke, like "Get me 50' of water line" or "Go find some relative bearing grease"

The valve stems get longer because the valves recede into the head.

[1948man]

Don't know where you read that it was an intake valve? He clearly says in post # 7 that ..."mine is the exhaust on cyl 4."

Post 15, not the original poster. Shims range from 2.20 to 2.70?????

[qcktvr]

I'm getting old, but I am still learning as well as forgetting....
I gather "valve stretch" is a concern with old air cooled VWs, but I cannot believe that it an issue for our street driven GSs
Must have dreamt that it was an intake, but still would not want anyone to panic re their valve breaking after a rebuild and moving valves between heads, I believe that would be extremely unlikely.
I would expect Suzuki to give a dimension from the spring seat to the top of the valve stem as a reference for machine shops to adjust valve lengths after grinding valve seat and valve faces..
Thankfully no shims in my 1150, so I will go and install a new petcock and rethink a charging concern.
Then go for a ride...
Regards

[Fjbj40]

Valves will stretch. Especially the exhaust valve. Valve stretch is checked using a radius gauge between the stem and the valve face back. Or you use a vernier micrometer and measure the lower stem and compare to the upper stem, if it is narrower on the lower half then you have stretch.

This is a check that we do on aircraft engine valves.

Not sure if other engines have a similar check or if they just use height/length, either free or installed. Some stretch is acceptable.

A reduction in shim/valve clearance, depending on the tune of an engine, can be stretch or valve recession into the seat, or valve seat wear.

[qcktvr]

Good morning,
interesting re the radius gauge for the aero engines, I had heard of that, but would that not really be identifying distorted valve heads rather than what I would think of as actual "stretch"? The eventual failure mode likely being the valve head parting company with the stem, but also showing up as reducing valve clearances.
Have a good day

[rustybronco]

The valve stems get longer because the valves recede into the head.

Or the valve heads themselves tulip (dish out).

[Fjbj40]

Good morning,
interesting re the radius gauge for the aero engines, I had heard of that, but would that not really be identifying distorted valve heads rather than what I would think of as actual "stretch"? The eventual failure mode likely being the valve head parting company with the stem, but also showing up as reducing valve clearances.
Have a good day

The stretch usually takes place where the head meets the stem. As it stretches it gets narrower and the radius changes. Placing the radius gauge there during inspection will reveal the change in radius, therefore the valve gets rejected because of this.

Alot of the aircraft engines use hydraulic lifters, therefore the reduced valve clearances are not seen, they are automatically compensated for by the lifter. The hydraulic lifter has an allowable range during installation, and unless you remove the lifter, bleed it down, reinstall it and measure the "dry" lifter clearance you would not realize it is approaching the minimum allowable clearance. Which would occur if the valve is stretching, tuliping or the seat is receding.

Removal of the lifter may never occur during the life of the engine. Only if the engine does not perform as designed or there is rough operation may this inspection be carried out during trouble shooting.

I have never worked on a bike engine newer than my 83 1100.

Do new bikes have hydraulic lifters today?