Honda GL1000 Timing Advance Unit Details

OEM Honda Timing Advance Unit Details:

This simple device is critical to proper ignition function on Honda GL1000s!

The ignition advancer is a simple, but critical component of the GL1000 ignition.  It’s located behind the points cover on the end of the left camshaft …near the gear shift lever.

It should be checked during routine tune-ups and whenever you experience ignition or carburetor problems.

Why?  Problems with the advancer often mimic carburetor problems!

Symptoms that implicate the advancer:

  • Erratic idle
  • “Hanging” high idle
  • Low power output
  • “Surging”
  • Poor throttle response

Things to Check:

  • Advancer should move freely on it’s captive shaft.
  • Make sure the locating pin is intact.
  • Makes sure springs are installed correctly.
  • Make sure the non-adjustable “Stops” have not been broken by a prior “mechanic.”
  • Make sure the retainer bolt is secure and has the proper washer to permit free movement.
  • Make sure the advancer on your bike matches the engine / camshaft (see below).


  • Advancer requires No Lubrication! Lubrication is unnecessary and usually “slings” to compromise the breaker point surfaces.
  • The stationary pin portion that allows rotation by the movable portion should have a nice polished finish.
  • Springs lose spring rate over time and require replacement.  Unfortunately, there are no good replacements in the market at this time.
  • Many aftermarket electronic ignition replacements (like Dyna/S) retain the use of the the stock advance unit.
  • Make sure the advancer on your bike matches the engine / camshaft (see below).

OEM Specs / Unit Identification


  • Static initial timing: 5 degrees BTDC (“F” mark on crank)
  • Full advance: 37 degrees BTDC
  • Centrifugal Spark Advance Unit is marked “371” 
  • Advance unit turns at camshaft speed = 1/2 crankshaft speed
  • Advance unit provides 32 degrees of dynamic advance (at crankshaft)
  • 16 degrees of advance at the advance unit itself


  • Static intial timing: 10 degrees BTDC (“F” mark on crank)
  • Full advance: 37 degrees BTDC
  • Centrifugal Spark Advance Unit is marked “431”
  • Advance unit turns at camshaft speed = 1/2 crankshaft speed
  • Advance unit provides 27 degrees of dynamic advance (at crankshaft)
  • 13.5 degrees of advance at the advance unit itself

In both versions…

  • Dynamic advance begins at 1,450 rpms
  • Maximum advance at 2,600 rpms.

19 thoughts on “Honda GL1000 Timing Advance Unit Details

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    1. Hey Larry, unfortunately the fiches for 1975 are scarce and I cannot confirm this for you at this time. If you find out please reach out, we’d love to be able to confirm for the next guy and pay it forward.

  1. Hi everyone’s I have a 1983 GL1100 but it only has a spark on 3 and 4 cylinder. I checked the pickup coils and both have a 560ohm. It could be the vacuum advance issues? Please let me know.

  2. I have a 78 GL1000 with only 13,000 Kms on it that I am reviving, it has a Dyna s ign. that was installed a few years ago and after rebuilding the carb,s I attempted to set the timing on it. As per instructions I set the 3-4 module first then try to set the 1-2 module but can not move it far enough in the retard (anti-clockwise) direction. I found a note on a forum that stated that by removing the advance plate you would find an adjustment for the 1-2 sensor on the back. I found this adjustment and moved it as far as it would go which improved things somewhat but not completely. then he stated that using a dremel he notched the sensor slightly to allow it to adjust farther. I would like to do this but not knowing what is inside the sensor or how thick the plastic case is I am afraid to.
    Why would Dynatek make it this way? Is there some other way to correct this? My compromise is to run both sides slightly too far advanced

  3. 78 Gl1000 with 19k miles having trouble starting. The advancer’s springs seem sloppy. The two lobes flop loosely the first 1/8″ of centrifugal travel outward till the springs gain tension. Should I replace the advancer?

  4. Ignition Woes! I have just purchased a 1976 Sulphur yellow GL1000 with 49,000km on the clock. The bike was shipped to me from another city; it was going well prior to shipping. When it arrived the battery was flat as (reading 3V); after charging the battery both neutral and oil pressure lights were out although horn, lights, indicators etc worked. I found the fuse to these lights and the 7V regulator was blown so changed this. The neutral/oil lights were then working although fuel gauge was not. The engine was coxed into life and all seemed good apart from fuel and temp gauges and I had a brief ride. A day later I started the engine briefly but when I shut off the engine it did run on slightly. However on going to restart the engine the neutral light was out and engine would only turn over with clutch pulled in but it would not start. I spent a lot of time with a multimeter and circuit diagram trying to fault find; what I found was a blown neutral bulb; wiring from neutral switch all OK. The engine would then turn over with clutch out but not fire up. Checked for spark and there was none. I have checked all connections and resistance of coils OK (4.3 Ohms); getting 12 V to coils; has Dyna S module and this had power to it. However on testing as per Dyna website it would seem the module is dead. All other electrics seem to be fine. While I could purchase another Dyna module and fit it I am worried that whatever has caused the electrical gremlins remains and could destroy the new unit. I wondered about reverting to points. I would be grateful for any suggestions as to what may be going on and advice on whether to revert to points or replace the dyna unit

  5. Good afternoon,

    I’ve recently been reviving a 78″ GL1000 and I am trying to track down one last (hopefully) running issue that I believe I have narrowed down to be ignition related. The bike will idle and rev freely to redline while not under load, though when under load it tends to fall on its face around 3K RPM, sputter, and have generally low power even when the sputtering clears up about 1,500RPM later and lets the revs rise towards redline. There have been a number of times when I can get the revs up past 5k and feel a nice (normal feeling) surge of power but it is definitely not consistent. Does this sound like the advance might be sticking?

  6. I am having an issue with a 1978 GL1000. It starts and runs fine and has a good idle. The issue that I am having is that if I really get into the revs under load and then back off and settle back into a lower rpm cruise it starts missing and popping. As long as I take it easy this does not happen. Lets be honest though who isn’t going to get on a GL1000 from time to time. This issue does go back away after a few minuets of easy cruising. I’m thinking that this could be caused by a sticking advance as this bike has recently been resurrected from a 14 year garage nap. I have spent the last six months getting it back onto the road. Does this sound lake a reasonable diagnosis?

    1. Yes. The advancer would be a likely suspect given that symptom. Other possibilities include: sticking CV slides, a minor ignition problem, low fuel pressure, bad gas cap vent, minor vacuum leak, exhaust leak, etc.

  7. Hello. The GL1000 that I bought has an electric ignition module installed on it that is starting to show wear on the rotor. It is a magnet type, not infrared, and it has no markings or part numbers on it so I am having trouble finding parts. It has a completely different design than the Dyna S modules that are common for this bike. Can you help me find a replacement rotor, or should I plan on buying a new ignition kit?

    1. Not sure what you have, but a number of companies made electronic ignitions for the GL1000 “back in the day.” Most likely, no service parts are available now for your unit. I recommend a new Dyna/S as the best path to get your ignition sorted.

  8. I would like to replace the springs on my “371” timing advance unit with springs from a “431” (better shape) is that a match ? thanks Larry

  9. Good morning. Great to find your website. I now live in central America where it’s always summer and all those beautiful winding jungle roads have no traffic cops.
    There is a good looking 1977 GL 1000 for sale a few hours away. Paint, mufflers, plastic, everything, all original.
    Naturally I am curious about parts availability for a bike that’s basically older than God. I will be riding it lots.
    Before I buy would like to hear what sort of assistance (parts and maybe advice/info) you could provide.
    All comments welcome. Thanks.
    Regards….G Spohr.

      1. hello there could you tell me the reason for the centre punch or pop mark on the end of the advancer unit where the 10mm bolt and washer bolts up on end of cam shaft.thank you ,chris

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