Suggestion on valve shims
Ted Mittelstaedt
OK it's valve adjustment time for my 1980 CB750. So before pulling the
cover I
went by my local Honda dealer parts dept and asked about shims since I'm
sure I'll probably
need 1 or 2. To my disappointment they had none. (plenty of the small size
shims
for newer bikes, nothing for mine though) They can order them - if I want
to wait
a week, and the shims are $8 -each-.
So now what? Do I go to the trouble of taking everything apart just to
get some
shim measurements then putting it all back together, waiting a week, then
taking it
all apart again? Do I get an expensive shim kit that I'll never use 99% of
the
shims in the kit? Do I call around to other bike repair shops with the bike
apart
and ask if they have a shim in the measurement I need that they will sell or
swap?
Do I scavenge bike wrecking yards for hashed-up bike engines that I can get
for a song?
Any ideas of where I could quickly get a few shims that I need for a few
bucks would be most appreciated. What do other people do? (besides
take it to some mechanic and let it be his problem?)
Ted
paul c
Apparently (just saying this based on a couple of links I found), Toyota
twin cam engines use 25 mm diameter shims, so do some Triumphs and quite
a few Yamahas - perhaps Toyota shims will be easier to find locally.
By the way, I've never adjusted any kind of shimmed valves, but suspect
I may have to soon on a friend's 1982 CB750C - am a little puzzled that
clearance is supposed to be something like .05 mm whereas the shims
people seem to be selling online for cb750's all seem to vary in
thickness by exactly .05 mm. I'm assuming that if the valve springs and
tappets/cam surfaces aren't too worn then usually valve wear would cause
clearance to become tighter over time (I'm guessing because of valve
shoulder wear), so one would likely find after measuring that clearance
needs to be increased. Say for argument's sake that one finds it is
necessary to remove .03 mm of shim thickness, wouldn't that mean
removing, say, a 2.35 mm shim and replacing it with a 2.32 mm shim? Or
do these bikes come stock with several shims whose thickness isn't a
multiple of .05 mm or is my understanding all balled up?
paul c
...
>
> By the way, I've never adjusted any kind of shimmed valves, but suspect
> I may have to soon on a friend's 1982 CB750C - am a little puzzled that
> clearance is supposed to be something like .05 mm whereas the shims
> people seem to be selling online for cb750's all seem to vary in
> thickness by exactly .05 mm. I'm assuming that if the valve springs and
> tappets/cam surfaces aren't too worn then usually valve wear would cause
> clearance to become tighter over time (I'm guessing because of valve
> shoulder wear), so one would likely find after measuring that clearance
> needs to be increased. Say for argument's sake that one finds it is
> necessary to remove .03 mm of shim thickness, wouldn't that mean
> removing, say, a 2.35 mm shim and replacing it with a 2.32 mm shim? Or
> do these bikes come stock with several shims whose thickness isn't a
> multiple of .05 mm or is my understanding all balled up?
Looks like I was a little balled-up, just found some manual pages at
http://www.cb1100f.net/Other/CB750FManual/Honda1979thru83CB750ServiceManualChapter03InspectionandAdjustment.pdf
and it seems that clearance is .08 mm with tolerances of plus .05 and
minus .02 mm. There's also a chart to follow for replacements. So I
guess the key is that plus tolerance. It also sort of makes sense to me
that the plus tolerance would be greater than the minus, as I imagine
it's better for valves to be slightly 'loose' than slightly 'tight', at
least as far as engine wear is concerned.
The Older Gentleman
> So now what? Do I go to the trouble of taking everything apart just to
> get some
> shim measurements then putting it all back together, waiting a week, then
> taking it
> all apart again?
Its not a matter of taking it all apart. Just whip off the cambox cover,
measure the clearances, and see. If it needs nothing, fine, and if it
needs a shim or two changing it's not exactly a big job to replace the
cambox cover and petrol tank.
--
BMW K1100LT Ducati 750SS Honda CB400F, SL125 & SH50 Yamaha XT600E
chateau dot murray at idnet dot com
"What you're proposing to do will involve a lot of time
and hassle for no tangible benefit."
Ted Mittelstaedt
"The Older Gentleman" <totallyde...@yahoo.co.uk> wrote in message
news:1iiwa45.3zi8nhs228eN%totallyde...@yahoo.co.uk...
> Ted Mittelstaedt <te...@toybox.placo.com> wrote:
>
> > So now what? Do I go to the trouble of taking everything apart just to
> > get some
> > shim measurements then putting it all back together, waiting a week,
then
> > taking it
> > all apart again?
>
> Its not a matter of taking it all apart. Just whip off the cambox cover,
> measure the clearances, and see. If it needs nothing, fine, and if it
> needs a shim or two changing it's not exactly a big job to replace the
> cambox cover and petrol tank.
>
Just curious how do you normally keep the rubber gasket in it's channel
for the minute or so your putting the cover back down? I was figuring
just a few blobs of heavy grease. (or I could turn the engine upside
down - just kidding)
I know it's not that big of a job to do - although I don't have the
spring compressor tool on hand, and I had to order it so it will be
another week before that comes in (unbelievably, none of the
dealers here had them in stock even though we have FIVE that
are Motion-Pro dealers) since I'm unwilling to jam a screwdriver
down there.
It's more the principle of the thing - it just seems like it is something to
where I should be able to just pop the cover, and if a shim is needed
ride the other bike a couple miles to a bike shop where they would have
a box of new and used shims and could just fish out the one I need,
take mine and a few bucks, and I'm off and running.
I guess if I had a nice NEW bike then it would not be a problem since
they use different tools and different shims. :-(
Ted
The Older Gentleman
> Just curious how do you normally keep the rubber gasket in it's channel
> for the minute or so your putting the cover back down? I was figuring
> just a few blobs of heavy grease. (or I could turn the engine upside
> down - just kidding)
Yes, grease is what I've used in the past. Works a treat.
>
> I know it's not that big of a job to do - although I don't have the
> spring compressor tool on hand, and I had to order it so it will be
> another week before that comes in (unbelievably, none of the
> dealers here had them in stock even though we have FIVE that
> are Motion-Pro dealers) since I'm unwilling to jam a screwdriver
> down there.
Last time I faffed around, I found a C-spanner that I used for adjusting
shocks worked perfectly.
Alternatively, you can just treat it like an air-cooled Kawasaki 650/750
and displace the cams.
.
> Just curious how do you normally keep the rubber gasket in it's channel
> for the minute or so your putting the cover back down? �I was figuring
> just a few blobs of heavy grease. �(or I could turn the engine upside
> down - just kidding)
Last time I adjusted the valves on my GSXR, the valve cover gasket
slipped and leaked oil down the front of the cylinder head.
That was when I realized why Suzuki glued the rubber valve cover
gasket in place with a grey rubber cement resembling Yamaha Bond.
So, I degreased the valve cover and the rubber gasket and then glued
the gasket in place with silicone rubber sealer.
.
> It also sort of makes sense to me
> that the plus tolerance would be greater than the minus, as I imagine
> it's better for valves to be slightly 'loose' than slightly 'tight', at
> least as far as engine wear is concerned.
I once tried to extend the valve adjustment interval on my GS1100 by
setting the
valve clearances to the minimum, wrongly assuming that the cam lobes
would wear and that the valve clearances would loosen up...
I set all the intake valves at less than 0.003 inches. They burned
after about 30K miles, but I was also having fuel starvation problems
and worn valve guide oil seals leaking oil onto the valve heads, and
keeping them from seating properly.
Normal valve seat erosion under normal operation will cause the valves
to "sink" into the seats by a few thousandths of an inch, taking up
valve clearance at the stem end.
.
> it seems that clearance is .08 mm with tolerances of plus .05 and
> minus .02 mm. �
.08 mm is 0.003152 inches. An American feeler gauge would work just
fine.
.13 mm is 0.005122 inches. Again, an American guage would work just
fine.
.06 mm is 0.002364 inches. That's a very tight valve clearance...
You can futz and putz around with metric tolerances and waste a lot of
time if you
don't realize just how small the variations are. I use American
guages, which are close enough for a reasonable individual to use.
paul c
Indeed, but I live in Canuckistan where some measures are metric and a
few are SAE or "standard". One can go crazy here (if one isn't already)
trying to find high tensile fasteners in metric because unlike oil, milk
and coca-cola, many of those come here from the USA. When buying tools,
it's even worse, for example if I want a socket set I wait until it's on
sale for half price, but it still costs me the full price in effect,
because there will two sets of sockets, one metric and one SAE. I give
away the SAE ones even though I have a Ford car. (I've had a few Fords
and as far as I'm concerned they're rough enough brand new that I'm not
hurting them much by using slightly off-size metrics on them - don't get
me started on Fords!)
I was in my twenties when we supposedly went metric, so I'm forced to
keep a few length, volume, weight, temperature, pressure et cetera
ratios in my head as I can recognize something that's a quarter-inch on
sight but never developed the same visual recognition of centimetres.
Seems to be something that only young minds are good at learning to do.
Gov't here is fond of regularly apologizing for all kinds of past
wrongs to various people, but they never said sorry to to me! Oh well,
I guess my theoretical advantage is that I always measure twice, still
cut twice because of crappy eyesight - as the carpenter I knows said, he
cut it three times and it was still too short!
Had a few laughs at a course I took where everybody else was much
younger and had mostly grown up with metric. We had to line up at the
tool crib for torque wrenches but some of the kids were working from a
manual that spec'd newton-metres and if all of those wrenches were out,
leaving only SAE, they'd wait until the next day. I kept telling them
to add a third, but most of them couldn't handle that in their heads.
Ted Mittelstaedt
"." <Rhia...@gmail.com> wrote in message
news:68101483-ed98-4195...@s21g2000prm.googlegroups.com...
On Jun 21, 7:49?am, paul c <toledoby...@ac.ooyah> wrote:
>You can futz and putz around with metric tolerances and waste a lot of
>time if you
>don't realize just how small the variations are. I use American
>guages, which are close enough for a reasonable individual to use.
I use feeler gauges that have both the metric and SAE marked on them. ;-)
Ted
.
> I use feeler gauges that have both the metric and SAE marked on them. ;-)
It's not a matter of converting between metric and SAE, Ted.
The simple fact is that the difference between a .08mm metric blade
and a .07mm blade is only 0.000394 inches.
That's less than four ten thousandths of an inch. Valves don't need to
be set that precisely.
Brady T
.
> On the subject of obtaining valve shims, it is also possible to have
> existing shims modified at a machine shop with a machine called a
> surface grinder. �The shim is held down on a magnetic base as a special
> grinding wheel passes over it, somewhat like a radial arm saw.
First, find a friendly machinist that will agree to grind your shims
down for less $$$ than new shims would cost. There are some old timers
who do work like that more as a hobby than a money maker.
Good luck.
I installed a set of reground Iskenderian camshafts in my Jaguar
engine back in the mid-1960's.
Iskenderian was famous for his relationship with the now-defunct Ascot
Park which
produced famous flat track racers like Kenny Roberts Sr.
In order to get a high lift cam, Iskenderian's cam grinder would grind
material off the heel of the cam and then re-harden it.
This meant that the standard range of original equipment shims were
too thin.
The box contained a bunch of shim blanks that had been punched out of
steel plate, so I called up Iskenderian and asked what I was supposed
to do with them.
They said that I should take them to a machine shop and have them
surface ground to the required dimension.
I asked, "Well, YOU sold me the cams, how about if YOU surface grind
them for me?"
The guy on the phone said that they didn't like to "tie up a machinist
all day" surface grinding shims, but they grudgingly agreed to grind
them.
Paul Barrett
by laying a sheet of sandpaper on the workbench, then using a holder I made
from a wood block, and rubbing the shim around on the bench, checking from
time to time with a caliper. Takes forever, and I made sure to put the now
less slick side down rather than against the cam.
Or maybe you'll get lucky and find that some are too loose and some are too
tight and they can be swapped.
I've been told that some repair shops will supposedly even swap one size for
another, but I've yet to find one that will.
B. Peg
> I once resorted to grinding down a shim myself, by laying a sheet of
> sandpaper on the workbench, then using a holder I made from a wood block,
> and rubbing the shim around on the bench, checking from time to time with
> a caliper. Takes forever, and I made sure to put the now less slick side
> down rather than against the cam.
I fear that may remove the hard coating of the shim which may cause it to
wear sooner.
Of course, that's only if they do hard coat them though.
B~