RM/CR/YZ/KX250's should be mfg'd as 350's

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#1
My opinion, to keep pace with the YZ450F & CRF450's, a RM/CR/YZ/KX 350 new model release would have similar power/torque to the 4-stroke, less weight, and most of all, better turning!! How about it big 4?
 

92cr

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#2
Now that's something I agree with 100%.I thought that for years already.
 

BunduBasher

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#3
Are we talking two stroke here ? - are 250 cc MX bikes not the formula ones of dirt. Would a 250cc 4 stroke not make more sense running as a 300cc, and would running 175 cc or 200cc 2 strokes instead of 125cc machines be a better bet - I miss the old 175 enduro machines !

As to your initial suggestion - the big bores have yet to eclipse the 250 cc two strokes, and have not yetwon a national title. There are 300cc enduro bikes out there, Gas Gas KTM - would you be suggesting they raise the the 250cc class higher than this - would we not be looking for an open class again.
 
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#4
Yes, set the displacement requirement for 250cc 2-strokes to 350cc max. This would allow the 2-stroke to be able to match the 450cc 4-stroke hp, torque curve and spread of power. KTM has done this with 300cc, 380cc and even 200cc sizes, but it has'nt caught on yet, maybe for other reasons. My initial thoughts were for mx use, but it could work every where else.
 

jmics19067

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#5
Probably has something silly to do with the fact that it is 125 or 250 cc displacement class :think: The four strokes although twice the displacement and different handling characteristics offer no real advantage to the pros. The win list kinda proves that. Those guys would be fast ona Rupp minbike.

wait till you can race Vet then displacement isn't an issue.
 
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#6
Why restrict the big class at all? The production rule is great, but there is too much sameness in bikes these days and the 250 cc size limits manufacturers in producing the best powerband. A few years ago Dirt Bike ran an article on enlarged 250's, and Roger DeCoster was quoted in it as saying he would love to have flexiblity to tailor the best powerband through increased displacement. The 125 class makes sense as a farm league for the bigger class, but let the premier class be truly open - what works best be it 2 stroke or 4, 250cc or 331 or 462! JMHO.
 

jmics19067

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#7
Unfortunately the powers that be let go the open class for national racing a long time ago. there is some interest at the local level with the open/4stroke class.Atleast there is in my area.

In an effort to make the sport more NASCAR like in the fact that everything is the same we have the situation of making the equiment identical to see who is the best racer. Whether or not you and I belive it is a good I dea or not it makes sense too see who should wear the used to be #1 plate.

It is apparant that bike sales influence the racing budget and the bike manufacturers influence the racing sanctions. Unless the sales of KTM 300/380 and Kawasaki 500 outsell the "standard" or everybody at the national shows up with an illegal bike for a season so there is no legal winner by the standard rules, I doubt highly things will change.

The EPA and greenies are the ones who put the squeeze on future bike sales by trying to outlaw 2strokes. Most manufacturers wouldnt bother to make 4 stroke motocross bikes if they didnt see the possibility of losing lots of money down the road not being able to sell John Q Public a two stroke motocross bike for play riding.
 
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#8
To DeCoster's point mentioned above, imagine what cost savings would be realized within a manufacturer's R&D budget by using displacement as a way to get desired power characteristics instead of the substantial time & equipment currently used for flow bench, ignition, combustion chamber design & test iterations, power valve mod.'s, pipe, gearbox redesigns, etc.........maybe our new bike costs would drop by $500-1000 ????
 
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#9
You still have to do all the R&D you described, PLUS you have to do additional durability testing for the currently unknown stress and strain on the parts that were originally designed for a 250cc engine's power level. Not a trivial task, and that's assuming there is actually a market for a 350CC engine which is another great unknown.
 
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#10
Most riders (myself included) using KX310, CR285, RM285, YZ300 kits claim
performance is better than the 250 version. That's an indicator that some type of displacement increase over 250cc is goodness.
By the way, where & why did the 125-250-500cc displacement originate from? I'd guess those numbers were chosen as "round" numbers, or fractional round numbers of 1000cc or 1 liter of displacement, w/o consideration to power curves desired.
Maybe classes should be divided into 0-35hp, 35-60hp? Imagine keeping a calibrated dyno at AMA technical inspection for spot checks prior to a national MX event -
 

James

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#11
Is it really worth changing?

I like my 250 just fine and adding 100ccs to it would surely give it an unfair advantage over the 450s.

Besides, at our local races, you can run anything you bring over 255ccs in the "250" class. It makes sense to me that the pros have to run on 'standard' sized machines.
 
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#12
Originally posted by G92Joe
Most riders (myself included) using KX310, CR285, RM285, YZ300 kits claim performance is better than the 250 version. That's an indicator that some type of displacement increase over 250cc is goodness.
No one is arguing that point. But if an OEM were to produce a production 310 there would be an expectation on the part of the customer that the engine would have a certain level of reliability and usability. That level of completeness in a design can only occur with a major commitment in terms of testing and R&D. Performance costs, regardless of how you obtain. Some ways are just cheaper than others.

Given how competitive MX and SX is lately and how many different riders and bikes are on the podium it seems like the current setup is working pretty well.
 

jmics19067

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#13
assuming there is actually a market for a 350CC engine which is another great unknown.
A look at history says that it shouldn't be a market. Way back when there was 370/ 400 cc motocross engines fighting for the open class. well as it goes more is always better so bikes evolved into 490 and 500 cc monsters. At this time stadiums and man made jumps where becoming the hot ticket. Negotiating a cr 480 or a yz 490 around a stadium must be a hair raising event. Up until the point that there was no open class stadium events. Why would anyone want to risk eating it on these huge man made jumps when their lap times wheren't as fast as the 250's?

At this era nobody ever got the bright idea of sleeving down/destroking an open class bike, which should have been worlds cheaper and easier to do then making a 250 bigger. Scratch that, KTM and Maico where playing around with displacement options looking for what is big but not too big but they could not concievabley come up with the sales numbers of the "big four". With 2 of the big four dropping out of open mx bike sales altogether. Yamaha barely scraggling on with selling the old YZ as a WR and Honda and Kawasaki selling old designs with left overs from the last year's 250's improvements.

Noleen had a short run on trying to make a 360<?> out of the Yz250. Very few people though that it was advantageous to buy a brand new motorcycle and dump 1/2 as much more into the engine to run a different class against bigger bikes.

So what we have now is Honda discontinuing the cr 500 line, Kawasaki selling ancient 500's to the more is better crowd and European "cottage industries" selling the "little bit more than a 250 but not anything brutal"

Unfortunately for the US you are going to have to wait and see if two strokes will be allowed to be manufactured for sale, the KX500 discontinued, continued success of the European 300's and then somebody saying" hey we should be able to sell something bigger" before you would hit a 350/400cc target again.
 
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#14
The kx500 is still a great bike for what most use it for. It still wins out west Its design is not cutting edge but is by no means ancient.
I'm 41 years old and can still run quite well(top 10-20 o.a.) in the desert on one.
 
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#15
I dont think that the manufactures would go for a 350 2-stroke mx bike competing with their brand new four-strokes. the 350s would absolutly eat up those thumpers. They would those a lot of money if 2-stokes came back and beat up on the strokers, they have invested way to much money to do something like that. I think the ideal displacment would have to be around 300cc or so. Hopefully Boyesen can get his trapping valve perfected so he can sell it to the factories. Thats the day when the 2-stroke will be back in full force!