Question on fuel mixture for XR200

Firstly, if the baffle is missing, Get yourself a replacement or
aftermarket pipe. Loud is not good. If you replace the stock baffle,
your problem will probably go away. If you choose an aftermarket pipe,
your wise to rejet. If so, aerate the airbox (install some extra
inlets, preferrably in the top where water will be less of a
detrimental factor). I like to read the plug under load, you don't
want to starve for fuel. I like to get on a hard road where there's
plenty of straightaway & no cops, hold it wide open in last gear
(where the most fuel will be needed), kill the engine, coast in THEN
read the plug. I like to see a hint of brown, reading the plug after
a few minuites of idle will be a very false indicator. Good luck.
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 >On 22 Dec 2003 05:50:18 -0800, joe.fanelli RemoveThis @dla.mil (Joe) wrote:

 >I have a 99 XR200 and have been riding in colder weather, 30-40
 >degrees, zero altitude, and think that the fuel mixture is lean
 >because the plug is on the light side, between white and tan (after
 >letting the bike idle for a few minutes after it's been running).
 >Also, there's popping on decelerating. I bought the bike used, and
 >the baffle had been removed. It still has the stock air filter and
 >the snorkel is still there. I have the Honda Service manual and have
 >read over and over the carburator section especially on the correction
 >factor for jetting and the pilot screw, but I just don't have the
 >technical background to be sure about it.
 >
 >The bike starts and runs OK but if it's running too lean, is it doing
 >damage to the engine?
 >If I did need to make the mixture richer, would turning the pilot
 >screw counter clockwise accomplish this?
 >
 >thanks,
 >Joe


Classic lean symptoms.
The stock jetting is a bit lean. This is made worse by cold thick air,
and a missing exhaust baffle.

Eric is probably correct in his assessment. However, when you
change jets, do it one jet/circuit at a time. Test between changes.
This will keep you from masking the results of each individual
change.

A plug reading will work pretty well on a 4-stroke, but I'd wait
until everything felt good, and then read the plug (with a new plug).
For individual changes, a "seat of the pants" result from a test ride
will tell you more, (and take a lot less time than yanking the plug,
etc.).
Start with the pilot circuit, and work up, with the needle/clip
next, and the main last. Each different circuit overlaps into the
next one. "Build" your power delivery with the jetting as the throttle
setting changes.

Any quest for accurate jetting will only yield temporary results, if
you change the system afterward.
Before even starting to sort out your jetting, decide what
configuration exhaust you are going to run on your bike. If you don't
stay with the stock set-up, I'd recommend a system that passes the
USFS legal sound output. (I believe that is 96 db at half that
particular engine's rpms at 20" distance measured at a 45 degree
angle.) Loud ain't cool, when it costs us land.

Gooc Luck, and Happy Trails!



Jim
Ole Man in the Trees
'99 Gas Gas EC274
Team LAGNAF
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