Valve Clearance Question: 1984 KZ550 LTD

Hi Everybody,

I bought an old non-running KZ550 LTD, from trustworthy-seeming guy
that told me it had been on the road a couple of years before, but had
carburetor issues.

I pulled the carbs and de-gunked them, being careful to clean all the
jets & needle/seat. When I put it back together (it was a major pain
with all the hardened rubber, it would start & run, but only with the
aid of starting fluid. Once warm, it would idle on 2.5 cylinders, but
would run well on the mains at higher rpms/load. The #3 cylinder
appears not to be firing at idle (based on my scientific hand against
hot header test).

I checked the valve clearances, and the #1 & #4 exhaust valve
clearnaces are running around .11mm when the spec. is .15mm-.20mm.
Seems to me that .05mm out of spec wouldn't cause the hard starting
problems I'm having-- also the #3, which seems to be the problem, is
in spec.

I pulled the pilot blanks & screws and de-gunked with B-12 chemtool and
blew out with compressed air. If anything, the bike has gotten worse
after the pilot circuit clean out.

My main question: is it more likely than not the valve clearances are
causing the problem? I would like to get the bike running before
spending the money to get the valves done (or doing them myself).

On this bike the cams need to come out after the cam chain tensioner
plunger is depressed which appears to necessitate removal of the
carburetors. Have I mentioned that I'm beginning to hate working on
this old bike?!?! Have I?!?!

Thanky!

 

I would be suspicious of the ignition system. The ignition system
probably uses two coils for that engine. You may have a weak coil that
only produces an adequate spark at high rpm. At low rpm, the spark is
too weak to sufficiently fire the air/fuel mixture.

charles

 

While attention to the carbs is a good idea, I can promise you that
over-tight valve clearances does indeed make for hard starting. I'd get
them re-set.

 

Hi Guys,

I am getting spark on the #1/3 cylinders, but was noticing yesterday
the #3 was a bit orange... I'll get one of those air gap testers and
check it out.

Hey, I have a 1976 CB400F - Parakeet Yellow (apparently before the days
of canary yellow). Beautiful bike, fits me perfectly!

I guess there's no way to know whether a clearance of .11mm on a .15mm
spec would cause starting trouble. Was just thinking that .04 out of
spec would be something you'd encounter during normal operation between
inspection periods.

You all are holding my feet to the maintenance fire, ain'tcha?

Thanks!

 

It seems to me (no expert on these bikes) that if you've got a weak coil
causing the 1.5 cylinders to miss, swapping coils should cause the
cylinders in question to fire. Or, if you're getting a tester anyway,
compare the spark in a cold cylinder to that produced in a good one.

You could get your valves back in spec and see whether the starting
trouble remains...

--
Later,
John



'indiana' is a 'nolnn' and 'hoosier' is a 'solkk'. Indiana doesn't solkk.

 

Have I mentioned the cams & possibly the carbs have to come off to set
the valves? Isn't there some sort of gas additive or perhaps new
sparkplug wire that will make all of my troubles disappear? *removing
tongue from cheek*

 

Yeah, and I sympathize. I've got a '94 VFR with shims under buckets, so
if my valves need adjusting, I've got to do the same thing. I don't have
to worry about the camchain, though, which is nice. ;-) Still, suck it
up and do the valves is my advice.

--
Later,
John



'indiana' is a 'nolnn' and 'hoosier' is a 'solkk'. Indiana doesn't solkk.

 

The carbs don't have to come off, no.

The cams have to be displaced, yes, but not totally removed. The valve
shims are under the buckets.

To displace the cams, undo the camchain tensioner (two bolts, back of
the block). Then zip-tie the camchain to the cam sprockets, passing the
ties through the holes in the cam sprockets. That way you never lose the
cam timing.

Then all you need to do is shift the cam sideways while you pull out the
bucket and shim.

Top tips: rag, lots of rag, stuffed into every crevice. You do not want
to drop a shim into the engine. Also, be very very careful when
re-bolting on the tensioner unit. It just needs to be nipped up, and
even tightening to the low (recommended) torque can strip the threads.
DAMHIKIJK,OK?

 

the carbs are still not clean they need to be totally dissassembled and
soaked in a commercial carb solution and put back together with new rubbers
and gasket and possibly new float valves the valve being out of spec is not
your starting problem or running theirs alot of passages in the carbs that
you cannot get unless their soaked. i dought your ignition is the problem
either.

 

Actually, sweetie, valves being too tight really *does* cause starting
problems. Although I agree carb troubles are more likely.

 

Thanks, guys. As between the carbs and the valves, I would prefer to
tackle the job most likely to get the bike started and running.

I do understand how valves will make the bike hard to start-- I just
didn't know if .11mm clearance on a .15mm spec would cause the hard
starting problems, and it seemed like someone would know whether it
would.

So, first the carbs come back off-- maybe take them someplace to get
them cleaned, and then if the bike still doesn't run, the valves will
get done.

Regardless, the valves will get done-- just hate to do the valves only
to find out I can't get the carburetors right and the bike is a
write-off.

Thanks, all!

 

My advice would be to do them yourselves unless you know, absolutely and
for certain, that the guy who will be doing them knows his/her stuff and
will _actually_ do the job right. While my experience with such things
is limited to one crappy mechanic, I've heard too many stories that
match up with mine: paid lots of money to a professional who either
muffed the job or (what I suspect happened in my case) simply didn't do
anything. It's not hard to clean out a carburetor, you just have to be
patient and accept that no corners can be cut. The procedure has been
posted here hundreds of times in the past, so check the archives.

--
Later,
John



'indiana' is a 'nolnn' and 'hoosier' is a 'solkk'. Indiana doesn't solkk.

 

acually older sweety if it has some clearance the valve is closed at startup
their for having no affect. when warm is wear a tight valve will show up
exspecialy at idle

 

You're wrong. Sorry, but you're wrong. It varies in effect from bike to
bike, but trust me - over-tight valve clearances degrade starting
performance.

My own 1200 is *particularly* susceptible to it - it's a known Trophy
issue

Have a look at

http://www.motorcycle.com/mo/mcdirt/trailrider/toolbox2.html for another
mention.

Now go away.

 

ive read your artical and yes it can cause hard starting (i beleive their
talking about a hot startup}if the valves are neglected however this would
be a severe case to where again their is NO clearance and acually holding
the valve open ever so slightly then i could see poor starting issues along
with a lot of other running problems. i am not wrong on this i have worked
on motorcycles my whole life i know what im talking about. im currently a
certified tech. with more factory training then i can stand funny you should
mention your triumph i am a factory trained triumph tech i have been to the
triumph school just south of atlanta at least a dozen times.yes i was in the
dealership back when the trophy 1200 came out. ive worked on kaw for at
least 25 years. also very high up the ladder in harley and buell training.
do some checking into this if you want prove to me that im wrong and ill
admit to it. also think of this hydralic lifters hold vertualy a ZERO
clearance at start up. but they in no way hold the valve open. again i
beleive if the valve has some clearance it will not affect startup. it will
however if the clearance is very little on solid rockers as the engine gets
warm the clearance goes away and can affect idle and a WARM OR HOT startup
depending on how little clearance the valve has at cold startup. ps we
should be receiving our new triumph 675 tommarrow.

 

Well, yes. But it's still an issue.

Thank you. That is what I said. Incorrect (too tight) valve clearances
*can* affect starting. I agree it's rare, though - but my Trophy is
certainly one that is so affected, and I know of two others that have
the same complaint if the valves get out of spec, and my local Triumph
dealer admits it's an issue on them.

Now there is a nice-looking bike.

 

I recently spent an inordinate amount of valuable time cleaning my carbs
over and over again,after having mistakenly assumed they were the cause of
my hard starting issues. My bike would absolutely not start unless I put a
cover over it and stuck a small space heater underneath it for an hour or
so. On the advice of a fine fellow at oldbikebarn's tech forum, I checked
and adjusted the valve clearances on my 85 GPz900R and lo and behold, it now
starts like a new bike again, even in our -15C weather!