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Discussion Starter · #1 ·
OK - here's what happened. CM400A 1979 with less than 3000 original miles. Did an oil change and adjusted valves on Saturday, as I has some valve noise (and I am not sure anyone had ever looked in there before). Ran great, no issues. On Sunday I met some friends for a charity ride and BBQ - did about 100-120 miles total between meeting up, coffee and the run itself, mostly back-roads under 50mph, except for the last 20 miles. The end of the run back to the BBQ was on the highway - I was at 65mph steady for that last part - everyone else left me in the dust, (thanks guys - but that's a different rant.) and I pulled in about 5 minutes after everyone else. But when I pulled off the highway and slowed, the bike ran rough and hesitated a bit. I assumed the old girl had enough - I parked it at my buddy's garage and had a few adult beverages, got a ride home and came back for her the next day. 20 minutes of back-roads to get home and when I do - there is a very distinct ticking noise at idle now. Checked the oil and it was a bit on the low side, but just at the bottom mark, so I topped it off and drove around the block. The ticking is still there, but less now. I am going to check the valves again tonight to make sure I didn't mess up something, but could a relatively short high speed ride like that do serious permanent damage? What should I be looking for?
 

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If possible use a stethoscope to identify the source of the ticking. If you're one of those rare individuals who doesn't happen to have a stethoscope handy you can use a screwdriver or a metal rod. Just hold one end against your ear (a rubber cap makes this more comfortable) and hold the other end at various points on the engine. The ticking will get louder when you get close to the origin.

As long as the oil level didn't get below the add mark that should not have caused any damage.
 

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My first guess would be that one of the valve adjuster nuts came loose, or even came off. I have seen this happen several times on the 400/450 engines. Take the valve cover off and have a look. As for high speed run, that bike should be able to do it all day long.
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Discussion Starter · #4 ·
My first guess would be that one of the valve adjuster nuts came loose, or even came off. I have seen this happen several times on the 400/450 engines. Take the valve cover off and have a look. As for high speed run, that bike should be able to do it all day long.
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Thanks - that's my plan when I get home. I am still a bit worried - It was 80ish degrees out with a breeze and the bike had been running for three hours or so, not what I would call a real torture test. A loose adjuster seems likely - I had just done them up the day before, I have been known to muck things up occasionally. I was just happy it started up when I was done!!
 

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Discussion Starter · #5 ·
UPDATE - I went home last night to a nice cold motor and checked all the valves - nothing obviously damaged, one exhaust valve was a bit loose. Checked everything again, reassembled and she started right up and the ticking was gone. THEN...this morning after a few minuted idling in the driveway, I headed to work...but ten minutes in and the motor started making an awful rattle. But here is the weird part - at low speeds, no noise. Full on the throttle - no noise. But midrange suburban traffic - 30-45mph and the noise comes back. I don't know how to describe it - not the same ticking as before, more like something was loose or out of balance - but it didn't sound right. I limped back home and parked it so I wouldn't do any more damage. Any ideas people? I am out of my depth now...
 

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Change the oil and be looking for little bits of hard black stuff. This sounds like the balancer dampening rubbers have crumbled and not at certain rpm/load conditions the 2 halves of each balancer are banging against one another. Almost as deep a sound as a rod bearing but it's sporadic.
 

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Discussion Starter · #9 ·
Thanks - I'll do that tonight. I have been thru the valves three times, and it's not getting better. The bike still starts on first try, idles fine, and runs strong. But in mid throttle range it sounds like it's going to come apart. I hate taking the car to work when the weather is this nice...this is killing me. And if I can't fix this in my driveway in the next couple of weeks, its going to end up back in storage until spring....UGH!!
 

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Discussion Starter · #10 ·
Anyone actually fixed the balancer dampening rubbers? If that what it turns out to be - what am I looking at? I have a download of the service manual at home - is the replacement procedure spelled out? Any tips about methods or special tools needed? Just trying to prepare myself - and psych myself up for the job...
 

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Need to confirm that there are rubber bits, look and feel like hard plastic, in the oil.
The engine has to come out and the lower case has to come off for access. The easiest thing to do is get the balancers from a 450 engine, they're one solid piece. The FSM covers all the different removal/service procedures like torque converter, stator, balancers, etc. Really a one or maybe 2 day process depending on how fast you work, parts availability, tools, etc. Trickiest part is getting the timing of the balancer right.
Parts I would have on hand would be the 450 balancers or 400 rubbers, the 450 tensioning spring, maybe the chain, gaskets and Honda Bond. Might replace the output shaft seal and shifter seal while it's apart and easy.
 

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Discussion Starter · #12 ·
Big job - looks like my riding season may be over. My work space is under a canopy in my driveway in a rented duplex. I'll need to clear space in my mother in law's garage, since I can't afford to rent a work space. My only other option is pull everything electrical from the running bike and see if I can get the parts bike running...the one with the crap CDI and/or stator. Then I'd have to move the tank/tires/cables/controls/etc ...still probably less work. Either way, with full time work and kid and family, my only wrenching time is after dinner until sunset and the few weekend hours that it's both not raining and I have no plans....
 

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First confirm if there are rubber bits in the oil. If so then keep riding, nothing is going to fail immediately. If not then there's another problem.
 

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Discussion Starter · #16 ·
No rubber bits. Oil looks brand new. Which is not surprising its only got a couple hundred miles on it. Back to square one.
 

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Discussion Starter · #17 ·
If anyone knows of a mechanic in the Boston area with Hondamatic experience, I could really use some insight. I will even do the unthinkable and pay money for someone else to work on my baby. I won't like it, but I will do it.
 

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Definitely need someone with some experience in older Honda's to take a listen then since the simple answer is no good. Really thought it would be the balancer rubbers.
 
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