GPZ600R Enginer & Handling Issues - Any Suggestions?

Hi. I've been having a couple of issues with my 1985 GPZ600R recently.

Firstly, occasionally the engine does a wierd thing. After starting
the bike (which goes as planned) the engine will run as normal. Then
shortly afterwards it may bog down and won't rev past about 3k rpm, no
matter how much you twist the throttle or play with the choke. It runs
like this for quite a while and then seems to clear itself (it also
fixes itself if you leave it off for a few minutes). When it does
clear out it gives some smoke out the back as it revs, then it will
run fine for a long time. I have checked the spark plugs (new set in
now) which were quite sooted up. I believe she is running quite rich
at the moment. Does anyone have any ideas what might be causing this?
The next step I'm taking is to replace the air filter and then re-tune
the carbs to be leaner.

Secondly, I am having an issue with the handling of the bike. I'm not
sure how best to describe it. If your travelling along in a straight
line at about 70mph the problem is noticeable. It feels almost like
the rear is moving slightly from side to side (or it could be an issue
from the front). It's like it's trying to track in a straight line but
doesn't. It doesn't seem to oscillate and get out of hand. I think it
occurs at all speeds and when cornering but it is definitely worse the
faster you go. I have recently replaced the swingarm bearings, shock
lingage bushes, rear bearings (including sprocket), chain and both
sprockets. I have a fairly recent pair of BT45s on and the tyre
pressures are correct. I am at a loss for what could be causing this,
I was thinking it might be an alignment issue somewhere or maybe the
shock and forks are shot. Does anyone have any suggestions? I don't
really enjoy riding the bike at the moment.

Cheers

Rabbit

 

The fuel system may be dirty, all the way from the fuel tank into the
float bowls and into the idle mixture system.

When the idle jets and idle ports really gets plugged up with gum and
varnish and little bits of rust from inside the gas tank, the engine
will not respond to the throttle but will still run on the "choke".

The "choke" is not actally a plate type choke at all, it's an air
bypass passage built into the side of each carburetter. When the
"choke" lever is moved, a small air valve is opened and fuel is sucked
up from the float bowls through a small brass tube.

Well, actually, the "choke" system will supply an air/fuel mixture of
about 1:2 or 1:3 in dorder to start the engine, as compared to a 1:14
mixture for cruising operation, so the indications you'll see on the
spark plugs give the correct impression that "she is running quite
rich."

But if you're running the engine on the choke to avoid fixing a dirty
fuel system problem, whose fault is that?

See above.

No, clean out the fuel system first. You can drain most of the
gasoline out of the gas tank and remove the two little screws holding
the fuel selector lever onto the
automatic fuel petcock.

If there is a bunch of rust particles in any of the four fuel ports
you see facing you, you should remove the petcock completely and clean
the fuel filter screen and flush out the fuel tank.

Also, be sure to check that the small vacuum hose on the backside of
the fuel petcock doesn't have a split end, causing a vacuum leak and
intermittent fuel supply.

If the fuel tank doesn't appear to have water, rust and other debris
in it, you can try cleaning out the carburetors without dismantling
them by adding about 4 ounces of CLEAR carburetor cleaner to a fuel
tank of gas and riding until the engine begins to run better.

It's a good idea to know where the master idle adjustment knob on the
carburetors is located before you set out on a ride with carburetor
cleaner in the gas tank, because you will need to turn the idle RPM
down at some point.

A motorcycle is ALWAYS trying to fall over to one side or the other,
and the front steering geometry is ALWAYS trying to push it back
upright.

To the observant rider, it feels like the motorcycle is rocking
slightly from side to side.

Well, save your money until you figure out what motorcycle do
NORMALLY.

You'll waste a lot of hard-earned ca$h chasing imaginary handling
problems.

BT45's are a dual tread compound tire. I have a set on my old GSXR-750
and I don't like them.

You might just be feeling the difference between the center compound
and the side compound as the motorcycle normally rocks a little from
side to side.

This rocking is exaggerated with 16-inch wheels...

 

On Aug 14, 4:18 pm, schwarzesonne <>
wrote:

Oh piss off you pervert...Thanks to reading what you cut and paste
you've finally learned to relay it by rote. As for the BT45's they are
fine and how would you know? You do not own the motorcycle you claim
to own and for that matter you've never ridden a motorcycle in you
geritric lying life.

 

Drain the fuel tank and refill with fresh CLEAN fuel. That means put
it on reserve and let it sit...tilt it to the side where the petcock
is. Then put in a quality fuel system cleaner. In the states the
prefered stuff is called SEAFOAM, not sure what is available where you
live but whatever the guys at a marina use can't hurt.

If that doesn't help you will either end up rebuilding the carbs or
having it done.

As for handling I'd check ALL the bushing the headstock bearing etc
for excessive wear. There are some good tutorials on the web for
checking these things. Unless your tyres are worn it isn't the
tyres...no matter what that fraud 'schwarzesonne' aka krusty kritter
says, he is an unskilled fraud that parrots what he reads and usually
gets compleately wrong.

 

SeaFoam is just about worthless for cleaning out motorcycle fuel
systems because it's just a light, straw-colored oil to free up seized
pistons from rusty cylinders and isopropyl alcohol that will absorb
water.

The hot mix for cleaning motorcycle fuel systems in the USA is
Berryman B-12 Choke and Carburetor Cleaner which is a powerful mixture
of methyl alcohol, toulene, xylene, and acetone which will cut right
through gum and varnish.

B-12 comes in liquid form and in an aerosol can for about $3.50 a
Wal*Mart.

You can spent hours and hours looking for mechanical problems and
discover in the end it's just a matter of suspension setting and tire
pressure *adjustment*.

 

Absolute nonsense. And why have you morphed again?

 

Yes, it's running rich. Gunged up carbs: very common. Has the bike been
standing for long? I suspect so. You could try carb cleaner but if
they're reall bad, ulrasound cleaning is the best way.

Check everything again. Check also the head races. Check you've actually
got the right size tyres fitted. Check the swingarm pivot hasn't been
under-rightened so is loose. The 600R has 16" wheels fore and aft and
does feel twitchy as stock.

 

Hi I have been riding bikes since I was 15 and am 76 now .
so I have a little experience.

I use Lucas fuel conditioner in my bike with each tankful of gas This
helps to keep the grunge out of the carbs and fuel lines as well as
any condensation in the tank.

I use the same Lucas fuel additive in my 2002 Camry -4 and havent ever
had a problem in either vehicle

For winter storage I fill up with FRESH gas and then add the Lucas and
FUEL STABILIZER , TWICE AS MUCH AS WHAT IT CALLS FOR .

And the bike is stored for almost 6 months here in Ontario Canada.
NEVER had a problem with spring start-up .except once when the battery
died , a new battery fixed that problem.

I FILL UP THE TANK AS FAR AS IT WILL GO LEAVING SOME ROOM FOR
EXPANSION.THIS ELIMINATES CONDENSATE WHEN THE TEMP CHANGES

Condensate will encourage the formation of gas line sludge , blocking
the fuel filter and possibly the gas lines.

Something else I have been doing when I go out for a ride is lubricate
the chain each time (2001 750 Shadow)

I also run the bike on RESERVE for several miles to make sure THAT
line isnt plugged and I have free gas flow when I need it.

Sounds to me that your fuel filter may be partially blocked and as
suggested on here a GOOD carb cleaner might help.

If you follow the procedure like I mentioned afterward ? when the bike
is running good you will NEVER have another fuel related problem

I have ridden everything from an Excelsiour two stroke CB 500
Honda ,to Intruder 1400, Goldwings and Venture Royales .

A bad back keeps me to the 750 Shadow now.
good luck

 

Might not hurt to also check the swingarm and maybe the
wheel bearings and just for laughs, dump the whole tank
of gas into your car's tank and refill the bike with new. I
usually figure any fuel problem will get well diluted in the
car's tank, especially if I top off afterward.

 

Yeah right this coming from you? HAHAAHAHAHAH you fucking liar. The
difference betwee you adn I is that I DO things and tell people how
they worked and you just talk out your ignorant stupid eneducated ass.

Reading the web page again I see.

In you infinate stupidity you ASSUME he lives in the states.

No you'd be wrong as **** yet again.

 

Because I have full permission from my ISP and from Google Groups to
express myself as I please.

http://vampster.com/images/gallery2/schwarze-sonne-wei%DF.jpg

 

Nope. I was replying to YOUR assinine assertion that SeaFoam was a
good carb cleaner.

And I know *exactly* where to find ewe, goatse...

 

Firstly, thank you for all the replies. Hopefully these issues can be
fixed.

I'm not running the bike on choke, I just said it didn't make a
difference. I think it's just being tempermetal when it hasn't run for
a while, but it's a relatively new issue. Maybe I'm not running it as
often as I used to.

I think I'll give this a go as it will certainly do the bike some
good. I have cleaned out the carbs before but I haven't done anything
to the tank, filter or fuel hoses.

I'll give that a go before taking the carbs apart again. It's not so
much hastle taking carbs apart, just getting they in/out og the bike
due to the rubber etc. It's a biatch.

I am aware of this and it is not the problem. My bike used to be fine,
it was fine up to about 100mph (rarely take it faster) with no issues.
The issue I have is not just normal bike riding.

This can't be the case because it occurs when riding in a straight
line as well as learnt over.

I am familiar with the bike when it was working better. True, it could
be caused by my recent change in tyres but it certainly doesn't feel
right.

Again, this has been done (although not recently, and it has sat for a
little while).

During this summer I've done the front wheel bearings, rear wheel
bearings (inc sprocket), swingarm bearing and the linkage bushes. I
haven't replaced the cushdrive but it looks alright. I had a friend
have a quick look at the headstock bearing whilst I pushed down on the
seat and he said it was fine, but then I might go have a look for
myself (as it sounds like that might be the issue).

I will be taking the bike to a garage soon to check that all the bolts
etc that were done up when the bearings/bushes were done are done up
to the correct torque. I'm not an expert but there doesn't seem to be
any play in the rear end.

See above.

Basicaly I'll take a look at the fuel system and the bearings and see
what I can do. I have been planning to sort out the shock and forks at
some point soon as they are probably knackered by now. Do you think a
knackered shock could effect the handling in this way.

Thanks again for the wisdom. I'll let you know how I get on.

Rabbit

 

Oh yeah, by the way I'm in the UK, not US. But cheers for giving names
of the products, we can get a lot of similar stuff over here.

 

Trans: Because I'm trying to set up a new ID so that newbies won't see
my past record.

OK, what do you know about GPZ600Rs? I rode my first in 1985 and have
had a lot of fun on them since then. You've almost certainly never
ridden one at all.

 

There was a Buyers' Guide to GPZ600Rs printed in a recent issue of
Practical Sportsbikes in the UK. Might be worth getting a copy.

It'll be more value than Krusty's pronouncements.

 

Indeed. What you quoted was utter crap.

As was the quoted text here.

 

<shuffles feet>

I thought I was the only cheapskate to do this....

 

<shuffles feet again>

(bloody shoe soles are wearing out in this thread)

 

Use it to light a BBQ?

No, I made that mistake once, and a whole gallon of fuel ignited. Big
mistake. BIG.