Motor/Clutch must read info

[byeatts]

I ve started this on a better titled post as I believe this should be read, This is something everyone should try and regardless what you have there will be a change in smoothness of motor, QUOTE:

Well this current fully Mod completely new" SHR 880", has everything under the sun possible ,Run this setup last year as well and its a Powerful Mountain Motor, the crank is trued and straight.less than .0005. My clutch was balanced years ago[Perks} and I replaced all bushings /cup O -rings Arm bushings everything, Weighed each arm/ ramp and balanced.I have run around 100 different setups testing arms springs combos,ect. so thought Id send it to perks to check balance with my current proven favorite Mountain setup. So I boxed her up.taped shut and took to the local hardware store to get -er done just because have time before snow flies.. Something wasn't sitting right and in the back of my head ,something told me not to ship it,been putting this off for over a week., Didnt really sleep and first thing in the morning I grabbed the package before UPS arrived.I keep thinking that if a crank is 100 grams out of balance which I believe is grossly exaggerated , However I buy the fact that its probably not perfect or far from it. I also believe the balance changes under load due to a laboring motor. Started Wondering about indexing the little out of balance of clutch and out of round to offset the crank. So i took a center punch and on the end of crankshaft marked TDC on PTO.Then started to index the Tra arrows first at One -O Clock and run it without a belt ,noting the smoothness, Proceeded at 2 then 3 ect.I found that at 8 o clock this motor went completely smooth ,No movement at all from idle to 8000,at "3 "it shook. Hmm. could one be able to off set the crank balance with this method. I prove it can be done , surely there are limitations ,and now have an alignment mark on Tra to match Crank mark..Anal or just an as-hole,My X wife has suggestions. However this works. Has been suggested to align the removed Tra weight area to 2" O clock and mine shook there. Not much but noticeable.If the Clutch is Zero-ed and balanced why would this matter,It must change as the sliding half shifts and the out a Round will increase vibrations.this is worth a try and the smoothness was substantial.This will effect every motor and its smoothness,Some more than others.like to hear results from others who try this

 

[byeatts]

Additional info. If a motor is spun with all moving parts and the crank counter balance weights offset the pistons upward movement without spark plugs or compression,Then under compression the apparent weight of the pistons is considerably altered since the compression in a sense removes that actual apparent weight and is a moving target under different motor demands and throttle positions.This upward apparent piston weight also changes when the spark plug fires.I have unsettled thoughts about balancing a Motor under a Non normal RPM running condition.This could be the reason a static motor is suggested to be over a 100 grams out of balance on the bench.This explains a balanced average when running at over 8000 RPM,s,.My suggestion is to get the Clutch balanced and spin smoothly as possible by indexing the crank runnout to the clutch out of" round" which is accumulative as all the clutch components are assembled and wear and dont mess with the crankshaft balancing, I believe it is good at the RPM,s we run at.A calculated average ,Lets give credit to the Engineers on this one.Perhaps that why Doo motors make more power than the competitors!

 

[sledsrock]

Very good info here!!

 

[BBP]

Did you rebalance the clutch after matching the arms & ramps? Any idea what the relationship of the lightened part of the clutch is to the position of the .0005 runout? In other words, is indexing the clutch offsetting runout or crank unbalance? Thanks for the great info. I take it your not sending the whole motor to Perks afterall?

 

[byeatts]

Did you rebalance the clutch after matching the arms & ramps? Any idea what the relationship of the lightened part of the clutch is to the position of the .0005 runout? In other words, is indexing the clutch offsetting runout or crank unbalance? Thanks for the great info. I take it your not sending the whole motor to Perks afterall?

The clutch with ramps and arms was balanced several years ago, I,m sure after all the clutch testing its off just a bit however cant be much, was going to send to just have it checked.The red flag I see are suggestions that the Crank was over 100 grams out of balance,I feel there is a reason a static motor without compression is off that far and dont really think any engineer could make this much of an error for as many years as these motors have been developed. the runnout is at a different location on every crank,and the out of ROUND /balance is at a different location on every clutch, The method assist in minimizing the accumulation of errors to neutralize the vibration[with limitations}and will have an effect on every motor unless your motor has Zero runnout and Zero out of round and perfect balance,Wont happen!Two motors after doing this testing are extremely smooth at 8- O clock, 3- O clock respectively and not smooth elsewhere.

 

[winter brew]

Now turn the idle down as far as it will run...like 8-900rpm and do the same procedure again.

http://www.intuitor.com/resonance/abcRes.html

We deal with this at work daily. When you change something (anything) it will alter the frequency of resonance (when you visually see it bouncing up/down). You havn't changed the "balance", but rather changed the resonance to a different RPM.
The question is, does it help to have it smoother at low RPM (besides just looking smoother)? Does this make it worse at 8,000RPM where we cannot see or measure what is happening as easily?
The same thing happens with a lighter or heavier clutch.....that's why Doo stays with the ring gear on the primary...they have the equipment (accelerometers) to measure this stuff and know what frequency this thing wants to tear itself apart.

 

[byeatts]

Now turn the idle down as far as it will run...like 8-900rpm and do the same procedure again.

http://www.intuitor.com/resonance/abcRes.html

We deal with this at work daily. When you change something (anything) it will alter the frequency of resonance (when you visually see it bouncing up/down). You havn't changed the "balance", but rather changed the resonance to a different RPM.
The question is, does it help to have it smoother at low RPM (besides just looking smoother)? Does this make it worse at 8,000RPM where we cannot see or measure what is happening as easily?
The same thing happens with a lighter or heavier clutch.....that's why Doo stays with the ring gear on the primary...they have the equipment (accelerometers) to measure this stuff and know what frequency this thing wants to tear itself apart.

Not sure i understand your point, I try to get it to operate smoothly at normal operating rpm,s, I dont buy the fact that its good for a motor to shake at idle, My suggestion is to address the runnout and index it to the out of "Round"/balance in the clutch.These anomalies were" Not" engineered by Doo but exist in every motor..in a perfect world all these parts would be trued and balanced without and irregularity's.the motor now runs smoother at 2000rpm,s and flawlessly smooth at 8000rpm,s. Before it would have a continuous vibration everywhere which could be felt in the bars. there's no doubt the frequency of resonance alters with RPM,s

 

[winter brew]

Im terrible at trying to put thought into words.... with the same clutch on the same engine you have not "changed" anything, unless the clutch is terribly out of balance and the engine is also out of balance. Then they could be clocked to offset one another (counterbalance).
Assuming it is balanced what I think is happening is the RPM that resonance can be seen or felt has changed. It's still there you just can't feel it at higher frequency (RPM).
Like a tire out of balance on a car.....it shakes noticably at 35-40 mph but at 80mph it's smooth as butter....but you know the tire is still out of balance, so how can it be smooth??? ...and even though it looks and feels smooth you know it's still hard on wheel bearings.
By moving things I believe (and maybe I'm wrong, just throwing thoughts out there), that we are simply changing the RPM of resonance slightly. It will appear smoother at low RPM and once above 3,500-4000ish everything always seems smooth anyway.
I'm still not making sense am I

 

[byeatts]

Im terrible at trying to put though into words.... with the same clutch on the same engine you have not "changed" anything, unless the clutch is terribly out of balance and the engine is also out of balance. Then they could be clocked to offset one another (counterbalance).
Assuming it is balanced what I think is happening is the RPM that resonance can be seen or felt has changed. It's still there you just can't feel it at higher frequency (RPM).
Like a tire out of balance on a car.....it shakes noticably at 35-40 mph but at 80mph it's smooth as butter....but you know the tire is still out of balance, so how can it be smooth??? ...and even though it looks and feels smooth you know it's still hard on wheel bearings.
By moving things I believe (and maybe I'm wrong, just throwing thoughts out there), that we are simply changing the RPM of resonance slightly. It will appear smoother at low RPM and once above 3,500-4000ish everything always seems smooth anyway.
I'm still not making sense am I

I fully understand your thoughts, But I,m talking about addressing the NON Engineered issue of" Crank Runnout" that exists in every crank and the out of "Round- balance "which exists in every clutch. These cannot be engineered into to puzzle and could be described as defects, Were simple minimizing the effects from defects and not altering the engineers vision of resonance of the motor.I believe were on the same page

 

[BBP]

It would be interesting to put it on a track dyno & see if there's a difference with indexing.

 

[7perk]

clutch/motor balance

Everything that rotates has a "Resonance Speed " in which there is a greater unbalance.
When you purchase a Engine Balance Kit I Balance the clutch separately first then place it on my 2010 800 Ski-Doo and set-up the balance machine right on my sled and run it under the power of the sled 2500 rpm (it doesn't matter what rpm as long as it's not the resonance speed rpm). The CRANK ASSY./ CLUTCH/ MAG ROTOR HAVE THE SAME UNBALANCE AMOUNT (115 GRAMS PER SIDE OF MOTOR ON 800R) AND THE SAME ANGLE OF UNBALANCE. I USE THE SAME BALANCE MACHINE ON THE SLED OR ON THE HARD BEARING TABLE. THE RESULTS ARE THE SAME.
THE CENTRIFUGAL FORCE CHANGES WITH RPM CHANGES. THE CENTRIFUGAL FORCE AT 8000 RPM WITH 115 GRAMS OF UNBALANCE IS 922 LBS. 125 REVOLUTIONS PER SECOND. AT IDLE 1400 TO 2000 RPM IT'S MUST LESS BUT YOU HAVE ALL THOSE LOOSE MOVING PARTS, SPARK PLUGS FIRING, EXHAUST PIPES, ETC.
At higher RPM's the loose parts seem to become a round moving assy. With a balanced motor at 2000 to 2200 rpm and up it becomes as smooth as glass (just exhaust movement). The best part is no more crank breakage, less belt breakage, little or no vibration, and the life of the motor. When you question my comments just look at the Polaris sleds there clutches are half the weight and the clutch is balanced to 2 or 3 grams from the factory and yet they are still breaking cranks left and right. I know a high performance shop that purchased the sled of the year 2011 Polaris Pro 700 miles broken crank.
I say this again the run out of the crank is only a small factor in the unbalance. THE MAJOR REASON IS THE UNEQUAL DISTRIBUTION OF MASS IN THE CRANK ASSY. (PISTONS, RODS, ETC.).

 

[BBP]

Perks, have you balanced an 800R bigbore? If so, how many grams off are they?

 

[7perk]

motor/clutch balance

I set-up my balance machine on Kelsey's at RKtek at the end of the season last spring and his two sleds about the same unbalance numbers as the 800R. I just need to get back with him with the new improved mag. rotor for his two sleds.
I need to mention about this clutch indexing on the crank yes, there is a best position and when I balance your primary I mark or vibro-etch that best position for crank alignment. The problem with this is when I set-up the balance machine and when working on either side of the motor there is this thing called cross-affect which means if I remove mass or add mass or rotate the mass to a different angle with the clutch or mag. it changes the unbalance numbers on the other side of motor. Therefore the guessing game only helps a little and just on that side of the motor. My state of the art balance machine tells me how much weight to add and what angle there's no guessing. For example when I balanced the mag. rotor on a 900 cc polaris it increased the clutch unbalance by 20 grams but when the job was complete the numbers ended up the same when I worked on the right angle of unbalance. Call me I will explain. Joe 435-720-3162

 

[hitekbalancing]

What balancing percentage do you use? Can you show us a typical bob weight calculation? Like 60% of reciprocating and 100% of rotating?