xr100 carb adjustment

HiG4s

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Joined
Mar 7, 2001
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#1
Ok here are the symptoms.
bike never needs choke to start
Until it warms up if you barely give it gas is stalls
the idle adjustment is almost all the way out to get the idle down to normal
Adjusting the air screw out, starting at 1 3/4 out as the owners manual says, has no effect until it falls out then the idle goes up about 500 rpm.
And the bike fouls plugs every couple weeks, the 1st 4-stroke I've ever had that fouls plugs.
My two thoughts are the pilot jet is too rich, or the carb is just screwed up. I've taken it apart and cleaned it but I didn't check to see what the pilot jet # was.
Oh, and the air filter was just cleaned.

Just wanted to know if anyone has any other ideas before I change the pilot jet, or anything I should do at the same time.

Thanks
 
Joined
Jun 6, 2000
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#2
I just played with my nephew's XR100 yesterday. He also complained of bogging and fouled plugs. I'm sure its real hot there now (it is here). They run rich when its hot, especially with the stock pipe. The "air screw" is actually a fuel screw. I pulled the airbox snorkel, and removed the cleanout plate on the bottom of the muffler. The bike now breaths and runs a lot better. The float level was also to high (rich). I have no problem getting the bike to idle fine with the fuel screw at 2-2.5 turns out. On another XR100, I had good results dropping the needle 1 clip when it got hot, I'll try this next.
 

BadgerMan

Mi. Trail Riders
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Jan 1, 2001
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#3
I had similar problems with an older XR100 that belonged to my wife. It turned out that the needle was worn and a replacement (same size) took care of the problem. This bike was an '81 model with ALOT of hours on it. I don't know how old your bike is but you may want to check it if it's well used. I have since replaced it with a newer model XR100R and have not had any carb trouble with the new bike. I was told (take it with a grain-o-salt) that little Honda's are sensitive to carburetion problems due to worn needles.
 

weimedog

Damn Yankees
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Nov 21, 2000
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#4
We have a 89 Honda XR100. Funny thing with it is when I THINK its carburation...its usually the points. No kidding. Your symtoms are ones I have experienced several times. Went crazy on jetting ... and one time it was the valves and the rest the points. Chech them if you feel like you are running in circles. Simple to check and simple to adjust.:) No idea why. Just imperical data.