Yamaha 2007 YZ125 and 250 two-strokes
By TMX Archives on 21st Sep 06
2007 Yamaha has definitely worked on the theory 'If it aint broke, don't fix it', as far as the YZ125 and 250 two-stroke weapons are concerned.
The Japanese firm made big changes in 2005 and 2006, and some more chassis updates were developed, but for next season the bikes have been kept very similar!
Is this because two-strokes are finally coming to an end and the big manufacturers are no longer developing them? Who knows? Only time and a test ride on all the other Japanese two-
Both bikes look pretty much the same. For 2007 the main changes are the Pro-Taper handlebars as apposed to the Renthals from last year, a pair of redesigned Kayaba front forks, the thickness of the outer tubes has been optimized to reduce weight and gain rigidity, and at the rear-end a redesigned shock has been fitted with lighter components, along with a titanium spring, which was new for last year, and makes the overall dry mass of both bikes even lighter, with the help of the 'state of the art' aluminium chassis. Other than those few changes the only other difference is new style graphics on the rad scoops.
Johnno White - YZ250...
FOR 2007 Yamaha has definitely worked on the theory 'If it aint broke, don't fix it', as far as the YZ125 and 250 two-stroke weapons are concerned.
The Japanese firm made big changes in 2005 and 2006, and some more chassis updates were developed, but for next season the bikes have been kept very similar!
Is this because two-strokes are finally coming to an end and the big manufacturers are no longer developing them? Who knows? Only time and a test ride on all the other Japanese two-strokes will tell us.
Both bikes look pretty much the same. For 2007 the main changes are the Pro-Taper handlebars as apposed to the Renthals from last year, a pair of redesigned Kayaba front forks, the thickness of the outer tubes has been optimized to reduce weight and gain rigidity, and at the rear-end a redesigned shock has been fitted with lighter components, along with a titanium spring, which was new for last year, and makes the overall dry mass of both bikes even lighter, with the help of the 'state of the art' aluminium chassis. Other than those few changes the only other difference is new style graphics on the rad scoops.
ON THE track the first bike I rode was the YZ250, and without trying to sound like a prima-donna (looking more more like Madonna - Ed) the course was unfortunately pretty sloppy early morning, which doesn't always go down well with testing a brand new, non-run-in bike, but being an old hand to this testing game (old being the appropriate word there, old son! - Ed) I gave it my best shot.
The overall feeling of the YZ250 was nice and neat with a real firm seat foam which enabled me to move up and down the bike really easily and which also made cornering feel smooth.
The new Pro Taper handlebars have quite a decent bend on them and are pretty similar to what I would run on my own bike. They are a major breakthrough because they are a top quality bar and are something most riders would go out and buy when they get a new bike.
The brakes felt really sharp especially the front with its new ergonomic brake lever and stopped me when and where I wanted to be stopped and the rear helped set the bike up for entering corners well.
I found the YZ250's power quite easy to use with a lot of low to mid-range grunt but also had a nice over rev, I don't know whether it was down to the slick conditions but I found it easier to pull a higher gear than I normally would and let the motor labour rather than rev like mad.
This combination worked perfectly all day in the mud, it would be nice to try it on a sandy surface to see how fast it really was, but overall the basic feel of the motor was really good.
In the gear box department, everything seemed quite smooth although I felt the gear lever was a bit low, I like it set one notch higher on my own bike.
If the conditions had been a bit better I would have had the Yamaha guys lean the jetting off because it was running too rich, which would tell me they were probably straight from the crate and had never been tweaked, which is a good pointer for anyone buying a new YZ - the jetting will obviously need tweaking.
I also did a couple of practice starts on the bike, which is always a good measure on what sort of bottom end the motor has and the 250 pulled second gear no problem at all, and to be honest, on the right kind of surface, I reckon you could probably pull a third gear start.
In talking about the suspension, the quarter-litre machine's was okay, but not brilliant. However, this is not down to the set-up of the bike in fairness, it was down to the condition of the track at the time of the test.
Although the track was quite muddy there were a lot of pot-holes and hard-faced bumps under the slime which are a good test for the suspension on the rear as opposed to the front forks because you have to keep the front end light anyway.
The rear-shock had a nice progressive feel to it which is probably down to the new settings, the 250 in particular has a fully redesigned rear unit for a 2007.
It not only has a titanium spring but to make it even lighter it has had quite a few of the steel components inside the shock replaced for aluminium ones, including the spring guide and the lower mount and damping adjuster mechanism.
I found the front-end worked well when landing from jumps, but on the stutter bumps they didn't have a right lot of give in them and felt far too twitchy for my liking, however, as far as cornering was concerned and as long as there was a nice rut to drop into there wasn't a problem, but on the sloppy stuff, where you wanted the front-end to dig in it felt a bit too firm.
THE overall feeling of the YZ125 was also very nice and neat with the firm seat foam and I could move up and down the bike really easily, like on the 250, and the cornering felt smooth and slick because of it.
The new Pro Taper handlebars are excellent and yet again riders will enjoy using bars they would probably put on themselves.
The 125's power was obviously different from the grunt of the 250, as 125s usually are, I rode the 125 like it should be - on the pipe - everywhere.
I found it had a good bottom-end feel to it, and then a really broad mid-range, but even then I felt it went a bit flat on the top, but after a few laps I got used to the mega mid-range power delivery, and actually found it quite easy to ride.
I'm not sure though whether it was running a bit rich which would stop it revving right out on top end.
Again, in the gearbox department, everything seemed quite smooth although the gear lever was a bit low for me, I would have notched it higher on my own bike.
As a new, untweaked machine, it was running too rich, which would tell me it too was probably straight from the crate, anyone buying a new YZ, remember, the jetting will obviously need tweaking.
In talking about the suspension, the quarter-litre machine's was okay, but not brilliant. However, this is not down to the set-up of the bike in fairness, it was down to the condition of the track at the time of the test.
The 125 was definitely better starting in first gear, whether it was because of the mud I'm not sure, but it struggled in second.
The pot-holes and hard-faced bumps under the slime was a good test for the 250cc's rear suspension and was again for the 125cc machine's rear set-up as opposed to the front forks as we kept the front end light.
The rear-shock had a nice progressive feel to it which is probably down to the new settings and helped set me up in and out of the wet, sloppy corners.
Again, similarly to the 250's front-end, I found the 125's front-end worked well when landing from heavy jumps, but again on the stutter bumps they didn't have a right lot of give in them and were too twitchy.
However, as far as cornering was concerned if there was a nice berm to drop into there wasn't a problem, but like the 250, on the sloppy stuff, where you wanted the front-end to dig in, it felt a bit too firm.
The brakes felt really sharp especially the front with its new ergonomic brake lever and stopped me when and where I wanted to be stopped and the rear helped set the bike up for entering corners well, which is fairly common nowadays on modern bikes, you aren't going to get a 'dodgy' set of brakes, or for that matter, a dodgy bike.
SPECIFICATIONS 2007 Yamaha YZ250
ENGINE
Type: Liquid-cooled, two-stroke, reed
valve, forward-inclined single cylinder
with YPVS
Displacement: 249cc
Bore x stroke: 66.4 x 72.0mm
Lubrication: Premix
Carburettor: Keihin PWK38S/1
Clutch type: Wet, multiple-disc coil spring
Ignition: CDI
Starter system: Kick
Transmission: Constant mesh, five-speed
Final transmission: Chain
CHASSIS
Frame: Aluminium semi-double cradle type
SUSPENSION
Front: Telescopic forks
Travel: 300mm
Rear: Swingarm (link suspension)
Travel: 315mm
BRAKES
Front: Single disc, 250mm
Rear: Single disc, 245mm
TYRES
Front: 80/100-21 51M
Rear: 110/90-19 62M
DIMENSIONS
Overall length: 2,184mm
Overall width: 827mm
Overall height: 1,309mm
Seat height: 997mm
Wheelbase: 1,481mm
Ground clearance: 385mm
Dry weight: 96kg
Fuel Capacity: 8 litres
Ben Johnson - YZ125/250
THE fact that the YZ models receive only cursory changes and developments for 2007, and with the industries seemingly unrelenting march towards a four-stroke-only future, it seems that the YZ250 and YZ125's days will be numbered in the not too distant future, which is a real shame because as far as I'm concerned both of these machines are right up there at the top of their respective classes and more than competitive with four-stroke machines in the hands of the majority of weekend warriors.
Having received a complete redesign just two seasons ago, the YZ250 and YZ125 are the most developed and refined bikes on the two-stroke market and although relatively minor, the developments included on the 2007 machines further enhance the impeccable handling and excellent chassis that they are renowned for and reinforce just how much fun a good, well balanced two-stroke is to ride.
YZ250...
ALTHOUGH the heavy overnight rain had turned the hardpack Mallory Park test venue into a slick skating ring, which was far from ideal for a thorough test of the peaky power of a 250cc two-stroke, the YZ250 remains probably the most powerful yet progressive motor in the class.
Strong yet smooth all the way through the REV-range the YZ250's power delivery is not for the faint of heart - or ten stone weaklings on wet tracks - but it is everything a 250cc motor should be, crisp, light-switch responsive and formidably strong in the mid-range.
Give this bike something to turn against and it will pull you out of a corner and down a straight as fast as any 450. The bike was jetted a bit rich right off the bottom, which given the track conditions actually worked to the bike's favour, but I would personally re-jet the bike to make it a bit crisper and more responsive off the bottom end.
It is the handling that most impresses on the YZ250 though with the re-designed Kayaba front forks and shock and the great new Pro Taper 'bars all combining to further improve what was already an incredibly light, nimble and stable machine.
The twin-spar aluminium frame is, in my opinion, the best on the market and creates a very stable, forgiving and fast turning bike that feels closer to a 125 than an Open class machine in terms of its nimbleness.
Although quite tall, the YZ250's forte is its cornering ability, with the excellent ergonomics and riding position making for a bike that just begs to be thrown into corners. Tight rutted hairpins, choppy sweepers, or deep berms, the YZ250 excels at them all and the new suspension on the front in particular enhances this further, creating a slightly more predictable front end, especially on the choppy stuff.
Overall, the suspension performance is good but nothing special. I think both myself and Johnno found the units to be a bit harsh accelerating out of corners over square edge bumps, and for my weight and speed the whole set-up was a bit hard, but landings from jumps were soaked up no problem and the whole time out on the track the action was stable and predictable.
YZ125...
HANDLING is big selling point of the YZ125 in my opinion also. The combination of the ultra-light aluminium chassis, excellent suspension and general all-round comfort make the bike just about one of the best handling and most enjoyable on the market.
I don't personally think that there is a better handling bike out there than the YZ125, it is just so light, quick turning and generally fun that it flatters you as a rider and encourages you to push harder and harder.
Whether it is in corners or over jumps, the YZ125 rewards aggressive riding.
This wouldn't be possible without good suspension and the Kayaba units are among the best OEM bouncers out there delivering plush, progressive and very stable travel in all circumstances.
It took a bit of effort to even get the bike to get out of shape, although when I did, I went down pretty hard and ruined my new kit - nice.
SPECIFICATIONS 2007 Yamaha YZ125
ENGINE
Type: Liquid-cooled, two-stroke, reed valve,
forward-inclined single cylinder with
YPVS
Displacement: 124cc
Bore x stroke: 54.0 x 54.5mm
Lubrication: Premix
Carburettor: Mikuni TMX38
Clutch type: Wet, multiple-disc coil spring
Ignition: CDI
Starter system: Kick
Transmission: Constant mesh, six-speed
Final transmission: Chain
CHASSIS
Frame: Aluminium semi-double cradle type
SUSPENSION
Front: USD Telescopic forks
Travel: 300mm
Rear: Swingarm (link suspension)
Travel: 315mm
BRAKES
Front: Single disc, 250mm
Rear: Single disc, 245mm
TYRES
Front: 80/100-21 51M
Rear: 100/90-19 57M
DIMENSIONS
Overall length: 2,139mm
Overall width: 827mm
Overall height: 1,318mm
Seat height: 998m m
Wheelbase: 1,443mm
Ground clearance: 388mm
Dry weight: 86kg
Fuel tank capacity: 8 litres
Specification:
