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Author Topic: 4T or 2T?  (Read 66877 times)

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Offline Pom17

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Re: 4T or 2T?
« Reply #40 on: July 18, 2013, 11:45:53 am »
Please explain. Hoe werk dit en waord daardie pyp nie moer warm onder die seat nie
 

Offline Beserker

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Re: 4T or 2T?
« Reply #41 on: July 18, 2013, 12:49:15 pm »
But it does not have an exhaust valve in the cylinder head, it still uses ports.

The exhaust valves are there to minimise the outflow of vaporised, unburnt fuel from the transfer port to the exhaust port, as they are open at the same time.
Direct injection circumvents this issue, and also the need to scavenge.

Powervalves are also used to alter port timing, or by altering the volume of the exhaust.  The Ossa uses sub exhaust chambers that extend the 'tuned length' of the expansion chamber.

In this manner they keep the 2T to what it should be, a simple engine with few moving parts.

Check out the advances that especially marine and snow mobile manufacturers made in terms of 2T development, specifically as far as fuel efficiency and pollution is concerned.

Honda was on the right track, amazing for a predominantly 4T company.

Please explain. Hoe werk dit en waord daardie pyp nie moer warm onder die seat nie

Daai pype word nie baie warm nie, dis meer vir resonansie, en die hitte behoort redelik maklik gesink te word, daar is fantastiese produkte op die mark wat dit kan doen, soos bv as jy 'n engin will sweis langs 'n rubber seel .

Dan, ek dink hulle teikenmark is die BMW meerkatte  :deal:
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Offline Rough Rider

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Re: 4T or 2T?
« Reply #42 on: July 18, 2013, 02:26:30 pm »
But it does not have an exhaust valve in the cylinder head, it still uses ports.

The exhaust valves are there to minimise the outflow of vaporised, unburnt fuel from the transfer port to the exhaust port, as they are open at the same time.
Direct injection circumvents this issue, and also the need to scavenge.

Powervalves are also used to alter port timing, or by altering the volume of the exhaust.  The Ossa uses sub exhaust chambers that extend the 'tuned length' of the expansion chamber.

In this manner they keep the 2T to what it should be, a simple engine with few moving parts.

Check out the advances that especially marine and snow mobile manufacturers made in terms of 2T development, specifically as far as fuel efficiency and pollution is concerned.

Honda was on the right track, amazing for a predominantly 4T company.

Please explain. Hoe werk dit en waord daardie pyp nie moer warm onder die seat nie

Daai pype word nie baie warm nie, dis meer vir resonansie, en die hitte behoort redelik maklik gesink te word, daar is fantastiese produkte op die mark wat dit kan doen, soos bv as jy 'n engin will sweis langs 'n rubber seel .

Dan, ek dink hulle teikenmark is die BMW meerkatte  :deal:

Excellent explanation Dave  :thumleft:
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Offline Buff

Re: 4T or 2T?
« Reply #43 on: July 18, 2013, 03:41:42 pm »
Your ass will still be ring-ting-tinging for 30mins after you've climbed off the bike ;D
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Offline Cheetah

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Re: 4T or 2T?
« Reply #44 on: July 18, 2013, 04:52:58 pm »
 :sip:
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Offline Buff

Re: 4T or 2T?
« Reply #45 on: July 19, 2013, 12:29:37 am »
Do yourself a favour and search for "fuel injected YZR500 2 stroke" on YouTube. OMG, I think I'm in love !!
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Offline Beserker

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Re: 4T or 2T?
« Reply #46 on: July 19, 2013, 08:15:43 am »
Do yourself a favour and search for "fuel injected YZR500 2 stroke" on YouTube. OMG, I think I'm in love !!

I saw this awhile ago.

IMHO...2 stroke, of the bat, has such good power:weight ratios nobody bothered to develop it any further.

Having one of the major players (Honda) as a rabid 4T developer, compounded the issue.
Uninformed tree huggers, like the Sierra club in the USA, added even more weight to the 4t advocacy momentum.

There is huge scope for the development of a better, cleaner, quieter, more powerful, well behaved 2 stroke that can be run cheap compared to 4T...hence the fact that the European bike manufacturers (GasGas, KTM, Husky, Sherco, Ossa) are pushing it.  They are in the process of kicking the Japs, even with their build quality, in the balls.

This is underpinned by development in the marine and snowmobile markets.
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Offline Pom17

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Re: 4T or 2T?
« Reply #47 on: July 19, 2013, 08:32:35 am »
 

Offline BlueBull2007

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Re: 4T or 2T?
« Reply #48 on: July 19, 2013, 01:13:38 pm »
 :drif:  :sip:
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Offline Rough Rider

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Re: 4T or 2T?
« Reply #49 on: July 19, 2013, 01:20:25 pm »
Fuel injected YZR500 2 Stroke

Can you imagine that bite that thing must have. My RM250 already has a bad enough bite, which has bitten me a few times.

Not my proudest day, both these incidents happened on the same ride.

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Crash into da trees
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Re: 4T or 2T?
« Reply #50 on: July 19, 2013, 01:59:40 pm »
@RR....love the sound track (Ring ting ting), and the Ah F! Ah F! rappin'

FWIW:  the fastest, stock, full height motocross bike, officially timed:  KX500 @ 201 KM/H

Some more 2T Brutes:







Out of interest...on a MX track the 500 2T is not faster than a 250T.

I can't remember much from the few times I rode a 500 2T (VER-R-R-Y Blurry), but getting that thing to lean over in a corner was difficult.

Read later that the centrifugal forces from the mill makes the bike want to stand up, regardless of the riders  intention, which means very little to the beast.

When you do get it to lean over....it is a berm destroyer of note  :o

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Offline Beserker

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Re: 4T or 2T?
« Reply #51 on: July 19, 2013, 02:03:37 pm »
Sincere apologies, I have just hijacked the 2T vs 4T thread.

Someone please post some 4T awesomeness !!
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Offline Rough Rider

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Re: 4T or 2T?
« Reply #52 on: July 19, 2013, 02:14:53 pm »
@RR....love the sound track (Ring ting ting), and the Ah F! Ah F! rappin'

FWIW:  the fastest, stock, full height motocross bike, officially timed:  KX500 @ 201 KM/H

Some more 2T Brutes:







Out of interest...on a MX track the 500 2T is not faster than a 250T.

I can't remember much from the few times I rode a 500 2T (VER-R-R-Y Blurry), but getting that thing to lean over in a corner was difficult.

Read later that the centrifugal forces from the mill makes the bike want to stand up, regardless of the riders  intention, which means very little to the beast.

When you do get it to lean over....it is a berm destroyer of note  :o



All I remember from the time I rode a KX500 was how it flattened a pretty steep hill that I used to struggle to get up on my KDX and also how it made a roost in the sand like a jet ski makes  :3some:
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Offline Cracker

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Re: 4T or 2T?
« Reply #53 on: July 22, 2013, 03:54:11 pm »
That KX has styling like a modern 450, what year is it?
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Re: 4T or 2T?
« Reply #54 on: July 22, 2013, 04:31:36 pm »
That KX has styling like a modern 450, what year is it?

They are all done by Sevice Honda in the States.

Started of by fitting Honda CR500 engines in the CR250 aluminium frame.
I speak under correction, they buy the engines direct from the manufacturer.

The frame was matured, and is manufactured in house.

Subsequently, they did the same with the KX500 powervalve (KIPS) enjine...

So, it is this years model. (And last years, and next years.)
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Offline 2StrokeDan

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Re: 4T or 2T?
« Reply #55 on: September 20, 2013, 09:43:32 pm »
Sincere apologies, I have just hijacked the 2T vs 4T thread.

Someone please post some 4T awesomeness !!

Nothing awesome about a 4stroke. Only role I can support it in is touring, where you want it's lean run economy. Rest is 2stroke world.

4Strokes also make rude fart-like noises. :xxbah:
 

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Re: 4T or 2T?
« Reply #56 on: September 20, 2013, 09:54:12 pm »

Nothing awesome about a 4stroke. Only role I can support it in is touring, where you want it's lean run economy. Rest is 2stroke world.

4Strokes also make rude fart-like noises. :xxbah:


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Re: 4T or 2T?
« Reply #57 on: September 20, 2013, 10:19:15 pm »
You old timers must be bored  :biggrin:
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Offline wreckit

Re: 4T or 2T?
« Reply #58 on: October 31, 2013, 08:48:18 pm »
I owned a Service Honda CR 500 AF (Aluminium frame). Due to the motocross gear ratios, no more than 120Km/h with stock sprockets. The Kx 500 was almost identical in top speed. As a matter of interest when I was racing in 2012 I swopped my race Honda CRF450R with a crf450x gearbox and e/start for a Ktm 300. In race trim they weighed almost  the same (The Honda was about 2 Kg's Heavier). This was because of the fuel capacity (11.5 liters on the KTM 300) compared to 7.5 liters on the CRF 450 R to do the same range and the addition of a stainless steel pipe cage to protect the 2 stroke pipe  (A must have if you race WfO'S and hare scrambles in Kzn) which added another 3 kg's (4 kg's for the fuel and 3 Kg's for the pipe added 7 Kg's to the Ktm). Even thought they weighed almost the same the Crf450 always felt a bit  heavier due to the inertia of the 4t motor. Having owned over 40 dirt bikes and 9 four strokes, I can't even make up my mind which is better as both 2t's and 4t's each have their own ups and downs.

We are lucky to be able to make the choice .Pre 98 we only had a few trail based bikes like honda xr's to choose from if you didn't want to ride a 2 t and my personal opinion, try and  do some proper rides on  both and see what suits you. A spin up the road is not enough to make up your mind as it takes time to get used to a 2t if you ride a 4t and vice versa.
 

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Re: 4T or 2T?
« Reply #59 on: November 01, 2013, 08:33:45 am »

I can't even make up my mind which is better as both 2t's and 4t's each have their own ups and downs.


One can never have enough bikes, 2-3 of each, per rider, should settle this  ;D
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