shim size < 2.20, what now?

[psyguy]

some of my shims are at 2.25mm :shock:
the z1 lists 2.3mm as their smallest size (although bike bandit lists them down to 2.15)
i'm wondering what happens once you get to the smallest size
the repair manual suggests the valve stems can be grinded/shortened (if i understood that correctly)

has anyone done this and with what sucess?
what are the alternatives (other than replacing the head)?

your experience appreciated

[catbed]

the shims should go down to 2.15.

if you want to do it, you can replace the valves and seats. thats a way so you dont have to get a new head.

[psyguy]

you can replace the valves and seats.

thanks catbed
how do you replace the seats?
i can't see them on the parts fiche

[Suzuki_Don]

You need a machine shop to fit the seats for you. I know I will get a slap on the wrist for suggesting this, but some people (no names mentioned) have had the shims ground down on a surface grinder to a slimmer size and it has worked for thousands of kilometers without any problems. If you pull the head to grind the valve stems it means removing the barrel as well to replace the base gasket. The other way only requires removing the cylinder head cover. Try your susuki dealer they list shims down to 2.15mm. Just a few ideas from me.

[psyguy]

You need a machine shop to fit the seats for you..

thanks don
can you maybe explain how this is done, are you sure the seats are removable, and how do you go about finding the new seats?

[Suzuki_Don]

thanks don
can you maybe explain how this is done, are you sure the seats are removable, and how do you go about finding the new seats?

Cast iron seats in aluminum heads can be removed by using a die grinder to cut through the seat. This relieves pressure and allows the seat to be easily removed. The danger with this technique, however, is grinding all the way through the seat and into the head and wrecking the counterbore.
The machine shop that removes the seats will supply the new seats to be pressed into place. You would need to use an engine building business that does this type of work on a regular basis.

[bwringer]

Actually, I'd bet you have a couple of burned valves. How's compression?

Guess how I know about the symptoms of this problem...


Bad intake o-rings = lean mixture = EXTREMELY high exhaust gas temps = burned valves.

[psyguy]

Actually, I'd bet you have a couple of burned valves. How's compression?

compression's great, thanks for asking :-D
no burnt valves either - i have recently completely rebuilt this engine and am thinking about keeping the bike for a while - but those thin shims do worry me

[bwringer]

Glad your compression is good! Wouldn't want anyone to repeat my sad experience.


At the edge of the valves, how thick is the margin? The heads of the valves should be sort of blunt all the way around.

In the manual, there's a spec for the margin at the edge of the valves. If it's gone, meaning the valves are sharp at the edges, then you'll want to replace those valves eventually. You may need a bore scope or something similar to get a peek at your valve edges with the head still installed.

During the rebuild, did you have the valve seats ground or cut?

As others have noted, you can get shims down to 2.15mm, and there's nothing wrong in principle with grinding shims a bit thinner, as long as you can find a way to do it perfectly even and square, and place the ground face down.

Personally, I'd order up some 2.15 shims or have some shims ground down and keep riding as long as possible before taking it apart again.

[psyguy]

In the manual, there's a spec for the margin at the edge of the valves. If it's gone, meaning the valves are sharp at the edges, then you'll want to replace those valves eventually.
During the rebuild, did you have the valve seats ground or cut?

yup, the margins were all well in spec
i had the valves/seats ground

[Nessism]

Sounds like when the valve seats were ground the valves sank into the head some. Assuming all it well there, just order some of the thinner shims. Worst case is take some of your old shims and find a machine shop to surface grind them to your spec - 2.10 for example. Ask them to demagnitize them when finished since surface grinders typically use magnitism to hold parts in place on the machine.

Good luck.