Diesel Clatter in Honda GL1000?

Does your early GL1000 sound like a rattling bucket of bolts when idling? If so, you might have a serious engine problem but most likely you do not. Read on…

Diesel

The GL1000 engine design is “blessed” with 3 internal chains:

  • Primary Chain (connects crankshaft to primary driven gear at clutch)
  • Oil Pump Drive Chain (connects oil pump driveshaft to outer clutch basket…this drives both the main oil pump and the rear scavenger oil pump)
  • Starter Chain (connects starter motor to starter clutch mechanism which is integrated with the alternator)

The starter chain moves only when the starter motor is energized, so it’s just along for the ride in normal running and is not usually the source of any unusual engine noises. (In very rare cases, I have seen starter clutches fail in the “engaged mode.” In these cases, when the engine is started – the starter is spun considerably faster than it can handle. This situation doesn’t last long. The starter is rapidly destroyed.  In the process, it will make very loud and horrible “death noises.” Sometimes the starter chain even breaks.)

The Primary Chain and Oil Pump Drive Chain run continuously and do make a considerable amount of noise…especially the Primary Chain. All 3 of these chains are located in the same general area – left rear (near the #4 cylinder).

Unlike most modern engines, there is no provision in the early GL1000 design for manual or automatic tensioning of the Primary Chain. So, as mileage accumulates – the clatter caused by primary chain slack will increase. Generally, this is only a problem when there is no load on the engine, i.e., at idle. Once under way, there is constant tension on the chain and the rattle will disappear.

Noise from Primary Chain slack is often misdiagnosed as piston slap, worn rod or main bearings and other serious engines problems.

I’ve heard 100K+ engines that sounded like they were about to grenade at idle which would purr like kittens down the road.

So, if your clatter disappears above idle speed when a load is applied, you have nothing to be concerned about. Such clatter is a just a quirk and a minor nuisance …nothing to worry about really.

Engine cases were slightly modified in ’77 to mask normal engine noises so the “problem” seems worse in ’75 and ’76 bikes as compared to ’77 bikes with comparable mileage.

Primary Chain clatter is exacerbated by poor ignition timing and carbs that need synchronizing, so make sure these issues are in order.

Here’s one more possibility brought to my attention recently by Arthur Osterholtz:

“Hi..I recently purchased a 1979 Gold Wing with a rattle in the engine at idle that went away when revved up. It was not the primary drive chain. Turns out the 12 mm bolt on the end of alternator rotor that you use to turn engine when setting points was loose. Apparently someone turned it backwards and loosened the bolt in so doing. A good thing to check if someone has a rattle in engine..Arthur”

If you have any knocking or dieseling sounds which increase with load or rpm, then these indicate serious engine problems which should be addressed immediately.

 

Comments

  1. 77 GL1000 I have installed new timing belts water pump and rebuilt carbs with your kits and video. 120 psi compression on all 4 cylinders checked and set points and timing, and synched carbs, runs smooth but seems to run a little hotter than I think it should, and seems down on power below 5500-6000RPM,above that it really hauls. Could I have it 1 tooth off on a cam belt??

  2. Mike Tucker says:

    I have a 1982 gl 1100 standard with 70000 miles. I have a rattling chain sound only while engaging the starter, and it can be hard to turn over like out of time. Sometimes the starter doesn’t engage, just zings. I changed the oil and it got better initially but now is back to where it began. As I was putting Lucas oil treatment in with the new oil, it dawned on me this might actually make matters worse. Any help is greatly appreciated, I really don’t want to pull the motor.

  3. Steven Fahnestock says:

    1983 GL1100 ….Went to check the timing, oil comes spraying out of the timing check hole. Also have a clanking sound at idle. How can oil come out the Timing check access??? Any help appreciated.

    • Dynamic timing method via the viewing port requires a special Honda viewing port tool part. I never do it that way as it is difficult to get a good angle with a timing light.

  4. larry spooltra says:

    got a 75 gl1000 barn bike with 17000 miles on , runs well but have a lot of noise at idle that fades away when the cultch is pulled in ,,,, engine not real smooth( tach bounces a bit) at idle but smooths out completely above 16-1800 rpm. the noise reminds me of a bad throwout bearing on a chevy 6 stick , Could this just be chain noise or ? Thanks

    • Yes. It sounds like you have a classic case so long as the “clatter” disappears with a bit of rpm and load. Super perfect tune-up, improved ignition, good synch and a slight increase in curb idle speed is about all you can do. Then ride and ignore!

  5. Crazy! Recently just purchased a 77′ gl1000, and the problem doesn’t seem to be during idle, but when shifting from neutral into first, then accelerating, i (sometimes) hear that diesel clatter! But heres where it gets interesting… When I’m on the freeway/road, i would be riding 45-50/70-80mph, and out of nowhere my bike would seem to lose acceleration power for a couple of seconds! (roughly 20-30 seconds). Could those 2 issues be the same problem? Because when idling or in low rpm’s, it sounds a little “diesely”, but down the road it purrs! until the problem happens for a couple of seconds again!

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