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Discussion Starter · #1 ·
Here's another long-distance troubleshooting puzzle. My '82 GL500I with 37K miles has an occasional "clunk" that I've so far only noticed at idle while stopped or barely moving. The noise and feel is similar to putting the bike in gear from neutral, but not nearly as severe. I first noticed it while waiting at a light, and I thought it was just a cylinder mis-firing one stroke. The RPMs dropped enough that I thought the bike might die, but I immediately gave it some throttle and recovered it. That's been the case most of the time. I don't notice it if I have the RPMs around or above 2000, but that may be coincidence. I've had the bike since May, and have put a little less than a thousand miles on it. Symptoms are:



• occurs randomly, but usually at least once every 2-3 minutes

• occurs if clutch is in (while in gear) or out while in neutral, and happened once last week while pulling out of a parking lot at low speed (not gearcase?)

• isn't noticeable at highway speeds, but maybe I just can't sense it

• RPMs drop after the noise, and yesterday for the first time the bike died while I was listening for it to happen. Normally the recovery is immediate (not carb-related? Carbs have been rebuilt with the "Larry" method by me and synced)

• it's a heavy sound, not like a cam chain rattling or scraping. I think something solid is hitting or binding with something else solid enough to almost stop the engine. (Cam chain has not been adjusted by me, but I'll do that next)

• I haven't changed the oil since this started happening, but I'll do that and look for metal.



I don't mind dropping the engine, but I'd like to have some idea what to look for before I do. Anybody got any experience or guesses on where to look next?
 

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This sounds like one of two things.



1:Worn gearbox dogs/shafts



2:play/wear in final drive shaft/drive-box.



1st thing I would do is change over to 15w40 diesel engine oil(Rotella).This sometimes will help lubricate the gearbox better and quieten the problem and extend the life.



Otherwise it's best to get a low mileage gearbox and or drive box/shaft once you determine the exact course of action.

As gearbox/drive changes are a pretty big-ish jobs try the oil change first.You can also add a tablespoon of Moly paste



http://cgi.ebay.com/ebaymotors/Genu...2619247QQptZMotorcyclesQ5fPartsQ5fAccessories



to the engine oil(Mix with some fresh engine oil in a rattle can top to thin it down before adding to warm engine) which improves lubrication.I run both my engines on Moly added to the oil,no clutch slip.
 

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You can also add a tablespoon of Moly paste


Dear Shep,



Please confirm the above dose. A genuine, official, kitchen implement leveled tablespoon of the Genuine Honda Moly,... yes? I'm thinking that this would also help in lubricating the valve train in CX engines (especially the rocker shafts/rocker arm bearing area). Just one of those places where I feel things are a bit under lubed....bothers me somewhat.



Snowy Cheers,

Hoppy
 

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Dear Shep,



Please confirm the above dose. A genuine, official, kitchen implement leveled tablespoon of the Genuine Honda Moly,... yes? I'm thinking that this would also help in lubricating the valve train in CX engines (especially the rocker shafts/rocker arm bearing area). Just one of those places where I feel things are a bit under lubed....bothers me somewhat.



Snowy Cheers,

Hoppy


It's just a general measure.About a third to a half of a tube from link posted will do.If you use too much it would do no harm as it just wouldn't get used by the meshing metallic parts and would just be held in suspension.I actually use a ready made product called Molyslip



http://cgi.ebay.com/Molyslip-2001-s...arts_Vehicles_CarParts_SM&hash=item483b8bfc3f



but it may not be available over there so you can basically make your own.I've been using Moly based products in my engines for over 30 years,



I construct all my engine bearing faces using Moly based products,



http://www.engineparts.com/it_cambreakin.asp



Including Crank shaft Main and big-end shells-bearings,cam shafts,valve train rocker bushes etc.



The low friction qualities of Molybdenum Di-sulphide are well known and have been used in industry for years even as a,"Dry" lubricant,



http://en.wikipedia.org/wiki/Molybdenum_disulfide
 

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Interesting problem. While it could be transmission related, since it does it in neutral as well as in gear and the clutch seems to have no effect on the problem, I would suspect something else. If you are correct in that the noise occurs before the RPMs fall, this would lead me to believe that it is probably not fuel delivery related.



And the fact that it seems to only happen at low RPMs, would point towards areas that change configuration dependent on RPM. The only areas that do that is possibly the cam chain running a little "floppery" at low RPMs and the starter clutch assembly. The cam chain can be eliminated with an adjustment which you probably should do first. I'm guessing that from your description of the noise that it isn't cam chain slap tho. Good job on the problem description, by the way.



That leaves the starter clutch. There are 3 rollers, 3 spring keepers and 3 springs that are held in contact with the crankshaft before starting. As the engine increases RPMs, centrifugal force causes the rollers to retract against the springs and move outward from the crankshaft. This assembly is held in place by 3 Torx screws in the rear of the flywheel. These screws can loosen and allow the cover plate over the rollers to shift. If for some reason the springs now exert just a little more force on the rollers, one of them may contact the crankshaft and cause a "kunk". Or maybe one of the screws backed out enough to contact the starter drive gear.



I had one of the Torx screws loose on my 650 when I had it open for a stator replacement. I was having starting issues on it. I replaced the rollers and springs and tightened up all the screws. The recommended course of action is to replace all Torx screws that have loosened with a new screw. This was the subject of a long post on the Oz site last year. Something to do with the screw stretching during torquing down.



Unfortunately, the engine rear cover and flywheel need to be removed to check on if this is the problem. Hopefully someone else may chime in as having and solving this same problem in the past.
 

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Discussion Starter · #6 ·
This sounds like one of two things.



1:Worn gearbox dogs/shafts



2:play/wear in final drive shaft/drive-box.



1st thing I would do is change over to 15w40 diesel engine oil(Rotella).This sometimes will help lubricate the gearbox better and quieten the problem and extend the life.


Thanks Shep, good advice that I think you gave me on my first post ever back in May. I do run Rotella 15w40, but no Moly added (yet). I was shying away from final drive issues since I notice it sitting parked on the side-stand in neutral. When you say drive-box are you referring to the rear wheel gear case?



Blue's starter thoughts are a place to go if the cam chain tensioning has no effect. My gut feel is that it's deeper in the engine than the starter, but hopefully not. I'd really like to get it on the road to break in some new tires, but I'm worried I might bugger something up internally. I've got two weeks off for the holidays -- looks like some wrenching is in store!
 

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Thanks Shep, good advice that I think you gave me on my first post ever back in May. I do run Rotella 15w40, but no Moly added (yet). I was shying away from final drive issues since I notice it sitting parked on the side-stand in neutral. When you say drive-box are you referring to the rear wheel gear case?



Blue's starter thoughts are a place to go if the cam chain tensioning has no effect. My gut feel is that it's deeper in the engine than the starter, but hopefully not. I'd really like to get it on the road to break in some new tires, but I'm worried I might bugger something up internally. I've got two weeks off for the holidays -- looks like some wrenching is in store!


Yes.change the oil in the drive box(Hypoid 80/90 marked on the case).Also grease the nipple as well.Don't over-fill the box as it only needs the correct amount.You can mix a bit of Moly on that as well before adding.



Check security of the drive shaft pinch-bolt as well.I can be a worn UJ on the shaft.I'replaced one of mine with a decent 2nd hand one off Ebay some years ago.



I ran a whole season with a similar clunk/gearbox lash until I couldn't stand it any longer




So it won't cause major harm and you can use smoother rev/gear-clutch changing to keep it down for now as well but it does need addressing as it will cause premature wear of other parts.
 

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1978 CX500 "The Grub", 1983 GL650I "Nimbus"
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Yes.change the oil in the drive box(Hypoid 80/90 marked on the case).Also grease the nipple as well.Don't over-fill the box as it only needs the correct amount.You can mix a bit of Moly on that as well before adding.



Check security of the drive shaft pinch-bolt as well.I can be a worn UJ on the shaft.I'replaced one of mine with a decent 2nd hand one off Ebay some years ago.



I ran a whole season with a similar clunk/gearbox lash until I couldn't stand it any longer




So it won't cause major harm and you can use smoother rev/gear-clutch changing to keep it down for now as well but it does need addressing as it will cause premature wear of other parts.
He said is happens in neutral, so it can't be a drive shaft/rear unit issue! Please read the whole post.



Showmwdude - I wonder if it isn't a cylinder (or more) dropping out, as you originally suspected. Check you main harness ground. I'm not sure what mechanism would account for the "clunk" you're hearing (maybe post-ignition of unburned fuel in the exhaust header?), but an intermittent loss of ground would cause the engine to cut out for an instant and lose RPMs. And it's an easy check/fix.



R
 

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The first thing I thought of when I read the symptoms was maybe one of the magnets was coming loose from the rotor.
 

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Hmm interesting

It may be some mechanical fault for all I know but first thing I'd do

to eliminate suspects is

open check and clean all the ignition electrical connectors and grounding

Its possible there's a bad connection prone to break down at the lower power/rpm stages.

It does no harm to check and clean these from time to time anyway





I wondered about sticky/faulty starter rollers too

and got thinking

Lets say rather than stay recessed and out of the way they sometimes

foul the starter gear, this could spin the starter motor too



How to test for this prior to strip down?

I experimented with my spare starter and spinning it by hand produces no

appreciable voltage.

But, if the starter gear is getting nudged then you'll see a small changes in resistance

as it moves

The numbers arent important, if the starter is still, the meter will show a steady, low

resistance.

if meter shows changes when you hear the 'clunk' this suggests the starter gear has been nudged.



A meter set to read low resistance and leads clamped to the solenoids starter side terminal and

battery ground may help show if this is occurring



Someone else had a recent intermittent noise which turned out to be cam chain related

and the auto tensioner was found to be at its limit of travel

what the history of the chain? has it an auto tensioner?
 

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Randall, I thought electrical too. But he says that the "clunk" happens, and then the RPMs drop. If it was electrical or fuel related, I would think that the RPMs would drop first, then if a jag of unburnt fuel entered the cylinder there could be a clunk. But it is happening opposite of that.



Alan, I just worked on Rickberts engine with a dropped magnet. He was having a constant problem, but his noise was likely the magnet holding screw scraping on the case. I suppose that if the screw came completely out, that one of the magnets might cause intermittent noise when contacting the stator. Engine out and flywheel off for that check too.



Showmedude, have you tried lowering the idle RPM to maybe 800-900 just for a quick test to see if the noise happens more frequently? You don't want to run at these RPMs for an extended time, (oil pressure suffers at low RPM), but a couple of minutes may help pinpoint how related the noise is to low RPMs.
 

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1978 CX500 "The Grub", 1983 GL650I "Nimbus"
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The first thing I thought of when I read the symptoms was maybe one of the magnets was coming loose from the rotor.
We have seen that a couple times in the past year. Was Rick getting similar symptoms?



R
 

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Randall, I thought electrical too. But he says that the "clunk" happens, and then the RPMs drop. If it was electrical or fuel related, I would think that the RPMs would drop first, then if a jag of unburnt fuel entered the cylinder there could be a clunk. But it is happening opposite of that.
In my mind, the miss-fires are of such short duration, and any post-ignition would follow so closely after, that it may be perceived as preceding the RPM drop, when in fact the noise would be simultaneous with the beginning of the drop in engine speed.



It's probably a long shot. But since it can be corrected without major surgery, it would be well worth checking, if only to eliminate the possibility.



R
 

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It is all guessing at this point,,I would do all the tests and checks listed above and if nothing definite shows up I guess the only option would be to pull the engine and go in for a look. Even then it may not be readily apparent what is causing the problem.



I would say maybe you could live with it unless or until it got worse, but if it ever seized up while driving it could cause an accident.



Maybe you could post a video of it, it is a longshot but it may help.
 

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you have had lots of good advice.

with engine not running,try turning the 17mm nut on the front crank,plugs out,try in neutral,in gear,clutch in and clutch out.

see if you can hear anything that is similar to your noise.


just make sure you turn the nut clockwise[tighten]
 

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Discussion Starter · #16 ·
Thanks, guys, good stuff. I'm at work now but will start doing some ground and ignition checking later tonight. We're in the middle of a week of storms in SoCal anyway, so it's not a good time to take fresh rubber out on the road.



I do have new plugs in, but understand there's lots more to getting good spark than that. Lower idle speed for a check is intriguing -- I imagine that a tendency for binding or backlash may happen more if the engine is chugging along instead of whining at high revs.



Bandit or anyone, any issues with putting a socket on a drill and spinning the engine from the front that way? I think with a ratchet I'll be there till the cows come home waiting for it to happen.



This is sort of like my old days of fixing F-111 fighter jets when the pilot came back from a mission and said, "It doesn't work right".!
 

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I seriously doubt you will be able to spin the engine with a drill. A big Milwaukee Hole Hog might spin it if you can rig up the adapters to make it work. But the noise of the drill will drown out any noise from the engine. Unless the engine did lock up enough for the drill to twist out of you hands, keep running and wrap the cord around the drill and your wrists, and then you can probably hear some sorta noise. I would put the small children to bed before I tried this.



I think what Bandit meant was to try a few revolutions just to see if you could feel any "hard" catching. Let's see, if the bike does it every 3 minutes, and you are running 1100 RPM, you would only have to turn the ratchet 13,000 times before it did it. That's at a 1/4 turn per stroke. You mentioned that you have two weeks free, let's start counting.



What Reg said about measuring starting motor resistance while this is happening is a novel idea. You would have to start the bike, then remove the cable to the starter and put a meter from it to ground. I don't know if the rollers dropping would turn the starting motor or not. But, it may not hurt to try it.



Or you could just finish you 650 and ride that.
 

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Discussion Starter · #18 ·
I seriously doubt you will be able to spin the engine with a drill.


Blue, With the plugs out it should turn pretty freely. Haven't tried it with a drill, but with a ratchet I seem to remember it being easy. Got it on the listening/feeling for a catch -- perhaps the small children can turn the ratchet for their allowance while I stand by with a stethoscope and "O-meter".
 

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What Reg said about measuring starting motor resistance while this is happening is a novel idea. You would have to start the bike, then remove the cable to the starter and put a meter from it to ground. I don't know if the rollers dropping would turn the starting motor or not. But, it may not hurt to try it.

Blue Fox

You wouldnt need to remove any cables

Once the motor is running the cable from the solenoid starter terminal and the starter

is open circuit at the solenoid end and will have a low ground reading at the starter

unless it moves which might give a few 'spikes' in resistance over the brushes.

A reading at the solenoid would be easier then at the starter.

Whether the starter rollers are dropping is unknown of course but IF they are

dropping enough to move the idler wheel then they must move the starter motor a bit.

Its just a theory/wild guess of course I wouldnt put any money in it.



I'd check the electrics first to see if any bad connections are causing an occaisional misfire at low revs.

BTW the solder joints on the coils have been known to go dry and cause odd symptoms

as have bad earths/grounding

I might have a flutter on that
 

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you could do a quick check to see if it is the starter clutch

remove the starter motor - and try and turn the reduction gear in both directions

should be totally free in one direction with no noises - and no movement whatsoever in the reverse direction, it should lockup when turning the opposite way



another one could be (god forbid) a loose pickup coil banging on the flywheel timing nub.



does it also jump out of first or second gear under load or not select these gears properly ?? and is it easy to find neutral ?
 
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