Two-stroke performance tuning?

[bucketracer]

Oooops Fastboris there is a spelling mistake in your name!

Now if your going to bring a knife to a gun fight, at least have the brains to make sure its sharp first!

Sharpen up Boris

[F5 Dave]

so the crankwebs are heaver so the answer is B

thanks SS90

piston rod = 25% of crankwebs (counterweights)

The difference in weight of the crankwebs, if it was just the crankweb then it could be a consistent weight all the way around, it would rotate at any speed & as long as the piston & rod were weightless there would be no issue.

And for the love of Elizabeth, will people stop spelling You're as Your (well I've got to score points somewhere in this game don't I?)

[bucketracer]

The difference in weight of the crankwebs, if it was just the crankweb then it could be a consistent weight all the way around, it would rotate at any speed & as long as the piston & rod were weightless there would be no issue.

And for the love of Elizabeth, will people stop spelling You're as Your (well I've got to score points somewhere in this game don't I?)

"Respect" F5 Dave "Respect" an honest effort, a great interpretation, of someone else's crap but even better it's so so true, you're the first to score points. 3 points for spouting crap, 7 points for creativity and imagination, 12 points for knowing its crap yourself and double extra bonus points because the crap is also true and 3 points for teaching us something worthwhile (ie. stop spelling You're as Your). What a score from just two sentences, very impressed I am.

[speedpro]

It seems that most people are finding it too cold to do anything constructive.

[Buckets4Me]

It seems that most people are finding it too cold to do anything constructive.

tripple points for that

minus twice that again for not turning up sunday

[SS90]

Sigh.

While I am finding it hard to even respond to your nonsense Bucket racer (I feel that this only encourages you) I will exapain AGAIN

First though, I have No idea who Fastorrisracer is.

You will notice his post was at 14:23 (that's 2:23PM NZ time)

Erm....that's 4:23 AM where I live...... I had been asleep for about 6 hours at that point.

I assure you I am above the kind of childish nonsense you are demonstrating.

"a modern approach to balance factors"

Ok, (again)

What is "high RPM?" 40 years ago, maybe it was 7,000 RPM, now, a tuned 125cc aircooled two stroke engine will spin to 12,000 RPM

So, on this basis alone, if a balance factor of 65% was applicable for an engine (spinning to 7,000 RPM that is), what would the factor be for an engine spinning to 12,000 RPM?

We have already established that the higher an engine spins, the lower the %age needs to be

I am sure you are unaware what the balance factor is of a 125GP bike......

it's 52%

The accepted balance factor for a modern 125cc 2 stroke, revving to 12,000 (or higher is 52%)

all the nonsense you are reading off the internet is for "general commuter items)

Tuning for speed was (thanks Kickaha) written in 1945.

RPM limits have moved on a bit since then.

You are not really folowing what I am saying, you just try to find fault with it, because you don't truly follow it and understand it.

I have been a motorcycle mechanic for 15 years.

I have a good understanding of this.

With regard to primary compression ratios having an effect on what balance factor you chose.....what do you not understand about that?

I have (several times) explained the theory of pumping losses (when the crankcase volumes are too small)

If you increase the crankcase volume, the engine operates at a higher RPM, therefore, you need to have a lower balance factor (that if the engine was operating at a lower RPM)

What is so hard to understand?

[bucketracer]

I have been a motorcycle mechanic for 15 years.

I have a good understanding of this.

So you say SS90 but it's just Talk Talk Talk

So once again, when a balance factor is greater than 50% which is heaver, (A) the reciprocating weight of the rod piston assembly or (B) the counter weight of the crankshaft.

(A) or (B) SS90

Its the crux of the whole thing and realy simple.

And SS90 although I admire the effort you have been putting into keeping up the pretence of knowing something.

If you can't say (A) or (B) and get it right you know jack shit!

Its such a simple question, like "is a spark plug a left or right hand thread". Something a motorcycle mechanic thats been in the trade 15 years and has the understanding of "Balance Factors" that he claims, should be able to answer easy piesy.

.

[Skunk]

Someone just answer the fucking question so I can learn something instead of this mindless one-up-man-shit!

[bucketracer]

Yes answer the question SS90.

[TZ350]

Sorry if I am stealing someones thunder but:-

The answer is (A) as the counter weight only counters a % of the reciprocating weight and is lighter than the reciprocating portion of the rod/piston assembly.

Yes, the counter weight portion of the crankshaft is the lighter of the two.

As an example, a balance factor of 65% means that the counter-weight portion of the crankshaft counter weighs only 65% of the reciprocating mass of the rod/piston assembly.

The Balance Factor could be anything, 25% 48% 50..............65%......85% whatever you chose/works for that engine/frame/rev's/and everything else combo.

The counter weight portion of the crank may or may-not necessarily be dead opposite the bigend.

Interestingly Phill Irving suggests a balance factor of 66% as a good place to start and the 2009 Kawasaki KX250F and KX450F (4-Stroke) Motocrossers both have Balance factors of 60%.

2009 KX250F
Engine Displacement: 249cc
Max Horsepower: 32.8 HP @ 12,200 rpm
Max Torque: 17.2 lb-ft @ 8400 rpm


Remember you heard it from TZ350 first.

.

[Buckets4Me]

all the nonsense you are reading off the internet is for "general commuter items)



thats what i thought we where using to build our buckets
not 14000 rpm rs125 hondas or Aprillia gp bikes

[k14]

all the nonsense you are reading off the internet is for "general commuter items)



thats what i thought we where using to build our buckets
not 14000 rpm rs125 hondas or Aprillia gp bikes

No what everyone is doing is taking a "general commuter item" and trying to turn it into a 14000rpm honda or aprilia gp bike. So taking the tuning data from one of those and applying it to what we have is the already proven method. Of course there are compromises but those bikes are the benchmark and by copying as many aspects of them as possible everyone hopes to end up with a fast bike!!

[FastFred]

No what everyone is doing is taking a "general commuter item" and trying to turn it into a 14000rpm honda or aprilia gp bike.

Very much like picking up an ugly one then! and drinking enough piss untill they look good. SS90 I've got the money honey if you got the time! I'm not fussy. you know you would like it, don't you! and wear that little black number I saw you in last week.

[F5 Dave]

"Respect" F5 Dave "Respect" an honest effort, a great interpretation, of someone else's crap but even better it's so so true, you're the first to score points. 3 points for spouting crap, 7 points for creativity and imagination, 12 points for knowing its crap yourself and double extra bonus points because the crap is also true and 3 points for teaching us something worthwhile (ie. stop spelling You're as Your). What a score from just two sentences, very impressed I am.

What? No rep bling awarded?

sheesh I need to get a more fanatical following that will do my bidding.

Perhaps overthrow a building tenancy committee in a hostile take over. Then Austria.

[F5 Dave]

Someone just answer the fucking question so I can learn something instead of this mindless one-up-man-shit!

I've just worked it out. SS90 = Winston Peters.

Well think about it; - can't answer a straight question in anything other than "I've already answered that question" or dodging around it with another supposition.

I mean it makes sense, he turned up at about the same time, cagey about his identity. . . Well?

I hope you've given that ministerial car back buddy!