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Valve shim clearance/sizes

  • Thread starter Thread starter jizracer
  • Start date Start date
J

jizracer

Guest
Just Checking valve clearances on the 78 750 and come across something weird. (new bike, haven't ridden it yet)
All the clearances are quite large around .3mm some of them. Didn't do exact check, just a quick check at the end of the day.
So I whipped the two out from number one cyl to see and measured them and stuck them back in and one was 1.93mm the other was 1.9mm.
Now im on computer looking about to see where I can get replacements from and looks like they start at 2.3mm so looked at Suzuki manual and they start at 2.15mm!
Has some idiot cocked up .03-.08mm for thou/inch and ground them down? Theres no markings on them either.
A couple were around .1mm
Am I missing something here.

Also did a compression test before pulling cam cover and all four cylinders showing 175psi which seems very good, almost to good. Is this normal compression.
Don't know any history of the bike except its a race bike (someone elses unfinished project) came with a spare engine. There is a pick of it in my first post.
This is my second post!
Cheers, Steve.
 
Maybe someone did some valve seat work causing valve stems to rise up too far and rather than grind stems down, he ground shims too fit.
 
Trying to figure out what was in a PO's head is not easy. You don't even know if this is the 'finished' plan or a work in progress. As Tom said maybe the valves came up, compression is good so that's consistent with valve work. If you can get in touch with whoever worked on this you might get an idea of what's going on. I would be starting to check things like are the cams and springs original. Either way I would be trying to make sure that an attempt to get back to stock clearances wasn't going to cause unforseen problems. Someone could have put the decimal point in the wrong place and was shooting for 0.3 but someone with the facility to source or grind thin shims couldn't make that kind of mistake surely. :)
1.9 seems too thin for the job they have to do.
 
you need to get it sorted now, those clearances will only get tighter so even thinner shims will be required later. if your measurements are correct then i agree, sounds like it has had a valve job and instead of shaving a bit off the top of the valves, they have ground the shims down to size.
 
Why not take accurate clearance measurements then figure out what shims you would need to get .03 - .08. If they are normal size shims then set to correct clearance and go riding.

i can see your excessive clearance giving high compression because it would noticeablely reduce valve overlap. Could it be a sales strategy; "can't start bike but hey it has real great compression"

Brian
 
Once you figure out whether stock clearances will not hurt anything, feel free to take advantage of the offer in my sig.

.
 
Ok, thanks for the replys.
On this subject do these bike clearances generally tend to tighten up over the years or loosen or random?
I know on my yammy FZR the intake valves all tighten. the exhaust valves stay good.
 
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Ok, well ive taken accurate measurements and still same result which doesn't make much sense. Especially since the seats tend to recede.
Every single shim is very small (all between 1.80-1.90mm)
Every single clearance is large except one which is in spec (all the rest are between 0.15-0.30mm)
So I need a bunch of shims around 2.0-2.1mm which aren't available. Could take the shims out of the spare motor and grind them down.
Or I could just leave them in there for a while till they come back into spec!!
 
"Or I could just leave them in there for a while till they come back into spec!!"

forget this idea- it will take too long. Besides I'd worry about a shim exiting a bucket.
The easy way is to go into the shim grinding business , knowing that you or next guy will be grinding again.
The better way unfortunately is to shorten valve stems aiming for needed shims in the 2.7 mm range which are plentiful.
 
Just how thin can the shims be made before the cam lobe hits the bucket before it hits the shim? Might be the reason that Suzuki only made shims down to 2.15mm.
 
I don't know how far down a shim can safely be ground without the bucket interference, but there are quite a few engines that are using shims that are under 2.15. I remember one shim club member that needed a 1.90 in one valve.
 
I'd still double check that the cam lobes are not getting ground down along the outside edges.
 
I measured the lip on the bucket once upon a time, but don't remember what it was. Maybe about 1.5mm?

What I can tell you, though, is that even a 2.70 shim can get spit out if you catch a 'false neutral' between 2nd and 3rd gears and hit the throttle. :-\\\

.
 
tom203 said:
"Or I could just leave them in there for a while till they come back into spec!!"

forget this idea- it will take too long. Besides I'd worry about a shim exiting a bucket.
The easy way is to go into the shim grinding business , knowing that you or next guy will be grinding again.
The better way unfortunately is to shorten valve stems aiming for needed shims in the 2.7 mm range which are plentiful.
Click to expand...
Yea man. looks like im surface grinding. No worries, my brother is a machine shop foreman.
The waiting till they come back into spec comment was me cracking a silly joke!!
 
I think, at this point, I would be pulling the head off and see exactly what is going on with the valves, before grinding down the shims. The valve faces might be overground or the seats may have been butchered. If things look OK then you could grind the stems so you can use normal shims.

Brian
 
canuckxxx said:
I think, at this point, I would be pulling the head off and see exactly what is going on with the valves, before grinding down the shims. The valve faces might be overground or the seats may have been butchered. If things look OK then you could grind the stems so you can use normal shims.

Brian
Click to expand...
Normally I would agree, but before I did valve measurements I did a compression test and come up with 175psi on all four cylinders. Also looking down spark plug holes at the valves/valve seat area. They looked good and flat. Not mushroomed.
 
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Well another quick and dirty way to gain more room for shims is to machine the button on the underside of the buckets....Carbide tip does it.
 
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