How-To: Carburetor Idle & Pilot Screw Adjustment Honda XR70
Year, Make, Model
The bike in this video is a 1999 Honda XR70R. This will also cover all 1997 thru 2003 models.
Symptoms
The XR was bogging pretty bad at full throttle when it was brought to me. Also, the idle was not smooth and set at a very high RPM. The pilot air screw was turned all the way in and would only run with choke on.
Diagnosis
I found out that the the carburetor needed to be cleaned, and the main jet and needle clip position were both too lean due to the aftermarket air filter pod. Check out this post on tuning the main jet.
Once the carburetor was clean, pilot screw & idle adjustment was necessary. Pilot jet and air screw adjustment was already covered in detail in this post, so I’ll jump right into today’s video.
How-To Video
This How-To video on how to properly adjust idle and pilot air screw on your XR should make it run smooth now! Scroll to top of page to view video.
Comments
Has this video helped you? Please comment below.
Good video, it explains what to do and how things work. Now I got a ’93 DR 650 and I´ve been through different mufflers.
Now I have a “corked” CZR muffler on the bike and it starts and idles fine, but adjusting the pilot jet doesn’t make any difference? Even turning it gently all the way in doesn’t make the bike stumble? In your video, the bike reacts immediately to pilot jet adjustment. what are your thoughts about that?
Sincerely Lasse
That carb has a fuel screw correct? Is your idle set pretty low?
The carb has a fuel screw at the front. The idle is set as recommended ( approx. 1500rpm)
If the screw is not responsive, then pilot jet is the wrong size, or carb is pulling fuel from other sources (could be a vacuum leak also).
Will the engine die or stumble when you turn screw all the way in?
The engine doesn’t die or stumble when I turn the screw all the way in. It did, when I had a “medium-flow” muffler on it, but the CZR muffler is really “high-flow”…
Well, try reducing pilot jet size by 1-2 sizes. I find it a bit strange since I always see a trend to jet richer, not leaner.
well this is embarrassing… I just found out that I forgot to plug the vacuum hose, after reinstalling the BST 40 and I have a Acerbis gastank on with no vacuum connection. Would this explaine the bogging, comming off idle, and the pilot jet not responding to adjustment?
Yes. Causes a lean condition.
Hello there
I have question
Can we replace the Honda 70cc carburator with Honda 125 or 150 carburator??
Is your 70 stock or modified?
Matt I have a 1986 Suzuki DR100. I can’t seem to find an extended pilot adjustment screw for the carb on this bike. It’s a 4 stroke bike with a Mukuni carb. Would you happen to know where I can get one that would work for my bike.
Best thing to do is find the model name of carb and do google search with that term.
Otherwise, can you make a custom tool for the job?