Honda Magna V30 won't start in cold wether

I entered a topic in the past regarding my bike not starting several
weeks ago and all the great advice from users got it started, thanks.
Anyway the problem at that time was the bike would not start at all.
To make a long story short it was the carbs being pluged with old
congiled fule. After cleaning out the carbs and setting the idle the
bike ran great. By the way this was a complete tear down of the carbs.
The choking system worked I know this because when it was about 40
degrees I could start it with the choke and as it warmed I would
release the choke partialy until the bike was warmed up. So that being
said I was wondering what might cause the bike to start when the temp
outside is around 30 degrees. That is the only difference so you know
I started the bike twice a day to make sure that I ran a full tank
through the system of fresh gas. The fule in the bike now is fresh so
that shoudnt be the problem. Please let me know if you need any more
info.

Thanks
Jim

 

Well, the engine needs to get a burnable mixture before the ignition
spark can light the fire. In really cold climates, the gasoline just
won't break up into fine droplets or evaporate, and that's when a lot
of car owners resort to ether injected into the carburetor.

It's hard to get ether into a motorcycle intake system, though. Too
many parts to remove.

But 30 degrees isn't that cold, the engine should start on gasoline if
the idle mixture is set right and you put the choke lever into the ON
position. If everything is set correctly, you shouldn't have to fool
around with the throttle position, you should be able to put on your
helmet and gloves without nursing the throttle or continuously
adjusting the choke lever.

Modern motorcycle carburetors don't have a real choke, with a separate
plate that restricts air flow.

They depend upon the throttle butterfly to restrict the air flow
instead. There is a bypass passage that goes around the butterfly and
it has a little valve in it that is opened and closed by the "choke"
cable or lever. The bypass draws gasoline right out of the float bowl.

The bypass passage is so big it doesn't get plugged up with gum and
varnish.

But the position of the throttle butterfly affects vacuum in the
carburetor mixing chamber downstream of the butterfly. If the butterfly
is too far open, the bypass system just doesn't work, and the rider is
mystified.

Old time British motorcycle riders knew what to do. Every time they
started their engine after the machine had sat unridden for a week or
so, they would turn the idle speed knob all the way down to close the
throttle all the way and make the engine suck gasoline out of the float
bowl. Then they would readjust the idle speed once the engine was
warmed up.

The throttle butterfly also has to interact with the idle mixture
system. It barely covers the last in a triangular pattern of three
transition ports, and the setting of the throttle butterfly is critical
for good acceleration and correct off-idle performance.

Possibly you didn't do a good enough job of cleaning out the idle jets
and passages and there may still be a bit of crud in the carbs. I
recommend pouring about 3 or 4 ounces of Berryman B-12 Chemtool Choke
and Carburetor Cleaner in a full tank of gas and going for a slow ride
to clean the passages out.

If the engine starts idling too fast when it warms up. turn the master
idle knob down.

Believe it or not, this will help cold starting, because it increases
vacuum downstream of the butterfly.

Drilling out the EPA anti-tamper plugs and removing the idle mixture
screws and cleaning the passage thoroughly with aerosol carburetor
cleaner helps a lot. When you re-install the screws, leave them open
about 1/8th to 1/4th of a turn more than the factory setting to make
your machine easier to start.

I have explained how to drill out EPA plugs about a bazillion times, so
you can google that up.

There is a very large difference in idle jet sizes amongst various
motorcycles, so nobody can tell you exactly how many turns your idle
mixture screws have to be from lightly seated. You have to count the
number of turns they were set at the factory and write it down to
return to the original setting plus a fraction of a turn, then you have
to test ride the machine to see how the carbs behave when the engine is
hot.

 

Does it idle smoothly?
Is the idle adjusted properly?

It might be a carb synchronization issue.

Or, it might be a battery that gets marginal when it's cold (load-test
battery, and you'll know for sure).

HTH

--
Later,
John



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