Little rubber blocks

Today when I started my bike a little rubber block (about 5mm x 5mm x 7mm) fell on the ground, I found there are a few wedged in between the cooling fins of the engine block. I am guessing these are for damping vibration? Not sure, are they necessary, what are they for? There are a few on both sides of the engine, hope you can see them in the pic.

Thanks,

Timekeeper

1985 XJ700 Maxim

 

Yep, damping vibration is correct. I've heard the engine can "sing" pretty loudly at highway speeds without them.

 

I read that they reduce a weird noise that occurs at certain RPM's. I have not run any of my XJ's without them so I can't say what will happen.

 

Not just at highway speeds. Without them there are a few "resonance ranges" RPM-wise, that the motor will go through; you can actually pick up on the "singing" more easily riding around town.

Try it sometime; you won't hurt anything but you'll put the rubber blocks back.

 

I've replaced these on some 2 strokes (with much taller fins) with some short cuts of vacuum hose

 

Great, thanks all for the feedback. Next question is, how many are there supposed to be? I have no idea how many may have fallen out before I got the bike.

 

I have blown a few out with a pressure washer and lost them I have not noticed any dofference, but I suffer from a bit of industial deafness.

 

Which bike? It varies by model/displacement.

 

Fitz, back to the Original Post, it is an '85 700 max.

 

Oh, sorry; missed that.

According to the fiche, there are (8) of one size (probably the larger ones) and (14) another size (probably the smaller ones) used on the aircooled XJ700.

 

Those Rubber Dampers are alleged to dampen a Harmonic Frequency that is said to be a cause of fatigue while riding.

I believe it's true.

 

I have never even noticed those things before. I'm making it a point to look at mine when I get home...

 

Anyone know if they should be located in specific locations on each side of the engine ? I would assume so, but how to determine this .... Say for a 1980 for example.

 

You can position them to be even or in a pattern.

The idea is to keep the Cooling Vanes from vibrating.

3/8th Inch sections of High-temp Vacuum Hose wedged between the Cooling Vanes will do the trick.

 

Yep! Eight on each side.
Man, how do you get that engine so clean? Mine has that nasty old aluminum look to it all over.

 

Yep! Eight on each side.
Man, how do you get that engine so clean? Mine has that nasty old aluminum look to it all over.

 

pnthubb, I believe this bike has been kept in a garage most of it's life, I have done some cleaning with simple green. I think the engine is painted silver, and the camera flash enhances the brightness of its appearance. You can see in the pic the spark plug has some corrosion but the bike was really clean when I got it. New plugs soon.