GPZ600R Won't Start - Compression Issue

This is Krusty. Accuracy is optional.

 

And that qualifies you to speak about engines incredibly more
sophisticated and with massively higher specific power outputs? With the
best will in the world, I've heard loads of people pontificate "because
they know about cars".

Loads of people have told me that the bike I'm thinking of buying, and
which I can see has been bodged, has been serviced by their dad who
"knows all about motors"[1].

Even if it does, the point is one of simple probability. You can
half-remember *one* vehicle which had some sort of issue in the last
decade.

This ng gets loads of people complaining that their bikes don''t start
after (usually winter) lay-offs. And I can't remember one that *wasn't*
fuel related, though there may have been one.

Now, winter can bollox carbs in a surprisingly short time. I left one of
my bikes parked outside in January 2010. I'd been using it as a daily
commuter, and it ran perfectly, every day. Went on holiday. Came back.
Would it start? Would it buggery. It had sat in two weeks of the
nastiest winter we've had here for many years. I tried everything.
Heating the plug, new plug, fresh fuel, you name it. Got it going in the
end and it ran as rough as feck. I ended up stripping down the carb and
cleaning it and rebuilding it *properly*, and all was well.

What had happened to the carb while it had been standing for a mere
fortnight? No idea. I'd guess at something condensing in the carb and
then freezing, but really, I've no idea. All I knew was that the problem
wasn't going to be the head gasket )although there's a tiny weep from
it) nor the compression, nor the ignition, nor anything *except* the
carb.

And here's you asking him to check the oil, check the type of oil,
suggesting checking hydraulic lifters, saying that it has two dead
cylinders when it doesn't, suggesting the valve stems may be carboned up
and stopping the valve from closing, suggesting plugs may be carbon
tracked (when did that last happen on any Jap bike other than a
two-stroke??), and all kinds of similar, highly unlikely, things when
the most likely problem area is...

.... the carbs.

Could be a duff fuel tap as well, but that's so easy to check.

Incidentally, let's move onto the compression issue. The OP now says it
"ran fine the last time it was out". On ukrm a while back we had a bod
who had such incredibly low compression on *all four* of his cylinders
that I (and others) told him that the dealer couldn't have been checking
correctly. I can't remember what the readings were, but they were way,
*way* lower than the lowest reading on the one possibly-problematic pot
that this engine has.

I mean, you don't get compression failure on *all* cylinder
simultaneously unless something catastrophic has happened.

And then he admitted, shame-faced, that he'd accidentally run the thing
on diesel. OK, that'd do it.

Decades ago, I neglected the shims on a GS Suzuki (I was skint and just
couldn't afford to pay a dealer and didn't then have the nous to DIY).
Turned out it had compression that was damn near atmospheric, but it
still ran. One cylinder with a tested compression of 30-48psi, even
assuming that figure is accurate (I've nothing to say it isn't)....

Is

Not

Going

To

Be

An

Issue

Here.


[1] Or, almost as often, who "knows all about bikes" because he had a
BSA in 1960.

 

Cheers for all the excellent posts.

Some more details:

1) When I said it would occasionally plutter, smoke and then run fine
the smoke was black, not too thick and didn't hang around for a while.
It is generally after riding for more 5 minutes, during which it runs
fine. This is only happens occassionally but I can't see to see any
major patter, just generally within 5-20mins after starting.
2) I have tried starting it on a closed trottle.
3) When cleaning out the carbs I made sure of cleaning out all the
starter jets and passeways.
4) When I said it ran fine the last time it was out it did indeed run
fine. The last time I took it out was to a garage to check out the
shock. It ran fine there, the mechanic said it ran well when he took
it for a test drive the next day, and it ran well the following day on
my journey back home. Then, due to snow, it put away until January.
5) The carb slides all moved smoothly when I reinstalled them but will
check when the airbox is off again.
6) The fuel tap is fine, have tested.
7) I have had the bike tuned on a dyno before and it is these settings
that I returned the carbs to (double checked on disassembly), not what
is in the manual.
8) I filled the float bowls by putting tank on prime and opened the
screws at the bottom of the float bowls.
9) I have replaced the spark plugs.

I will try the following:

a) Fully unscrew the idle adjuster and try to start.
b) As above but with full choke applied.
c) I'll take out the airbox and hand choke the carbs.
d) Investigate air leak at rubbers - unscrew idle screws out further.
Should start but will get poor idle when warm
e) Reduce spark gap and try again.

I'll let you know how I get on.

 

Are you in the UK, or Canada?

Two possible causes would be (1) the float valve doesn't always seal
properly due to gum and varnish or debris coming down from the gas
tank, and (2) some mechanic has improperly adjusted the idle mixture
screws.

The latter is a very common error amongst shade tree mechanics. They
expect that the idle RPM will increase as they turn the idle mixture
screw more and more counterclockwise.

After about 3 full turns, the idle screw has *NO* further effect to
raise the idle RPM, it has the *opposite effect*, the idle RPM
decreases because the mixture becomes *too rich* and the engine
stalls.

The newbie mechanic then tries to adjust the idle speed screw and this
casues the throttle butterflies to uncover a pattern of three
acceleration transition ports that aren't supposed to be uncovered at
idle.

When the newbie blips the throttle to check for correct throttle
response, the engine gets extra gas through the transition ports and
the idle RPM hangs up at 4,000~5,000 RPM and may take 30 seconds to
fall back down to the specified idle RPM.

A motorcycle with a rich condition like that cannot be ridden safely,
the engine keeps driving it into corners and up to stop signs.

When the engine gets warm, the idle RPM will rise up and hang there,
and the newbie mechanic guesses that maybe there's something wrong
with his throttle cable.

The newbie mechanic may be smart enough to turn the idle speed knob
back down, but by that time he's lost track of what he did wrong,
which was when he opened the idle mixture screws too far.

I can usually find the factory idle screw setting from looking at
parts lists, but it's not in the online parts diagram for the 1986
Ninja 600 at www.powersportspro.com.

Nor does the parts list tell me what size the pilot jet is.

But a typical pilot jet for an engine that size would be around #30
and I would start with the idle screws set around 1.0~1.25 turns out
from lightly seated and check for throttle response upon blipping the
throttle and I would observe whether the RPM hung up when the engine
warmed up.

The engine should start on full choke, no throttle, regardless of what
the idle screw settings are because the cold enricher system
*bypasses* the idle mixture system.

If the engine starts on the choke with the idle speed screw turned out
the way out, you'll have to hold the throttle open to get it to run as
you re-adjust the idle speed upward.

Then, when the engine is warm, adjust the idle mixture screws if the
engine won't idle or if the idle speed hangs up upon blipping the
throttle or when the engine gets hot.

As I explained above, you don't want to open the idle mixture screws
too far.

The normal procedure is to turn the idle mixture screws *IN*, not out,
and adjust the idle speed *DOWN* not up.

http://www.powersportspro.com/pages...ki/ZX600-A2_Ninja_600_(1986)/CARBURETOR_PARTS

http://partstream2.arinet.com/Image...HNSKUVMQ2&aria=jqPY9vw5KHLzIQCm6WDPOw2&ariz=1


16014 16014-1029 SCREW,PILOT ADJUST | CN

16014A 16014-1054 SCREW-PILOT AIR | CA,US

92063A 92063-1008 MAIN JET,#100 | CN,US

92063B 92063-1009 MAIN JET,#105 | CN,US

92063C 92063-1009 MAIN JET,#105 | CA

92063D 92063-1115 JET-MAIN,#102 | (RACING USE ONLY)

92063E 92063-1116 JET-MAIN #108 | CN,US

92063E 92063-1116 JET-MAIN #108 | CN,US

92063F 92063-1117 JET-MAIN #112 | CN,US

92063F 92063-1117 JET-MAIN #112 | CN,US

92064 92064-1119 JET-PILOT

 

That all makes sense to me, at least for an engine that has no other
problems. Just want to mention that I suggested turning out the idle
mixture screws solely to see if that would help the engine start in
which case a manifold boot air leak would be easier to notice. I should
have mentioned I meant that as only a temporary measure. As you say,
it's not pleasant to ride with an engine that's set too rich.

 

I find his technical advice to be routinely pertinent. Over the last
five or six years it's been pretty obvious to me that he is the resident
expert on carbureted fuel problems. There have been a few other
regulars, such as Mark O and Rob K who also give sensible advice on a
variety of mechanical/electrical topics. I mean actionable advice,
without a lot of hand-waving or editorializing.

 

IGNORE this idiot...he's so stupid he couldn't pour piss out of a boot
with the directions printed on the bottom in large block letters.

 

They aren't dead you dipwad...you are starting to sound as smart as
Krusty.

It should...

 

You know that, I know that but the GM mechanic doesn't think so...then
again the worst mechanics I've EVER met worked in dealerships. Most
were incompetant at best.

 

TYVM...I do my best.

 

Uh, news flash chid molester...he's taller than you. You are taller
than me...but I can kill you with one hand behind my back and not even
feel a twitch of emotion or give a shit. Now do **** off you piece of
shit.

 

BULL SHIT...he just cuts and pastes without attribution from other web
pages. But he, go ahead, keep thinking he's smart...but that just
makes you even dumber than he is.

 

No, not it isn't hard to get them full to the proper level and it sure
doesn't take 10 attempts to start to do that. But hey, you obviously
went to krusty's ass sucking school of motorcycle exspurtease.

 

He can copy & paste. He has no practical experience, and he's also the
bod who advised a poster to rip out his ignition system when it was
patently obvious it was the carbs that were at fault.

As the poster admitted later, when he fixed them.

 

You're a lying sack of shit. It was your sock puppet's own idea to
remove his coils for testing.

 

Indeed, and as we've proved before by pointing people to the relevant
postings, you encouraged him to do it.

Next!

 

and you once again avoid admiting encouraging said actions much less
your own misguided and bad advice on the entire matter. Admit it...you
know nothing about anything that matters. Motorcycles, beer and pussy
being the only things in the world that matters. Being a nonriding,
perscription drug abusing pedarastic zoophile that makes it rather
obivous that your advice is best only observed for it's "What not to
do" factor.

 

Fine. The smoke came of of the coils of my ariel atom*...should I
clean the carb and relube the wheel bearings and see if that will help
it start?



*Note, I wouldn't mind owning an Arie Atom if for no other reason than
I could trade it for old suzuki parts.

 

Holt's Piston Seal was popular in the "heyday" of British auto and
motorcycle
production. Squirt a shot of that gummy red stuff into the plug
openings, crank
motor for a couple of minutes, take off.

 

Yeah, *right*. Up there with Instant Rebore (which was applied in the
same way) as one of the great Snake Oil rip-offs.