Topic: '77 550f engine clunk and brake issue

[Rev. Dr. Moses P. Lester]

i've got a couple confusing problems on this bike.  i did some searching and can't find anything on the board from the past that seems to fit them.


1. engine clunky noise at idle.  not related to clutch or trans, as far as i can tell, it happens whether clutch is in or out or in gear or not.  goes away at like 1600rpm or higher.  i had assumed it might be a screwed up timing chain adjuster that wasn't adjusting properly, but i'm not so sure.  what else could this be?


2. front brake behaves as if the floating arm it's on isn't floating, or something like that.  when i took the arm off once, it was extremely difficult to get it to swing.  i didn't know if that was normal or not.  it kinda bends the brake rotor a bit when engaging the brake.  this is with the adjuster screw tight or loose whatever.  leads to a rather squishy feeling on the brake.  also drags a bit, but not too much.


anyone have ideas on these?  thanks in advance.

[number13]

"1. engine clunky noise at idle."
 - have you synchronized the carbs?

"2. front brake behaves as if the floating arm it's on isn't floating"
- from your description, it isn't. remove, disassemble, grease and reinstall,
  it must swing freely to operate properly.

[Chris Schneiter]

I've developed a clunk too  this summer.. only mine is intermittent, and seems to come on after the engine is warm. I hear it at idle and it clunks upon accelleration. Last year, I switched to synthetic oil, and simutaneously  haven't been able to get the filter off... I have a question that maybe some sludge may have broken loose? I don't know.. or could it be something wearing out?.. I'm a little afraid to ride much with it like that... seems to sound like # 1 or 2 cylinder...

[hymodyne]

I've read here that these bike are "clunky" in low gears and prior to being warmed up...
It may just be the nature of our beasts...

hym

[mystic_1]

i've got a couple confusing problems on this bike.  i did some searching and can't find anything on the board from the past that seems to fit them.


1. engine clunky noise at idle.  not related to clutch or trans, as far as i can tell, it happens whether clutch is in or out or in gear or not.  goes away at like 1600rpm or higher.  i had assumed it might be a screwed up timing chain adjuster that wasn't adjusting properly, but i'm not so sure.  what else could this be?


2. front brake behaves as if the floating arm it's on isn't floating, or something like that.  when i took the arm off once, it was extremely difficult to get it to swing.  i didn't know if that was normal or not.  it kinda bends the brake rotor a bit when engaging the brake.  this is with the adjuster screw tight or loose whatever.  leads to a rather squishy feeling on the brake.  also drags a bit, but not too much.


anyone have ideas on these?  thanks in advance.

#1 sounds like classic cam chain chatter.  750's are notorious for this, dunno so much about the 550s.  Any history on this, has it been adjusted recently?


mystic_1

[TwoTired]

My 77 550 F clunks, too.  It is the trans.

The crankshaft is connected to the trans gear shaft via a primary chain.  The 550s primary chain has no tensioner. So, without a load, the slack side of the chain alternates sides with changes in the crankshaft speeds.  There's really not much of a flywheel to even out the crankshaft speed at idle, only the alternator rotor, and the mass of the trans gears, connected by that flopping primary chain.
The trans gear teeth are always engaged, even when the slider dogs don't lock them to the shaft they are on.  If each cylinder doesn't fire with the exactly the same strength as the others, the crankshaft changes speed and the mass of the rotating components make the gear teeth make contact on alternate faces.  This sounds like clunking or what I call gear train clack.  You'll note that even at idle RPM, with the bike rolling and in gear, there will be no clunking/clack.  The noise is reduced with the carbs synched and the ignition timing spot on the money for each point set.  The idle air screws and tappet adjustments can also effect cylinder firing strength/evenness at idle.

You can isolate the source of your clunk with a screwdriver handle placed in the your ear socket and the tip used as a probe.  The noise will be loudest at the source.

The front bake arm should pivot freely, with pads and the positioner bolt/spring removed.  I suspect rust, or an assembly issue/error with the front fender and washers/spacers.

Cheers,

[Rev. Dr. Moses P. Lester]

awesome, thanks for the help guys.  that explains the front brake which was confusing me.

i'm still a little unsure about the engine clunk, though, cause from what i'm hearing, it should go away if the carbs are synched and/or if the transmission is in gear and clutch is let out.  and i did sync the carbs.  maybe not closely enough?

i have the bike half apart right now, but from what i remember, the clunking continued whether or not in gear or clutch engaged.  it was always there if the rpm was low.

does this suggest timing chain or timing chain adjuster?  the chain seems to fit the upper sprocket tightly, with no play like you'd see in a worn drive chain.  the timing chain adjuster didn't adjust much before i took it apart, and i see grooves worn in it now.  could this be the culprit?  worth replacing just to be sure?

[TwoTired]

I've not heard a cam timing chain clunk.  If it was really loose it would be more of a ticking/slaping noise.  It doesn't have enough mass to clunk.
The cam chain adjuster is just a curved shoe next to the chain path to hold the slack side of the chain in place.

I don't know what your clunk can be.  Worn rods end bearings, worn piston pins, worn main bearings clunk.  Things wrong with the lower end clunk.

Needs isolation, localization with a stethoscope.

Cheers,

[mystic_1]

Got a video camera with sound?  Shoot some video and youtube it, then post it here.

mystic_1