Street Stock 250cc 4-stroke twins

[woodyracer]

What the Fuck?

Please explain this to me.

How the hell can having a 6th gear make a bike faster?

Its hard to explain to special people.

[huff3r]

Its hard to explain to special people.

It's not hard to explain. Seriously, because its wrong. Having an extra gear does not make anything faster.

The Hyosung is slower, not because it is a 5-speed, but because it is slower! Less power/more weight.

[SS90]

Its hard to explain to special people.

Have a go.

Explain why having a sixth gear would make a bike faster.

I think it is about time we dispelled a few myths (although I think we touched on this subject in the original "birth of a monster" thread... (oh sweet sweet memories)

[woodyracer]

Have a go.

Explain why having a sixth gear would make a bike faster.

I think it is about time we dispelled a few myths (although I think we touched on this subject in the original "birth of a monster" thread... (oh sweet sweet memories)

ok, because the gears are move divied out, jsut one question,

Why would manufacturers bother "wasting" all that money,time and weight to add a gear that does nothing????

There's obviously a reason for adding a sixth gear, otherwise it wouldnt be on bikes.

[SS90]

ok, because the gears are move divied out, jsut one question,

Why would manufacturers bother "wasting" all that money,time and weight to add a gear that does nothing????

There's obviously a reason for adding a sixth gear, otherwise it wouldnt be on bikes.

An amigious answer if ever I have seen one.

Well, in the interests of not confusing the issue, I will simplify things.

Manufacturers select available gear ratios (and amount of ratios, by that I mean (normally 5 or 6, but Cagiva did make a production 125cc 2 stroke with 7 gears) not solely on cost, but rather on "intended purpose"

Important concept here.

If you have an engine (air cooled v twin 4 stroke, like, say a Hyosung 250) that is designed to be easy to ride, economical and reliable (read LEARNER bike), then things like camshaft profile and cylinder compression, valve size are all set to deliver maximum torque and power in a linear fashion, lower in the rev range.

Therefore, you simply do not need 6 closely spaced gears (like, say a 4 cylinder 250, or even a 250cc two stroke, due to the fact that the power characteristics of the engine allow the power to come in the lower RPM's, and hold a long flat torque curve.

Making the bike easier to ride.

The fact that a 150cc two stroke has 6 six gears does not make it faster.

The reason is that a two stroke delivers a higher BMEP (break mean effective pressure) than a four stroke.

6 gears makes it easier to "keep in the power" (as a two stroke with high exhaust port time areas and coupled with high cylinder blowdown times, as a ss150 is) because the characteristic of such engines is a (very) narrow power band.

That said, there are plenty of 2 stroke tuners that can make similar power to a ss150 with engines that have 4 or 5 gears.

Ergo, 6 gears do not make a bike faster.

Let's see what this leads on to!

[woodyracer]

The fact that a 150cc two stroke has 6 six gears does not make it faster.

The reason is that a two stroke delivers a higher BMEP (break mean effective pressure) than a four stroke.

6 gears makes it easier to "keep in the power" (as a two stroke with high exhaust port time areas and coupled with high cylinder blowdown times, as a ss150 is) because the characteristic of such engines is a (very) narrow power band.

That said, there are plenty of 2 stroke tuners that can make similar power to a ss150 with engines that have 4 or 5 gears.

Ergo, 6 gears do not make a bike faster.

Let's see what this leads on to![/QUOTE]


It leads to this hahahha

After reading that i guess your right, ive just been looking at it wrong, but at the end of the day the ss150 bikes still have a better top speed.

Thanks for getting rid of my bullshit theories

-Max

[gatch]

6 gears does not make a bike faster, but funnily enough all the fastest bikes have 6 gears, simply to keep the engine in the rev range where it makes the most power I guess.

Unless a bike is tuned to deliver its power at high rpm (as ss90 said mentioning BMEP) then 6, 5 or even 4 gears may not be necessary..

[sil3nt]

My GPX has 6 gears. Top speed is acheived in 5th. 6th is for cruising.

[chaos rider]

the hyo has the power for a sixth but it would be as nesessery as rossi using nos

[ajturbo]

My GPX has 6 gears. Top speed is acheived in 5th. 6th is for cruising.

very much like the shitter i took for a test ride up in Auckland..

1580cc Vtwin shitter.....
newest shitter out there... and for good measure, it had 6 gears..

well, thinking to myself... with all that cc under me, 6th gear would be fine on the M/W of Auckland.......

FAIL....!!!!!!!!!!!!

it did NOT have the power!!! put it into top and it would SLOW down...it could not hold a steady speed.... so (being a KBer) i thought if i go faster then put it into 6th.. so i tried

120k... FAIL (slowed)
130k....Fail..(slowed)
140k...... hmmm... now it seamed ...Oh..no it slowed...
well i was going to try a bit faster, but there was a corner coming up and as they do not like going around corners (THIS model)... i had to slow (yeah i put it into top... hahahahahahah

but it was a big fail... that extra gear was not worth it (on THIS bike)

[SS90]

My GPX has 6 gears. Top speed is acheived in 5th. 6th is for cruising.

Interesting!

Try this. Either put a larger (3 teeth more) sprocket on the rear, or a smaller (1 tooth smaller) sprocket on the front.

It may well increase the top speed in 6th.

Of course it will increase the revs as well, but that is the idea!

[ducatilover]

SS90 - Nail, head and hammer. I like your example of BMEP, not many buggers know about this
Chaos, I doubt your bike would push another higher ratio, it has 5 gears already and would struggle to push past peak power in 5th. All the Hyo's I've ridden can't push to the limit of the gearing, because, hyosung compromised with the ratios to make a nice balance between cruising at given speeds and the amount of effort it takes to do so.
Like any 5.7 holden with the 6 speed manual, the 6th was very very over geared for the sake of high speed cruising and feul economy, a VY SV8 would pull 254km/h in 5th gear [redline @ 5500] and when in 6th would be pulling 236km/h at 3400rpm, which was as fast as it would go. [Australian test]

Keep thrashing the hyo Chaos.

[chaos rider]

i run my hyo past its peak power and into the redline in 5th just as fast as i do in 3rd so i dont see what your on about.

ill not even be half way down the straight at puki and im in 5th climbing 10.5rpm and wanting to shift to 6th BUT I GOT NO 6TH.

so maby hyo have a consistancy issue with their power output with the factry line

ive also riddin other hyos and a few have not got the same pull as mine did.

form what i gather the pre 09 models had lots of consistancy issues beetween the same model line

[woodyracer]

i run my hyo past its peak power and into the redline in 5th just as fast as i do in 3rd so i dont see what your on about.

ill not even be half way down the straight at puki and im in 5th climbing 10.5rpm and wanting to shift to 6th BUT I GOT NO 6TH.

so maby hyo have a consistancy issue with their power output with the factry line

ive also riddin other hyos and a few have not got the same pull as mine did.

form what i gather the pre 09 models had lots of consistancy issues beetween the same model line

Ken said to me, even the new 2010 model's power ranges from 27-30HP.....
A sixth would be good on the hyosungs, maybe 2011

[ducatilover]

i run my hyo past its peak power and into the redline in 5th just as fast as i do in 3rd so i dont see what your on about.

ill not even be half way down the straight at puki and im in 5th climbing 10.5rpm and wanting to shift to 6th BUT I GOT NO 6TH.

so maby hyo have a consistancy issue with their power output with the factry line

ive also riddin other hyos and a few have not got the same pull as mine did.

form what i gather the pre 09 models had lots of consistancy issues beetween the same model line

As fast as third? Don't be silly mate.
10.5krpm in fifth gear? What RPM was it doing at 100? I think from memory it was around 7-8krpm? Show me a video.....their max hp claim was 33hp on the older bikes....That would give a real life 150km/h plus or minus 5km/h