2 stroke V's 4 Stroke- Lets thump it out??

[DJRacing]

I own both- modern and old, but I thought it would be good to start a new thread since it is starting to take over in another.
  As I have said before, over here they are going to have the 250 2 strokes and 250 4 strokes run together. Better get the votes in on this one?

[Lozza]

That's 250 4T v 250 2T BRING IT ON. When the factories have to pump six and seven figure sums in just to beat privateer clubmen on 250 2T's The format will be deemed 'not workable' the rules will quickly revert to the 125 2T v's 250 4T.
HTH

[DJRacing]

I think its the cost factor over here and thats why they are looking at having a 250cc class 2t and 4t. Yeah I know this is getting a bit modern but I'm sure the same things would have been asked way back when 2 strokes took over. Bet ya the 4t boys (back then) hated that.

[Anthony.522]

Well you know which way i'm leaning on this. I think it will be interesting, bring it on. If they are faster hey cool, but i think it will be fairly even and it will come down to whats going to be easier the race at that pace for 30 minutes. Either way showrooms are still going to be full of 4 strokes. The lites bike will just need a good pipe and it will be ready to race.

[pokey]

I remember reading about the search for  Cubes  in Two strokes and the makings of the first  360cc husky engines. the 4 poke  guys didnt like it at all and kept raising the bar  as the much more agile smaller bore 2T  bikes were killing the 4T in open class racing.
 Two Stroke Tech is anything but at the  extent of its developement. the  calculations for  port  angle and designs have only been touched on . then there are the relatively new  power valves and associated  add on bits for  power delivery.
 The big Outboard  motor guys  have fuel injected 2T engines . Not that good for constantly  variable speed bike engines but  its only the beginning.
 Check the jetskis out for some damn finely designed 2T engines.

 Basic physics says an engine  will accellerate  faster  if it fires faster and at half the revolutions of a 4T to reach the power stroke that says a 2T will be first out of a corner everytime

 

[Tim754]

Strange is it  not ,that the big bore (and small bore) two strokes have been progressively outlawed in a lot of forms or motorcycle racing. If allowed the 4 strokes have been allowed to have larger cc capacities. Oh shite I just remembered at present I do not have a 2 stroke motorcycle!!! Cheers Tim

[AjayVMX]

I don't think the 2 strokes have been outlawed in racing - they've just been rendered uncompetitive by the rules allowing larger capacity 4 strokes to compete against them.  Recently in the USA, Steve Lamson raced a 125 in the lites class (and was thrashed of course), but he did do it!

[Rossvickicampbell]

I know it isn't the only reasons for the changes but apparently the two strokes are not favoured environmentally.  Saying that I hear runmours of fuel injected two strokes running at 100:1 ratios meeting emissions requirements.  At this point in time I am a two stroke fan - when a factory recommends a major service after 10 hours on one of these high revving four strokes that you have just forked out 10-12K for its too much for me - and I know people will say this is over the top and the factory are erring on the safe side etc etc etc but for maintenance you really cant beat a $50 set of rings etc once per season!!!


cheers

Rossco

[AjayVMX]

And on the subject of Environmental concerns...

I had a conversation recently with a person who was well known for 4 stroke tuning in the old days and he said that the environmental arguement just didn't hold water, due to the overlap in valve opening that happens in modern 4 strokes with their agreesive valve timing.  He thought it could be as bad or worse than a 2 stroke having the transfers and exhaust open at the same time.

He indicated that there might be some big surprises if someone actually tested the modern 4 strokes for emissions...

[vandy010]

put the two together in the one race and my opinion is it will always come down to the rider!
i've got a 2000 model cr250 and although i don't race it, i really enjoy a good practise day on a modern track.
it's near on impossible to hang out in a modern mx environment without having a conversation about valves.
this scares the crap out of joe average as his dollar is very important so most of us budget riders are on the two smokers even though we'd generally prefer a 4 banger.
it's the $ factor in my opinion thats keeping the 2stroke alive which brings me to what i'd really like to see.
remember when yamaha offered both the mx and yz?
gimme a mx250f please!
all the suspension of the yzf with a reliable mx style trailbike engine.
got my hacksaw ready, tt500 motor's in the shed, now where's that blown up engined yz450f on ebay?

[DJRacing]

Vandy what about a YZ490 motor in the modern YZF450 chassis. Dump the watercooling, slip her in there and ya probably saved a bit of weight and now ya will have the brakes to slow that beast down and the suspension to keep it WFO.

[vandy010]

yes! another quality idea there DJR!
i think it's pretty obvious these new bikes 2stroke or 4 handle well and make some pretty amazing horsepower/torque but that reliablity thing in some cases sounds expensive.
i guess my idea of a trailbike orientated engine in a modern mx chassis is a little off the main theme of this thread but i do wonder if we've kind of gone full circle with some of the bikes on offer today.
there was some good ideas in the past, some that may still be usefull today.
back onto the 2'v4' thing.
on my modern 2 smoker, getting traction is the key to going fast, in my case anyway.
if i can get that back wheel to hook up, then it's easier for me to just concentrate on enjoying the ride. if traction is poor, then the 4 stroke guys just seem to idle around getting grip where i can't.
i still don't think either is at any real advantage but it does give us some more bull to shit over a coldie or 2.

[DJRacing]

Vandy best we go into the 'Shed and Fridges thread' and open all those cool fridges and start empting them  . Yep I have to admit that I have a 06 YZF250 but I didnt buy it coz I wanted ta race full on MX on it, I just got it coz it was the yellow anniverary model. To be totally honest I actually like riding my older bikes, but on a trail ride the new one comes out coz she is a bit easier than riding a vintage 125 motocrosser on a trail ride.

[Nathan S]

remember when yamaha offered both the mx and yz?
gimme a mx250f please!
all the suspension of the yzf with a reliable mx style trailbike engine.
got my hacksaw ready, tt500 motor's in the shed, now where's that blown up engined yz450f on ebay?

I've been thinking about something very similar, everytime I see a YZ-F250 with a dead engine on EBay... Just add a 300cc kitted TTR250 engine and we'd be laughing.

Surely the market is there for such a beast to be produced by the factories?

In more general terms, the capacities are wrong - remember back when you could run a 400F against a 250T? Essentially, they give the 4-strokes an equvilance factor of 0.625 (ie: if the class limit is 250T then 250/0.625 = 400cc for a four stroke) - this seemed to work well - as each type of bike was pretty evenly matched over a variety of tracks/conditions.
Then - while the four-strokes were still getting faster - it got bumped to  0.55, and they allowed the lites a 0.50 equlivance factor - madness!

The noise thing is an interesting, and unexpected by-product. Booming four-stroke engine noise travels further than the higher-pitched two-stroke noise, so just when we'd started to get the noise thing under control, we went and buggered it up for ourselves.

The new performance four-strokes scare me. We talk about putting a piston into a new style 2-stroke once per season, but I was talking to a bloke (Mick Wating, the guy who runs the Full-Bore riding park) the other day. He has a 2000 YZ250 that's been ridden a lot and still has the original piston... Yes it's rattly, but he reckons it still starts first kick and goes well.
When I can buy a four-stroke that can go close to that, in terms of power, weight, real world noise output and reliablilty, then I'm seriously interested.

Until then, my four-stroke ownership is going to be limited to old trailbikes.

[Freakshow]

remember when yamaha offered both the mx and yz?
gimme a mx250f please!

Well yes......... they call the the WR 250F

I agree that the enviroMENTAL pressure on bikes going to four bangers has been the push for Decibels and Smoke out.

The missguided belief that developing 4  bangers would cut the Noise and oil emmisoins in half meant pressure and classes where skewed to make the MAnu facturers meet the tuff guidlines.  Even 500Gp was sent down the  4 stroke track.  A manufacturer wouldnt tool up and spend all that money to go away from a cheaper , sale-able and stable technology if it didnt need too  , the road emmisions  both noise and oil in the states were the down fall of bike, that mass market alone would have accounted for the call to find a 'freindly' engine that could be used across the board to  power all things to disperse set up costs.  Its probally not down to power, its down to Politically correct sustainable lobbying, otherwise your chainsaw and lawnmower would also still be 2 stroke.   Ever wondered why most chinese bikes are 2 eees cheap and simple, ooops and no rules cause it aint for road or track  use ?