Two-stroke performance tuning?

[TZ350]

What balance factor would Thomas suggest?

Its not, what balance factor would Thomas suggest, its your story, what do you suggest. Do you have any idea?

.

[k14]

Yes I do have three or four old cranks lying around in the shed but don't know if I can bring myself to mutilating one. They might come in handy one day

I know what you mean about the inertia, the JHA kit I bought came with another rotor that is about 5 times heavier than the standard one. Beats me if I could feel a difference though. I don't think its soley just a product of peaky engines, it's a combiniation that you get when you have a very high performance water cooled 125 running on unleaded etc. One thing you do need to be careful of is not making a crank too light (specially in a 4 stroke). You will start breaking valves if you make it spin too easily.

[speedpro]

The MB crank wheels are not the same thickness for the full circle. They are thicker opposite the big end pin. So yes they are full circle, and I suspect NOT hollow, but do have an offset weight for counterbalance. TS crank wheels are the same thickness all over but have holes drilled either side of the big end pin. Interestingly they are different sizes and I have seen somewhere that ideally the counterbalance should NOT be directly opposite the big end. Phil Irving makes a point of stressing the opposite.

I know from using my little jig and measuring a few things that it is unwise to assume balance numbers based on appearance. SS90s cut down crank has a large big end pin adding mass which is opposite the counterbalance mass of the crank.

[SS90]

A lot of talk about different physical layouts of crankshafts but still no explanation or formula to explain the "Balance Factor" or how its calculated.

PS. SS90 talk does not equate to knowledge.

I am begining to suspect you don't know what a "Balance Factor" is, how to calculate it or even its purpose and as a hint it has nothing to do with primary compression ratios.

And by way of a reminder.

Just a little thing SS90, A+B=C is an equation a string of numbers added and divided is an arithmetic sum.

Knowing the difference is probably important.

Bahahahahahhah!

I think it's the other way round.



I also suspect that you are just Bucketracer with another log in.

Are you on Prozac? You possibly should be.

Please explain how the volumetric displacement of a crankshaft does not effect the primary compression ratio.

Bahahahahahha!

[SS90]

Yes I do have three or four old cranks lying around in the shed but don't know if I can bring myself to mutilating one. They might come in handy one day

I know what you mean about the inertia, the JHA kit I bought came with another rotor that is about 5 times heavier than the standard one. Beats me if I could feel a difference though. I don't think its soley just a product of peaky engines, it's a combiniation that you get when you have a very high performance water cooled 125 running on unleaded etc. One thing you do need to be careful of is not making a crank too light (specially in a 4 stroke). You will start breaking valves if you make it spin too easily.

I know what you mean about saving cranks. I used to have mine rebuilt (using the old pin an rod, so not really a full rebuild) by using the big end bearing and thrust washer from a TZ250.

I would have to agree that the gains from a heavier crank on a 125 would be "hard to detect" for most of us, but the guys right at the top seem to.

Possibly the biggest advantage would come on the bikes that make 50PS (and have a rider the weight of a small child), as such a crank would resist the tendancy to "spin up" coming out of a corner.

[SS90]

The MB crank wheels are not the same thickness for the full circle. They are thicker opposite the big end pin. So yes they are full circle, and I suspect NOT hollow, but do have an offset weight for counterbalance. TS crank wheels are the same thickness all over but have holes drilled either side of the big end pin. Interestingly they are different sizes and I have seen somewhere that ideally the counterbalance should NOT be directly opposite the big end. Phil Irving makes a point of stressing the opposite.

I know from using my little jig and measuring a few things that it is unwise to assume balance numbers based on appearance. SS90s cut down crank has a large big end pin adding mass which is opposite the counterbalance mass of the crank.

Yea, I agree, I suspect the MB100 wheels are not hollow (due to the balance weight)

As you know speedpro, a single cylinder is impossible to balance correctly, so it seems that is why it is most important to chose a factor that suits it's operating range, opposed to a compromise for the entire rev range.

What was the balance factor you ended up with?

[FastFred]

Bahahahahahhah!

I think it's the other way round.



I also suspect that you are just Bucketracer with another log in.

Are you on Prozac? You possibly should be.

Please explain how the volumetric displacement of a crankshaft does not effect the primary compression ratio.

Bahahahahahha!

Sorry SS90 but there is more than one of us who are begining to think you don't have a clue.

Your confusing the "Balance Factor" the crankshaft has been made with, with its "Physical Shape".

Physical Shape is not the same as Balance Factor.

Physical Shape has a bearing on primary compresion ratio.

Balance Factor has a bearing on how much of the reciprocating weight is counterbalanced.


And they are completetly different things!!!!!


You had better go and suck some more prosac before you get over excited and start running off at the mouth talking rubbish again.

.

[SS90]

Sorry SS90 but there is more than one of us who are begining to think you don't have a clue.

Your confusing the "Balance Factor" the crankshaft has been made with, with its "Physical Shape".

Physical Shape is not the same as Balance Factor.

Physical Shape has a bearing on primary compresion ratio.

Balance Factor has a bearing on how much of the reciprocating weight is counterbalanced.


And they are completetly different things!!!!!


You had better go and suck some more prosac before you get over excited and start running off at the mouth talking rubbish again.

.

Again.....Bahahahahahahahha!

Removing the material from the correct place of a crank does TWO things

1) it changes it's physical shape (and volumetric displacement...physical SIZE)
2) it changes it's balance factor (the factor you get depends on how much you take off, and from where)


Bahahahahahahha!

What are you not understanding?

[SS90]

Its not, what balance factor would Thomas suggest, its your story, what do you suggest. Do you have any idea?

.

Read my post again.

I suggest a ratio there.

[FastFred]

that is why it is most important to chose a factor that suits it's operating range, opposed to a compromise for the entire rev range.

SS90 you still hav'nt explained what a "Balance Factor" is and you promised you would.

[FastFred]

Removing the material from the correct place of a crank does TWO things

1) it changes it's physical shape (and volumetric displacement...physical SIZE)
2) it changes it's balance factor (the factor you get depends on how much you take off, and from where)

What are you not understanding?

Yes changing a cranks shape by say cutting a piece of it will change both its balance factor and the primary compression ratio.

What I can't understand is a mind that can't see the difference between two entirley different properties, I guess your confused by the interrelationship between them. But prosaic does that to you.

I think by now every one understands that several cranks can all have the same balance factor but different physical shapes, no biggie there.

It's changes to the physical shape not balance factor that affects the primary compression ratio.

and you still have not explained the concept of "Balance Factor". Are you sure you know what your talking about.

[SS90]

SS90 you still hav'nt explained what a "Balance Factor" is and you promised you would.

Bahahahahahahahha!

Have you even read (and understood) the posts here in the last week?

That has already been established.

Start at the beginning.

It's all there.

[SS90]

Yes changing a cranks shape by say cutting a piece of it will change both its balance factor and the primary compresion ratio.


I think by now every one understands that several cranks can all have the same balance factor but different physical shapes, no biggie there.

It's changes to the phsical shape not ballance factor that affects the primary compresion ratio.

and you still have not explaind the concept of "Balance Factor". Are you sure you know what your talking about.

hahahahaha,

The first sentence suggests you are understanding it, you just get confused after that.

Your getting yourself confused now.

hahahahahaha,

You can change one thing (physical shape....which by the way....changes it's volumetric displacement) and that also changes it's balance factor, it just depends on where you remove (or perhaps add) the material.

What part of that are you not getting?

[FastFred]

As I said your a confused boy. Sorry SS90 up untill your latest ramblings I thought you might have something to offer about "modern" thoughts on balance factors but you can't even explain what a "Balance Factor" is.

.

[SS90]

As I said your a confused boy. Sorry SS90 up untill your latest ramblings I thought you might have something to offer about "modern" thoughts on balance factors but you can't even explain what a "Balance Factor" is.

.

Geee,

You havn't been following there have you?

I will write this REALLY SIMPLY.

Crankshaft balancing is simply the term used to describe changes made in the counterweights (webs) of the crankshaft to compensate for the weight of the moving components including the crankshaft,rod,piston,rings,gudgeon pin,clips.

The "factor" is simply a way of expressing this "counter weight" on the crank
compared to the weight of the piston rods assembly.

i.e the piston/rod assembly weighs this percentage of the crankwebs (counterweights)

What weight you chose (primarily) dictates what RPM the engine is best "balanced"