Mechanical Help! Mechanical Noise - TC88B

[the_monster]

the rotor is the big magnetic bit at the front of the primary !

clunk clunk or chink chink

primary side or timing side of the engine


what sort of pushrods have you got ?

[MadMax]

I would say that this is more like confirmation of a lifter problem Jake. At lower rpm when your oil flow rate is lower the lifter is not retaining pressure then as soon as your crank speed increases, the flow rate is enough to maintain pressure.

[Scotty]

Originally Posted by banquo

OK, so tensioners are still OK, but the knocking hasn't gone away.
When I posted the 1st time, I'd only done 5 starts since I first heard it, but now having been down to RTTW and back (there goes another 1000 miles..) I have a bit more to go on, as I can make it happen now.

If I start up the cold engine, and push the choke in so it's running at well under 1000 rpm (potato territory) then it does it constantly, and it doesn't go away. On a warm engine, the tickover is 1000 rpm or so, and I don't hear a thing, but if I engage 1st, and let the revs drop by slipping the clutch, then off it goes again - clunk, clunk, clunk. It sounds like something loose, because when the engine is running smoothly, I can't hear anything, but when at low rpm, and hunting a bit, you can hear the knocking, in time with the engine.

Does that eliminate the lifter as the problem? I'm guessing it does, because once it's pumped up, it should disappear?

Encouragingly, nothing propelled itself through a crankcase on the way down or back to RTTW, but clearly there's something not right.

I'm going to try and get it running slow, and take a screwdriver stethoscope, to see if I can get a better idea of where it's coming from. Might fit the stock pipes too, because it's hard to hear anything with the SEIIs...

Any more ideas out there, and Scotty, is there an easy way to check the rotor, or does it all have to come down...?

Get someone to hold a couple of big rags (towels) over the exhaust so you can hear the motor better.

To check the rotor you need to take the primary off, you could try and see if you can move it with a screw driver.
To check properly you would have to undo the compensator nut and move the sprocket away from it and see if you have any play.
Dont rely on listening to the motor, i had a mates fatboy here a couple of weeks ago with a knocking noise that sounded as though it was coming from the top of the front pot and it was the compensator nut that was loose.
These motors are a bitch for noises echoing around and sending you in the wrong direction.

[banquo]

Thanks guys. Yes, I know where the rotor is, and what it looks like, but I was kind of assuming that if the comp nut is tight, so is the rotor - isn't it the comp nut that holds it in place...? Or are you saying that the splines wear out, and it rocks on the crankshaft?

Scotty - I know what you mean about locating the sound, which is why I'm looking to try to screwdriver thing. At the moment, it sounds loudest at the front right, but although I'm convinced it's coming from the bottom end, sometimes it sounds like it's coming from the front head...

I'd describe the sound as a heavy clunk-clunk and not a chink-chink. Need to do more investigation until I can be sure (or more sure) where it's coming from.

I like the lifter idea (especially if it means I don't have to rip it down), and if they can carry on clunking at low RPM, just because of the oil pressure, then I can live with that. Engine is completely stock, apart from Stage 1 and 40,000 miles of wear... so pushrods and cams are stock too....

[MadMax]

Originally Posted by banquo

At the moment, it sounds loudest at the front right, but although I'm convinced it's coming from the bottom end, sometimes it sounds like it's coming from the front head

Lifter going soft at low rpm allowing pushrod movement between the lifter cup and the rocker arm socket .. clatter clatter from both ends of the pushrod ...

[Phil]

Just to throw another turd into the pot.

Sorry Jake. Over the hundreds of engines we see, there are two other things that spring to mind vis a vis the front cylinder, though rare.

Evos had a habit of the front rod (Big End) going slightly oval & knocking.

Rarely seen on a Twin Cam unless it has been well thrashed.

Also on well thrashed Twin Cams we have seen the front little end or piston pin bushing go bad. Fairly easy to replace.

Your symptoms could be the latter.

I am still thinking that you may have a tired lifter though.

[Scotty]

Originally Posted by banquo

Thanks guys. Yes, I know where the rotor is, and what it looks like, but I was kind of assuming that if the comp nut is tight, so is the rotor - isn't it the comp nut that holds it in place...? Or are you saying that the splines wear out, and it rocks on the crankshaft?

Scotty - I know what you mean about locating the sound, which is why I'm looking to try to screwdriver thing. At the moment, it sounds loudest at the front right, but although I'm convinced it's coming from the bottom end, sometimes it sounds like it's coming from the front head...

I'd describe the sound as a heavy clunk-clunk and not a chink-chink. Need to do more investigation until I can be sure (or more sure) where it's coming from.

I like the lifter idea (especially if it means I don't have to rip it down), and if they can carry on clunking at low RPM, just because of the oil pressure, then I can live with that. Engine is completely stock, apart from Stage 1 and 40,000 miles of wear... so pushrods and cams are stock too....

Yes it can wear on the splines on the crank.
And it does sound like a heavy clunk.
The loose comp nut the other week also sounded like a clunk and at times sounded like it was coming from front cylinder.
Either way i dont think you should just leave it, their is obviously something wrong and eventually whatever it is is gonna let go and it might be with a big bang causing all sorts of damage.
If it were me i would have to find it.

[the_monster]

I'm still on the lifters especially as it goes away once you oil is up to temperature and the flow rises.

[Scotty]

Just had a look round and found this, scroll to the last post on this page...
http://www.harley-davidson-hangout.c...end-knock.html

[the_monster]

post number 2 on that link is interesting too