The Single Most Common Carburetor Problem (Clogged Pilot Jets) and How To Fix – by Ari Henning

I’m happy to share this excellent video tip created by Ari Henning of Motorcyclist Magazine. Ari is a notorious AHRMA road-racer and all-around swell guy!

This is excellent information.

The best part of this short video is the concise DIAGNOSIS of idle jet problems. Ari details the classic symptoms of this very vexing issue. As usual, correct diagnosis is half the battle! 

Note: All the vintage Hondas supported by Randakk’s have Keihin carbs with idle FUEL (not AIR) mixture screws for adjusting pilot circuits. This means they are adjusted OUT for more richness and IN for more leanness.

Since the idle jets on vintage Keihin carbs are impossibly small, this is information you will eventually need!

Comments

  1. MICHAEL MCEOWEN says:

    Sirs:

    ’82 GL1100 65K miles, always ran well until today. Started and chugged a little like when it has been cold outside, Stalled and has not started again.

    I have spark at the plugs, I have fuel to the carbs, the engine turns over, the valves are opening and closing, the fuses are good but no start.

    Sounds like not getting fuel, plugs are dry.

    Ideas?

    • Things to check whenever you have full starvation symptoms like this:

      Verify compression first.

      Then make sure your ignition is PERFECT.

      These possibilities must be systematically eliminated one-at-a-time until the cause is isolated.

      Dirty air filter

      Blockage inside the fuel tank. If you suspect a tank blockage, siphon most of the fuel from the tank and remove the petcock. Blow compressed air through both the main and reserve circuits. With the fuel cap off, you should hear equal volumes of air rushing through each circuits. If not, that indicates a blockage.

      Blockage to the fuel inlet screens under the float valves. Carb disassembly required for inspection / cleaning

      Failing fuel pump. As the actuating arm on the pump wears where it meets the eccentric on the right camshaft, pump output and pressure will slowly decline. The Honda manual shows simple tests for volume and pressure minimums. Worn actuating arms can sometimes be reworked by welding on additional metal and grinding to restore proper shape. Such heroics aren’t usually worth the effort as a pump with this issue is already near the end of it useful life.

      Blocked main fuel filter

      Problem with float valve operation / setting restricting flow of fuel into carbs. They can be installed incorrectly upside down!

      Internal fuel circuit blockages

      Main or idle fuel jet blockages.

      Internally collapsed fuel line

      Faulty gas cap restricting venting and causing a pressure vacuum which will prevent fuel flow. Try removing the fuel cap briefly when the problem first appears to diagnose

      Large external fuel leak (usually obvious!)

      CV slides “sticky” and slow to open on acceleration

      Overly lean main jetting (note: overly rich main jetting will often yield nearby the same symptoms)

      Internally collapsed exhaust header

      Brakes “dragging”

      Extreme wheel bearing problems

Speak Your Mind

*