I learned about the downside of carbureted motorcycle enrichening systems the hard
way. In the first instance I loaned my KL-650A to a former riding companion for a long
ride in Baja. On the second day he rode the bike hard for 20+ miles with the choke full
open. Oil consumption increased dramatically thereafter resulting in a premature R&R of
the cylinder and piston.
In the second instance I let my first DR650SE (2002) idle too long several times with the
choke full on causing it to become an oil burner too early in its life. It’s simple;
enrichening systems on carbureted motorcycles when employed add extra fuel to the
mixture. Leaving a choke on too long can compromise lubrication between cylinder wall
and piston thereby dramatically increasing friction.
The stock Keihin carburetor on the KLR650 is the best I’ve had on a big single since I
began riding a million miles ago in 1955. The Mikuni on the DR650SE is not as good
during start and warm-up causing the bike to be cold blooded. The result is that some
riders leave the choke on way too long thereby ultimately increasing cylinder/piston ring
wear and resultant oil consumption.
If you have a KLR650, which is not cold blooded, you only need the choke for a few
moments at cold start-up time. Once the engine is running, shut the choke off. On the
DR650, which I believe has a more potent enrichener system, it’s best to use the choke
sparingly and once started use the throttle to keep the engine running. Close the choke
as soon as possible and by all means avoid the temptation to ride any motorcycle,
especially a big single with choke open.
Riders who avoid over use of the enrichener systems on their carbureted motorcycles
should expect better performance and longer top end life.
Although I don’t like the complexity of fuel injection systems on multisurface motorcycles,
I’d be the first to admit that they are far superior when it comes to managing fuel mixture
especially from cold start-up to full operating temperatures. Since we DR/KLR riders are
stuck with good old technology we’d best learn how to manage our cold start-up systems.
In other words, use the choke as little as possible.