crankcase knock???

Hi Everyone,
I am new to the forum so excuse me if this has been asked before...
I bought a 1982 XJ550J Maxim earlier in the week and I noticed today that it has a slight odd knock while letting out the clutch in first and second gear. Don't notice it in third or higher gears. It sounds like the noise is coming from low in the crankcase. It seams to drive alright. Is this normal for this motor?
Thank you in advance,
Old Biker Dude

 

knocks are never normal.

 

Probably clutch chatter but dont hold me to it . Is it only present when letting out the clutch?

 

Yes, you can only hear it when you let out the clutch.
Just how bad is this?

 

Wanted to add that as you give it throtle while you are letting out the clutch the knock speeds up as the rpm's go up.

 

Run the Bike on the Center Stand.
Use the Idle Adj Knob and obtain 15~17-Hundred RPM.

Listen for the Knock.
Then, ... One at a time.

Pull a Plug Cap off a Spark Plug.
1, 2, 3 & 4.

IF, the Knock "Goes-away" or "Diminishes" when the Plug Wire is Pulled.
The Knock is most likely to be a Connecting Rod Bearing.

If, the Knock persists, ... but sounds "Dull" the problem is likely to be a Crankshaft MAIN Bearing.
(Highly unlikely. The Main Bearings are well made and seated.)

If the Knock does not change in any way, ...
Use a long ROD or DOWEL, ... Placed on various spots in the area where you think the knock originates.

Stick one end of the rod on the Engine.
Hold the other end with your fist. Thumb on the end applying prpessure to the ROD.
Place your EAR down to your Thumb and listen to the mechanical sounds.

Probe all over.
Ascertain where the Knock is centrally located.

Report your findings.

 

Will try to locate the noise. Forgot to mention that the motor only has 11,600 miles on it. I have had other bikes that have made a simular noise. I have a brand new scooter also that only has 10 miles on it and it makes the same kind of noise. This is why I thought it may not be anything to bad. I appreciate everyones input. I may be able to take it down to a local performance shop tomorrow and have him listen to it also to see what he thinks. I will get back with you.
Thanks again.

Old Biker Dude

 

That's right on the money Rick, well done!! Like you, I suspect a conrod big end or center main bearing since those are most ofter described as a "knock low in the crank" but it will be interesting to hear what he comes back with.

OBD- I'm hoping that you just have aome clutch noise but if it were really the same thing that you are hearing from your other bikes, you probably wouldn't have posted this. Typically, the newer engines "tick" but don't "knock".

jeff

 

You need to know about this:

The 550s (unlike the bigger bikes) actually drive the gearbox via a primary chain off the center of the crank. It's a big wide Hi-Vo chain, tensioned by an hydraulic tensioner operated by oil pressure.

It will "slap" at idle, the slapping should go away when you blip the throttle. It is more pronounced when the bike is warm, less so when cold (high oil pressure.)

The sound can be greatly minimized by: Running the correct oil; and getting the valves adjusted, the carbs sync'ed and eliminating any "lump-lump-lump" from the idle; once it's idling like a sewing machine, the primary is nearly unnoticeable.

If it's more of a "feel" than a sound, and pretty much just as you're letting the clutch out, the clutch may need to have the results of all that sitting remedied. (It had to have sat, it only has 11K miles on it.) Take a look: http://xjbikes.com/Forums/viewtopic/t=29541.html Look at the 6th photograph down; chances are your plates look like that. If so, a "refurb" is in order.

 

Okay guys, I have been reading a lot about this and I think that what I may have is this....
http://www.xjbikes.com/Forums/viewtopic ... xj550.html
Which to me sounds like it is a somewhat normal thing. Guess I need to get better at describing tics vs knocks.
Anyway, I am going to keep an eye on it for a while to see how it goes.
Thank you so much for all your comments.

Old Biker Dude

 

That is precisely what I was talking about, above. It's very normal (I have two 550s, they both do it.)

Get the bike idling super-smoothly and it will all but vanish.

However, like I said, if you can "feel" it more than hear it, have a peek in the clutch.

 

Okay Bigfitz,
Thanks!

 

Some "Ticking Noises" are GOOD Noises.

They indicate that the Valves are not too tight and are fully closing, as they should.

As previously mentioned, one good noise control measure is to insure that you are running the right OIL.

Also, ... Small Exhaust Leaks will present themselves as "Knocks".
Tape a bit of Tissue to the end of a long probe and test the Exhaust Fittings.
If the "Flag Flutters" ... you've found a leak.