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

[ukjules]

I have the above scenario.
I did a head rebuild , the works and lapped the valves and 7 could be
set perfectly within tolerances.
All the obvious done - head skimmed etc.
The bike now goes better than it ever has done - like a new bike. It has transformed the bike

1 Valve gap however cannot and as I could not mentally take removing the head again
I found a chap who had a shim grinding machine that grinds shims to whatever thickness you so wish.

Stats:
tolerance: 0.03 - 0.08mm

Smallest shim possible via suzuki - 2.15mm

now I could not get a gap with the smallest shim.
To solve this i used 2 pence coin i measured at 1.8mm (The engineering firm measured it at 1.8034)
The gap was then 0.14mm

So i wanted a shim of - 1.91mm
this I did and is now in and bike is running better than ever with perfect valve clearances.

However

I am concerned at using a shim out of suzuki tolerance and want to grind the top of a valve -
well get an engineering company to do it. I will do this in the winter months.
Peace of mind and that it will give me on my priceless bike.

question:
How do i work out how much to grind off the top of that particular valve ?
to be able to use normal shims. Where am I measuring?
I am sure this is simple but I must ask as cannot take any more mistakes

[tkent02]

Remove the correct amount so it's in the range of the other valves, for instance if your other shims are around 2.50mm and you are using 1.91mm shims you need to take .6 off the stem. Should bring it to 2.51, so close enough. This will make it easier to swap shims around next time they need to be adjusted. Maybe take off a wee bit more so it uses the thicker shims you take out of the other valves.

Did you find out what's different about that one valve to make it need such a thin shim? Did it burn into the valve seat farther? Just a lot more wear on that one valve? That doesn't sound right. Has someone been in there machining things before? Did someone put in a valve from a different engine? Has the valve seat been damaged?

Did you try swapping the buckets around? They are not all the same height. Maybe you can find a shorter one to use, won't even have to pull the head for that. You can also grind the little tit off the inside of the one bucket instead of pulling the head to get a valve out.

You do realize the head will have to come off to do this grinding?
If I was taking the head off anyway I'd figure out what's different about that one valve and fix it. But I think modifying the one bucket would be a lot simpler.

[Brendan W]

I would just add that if the valve has been ground before there might not be a lot left to take off and if the problem is coming from wear at the other end a new valve could pull things back into normal clearance range.

[ukjules]

I think i am there on the maths now. Cheers for that
and great advice to reinstate my thoughts.

I have an engine now I had to rebuild for various reasons - non due to it being seized or
valve related. I have done all the work myself - bar the shim grinding.
I can have the head off in 2 hours no problems now - but will do this after the summer has gone.

The new engine is made up of a second hand barrel and a second hand head.
I am using my old pistons and rings, (Comprression fine), the new head has valves that to me looked ok
from one of the other heads, not my known original.

There was nothing "nothing" that appeared to look odd - but i did not measure anything.
the valve seats in the head all ok.

Anyway, valves cleaned up, lapped, new oil seals .....and the bike goes better than it ever has done - like a new bike.
It is fabulous. But being a perfectionist i will go through the process of sorting it by valve
rather than shim in the winter.

I did try swapping the buckets around and the gap remained the same !

I rechecked the clearances after a 30 mile riide and the gaps are the same so no
seating , bedding in issues.

I have zero knowledge of the previous engine bar the persons who previously owned having dreadful mechanical skills
with stripped threads etc. I have sorted all those now and the head is skimmed. it was 0.08" out.

I think it is head off in the winter and inspect more fully but in the end get the valve ground down by
the then new valve clearance calculation.

I have another question that the engineering firm who skimed the head told me to do
which would have stopped me putting on and taking my had off all the time.
I wont ask on this thread and wil start a new thread as it is easier to search for if others like
me wanted to know this.

[ukjules]

Stop the press - I did not find out where you measure ??
What exact point would you measure on the valve from ?

As it would not be the bottom but where it hits the head ?

[Brendan W]

Is it an inlet or exhaust?
The head of the valve itself could have thinned out. It might not be all seat wear.

[ukjules]

Sorry - i am losing it - it is as informed simply from the top when the calculation has been done.
I am having a mechanical overload.

mine is the exhaust on cyl 4.
no need to consider why on this thread - i need the head off for that but i know now
how much to tell the engineering firm to take off the top ..... when i do it.

point taken on wear on head and seat.

thanks.

[JTGS850GL]

A few concerns on this.

First: Not sure how deep the bucket is but if the shim is below the top of the bucket then you risk chewing up the cam. The stock shims go down to 2.15mm for a reason. Just make sure you don't have any interference with the shim bucket. Check the cam lobe on that valve and verify that the outside edges are getting rounded off.

Second: Did you record all the shim numbers you currently have? If grinding down the valve stems, you want to get back into the mid range of available shims. If the other's are close to the 2.15mm minimum, then you need to consider getting the whole set re ground to get them back into range. You'll probably have to replace most of the shims, but it would add years to the top end rebuild.

Third: Don't mix up the valves. Make sure that they stay with the location they came from when re ground and installed. If not you could end up with numbers all over the place.

[Agemax]

just measured the depths of 6 different buckets, they measure 2.15mm +/- 0.02mm.
I would not run that undersize shim personally!

[ukjules]

I have absolutely everything recorded. The valves will always remain in their current positions.
They came from all over the place though - i have a totally different engine now.
I have already lapped all the valves. the engine is perfect bar one valve clearance (sorted with my shim)
The buckets made no difference or not big enough for me to see a gap.
- i needed to see a gap so i used a 2p coin to create oine and calculate.

With the gap i got the exact gap i needed to play with.

I am ok with the shim. I have even taken the valve cover off to check gaps and all the same and no
undue wear. It sounds better than i could have ever imagined.
the shims are hard all the way through so i am ok with the minimal risk - in the olden days they did worse
and the engineering firm informed he has seen mad grindings going on.

When i have a few days spare in the winter ill take the head off and do the single valve that casues
concern. I can get it done for less than a fiver. I wont need to touch the others mind !they are in order.

I am in the lucky position as I now have two heads and i will build the other one (needs some work) "on the bench" this time
and make this a hot swap when i do the other one.
Ill keep you informed if this is an issue as it might help others but assume not until i add a post !

But trust me i am not discounting your concerns - deep in my heart i know i should not have done it but
its summer for goodness sake - the bike needs to be ridden ! I am not taking the head off
as my other is not ready and i MUST ride !

[JTGS850GL]

just measured the depths of 6 different buckets, they measure 2.15mm +/- 0.02mm.
I would not run that undersize shim personally!

Bingo!!! That would be my main concern. Suzuki created shims no thinner then 2.15mm for a reason. The cam will hit the edge of the bucket before it lands on the shim if the shim is too thin. It's the same issue as turning the cam over without a shim in the bucket.

[ukjules]

i assure you the cam does not hit anything it should not ! we are talking rather small amounts you know !
The shim is just fine and rosy !

Il give you a wave as i overtake you with the increase in power i have !

[JTGS850GL]

What every you say dude. Good luck.

[ukjules]

I will report on this as it is useful info ...... To reiterate I am down to 1.9mm shim ground down by professional with shim grinding machine . I had a 2.15 to grind down but chose a 2.55 just to see . To prevent the need for this I should have tested clearances with head on bench where I could have made adjustments to valve heads but only learnt that too late ..... I have now done 150 glorious miles in the UK summer and the engine is perfect. Before it was using oil, smoking , would not idle, lacked power and had blown gaskets. New gaskets, skimmed head, new oil seals, cleaned valves, valve clearances set is now like new. Assume all OK with single shim issue , I will report for info. I agree though - always test with head on bench ideally but if you have ballsed up and you have to ride ---- then this a option that is working for me.

[1948man]

I have two intake valves with 2.20 shims approaching the bottom end of acceptable clearance. I'm soon replacing them with 2.15. Looking head, how do you take buckets out? Do you just remove the cams and pull them straight up? I have a spare (maybe junk) engine with cams out but the buckets, which spin fine, don't won't to come out. My second question is, How much of a nub is there on the bottom of the bucket to be ground off? How many hundredths of a mm can you gain?