Noise

Have an 82 seca that runs great now that its all back together and tuned and thanks for the help given on this site. Problem now is with a noise I am hearing. It sounds like the classic cam chain noise, however their is a problem with that diagnoisis. I have removed the cam cover and phisically checked the cam chain and it is tight. It also sounds more like it is originating from the bottom end instead of the top. Using a mechanics stethescope it is coming loudest from the left and right crankshaft end covers, however ironically when these covers are removed it is much more quiet but still there, almost like the covers amplify the sound. Its not the rods as the sound is quite different and when pulling a spark plug the noise does not go away. I also checked for play when I had the head off and it hasnt gotten worse over the last 1000 miles.

Could this be the alternator chain, if so is there an adjuster for it? What else could it be?

 

Could be the starter chain, as there is no alternator chain. After a number of years, the rubber on the starter chain tensioner block starts to crumble, leaving the chain loose and the fallen pieces of rubber jammed in the transmission! Most of our bikes are old enough to experience this (mine has already). Another chain is located off of the oil pump, which should be in decent shape given the environment and stresses it is exposed to. I could not remember nor determine from my book, what drives the oil pump chain so I'm sorry, your on your own there. Someone else who has split the case recently might be able to help out there. Your covers being removed lessenes the noise you say? Odd, don't see how they would contribute to the sound but an interesting observation regardless. Wonder what part they play in all of this. Hope you catch the rattle gremlin, must be maddening!

 

I just posted about strange noises in the engine cover subject.... also the starter chain just for correctness does indeed also drive the alinator continously , the starter only pops in when to start........

search in forums, will come up with a way to check your chain in a quick but ruff fashion..

i would do it and post the link here, but i hate the thing as with me i always get irevelevt stuff back in the search result...

 

arrrg , and there is no adjustment for the primary chain....

 

Usually the primary chain being attached to the starter is a secondary function.. the damned thing connects the crankshaft to the rear whell.
Wear in any form is not good. Yamaha 'dicked' with this odd design several times before abandoning it in favour of a 'normal' gear drive to the clutch basket. Some engines had no tensioner while others had a oil driven tesnioner unit. Dunno which you have. Imprtant bit is these thing wear out at Hi mileages.. and MUST be replaced. no question on that one.
The Real trick is to determine just how much life you've got left before it fails. Take off the Alternator cover and turn the exposed rotor by hand The amount of slack /free play before you feel drive take up indicates wear of the Primary. New is NONE. 1/4" play is pretty well suspect in my world.
Other problem is the damned engine must be taken ..totally ..apart to replace the thing (no easy way Mate) and the chain is available ONLY frm Yamaha and expect it to be bewtween $175 and $200.
Ain't old bikes Fun ??

 

I couldn't find any reference to the alternator drive in my Haynes (bad book, you let me down). Mia culpa. I saw the drive shaft for the alternator but it looked like it was direct driven off of the adjacent shaft. I haven't had a case apart in over 18 months and I'm short on memory cells. The book does mention that the chains are in ideal environs and should be subject to minimal wear, suggesting that their replacement would be toward the end of the motors useful life. If the chain is dying with a relatively low mileage engine, I would be worried about other damage, i.e... the chain is a symptom, not the cause.

 

Just for "A drill" ... to see if what you are hearing is a resonant noise from elsewhere; give this Old School Test a shot.

Slip two wedges of soft-wood (pine) ... between the exhaust collector and the lower case. Run engine. Probe for noises.

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