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Motorcycle Mechanics - Motorcycle Technical Discussion.
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Posted by Rabbit on July 28, 2008, 12:42 am
Hi, I'm the proud owner of a GPZ600R from 1986 I believe. It was
sitting outside for about a year and was working before and now isn't.
So following have been tried so far:
* Fuel tank has been cleaned and refilled with fresh petrol
* Carbs likewise (primed etc)
* IC Ignitor replaced
* All wires checked for continuity
* Battery charged (and checked)
* New spark plugs fitted (old ones weren't bad)
* Sidestand switch removed (this was done ages ago when it still
worked)
* All earth points checked for continuity to battery earth
* Visual check for short circuits
* Checked the resistance of the ignition coils, seem ok but I have no
ballpark figures to compare to
That's all I can think of. The starter motor turns the engine over and
it sounds OK but it's not even trying to splutter into life. I've also
tried looking at the spark made against ground (sparkplug electrode
earthed to frame) and there were sparks but I have no idea of exactly
what to look for (eg too many, too few, too strong/weak, etc).
I have had a bike mechanic friend look at it but no good. Took it to a
garage and no good (without spending a lot of money trying to find the
problem).
Aparrently there is a sometimes common problem with these particular
bikes and I can't figure out how to fix it.
Sorry for writing so much. If anyone can help I will love you for ever
and ever :P
Thank you for your time.
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Posted by . on July 28, 2008, 10:03 am
> That's all I can think of. The starter motor turns the engine over and
> it sounds OK but it's not even trying to splutter into life.
When a motorcycle sits for a long time, gasoline---er, *petrol*, yeah,
that's it, the petrol evaporates in the carburetor float bowls,
leaving gum and varnish blocking the little ports and passages inside.
You need to drain down the float bowls (look for a drain screw on the
bottom of each float bowl). Then squirt some aerosol carburetor
cleaner down the fuel hose and fill up the float bowls and let the
stuff dissolve the crud in the carbs for half an hour so.
The kind of carburetor cleaner you want is in a spray can, and it
contains stuff like methyl alcohol, acetone, toluene, etc.
Then, reconnect the fuel hose and turn the master idle knob all the
way down. Your carburetors don't have a real choke, there is no flat
metal plate like a car carburetor.
Instead, you have to start the motorcycle with the throttle completely
closed and the "choke" knob or lever in the ON position.
This allows the engine to suck gasoline---er, petrol, yeah, that's it,
petrol, straight out of the float bowls.
Turning the master idle knob down (it should be between the
carburetors on the right side if it's a knob, if it's an idle speed
screw it will be on the left side) maximizes engine vacuum.
Once the engine starts, you will have to hold the throttle grip until
the engine warms up, then you can readjust the idle speed.
You may also need to remove the air intake hoses and crank the engine
over with your hand over each carburetor intake to get the engine to
suck *petrol* up into the idle jets for the first time in years.
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Posted by Rabbit on July 28, 2008, 9:21 pm
Thank you very much for your help. I have already tried what you have
suggested but haven't tried turning the idle speed screw or putting my
hand over the intakes. I'm working on it on Wednesday and will try the
whole process again then, fingers crossed. :)
By the way, any idea of how your supposed to take off and put on the
little rubber tubes that connect the airbox to the carbs. They come
off OK but are extremely difficult to get back on. Thanks.
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Posted by . on July 28, 2008, 9:30 pm
> By the way, any idea of how your supposed to take off and put on the
> little rubber tubes that connect the airbox to the carbs. They come
> off OK but are extremely difficult to get back on.
I squirt carburetor cleaner around the air hoses where they slip over
the carbs, and let it soak in and repeat the process twice.
The carburetor cleaner softens the rubber and it swells up, making it
easier to pull the hoses off.
It still takes some twisting and pulling and cursing to get the hoses
off.
Some motorcycles have airboxes that come right off when you loosen the
hose clamps, other require the hoses to be slid back into the airbox
to remove them.
When the carb cleaner evaporates, the hoses shrink back to their
original sizes.
I have used WD40 for a rubber lubricant, but it actually makes the
hoses stick *worse* when removing them the next time.
There are commercial rubber lubricants like RuGlyde that work better.
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Posted by The Older Gentleman on July 29, 2008, 2:09 am
> By the way, any idea of how your supposed to take off and put on the
> little rubber tubes that connect the airbox to the carbs. They come
> off OK but are extremely difficult to get back on. Thanks.
Warm them up with very hot water. It softens them and makes them more
pliable. Same trick works with carb rubbers.
--
BMW K1100LT Ducati 750SS Yamaha XT600E Honda CB400F MZ TS250/1
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."
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