SR500 valve adjustment

When I bought my SR (in 1984 no less) it had already been modified with a
cam and piston from White Brothers. For a long time I had capable
mechanics handle tuneups for me. They all told me the valves couldn't be
set to factory specs because of the modifications but I never found out
exactly what they were setting them to.

Now they're all gone and I'm stuck with doing the job myself. Does anyone
know the details of the old White Brothers cams and what the valve
clearances should be?

Or some general rule for adjusting clearances when the specs are unknown?

Thanks.

 

Oh, you've got one of my *favourite* bikes ever there!

Hm. I don't see why a cam and piston job should necessarily affect the
valve clearances. I can't see that even the humpiest piston and the
wildest cam is going to result in an engine where one thou (for the sake
of argument) difference is going to result in a piston/valve collision.

Unless the head has been skimmed as well to increase the compression
ratio? You don't say it has been, so let's assume it hasn't.

Right, SR500s tend to run a bit hot, especially when tuned. Exra heat
from a tune-up job in theory will result in expansion of the critical
engine components, thus in turn resulting in an over-tight clearances
when the engine's hot (read: worse than no clearance at all).

Working on the basis that it's better to have the clearances too wide
than too tight, I'd set the tappets perhaps a couple of thou (sorry;
don't do metric when it comes to valves) in excess of the recommended
factory clearances. They run 4 thou inlet and 6 thou exhaust as stock,
so go to 6 and 8 thou respectively.

With those settings, it'll probably rattle like a bastard when cold. Get
it up to working temperature, and if it's still clattering then, go down
a thou on each valve.

Ideally, when hot the clearances should be effectively zero or *just* a
bit more. Doing a clearance check with a hot engine will result in
burned fingers, as sure as fate, but it would be worth doing. If you do
a 'hot' test and you can get a one thou feeler blade in the gap, they're
probably a fraction too wide.

Mark Olson will be along in a minute, and he knows a thing or two about
these bikes.

 

Thanks. Sounds like your advice is nicely conservative. I'll give it a
try. I do have an oil cooler on the bike and the oil temperature in the
tank is seldom over 150 (it has an after market gauge) so I may well have
to redo it. But that sounds a lot better than setting them too tight to
begin with .

 

Sensible mod.

150 is an odd temperature. Seems too high for Centigrade and too low for
Fahrenheit, so I'd suspect a duff gauge.

 

Not really, my buddy owns one, and we split the cases to replace a gear
that had broken off a tooth once, so I am somewhat familiar with the
overall engine but know nothing specific about the White Brothers cam
setup. Tim had one or more SR500s and had quite a bit of mods done,
in fact he might have had the exact setup Larry mentions, so I will
ping him in another place.

I'm not 100% in agreement about what the specific clearance should be
when hot, except that it should definitely have *some*, and if it were
mine I would probably do exactly as TOG suggests, set them a thousandth
or two looser than spec and see what happens. It might also make sense
to ask the SR500 community, IIRC back in 2006 when we worked on my
buddy's SR500 he ordered a bunch of parts from a guy who is an SR500
specialist in Washington or Oregon, and I think he was known on
thumpertalk.com. Can't remember the name exactly but try here:

http://www.thumpertalk.com/forum/

 

And I would suspect that *you* are a congenital idiot.

 

Oh yeah, I joined that forum when I had my SR500! You're probably
right about there being *some* clearance when hot - probably too small
to measure, though.

Interestingly, my Ducati is supposed to have zero clearance on the
closing rocker arms, which begs the question of how the hell you
measure that with a shim set-up. The answer is that there's supposed
to be just enough clearance to let you twiddle the shim with your
fingertips.

Italian precision engineering. Love it.

 

Jolly good. Keep dancing.

 

I belong to a more specific one than that:

http://www.sr500forum.com/forum/

I asked there and got only one response, although it is quite active and
has given good advice on other topics. Did better here .

And the specialist in WA or OR is Mark Apland at:

http://www.thumperstuff.com/

I haven't asked him yet - I'll do that.

Thanks again to all.

 

he keeps projecting his inompetence and incontinence on others doesn't
he? I really wish he'd die or get killed.

 

Better be nice, you're not in my will yet.

 

I did ping Tim in another place, and he did indeed have a White Bros.
cam in his built SR500, he may yet drop in and give the group the
benefit of his experience.

 

<Watches thread>

 

Oh, marvelous!

Tim Morrow has more experience with motorcycles than any man alive
today!

At least that's what he claims...

 

Nice? Nice would be putting three through the back of your head in
your trailer. I'm not nice.

 

MOre than a loser like you that's for sure.

 

Do you always fantasize about murder when you're masturbating, Mr.
Rear Echelon?

 

far less than your fantasies about black cock and underage mexicans.