What is a compensator and what does it do????

[Boe Cole]

I keep seeing many posts about compensators and loose nuts, etc. but really am not sure what one does or is for.  My best 'guess' is that it acts as a shock absorber between the engine and the drive chain going to the clutch pack.

[WI Bob]

You are correct. It is trying to save the crank.
But it is actually part of a master scheme by the MoCo to keep us buying parts from them. ;-)

[wurk_truk]

Yes Boe, you are correct.  Thats exactly what it does.  Instead of having a simple sprocket on the end of the crankshaft, for that end of the chain, we have compensators.  A chain would transmit all of the harsh pulses from the engine and be hard on the whole rest of the drivetrain if hooked to a sprocket.  A compensator SHOULD rock back and forth absorbing those engine pulses.

[Dennis The Menace]

Good thread.  Honestly, I assumed what Boe assumed, but wasnt certain. Now we all know.  Thank you, gentlemen...you make this site great!

[tdkkart]

 Anyone want taqke a guess at why they insist on continuing to use the clattering banging metal to metal versions rather than something with an elastomer cushion of some sort?? Can't be that hard, probably being done in the industry already. Something like the center hub in an automotive clutch disk, which have been figure out for 100 years or more.

[VANAMAL]

its amazing that after 100 years the harley clowns havnt got this right. Their design and engineer people must have came off the street. Couple the poor design with poor manufacturing and we get stuck with a whole host of problems to deal with. Rumors of another new compensator in the works.

[Rags722]

I don't know if this helps or hurts in understanding, but I'm a visual kind of student and theory is fine, but pictures make things easier to understand.  http://partsfinder.onlinemicrofiche.com/ronnies//showmodel.asp?Type=13&make=hdmc&A=56&B=20&vehicleid=1985-Harley-Davidson-Street-Bike-FXEF-Super-Glide-Fat-Bob-(BB)-CHAINS-W/-SPROCKETS-AND-BELTS

Modified to put the correct picture in ( butthead that I am).  Also note this is an older style compensator, used only because I think the picture makes it simpler to understand how it works.


For the most part, ignore everything in the picture except 39 ~ 43, keeping in mind that inside 43 is a mongo strength spring that presses against the sliding cam(40) when bolt (43) is tightened.  That holds the valleys and peaks on the compensating sprocket against the valleys and peaks on the sliding cam.  Note the compensating sprocket is "driven" by the sliding cam, NOT by the crank in the motor.  The sliding cam is driven by the motor via the splines on the end of the crankshaft.  The mongo spring lets the cam slide in and out just a little under hard acceleration or downshifting. That lets the peaks and valleys on the compensating sprocket and cam move around a little to take up some of the shock.  While this may not be an Engineering 101 acceptable explanation, it should make it easier to picture in your head.  And finally, after the exploded parts breakdown above makes sense, then this photo really sums it up for you.  http://www.jpcycles.com/product/6000721?utm_source=retargeting&utm_medium=retargeting

[Coff 06]

Isnt the compensator also your charging system?(alternator)      Coff 06

[tdkkart]

Isnt the compensator also your charging system?(alternator)      Coff 06

No, The compensator is essentially the front drive sprocket and associated pieces, items 16 and 17 here:
http://partsfinder.onlinemicrofiche.com/ronnies//showmodel.asp?Type=13&make=hdmc&A=818&B=21&vehicleid=2011-Harley-Davidson-Street-Bike-FLTRU-ROAD-GLIDE%AE-ULTRA-(KGM)-BELTS-W/-CHAINS-AND-SPROCKETS

The alternator goes on the crankshaft directly behind the compensator, items 5(stator) and 6(rotor, held on by the compensator hub) here:
http://partsfinder.onlinemicrofiche.com/ronnies//showmodel.asp?Type=13&make=hdmc&A=818&B=11&vehicleid=2011-Harley-Davidson-Street-Bike-FLTRU-ROAD-GLIDE%AE-ULTRA-(KGM)-ELECTRICAL---ALTERNATOR-W/-VOLTAGE-REGULATOR

[Rags722]

Isnt the compensator also your charging system?(alternator)      Coff 06

While the charging system bolts up in the same place, I think the charging system and compensator  should be viewed as two distinct items.  True, they are both on the drive side of the crank, the assy would not be complete without both there, but they are not the same.

http://partsfinder.onlinemicrofiche.com/ronnies//showmodel.asp?Type=13&make=hdmc&A=518&B=11&vehicleid=2005-Harley-Davidson-Street-Bike-FLHT-ELECTRA-GLIDE-STD-(DD)-ELECTRICAL---ALTERNATOR-W/-VOLTAGE-REGULATOR

[rbabos]

A compensator is nothing more than a torsional damper. It can be placed on the engine, clutch or the rear wheel itself to provide a means of cushioning engine pulses between the engine and the device it actually drives. One or more locations can be used.  Length of pulse determines how much dampening needs to be in the system. High rpms engines require less but the long stroke low rpm engines need more. Elastomeric dampers as often found on the main drive pulley of auto engines is more to keep harmonics from developing in the crank reducing torsional pulses that will eventually snap the crank and are tuned to work well at only certain frequencies. This range of operation is not enough to give us what we need in our application. This is why we have a big clunky device with a large range of motion to cover the large range of rpms/loads the drive is exposed to. Actually it's design is ok and does fit the application. It works and works well, until it wears out. Pretty sure if it didn't wear out there would be no bitching about it. 
Ron

[Coff 06]

Thanks for the heads up,because of the location I thought they were one unit that took care of both items.       Coff 06

[Merc63]

When I was repairing my primary chain tensioner, I noticed the spacing on the compensator teeth to be about 0.250-0.350".

Is that normal???

Ps, awesome thread and good question, I wasn't too sure what the compensator did exactly either or how it worked.

[Dennis The Menace]

Coff, just goes to show, there are no dumb questions here.  I'm just amazed that I learn something new everyday. I was pretty certain I knew it all when I was 17. lol

So, current comp design--is the wear excessive, or is it about right?  I ask since some here are concerned about the oil flow to the comp assembly. Again, something I know nothing about.

[Coff 06]

Yep Dennis,the older I get, the dumber I realize I am  When do we catch up? You know it all at 16-17 ,and at 54 I'm not sure what I do know for SURE,LOL.      Coff 06

[Boe Cole]

Thank you all for the thoughtful and respectful responses.  Was a little embarrased asking the question as to many, it would seem obvious what it is for and did.  I just was not sure of the answer and felt that there may be others that did not know either.

Again - thanks for not making me feel like a fool.

[wurk_truk]

Thank you all for the thoughtful and respectful responses.  Was a little embarrased asking the question as to many, it would seem obvious what it is for and did.  I just was not sure of the answer and felt that there may be others that did not know either.

Again - thanks for not making me feel like a fool.

Dude. Ask Away!!!  I have asked some of the craziest questions on here with no regards to whether I will look like a dumbass,  sometimes yes, sometimes no.

[03cvo]

I was pretty certain I knew it all when I was 17. lol

reminds me of this one..



"When I was a boy of 14, my father was so ignorant I could hardly stand to have the old man around. But when I got to be 21, I was astonished at how much the old man had learned in seven years."
  --  Mark Twain

[Nebraskarider1]

Just never give a dumb answer or everyone will beat you up. 

[sfmichael]

Just never give a dumb answer or everyone will beat you up. 

haha 

[Merc63]

When I was repairing my primary chain tensioner, I noticed the spacing on the compensator teeth to be about 0.250-0.350".

Is that normal???

Ps, awesome thread and good question, I wasn't too sure what the compensator did exactly either or how it worked.

Anyone??

[FSG]

When I was repairing my primary chain tensioner, I noticed the spacing on the compensator teeth to be about 0.250-0.350".

Is that normal???

Ps, awesome thread and good question, I wasn't too sure what the compensator did exactly either or how it worked.

Not quite sure I understand what your asking.  The Primary chain is 428-2 and the pitches depends on what model bike.  The spacing between the teeth need to be enough to take the chain rollers which are .335"

Look here => http://www.diamondchain.com/files/DC_cycle_chain.pdf

[Admiral Akbar]

Maybe he's thinking the cams are teeth? 

Max

[Rags722]

I think I understand what hes asking, but not sure how to answer it.  When looking at the compensator from this angle http://www.jpcycles.com/product/6000721?utm_source=retargeting&utm_medium=retargeting     I think he wants to know the gap if any that should exist between the valleys and peaks (teeth?) on the compensating sprocket and the valleys and peaks on the sliding cam.

[Merc63]

I think I understand what hes asking, but not sure how to answer it.  When looking at the compensator from this angle http://www.jpcycles.com/product/6000721?utm_source=retargeting&utm_medium=retargeting     I think he wants to know the gap if any that should exist between the valleys and peaks (teeth?) on the compensating sprocket and the valleys and peaks on the sliding cam.

Exactly,

Are they called valleys and peaks I guess?? Mine has a gap between them, is that normal? I have no clue.

EDIT: Mine looks like that picture, with the gap and all.. I assume that's normal than. I just wanted to make sure in case that bolt/nut was backing off.