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New (to me!) '77 CB400F - US model
mattsz:
The discussion about the cam chain adjuster in the 350-400 section has me wondering - I don't really understand exactly how this thing works, and I haven't run the engine yet. is there any way to check how well the adjuster is working, if at all, without the engine running?
The shop manual just says to loosen the lock nut and tension adjusting bolt, then re-tighten both (engine running). How much re-tightening torque are we talking about here?
Bryanj:
you can replace the tensioner by just removing the lower crankcase but its still an engine out job. remind me what miles your bike has on it? If you have been reading about them you now know what goes wrong with the tensioner when chain gets slack, they don't work very well as the springs loose strength but you can use the small screwdriver down the blanked off hole to see if it is moving at all.
If it was running before it will again before deciding what to do and you will not loose anything except a small amount of your time, it can always be done later just do not get disheartened.
Nurse Julie:
--- Quote from: mattsz on March 08, 2019, 12:46:43 AM --- How much re-tightening torque are we talking about here?
--- End quote ---
There is no torque, its automatic spring tension that enables the process of adjusting the chain. You only undo the lock nut and adjuster bolt to allow free movement of the chain tensioner adjuster bar to allow the springs to push the chain tensioner adjuster bar to be pushed down further on to the horse shoe, which in turn, pushes the tensioner slipper on to the chain to take up the slack. It's an automatic tensioner. But for the process to work and remove any cam chain rattle from a slack chain, the chain must still be within service limit, the horse shoe pivot not seized and the spring not weak. As Bryan says, worry not now, sort it out at a later date if needed.
K2-K6:
It maybe worth a look into Julie's engine rebuild thread to fully view the component parts and give yourself a broader picture in overview.
If you want to check if tensioner is moving on a non running engine, loosen the set/pinch bolt, put something like a small screwdriver against the spring rod, and get someone to turn the crank anticlockwise (looking at ignition side) slowly.
This'll put the camchain into tension on the "wrong" side and should push the rod towards your hand if the pivot etc are free.
If it moves, then turn the crank clockwise and it should go back away from you again. At this point you can lock the pinch bolt again as all the camchain slack will be placed next to the tensioner and should be adjusted and held by the tensioner.
mattsz:
Thanks guys...
--- Quote from: Bryanj on March 08, 2019, 06:01:12 AM ---you can replace the tensioner by just removing the lower crankcase but its still an engine out job. remind me what miles your bike has on it? If you have been reading about them you now know what goes wrong with the tensioner when chain gets slack, they don't work very well as the springs loose strength but you can use the small screwdriver down the blanked off hole to see if it is moving at all.
If it was running before it will again before deciding what to do and you will not loose anything except a small amount of your time, it can always be done later just do not get disheartened.
--- End quote ---
Still just doing my research - not disheartened yet! The bike currently has 22K miles; three years ago when I rode it, it had 21.7K miles - so not much has changed in that time. On that ride, I recorded a video to try to capture engine noise - not because I suspected anything wrong, but just because I had no idea what sounds are "normal" for this engine. I posted this link waaaaaaay back in post #1 of this thread; here it is again FYI:
https://youtu.be/Szxke8bD_dg
I can say that while deep maintenance history is unknown, recent maintenance history appears to have been lacking...
--- Quote from: Nurse Julie on March 08, 2019, 08:53:27 AM ---
--- Quote from: mattsz on March 08, 2019, 12:46:43 AM --- How much re-tightening torque are we talking about here?
--- End quote ---
There is no torque, its automatic spring tension that enables the process of adjusting the chain. You only undo the lock nut and adjuster bolt to allow free movement of the chain tensioner adjuster bar to allow the springs to push the chain tensioner adjuster bar to be pushed down further on to the horse shoe, which in turn, pushes the tensioner slipper on to the chain to take up the slack. It's an automatic tensioner. But for the process to work and remove any cam chain rattle from a slack chain, the chain must still be within service limit, the horse shoe pivot not seized and the spring not weak. As Bryan says, worry not now, sort it out at a later date if needed.
--- End quote ---
We may be talking semantics here. Since there is a locking nut, I figured that the adjuster wasn't relying on torque alone to hold it in place, but the manual does say to re-tighten it, and to my mind that means some kind of torque - even if the intent is only to tighten it just until resistance is felt. The answer to "how tight should it be?" is a torque value, isn't it? The manual reveals nothing on this score...
--- Quote from: K2-K6 on March 08, 2019, 09:18:28 AM ---It maybe worth a look into Julie's engine rebuild thread to fully view the component parts and give yourself a broader picture in overview.
If you want to check if tensioner is moving on a non running engine, loosen the set/pinch bolt, put something like a small screwdriver against the spring rod, and get someone to turn the crank anticlockwise (looking at ignition side) slowly.
This'll put the camchain into tension on the "wrong" side and should push the rod towards your hand if the pivot etc are free.
If it moves, then turn the crank clockwise and it should go back away from you again. At this point you can lock the pinch bolt again as all the camchain slack will be placed next to the tensioner and should be adjusted and held by the tensioner.
--- End quote ---
I'll look again - I read her thread "cover to cover," but it was almost at a single sitting; like binge-watching your favorite TV series, retention sometimes suffers. Is your "screwdriver against the spring rod" the same as Bryanj's "screwdriver down the blanked off hole"?
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