CRANKSHAFT BALANCING MADE EASY | Finding Crankshaft Balance Factor | 2 STROKE TUNING
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- Опубліковано 21 сер 2024
- The wrong balance factor can cause annoying and damaging vibration in your bike. Balancing your crank to a different factor may be needed. In this video I explain what the crankshaft balance factor is, I show you how to find it, and I show you a super easy cheap way of making a crankshaft balancing stand.
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I recently made modifications to my 250 two-stroke. I added a slightly heavier piston, a larger crank pin and longer heavier rod. I also filled the balance holes with JB Weld. After getting it running I noticed at about 7000 rpm I was getting a bad vibration. I went back and checked Balance factor and it was 31. I then removed the JB Weld from the balance holes, that got the balance factor up to 38%. Evidently, JB Weld is fairly heavy. I could’ve tried it again to see if it was better, but I decided to add weights and get the factor up in the 50s. I added about 3 ounces of tungsten and it is now 55%. Will put it back together in next two days and see how it does.
Update, With my balance factor up to 55% there is much improvement. There is still vibration of course, but it’s better than it’s ever been. By the way, I used JB Weld to fix the weights in the crankshaft. So far so good.
Found myself back here and I wanna say I really like the concept of these little how-to videos! Consider mentioning them in your newer bigger videos every now and again, this is good knowledge!
I would like to add something to your informative video. Checking your balance factor with the parts that were working well together is a great place to start. Thanks for sharing your knowledge.
+Jim Marriott Thanks, good advice!
I really enjoy the do it yourself concept. You really are helping provide basic tools and concepts for us to take our 2 strokes to the next level. Keep up the great work!
+NicGyver Thanks! DIY is the way to go!
you form
Calculation made simple// First load the crankshaft to find the weight for static balance.// 50-60 % of that weight is going to be be the weight of the piston + pin for minimum vibrations. Thanks 2STROKE STUFFING !
Thanks for explaining👍
Actually you have it backwards I believe....50-60% of the Total weight will equal the static balance weight.
I may be dumb or somethjng but how do you apply that math to the actual balancing of the crank? What do you do when reassembling it to adjust the balance??
@@DrCHAOSBTW you figure this out?
ive known about balancing but never knew there was even math involved, you just earned a subscribe, well done.
Thank you sir for explaining the math in such an easy to understand manner. Greeting from Bharata - India.
been messing around for 2 hours thinking i could figure it out bit apparently not! thanks for giving us the sweet spots.. im gonna give this a try 2moro again and hopefully get the crank back in asap-
Absolutely excellent! Concise, clear well produced video! You answered more questions in 5 minutes than an hours worth of googling...
Thanks man!
I didn't upgrade to a big bore just a window so I gotta go the other way but this was what I needed to see 💯
Whilst this upload was of short duration, ( 5 minutes ) the subject matter is covered reasonably well, although it raises more questions than answers, which can be noted from the responses in the comments below.
However, the definitive book on tuning single, multi, parallel , opposed piston, and split single engines , whether two stroke or four stroke, is contained in the 1949 publication by Phil Irving, called " Tuning for Speed " .
This book is the Bible for tuning engines to maximum performance. Amazon sell it for a small sum, and it is still the best book for the home tuning person, without doubt.
you are the best/pro 2 stroke guy in the world!
Awesome video. I learned so much from watching your videos. Am in the process of installing a wiseco piston on my wife's yz250f 2013 and didn't think of the extra mass involved. Will be sure to tell the guys who is pressing the new crank and nikasil plating the sleeve to make sure they balance the crank with the new heavier piston. Thank you
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I did a big bore kit on a Husqvarna Chainsaw, but the new piston was lighter by about an ounce. It worked Ok. Not yet run-in, but it seems to be more powerful.
This is great , thanks for your time , when will we see the "tuning the crankshaft" to accept a heavier piston eg: big bore kit. You mentioned knife edging the sides .. good or bad ... what about polishing ... good or bad idea ... thanks again , Greg
I want to go for as little vibration as possible with 30cc 2-stroke single cylinder engines running 10,000 rpm to 13,000 rpm. (for RC helicopters, which are sensitive to engine vibration).
IMO, you should include the application of the "balance factor" in this vid, because your viewers are still in their shop with a crank on parallel bars.
+EarthSurferUSA My recent video where I rebalance the Spx crank could help, I'll put a link in the video. Thanks!
That is awesome. I also fly gasser helis and I'm looking into this as well since BH Hanson and Toxic Al wont be modifying engines forever.
Thank you for showing this, simplest explanations are always best. would you be able to hand the entire assembly with the piston and all the other recip parts and verify final modifications before you put it back? cant hurt to check.
Bro, I done r&r my 250cc at home.now I wish I would of seen this vid. First..saved a ton of money with a Big hammer &finess
Very well constructed explanation and video. Thank you.
I think your math calculation is incorrect. You use the partial weight of the connecting rod twice, (26.65 + 32.26 = 58.91) and also for the total reciprocating weight of 108 (26.65 + mass of piston/ring/pin/circlip). There is no reason to have the 26.65 gm in both top and bottom numbers of your equation. (58.91/108) Your equation could be 32.26/81.35 = .3965 or 39.65%. You are not taking into consideration the rotating mass with added flywheel and timing gear weight. I think if you want to static balance it, you have to figure out the counter weight of the crank without the connecting rod attached but with the fly wheel and timing gear mounted. You could use your hook method and add washers and weigh that mass. Then if you were trying to achieve a zero balance, then ideally you would want your piston/rings/pin/circlips/bearings/con rod to weigh the same as the counter weight of the crank. I think this is why balancing a rotating assembly requires metal added to the counter weights a lot of time. My 2 cents.
The rod has a upper end weight & a lower end weight. Weighing the upper end weight twice does not give the total weight of the rod. You also did not include the big end bearings. I balanced engines dynamic (spin balance) for years in a racing auto machine shop. The crank need to be taken apart & the rods upper & lower end weight weighed separate along with the lower bearing. The crank pressed back together & a bobweight made with the 55% upper weight added. Then balanced . When balanced Reassemble the crank. I know its more work but it will be much closer.
Good Video
i am going to try on my Briggs /stratton 250cc snow engine rebuild
+Joni English Thanks!
Hey guys, just got my new small bore kit in the mail! Can't wait to see how it runs.
coolest youtube channel ever!!! I know the channel is called 2stroke stuffing but do you by any chance have any tips and tricks for 4 stroke motors please
+Tristan Truebody Thanks! Sorry, I'm not much of a foul stroke guy 😁
Alex help me out...im back and forth with a pretty knowledgable guy bit he says u do this wrong..same way I do it. You counted the con rod in the recip mass than you added to the bobweight the con rod to get the full hang weight. Tgis hang weight is then calculated in% of the total reciprocating weight.He swears you are doing it wrong and Connor use the conrod twice ...please clear this up as I am referring him to this video
I'm not quite sure what part he's disagreeing with?
2STROKE STUFFING anyway I'd does not make sense...he says no using the small end of rod twice in the equation. It has to be added to recip mass as it is part of it. But then it hangs as u get static balance so it is added to the bob weight to get the full hang weight.he thinks you should only divide the bobweight into the recip mass not add the rod and use the full hang weight.
how would you go about doing the actual adjustment during reassembly??
Instablaster...
very good way of explaining
+Sveno Mick Thanks!
After I get my ballance factor what do I do next ? I didn't have to add any hung weight, does that mean my assembly is ballanced ? Thank You Very much ! I really like your video.
it helped me a lot thank you for sharing
I am your subsciber from indonesia. Thank's for giving me info. I want to ask if the standart motor manufacturer also apply 55%?
Is that count only for tune up machines only?
Thank'$
Thanks for subscribing! Manufacturers use various factors depending on engine orientation, frame design etc.
I dont your speaking.i dont speaking inglis
Dia bagi tahu, berdasarkan keadaan bentuk engin motor.
ha'a
Hi brothere nice to know your knowledge
I just have question about four stroke crankshaft balance factor is it same or different if different please make the video for fourstroke.
Thanks
Regards,
Your followers
Thanks! Same concept for 4t!
Thanks for the big tips
Nice video sir
waiting for the next video of this sir,,
+pepito roaquin It's coming. Lots of stuff on my plate atm.
dude, get a dialing gauge, no paper no black markers, just straight method of zero-ing a crank.
Didnt you read the title bro?
Great video, thank you! I have been trying to find whatever balancing factor i would need for a pitbike 4-stroke super motard. Has horizontal 1cyl engine 62mm stroke and 10-12k rpm. What factor would you go for here?
55% -/+
Awesome thanks that was really educational 👍🏻
informative, thanks dude from PH.
How many % for horizontal engine ?
Enjoyed video very much
+Doug Doty Thanks!
Very nice cleaned up version
+derk nobit Thanks! Btw, do you prefer being credited for your GENEROUS donation with "derk nobit" or real name? Nice to know when the kit arrives and I'm making the project unveiling video.
2STROKE STUFFING real name is fine
+derk nobit Cool!
setel kiringsaf paling mudah
I used a hammer and socket to rebuild my dt 175 rod and
You can explain to me for 4 stroke : if piston and conrod is heavier than crankshaft that make more torque or more RPM ? And with 4 stroke how i should do them when my bike has the fastest speed from 0m to 200m? Thank u so much
excellent simple way tob find your Balance factor. Is there any way to change it? I need c. half the piston weight to get the BF I need.
Hi I have seen and enjoyed many of your videos I especially liked your nitrometh moped. I was wondering if you're looking for power why don't you use efi. I have seen some efi kits that can even do duel fuel injection so you can vary the amount of nitro to methane. The company I found that looked best was ecotrons small engine efi. Thank you and keep up the good work.
+Karelin James I might look into that! EFI on high power, high rpm 2 strokes are extremely difficult to get right when running gasoline. Methanol/nitro is far less picky about afr qnd should be much easier.
+Karelin James ...and Thanks!
2STROKE STUFFING Thanks I also believe that the kit above can control the ignition timing as well. I have been looking at this kit for a while but have lacked the time and funds to pull the trigger (about $600) and I would love to see somone talented like you to try it first. Thanks for looking into it again its called ecotrons small engine efi kit.
Thanks, good explanation 👍☺️
Good stuffing i have a ? Will an increase in stroke , compression and bang cause the B.F. required to change ? Mine seems to be going up which tells me to remove weight from the piston .
U da best mannn!!
+David Chapman Thanks!
Hi From denmark.
Thanks for all the good vidios.
Some say that 50% balancing factor is the right amount??
I tune my own 23cc 2 stroke engines (Zenoah), I make the conrod and pistons lighter and the piston-pin, then I will have to remove material from the counterweights, right??
If I want the most RPM's out of the engines, what factor would be the best for that?
Or the smoothest running?
The engines are used in 1/5 scale TouringCar Race, the cylinder are sitting at about 45dg angel.
Hope you will comment this.
Thanks
Ole
This video is 3 years old, and I have the same scale!!
Hello, I am Felipe, I am a follower of your page, I have learned a lot about 2-stroke bicycle engines, I have a ZEDA YD100 50mm, my engine reaches 8000rpm, I corrected the balance factor of the crankshaft to 52.5% but I still have vibration from 6500 Rpm. The question I have? Do I raise the factor to 55%? What do you think? Thank you Felipe
Cristal clear 👍
Thank's for giving me info,,,informative, thank
so to make the balance factor can use two alternatives whether it can do drilling on the crankshaft and enlarge the piston diameter .. is it like that? Sorry, my English is bad
+Galih Putra GPS Racing To change the balance factor you need to either add/remove weight from the big end half or counterweight half of the crankshaft. Drill or grind to remove weight, add heavy metal(tungsten/Mallory) to add weight.
2STROKE STUFFING
thanks, I'm looking forward to the continuation of this video, you're the best
+Galih Putra GPS Racing Thanks!
Galih Putra GPS Racing ok baik megikuti berminat
may i ask more, such a balance is to let the crankshaft rotate at any rpm so that it is balanced when operating
Keep it up!
Great. But I want to know how it works. I mean how adding weight keep it still.
The counterweight on the crankshaft is meant to balance out the weight of the reciprocating mass (piston, connecting rod, etc). He kept adding weight until the weight hanging from the connecting rod is equal to the weight of the crankshaft counterweight so that no matter the rotation of the crankshaft the weight is equal. Check out "balanced rotating assembly" to learn more about what all is involved.
Would you have a suggestion for a balance factor on a yz490 engine? I'm starting an atv build using one, and I'd like as little vibration as possible.
In terms of engine performance, what is the difference between an unbalanced internals vs a balanced engine internals on a dyno? 🤔
Interesting question, never seen much research on the subject.
Vibration is lost energy get rid of vibratiion,,,,and
50% will balance for idle. Higher like 70% will balance for high RPM. You are converting up/down primary imbalance to fore/aft secondary imbalance.
hola una pregunta, para una scooter horizontal 90cc cual seria % Balance correcto para que vibre
Nice Video Dude!
But Can you Clear to me what hang weight means? weight to be added to obtain 55% balance factor, is that right?
It's the weight you hang from the conrod to find your balance factor.
Oh! Now i know thanks!
Do you have email or fb dude i have some questions regarding to modification. Can you help me out!
2strokestuffing@gmail.com
2STROKE STUFFING
Ok Bro! Thanks
Hi..tq for explanation..can i use this calculation for motorcycle that have a counter weight balancer?
How can we use the calculated balance factor? What is the wrong balance factor? If we get 55% balance factor, what is the next step? Do I need to take 55% weight off the crankshaft? Or add 45% more weight?
im sorry but thats where i was left at the end of video to.... i would think that 58 grams is what you want on the upper half.. so drill 50 grams out of the flywheels above the conrod?????? 108[stock weight]-58 [new balanced weight]=50 [desired removal amount?]
can you confirm this 2 stroke..im in canada here and its research and development season.. i got into this last summer and scratched up 3 cylinders.. i hate breakdowns and want to prolong and prosper instead of gouging them to death now
very good and obvious question. im so glad you exist and that we think alike.. no else asked this..were obviouslyvery dumb. or damn brilliant. or just awkwardly different.
Would the goal ever be to get to 100% balance factor? Wouldn't that mean the crankshaft was perfectly balanced with piston installed?
No, and static balance of 0 to things moving in different directions means little to vibration, this is why this is so hard. Now if you can connect the crank to a wheel dynamic balancer, and make it spin at the range you notice the worst vibration, you may get an accurate position to center a counter-weight.
Vibrations have a frequency, an amplitude (this directly relates to the weight off balance), and a vector (direction). The bottom of the rod moves along the stroke axis and vertically to it, and so does the crankpin, but not all of it, different parts of the rod move differently in oval kind of shapes, the part around the piston pin only moves along the stroke axis, and so does the wrist bearing, piston and rings.
Also, because the acceleration on a detonation stroke is much larger than the de/ac/celeration on the compression stroke, the vibration caused vertical to the stroke axis is not symmetrical on both sides. And it is the acceleration (+/-) of the counterweight that causes vibration, it is never 180/360' kind of counterweight. This then always causes the tdc/bdc to be asymmetrical as well.
This is why even a parallel twin 2 stroke will vibrate no matter what, or an opposing twin, etc.
Dynamic balancing is a science, and at some point the designer says enough, this is as good as it ever going to get.
Vibration itself is a wasted energy that also prevents the engine from revving faster without exploding, is also requires heavier bracing in the cases, but the final factor is how annoying the vibration is to the user of the machine. If a chainsaw rattles your arms out of their sockets you are not going to work as long, or ride as long. The funny thing is that we have some vibration that feels good and some that feels very annoying. You can ride a HD twin for 10hr straight, and you can ride an L4 and be numb in 2hrs. You put rubber mounts on one engine and they last a century, you put the same in a similar engine and they fall apart in crumbs at no time.
If you don't like vibrations don't ride a big bore single. A Suzuki GT750 had less vibration than an RE5 ... go figure!
Maybe I missed something simple, but didn't you effectively only weigh (about) half of the ConRod?? Isn't its contribution to the reciprocating mass about double what you would measure on the scale with that method?
It's just an estimate weighing it like that, but it gets you close. It's complicated cause the closer you get to the big end the more it's contributing to rotational mass vs reciprocating. As there's nothing like the "right" balance factor it doesn't really matter if the number you end up with is say 5% off what it would've been if you did the math as long as it works.
2STROKE STUFFING ok that actually makes a lot of sense, I never considered the fact that not all of the Conrod contributes to reciprocating motion... Weighing the whole conrod would cause you to be on the heavy side, then??
Totally understandable. Yep it would
Thanks buddy
What if i want a big result for the balance factor? Should i add weigth or reduce? Thank you
Add.
I weigh the conrod directly weighing 90gram but if weigh according to your way then the result 30gram.
this is a different result
What do you think?
"my way" will give you the approximate weight of the reciprocating part of it, that's why.
If we have number of balance static from your lesson, what can we use to that number (%) for engine??
Why was the Connecting rod included twice ? Once on it's own and as the group with piston/Pin/Rings ?
Cause you need to know the total reciprocating mass and just the conrod weight for the calculation.
Makes sense to me!
Why not split the crank to weigh the individual components accurately then reassemble to balance?
How do you balance a single cylinder engine with a separate balancing shaft?
+1 For this. Have you gotten any answers for this?
How would you go about measuring a counterbalance shaft? On the crankshaft the connecting rod is already at the right radius but the counterbalance shaft has no point to hang the weights from.
+Sketch1994 One way is to just calculate it, since it has no reciprocating mass it shouldn't be too difficult.
Typically it is indeed the same as the calculated mass at the crankshaft. Though I have fitted an aftermarket rod, I don't have the stock piston(I have never even seen one), and my only constant is the balance shaft which I can't measure! I have some pics of how I tried to measure it but it was very inaccurate due to all the crap that were involved.
Can you show us. Thanks for the videos
Actually the "balance factor" method was designed for 90 degree V8 engines- CARS! It's not a good method for motorcycle engines.. Only a good computer program can figure out the correct balance. go to www.dragonfly75.com/motorbike/vibes.html to read all about CORRECT crank balancing.
Can you do a video showing how to achieve a BF,ie you've found the BF is say 50%,but it should be 60%.
When just replacing the crankshaft bearings do you need to do this?
Nope!
2STROKE STUFFING thank you
The engine and all rotating masses should be dynamically balance, considering that there are compression and power strokes cycle to be balanced altogether. Peace!
I am still puzzled why the magneto ang other materials of the crankshaft isn't included while trying to balance the crankshaft. Are those mentioned not a part of the rotation of the shaft? Magneto isn't actually balanced and it act as a nominal counter to the shaft itself? Just asking.
@@MCircuits yeah, like the clutch! That thing isn't balanced and spins with the whole thing.
Guess the clutch gets balanced by itself.
I have a doubt, the hang weight is the weight that You put on the craftshaft to balance? With tugsten
Mine just goes straight down on the rod end ,, no weights. So adding weight wont do it should i assume i have to remove weight and or add to counterweight?
So if I measured my balance factor to be 54 percent, that means Im ok in balance and no weight has to be removed from crankshaft? Engine is 1 cylinder long stroke 45 degree engine.
Question. Will it hurt to drill balance holes below the center of "meat" on a motorized bike crank more towards the center? I have a theory I'm working on. Comments?
sir u have video how to add weight to to crank or remove weight to the crank to make it balance? 0.55 is the weight that u will add?
+pepito roaquin I'll be making one when I rebalance the new Spx crank. You basically add/remove weight to get to the desired number like 0.55
2STROKE STUFFING yes pls i really want to learn and u teach me a lot,, for now i know how to get the formula,,, but then what shoud i do with that,,
That diesel heater you use when it's cold. How pricey is it to use ?
Why does it have knife edged cheeks? Weight reduction or it is how it is?
75% for a ktm 300 exc two stroke is good? the motor is probably about 30 degrees away from the cylinder being pointed straight forward. i've got 295/395 which gives 0.746... so about a 75%; i am going to assemble it like this anyway, but i am curious if it's an ok number.
I have question...if piston 54mm how about head or squid bank..cut 2mm 41diememter and 13degre is better for piston 54mm 2stroke model kawasaki leo star
what does it mean if my rod is heavier then the balance weight though i didnt want to remove my crank bearings
that was good .. it was Lillehammer dialekt right? or Hemsedal?? Or even Baito .. maby Geilo accent? :D .. Greet from Aarhus
my crankshaft goes conrod down without any weight. what should i do?
+Olli Hakkarainen That was the case with my Doppler Endurance crank too. Haven't checked the ER1 yet, but I suspect it's the same. Hopeless... Depending on conrod weight your balance factor is probably under 20%, to raise it you must either remove material from the big end side, add heavy metal(tungsten, "Mallory") to the counterweight side, or a combination of both.
The calculations can be use on crankshaft balance on 4 stroke motorbike?
How many % is the ideal balance factor for a crankshaft.
+farhan hafiz impossible to say, depends on alot of different factors.
can I ask about the balance factor, I have a motorbike with a separate balancer, I want to remove the balancer and move the drop point of my crankshaft by adding weights to the crankshaft, can you tell me how to do it but not cause or reduce the vibration effect, because I have plans to added 4 weight points to increase torque and changed the crankshaft drop point to 5°-3° before the highest point of the crankshaft, thank you
What do I do if my crankshaft stays in position without any hung weight? Im working on the 66cc mb engine trying to balance my crankshaft. Also I can’t tell if it is really staying in position or if there is too much friction between the bars and the crankshaft, so I might try to use some bearings instead or the metal bars.
Then you do the same calculation with "0" as the hung weight.
Okay that's what I thought. So I guess that means I need to lighten the side of the crankshaft that the conrod is on so that I can hang more weight and increase my balance factor?
Yep!
The elbow is located at 12 o'clock so it's at 3 o'clock, can we apply this method?
i want to ask you, is balancing machine horizontal with vertical it different, if different what is the difference?
please reply for me,
thank you sir
Horizontal is typically 50%, every setup is different and there's impossible to say anything more specific, sorry.
2STROKE STUFFING
thank you very much sir
Is it same concept for the secondary balancer type motorcycle?
Thanks sir
Thanks 😊🙏
Why not lighten the piston??? Isn't that easier?
While scaling the con rod, you essencially have 2 reaction forces to one wheight. The scale only gives you one of the reaction forces, the other one is aplied to the crankshaft. IMO the weight of the con rod is twice the value of the scale. Great work tho!
Thanks! By weighing half of it you get the approximate mass of the reciprocating "part" of the rod.
you mean all this time they've been weighing trucks WRONG