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Grex Cars Item 115: motorcycle cooling
Entered by gull on Sat Aug 14 20:35:49 UTC 1999:

I got to wondering, the other day -- what keeps air-cooled motorcycles from
overheating at idle?  I've never owned one, but they appear to rely entirely
on ram air for cooling.  My Volkswagen is air-cooled, but it has a big
squirrel-cage blower and an elaborate sheet metal air shroud to ensure air
gets to the right places.

13 responses total.

#1 of 13 by scott on Sat Aug 14 22:53:46 1999:

High engine output only coincides with high speed?

#2 of 13 by avoodi on Wed Sep 22 18:57:10 1999:

hi, i need help about motorcycles, i have a kawasaki 500ex, and it is 
giving me flooding problems(not because of hurricane mind u...) does 
anyone know how to fix it, or a what could be the cause of it ?
any help is appreciated

#3 of 13 by gull on Wed Sep 22 19:22:51 1999:

Well, I don't know anything (obvously) about motorcycles, but assuming it
has a carburetor, a few possibilities are:

        - Stuck choke.  This is a biggy, and easy to check and fix. 
Sometimes varnish builds up in the carb throat and blocks the choke from
opening; other times the electric choke element breaks or becomes
disconnected.

        - Stuck float, trash caught in the float needle valve, float that
doesn't float (saturated with gas.)  Any of these will cause you to run
*way* rich and flood the engine.  In extreme cases I've seen gas overflow
out of the carburetor.  (Happens just about every spring on one of our
lawnmowers.)

        - Mixture too rich.  If this is the case your spark plugs will be
black and sooty and you'll see black or grey smoke in the exhaust.  The idle
mixture would be the most likely culprit.

Whether you have a carb or not, you should check your spark plugs and your
ignition system.  If the carb works perfectly but the ignition system is
bad, the engine can still flood.

#4 of 13 by n8nxf on Thu Sep 23 11:51:56 1999:

Does this thing have one carb or several?  (I assume it's a multi-cylinder
road bike and not a one cylinder dirt bike.)  How do you know it's flooding?
Can you get it started?  (Often people think a engine is flooding when it
actually has no spark, etc, and gas is runing out of the carb/s from being
cranked a lot with the choke on.)

#5 of 13 by avoodi on Thu Sep 23 15:41:10 1999:

Well thanks for ur responce.. I think it helps a lot.
it is a 2 cylinder bike, with a carburetor. yes i think i can check on 
the sparkplugs. and yes it starts well . Actually the previous owner 
told me to warm it up (before starting for the first time of day) by 
giving chock for some time, and the taking off the chock, and i could 
see the RPM changing with/and without chock, so i dont think the chock 
stucks.. well now as u said the other cause may be float stuck.. 
how do i know if it's flooding.. well it is my guess. it smells like a 
open gas tank when i am standing on idel.. then it gives these jerks.. 
and after turning the gas nob on reserve it gave me real trouble while 
starting, It just starts and makes chocked noice and stops.. but after 
some atempts like this it runs fine...

#6 of 13 by gull on Thu Sep 23 23:02:12 1999:

I'd check your idle mixture, first.  It's usually a regular tune-up item
anyway.  Got a service manual for the bike?

#7 of 13 by n8nxf on Fri Sep 24 11:21:21 1999:

If it's running rich I would expect sooty (black) exhaust.  I assume it
has two carburetors.  It's very difficult to set each carb properly on
a multi-carburetor engine.  You need special tools, such as a manometer,
to go it right.  If you smell raw gas, either one cylinder isn't firing
at all (But I would think you would notice half the engine not working!)
or there is a fuel leak somewhere.  It could be a very small one in
cracked fuel hoses, a worn gasket in the fuel valve or a missing
or bad gasket in one of the carburetors.  Have a competent mechanic
give it a close look.

#8 of 13 by avoodi on Fri Sep 24 17:31:49 1999:

yes u r right , i think i should go to some good mechanic.. as i dont 
have all these tools.
Thanks for ur help though.. it was my first experience with such chat 
session. and was very helpful.

#9 of 13 by mdw on Mon Sep 27 23:11:37 1999:

If it's an older bike, it could be old o-rings in the carburetor that
are allowing gas to flow past the needle valve.  To get the carburetor
adjusted to specs, yes, you need the manometer.  But if the carburetors
are rigidly mounted as a fixed assembly, you might be able to adjust the
throttle well enough just by eyeballing the throttle plates (typically
there are little holes the throttle uncovers as it opens).

#10 of 13 by gull on Mon Sep 27 23:13:50 1999:

Some people will tune dual carbs by ear, too, by holding a piece of vacuum
tubing with one end by their ear and the other perpendicular to the air
stream going into the carb throat.  This is an art, though, and I could
never do it.  The idea is to tune for the same pitch.

#11 of 13 by n8nxf on Tue Sep 28 11:20:01 1999:

You get better results with the right tools.  This motorcycle seems to be
way out of tune.  Find a good mechanic with the right tools.  Good luck.

#12 of 13 by quad on Mon Oct 18 17:42:35 1999:

what is this place whay go thur all this troble when it is a lot easer
to click onm webmaster a chat ther are any chat romm on the net?????

#13 of 13 by n8nxf on Tue Oct 19 11:34:25 1999:

Indeed.

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