HarleyTechTalk

Looking for some education here. Could some of you experts give me the straight scoop on what should be done to properly balance a crank? Particularly with regards to what parts should be taken into consideration when balancing.

Thanks

Quote from: Coyote on December 10, 2009, 10:37:34 AM
Looking for some education here. Could some of you experts give me the straight scoop on what should be done to properly balance a crank? Particularly with regards to what parts should be taken into consideration when balancing.

Thanks

Everything that connects to the crankshaft needs to be considered in the balancing process.  Rods, pistons, piston pins, and rings.

Thanks. I'm assuming no two rods, pistons etc are the same and for best results this should be with the actual components going into the motor?

Quote from: Coyote on December 10, 2009, 12:08:21 PM
Thanks. I'm assuming no two rods, pistons etc are the same and for best results this should be with the actual components going into the motor?

Yep.  Max

 

  Just curious, how much of a variation are you guys finding from side to side?

                                                                                Thanks jd-hd

Did you know that the MOCO stopped balancing cranks years ago?

The MOCO does lots of things wrong though.

My asking this question has to do with my paying to have my crank trued and welded. Only later do I find out that after the crank was balanced, the pistons were changed (not the same as it was balanced with). So it would seem I did not get what I paid for. And I believe the bike has more vibes at cruise than it should. This was the same motor that pulled 2 studs after all of this work was done. 

Just a thought ..... but unless you changed the piston size.... or type ( shorter or longer skirt ) ...the changes is each piston weight would be negligible and most likely not enough to change the harmonics enough to drastically increase vibrations... the 103....110.....113.....all use  ( as Larry said ) the same unbalanced OEM Cranks from HD and most have very little vibrations... although the 110s do have a ( Big Engine Feel ) to them ...I believe that changes in run out are more of a issue

When the pistons are different weight it changes the balance factor some, but it isn't like it is balanced with one set and out of balance with another.

Quote from: Coyote on December 10, 2009, 02:54:19 PM
The MOCO does lots of things wrong though.

My asking this question has to do with my paying to have my crank trued and welded. Only later do I find out that after the crank was balanced, the pistons were changed (not the same as it was balanced with). So it would seem I did not get what I paid for. And I believe the bike has more vibes at cruise than it should. This was the same motor that pulled 2 studs after all of this work was done. 

The different weight of the pistons changes the balance factor on average about 1%. Even if it was 2% it wouldn't make it vibrate more just moves the rpm range of the balance point. 60% used to be the standard but I've balanced them as high as 52% without problems.

Understood (but I still think it should have been done with the actual pistons since I wanted it done "right")

So the pistons are not likely the cause of the vibes. Could having changed the motor mounts cause an increased perception of vibes that might not have been there before?

If the run out was high, would I not hear that in the gear drive cams?

Sorry for all the questions. 

Are they OEM Mounts or one of the aftermarket ones?

I'm not sure. Says D/S Front Engine Mount. Around $20 if that helps.

The Drag motor mount is horrible, it will blur your vision. I recommend the Glide Pro.

Seen a lot of the harder aftermarket ones increase vibes big time ( Velvet Ride etc )

Quote from: Coyote on December 10, 2009, 04:45:00 PM
Understood (but I still think it should have been done with the actual pistons since I wanted it done "right")

The only way it would have been "not right" in the big scheme of things is if you had specified that you wanted it balanced to a specific factor.

I know Darkhorse asks for the weight of the pistons, ring, pins that will be used.

Have had several TC cranks balanced dynamically (significant difference), they always ask for the separate piston weights, pins, clips, and rings. I have done many three and 5 piece cranks here statically and always try to even out the pistons/rings equally but can't swear that it makes a difference. In both instances the rods, bearings, cages, and crank pin gets weighed.

overkill and prp nitro cranks are one piece and balanced at 60%. some of these motors are 195 cu in and hitting 950 horsepower. you would not belive how smooth they are.

Quote from: OKLARACIN on December 11, 2009, 04:43:04 PM
overkill and prp nitro cranks are one piece and balanced at 60%. some of these motors are 195 cu in and hitting 950 horsepower. you would not belive how smooth they are.

That's a killer HP to CI ratio.

my little pro drag motors are hittin bout 400 at 120 cu in. its all about how much nitro you can get in and burn. the stuff is rocket fuel ya know. the Nazis created it for there rocket program. it carries its own oxygen. the  air fuel ratio  is bout 1.6to 1 .the stuff is fun to play with butt it ain't cheep. last year it went to 40.00 a gallon.