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Posted by Richard Slay on November 4, 2007, 7:48 pm
>> I have an 85 VF700 Magna. It had been sitting a while when I got it
>> and never ran well due to dirty carbs. I finally pulled them off and
>> cleaned them. It runs perfect now but its very hard to start. When
>> I put the choke on it starts and runs for 1-2 seconds then dies. It
>> didn't do this before I cleaned the carbs. The only way I can start
>> it is without the choke which takes a while. Any ideas what it could
>> be? Is my choke cable out of adjustment somehow?
>Constant vacuum motorcycle carburetors are different from car
>carburetors.
>They don't have a plate type choke like a car. The "choke" on a constant
>vacuum carburetor is a little valve in a bypass passage that goes
>around the throttle butterfly.
>When you pull the choke knob out, or move the choke lever, you are
>opening that little valve, there is one in each carburetor.
>But, for the "choke" to work, the throttle butterflies have to be all
>the way closed.
>So, try turning the master idle knob down as far as it will go.
>That will increase engine vacuum so the engine can suck gasoline out of
>the float bowls through the little valve.
>When the engine starts, hold the throttle open a little bit until the
>engine warms up, and then readjust the master idle knob.
>If you're *still* having problems, you need to clean out the carburetors
>better.
>I use Berryman B12 Choke and Carburetor Cleaner.
>You need to get squirt the B12 into the smaller hole in the inlet bell
>of each carburetor/ That's the pilot air jet. You should get a strong
>spray of B12 out the idle jet, out the three transition acceleration
>ports next to the throttle butterfly, and out the single idle mixture
>port downstream of the transition ports.
>You may have to remove the idle mixture screws for cleaning, They are
>usually concealed behind EPA anti-tamper plugs.
>I have described the procedure for removing anti-tamper plugs many
>times, you can google rec.motorcycles.tech for that.
I found the problem. The vent tube near the end of the airbox that looks
like an umbrella handle was pinched off. When I fixed that everything
started working correctly. Gotta be more careful. Thanks for the info
though.
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