CHAIN BREAKS EARLY BIKES

[kp]

What has always intrigued me is how the problem of chains breaking and damaging the cases never became evident in all the testing carried out. We hear of the test mules being flogged and flogged so why did one of the major failings go unnoticed by the factory. Thoughts

[acruz]

Could it be that they knew of the problem but did not want to delay the release? 

[4pots1969]

It is just the quick link of the chain that broke every time... It was enough to put a riveted link and after more problem.
Of course it is very surprising that they have not been confronted with this problem of breakage of the quick link during the tests that had to be tough ...
So why Honda has not riveted the CB750 chains by precaution? That's the big question...
 
With my best friend, we ordered our CB750s, but in different Honda dealerships, so he had his CB750 a few days before me.
The same evening we went out for a ride, just to prowl "The Monster" and on the return it was almost dark and I followed behind with my 350 Avenger and there was a sheaf of sparkles on the road... The CB750 had just broken the quick link of the chain ...The chain had passed nicely around the pinion of exit to make no damage... A real big miracle !! We found the chain and the link on the road thanks to the light of the headlights... It remains a good memories.

[Steve Swan]

there was also rapid and excessive loosening of the chain; abrupt deceleration, with an excessively loose chain, the chain could wad into the back wall of the crankcase. i would suggest, in the severe testing Honda did on these bikes, they paid attention to the chain tension. I remember frequently needing to adjust chain tension on 4779, by the time i had got back from my California trip of over 2500 miles, the rear tire was nearly worn out, and the rear chain was nearly stretched to it's maximum adjustment.  I remember having to wait a few weeks before a replacement tire and chain were available, that was June of 1970.

[steff750]

  yes i tend to agree with you Steve i have owned three maybe four CB750s with engine case damage and i agree its the over run on the chain that is the main cause making the slack on the chain bunch up on the top of the sprocket and smash the cases because of its close proximity. i have never seen this on any more powerful models of the time,so for me i dont blame the chain ,and we all know how often we need them adjusted

[Steve Swan]

yes i tend to agree with you Steve i have owned three maybe four CB750s with engine case damage and i agree its the over run on the chain that is the main cause making the slack on the chain bunch up on the top of the sprocket and smash the cases because of its close proximity. i have never seen this on on more powerful models of the time,so for me i dont blame the chain ,and we all know how often we need them adjusted

agreed on chain wadding upon abrupt deceleration.  by the time i got back from California in June 1970, i had just over 4,000 miles on the clock.  when i arrived to California, the San Francisco area.  an oil leak had started, i discovered the leak was coming of of the neutral switch, i could actually see a crack in the plastic around the terminal. I went to the dealer to inquire about a replacement switch, of course he did not have one.  i remember removing the switch and making a repair using some sort of sealant or epoxy  i also remember asking about a tire, of course he did not have one, when i asked about using a tire for the 450, he advised against that and told me to "take it easy" on my way back home...  i remember not being able to ride 4779 because of the worn out tire, so i rode my back up bike.  picture attached.

[rickhahn]

If i remember correctly it was Dec 69 or Jan 70 I was posing to my mates on how quick my Honda accelerated from a standing start,a fist full of revs drop the clutch and  the chain snapped and shot straight out the back with great delight to the crowd as most of them owned oil leakers and not Jap Crap as the Honda's were commonly called back then.The embarrassment !!!!. The chains that Honda used I don't think were up to the power of the motor or a young bloke showing off . 
   
 

[Steve Swan]

If i remember correctly it was Dec 69 or Jan 70 I was posing to my mates on how quick my Honda accelerated from a standing start,a fist full of revs drop the clutch and  the chain snapped and shot straight out the back with great delight to the crowd as most of them owned oil leakers and not Jap Crap as the Honda's were commonly called back then.The embarrassment !!!!. The chains that Honda used I don't think were up to the power of the motor or a young bloke showing off .  
    
 

Rick you make a great point.  alot of these bikes were abused.  absolutely metallurgy was not of a spec to handle the quick revving hp and torque of the CB750.  i'm sure chain breakage was as much a cause as neglecting to keep chains properly adjusted.  in regards to the factory testing done in Death Valley, i'd be surprised if much or any burnout testing was done.  However, Kevin Dodge told me 2113 had a strip of rubber stuck to the inside of the rear fender, so i imagine various non-factory test riders were doing burnouts. i think the factory was more interested in how the engine would hold up to sustained rpm in various gears.  at least that's the impression i got from Bob Jameson.  as i said before, i am sure the factory paid close attention to chain tension.

as for "japcrap," i remember that term used often by brit and h-d people.  Summer of 70, i was sitting on 4779 outside a bar after a local club meeting.  i remember an ugly little human rapidly walking up to my bike, with garbage coming out of his mouth as he raised his leg in the air and kicked at tail light with his foot.  can still see the little douche bag's face and braided pony tail, he couldn't have been much older than me.  as soon as he kicked the taillight, he ran off.  the whole indent happened in seconds.  no doubt this little fellow was muttering something along the lines of "japcrap."