OzVMX Forum
Clubroom => Bike Talk => Topic started by: Digga on August 07, 2016, 01:53:06 pm
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http://www.pulpmx.com/stories/look-back-old-moto-mags/gps-classic-steel/gps-classic-steel-117-1984-yamaha-yz125
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Z spokes, what a "great" idea ???
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along with YEIS...Yamaha's Excellent Ideas Syndrome
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I love those articles. Thanks for the link.
Not Yamahas finest moment by all reports!
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at least the mags told it how they saw it.
were they really that bad ?
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My understanding is that the 84/85 were slugs for the same basic reasons as the 90~93 models were: all of the power producing parts were designed to work at different points of the rev range. Not that the fundamentals were wrong, or that any single part is "wrong", just that the parts didn't work together.
I've had a couple of YZ125Ls. I didn't think they were that bad, but nor were they bikes that I found easy to love.
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Engine should make really good power, I would look at the PV opening/pipe /ignition mainly the pipe
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Engine should make really good power, I would look at the PV opening/pipe /ignition mainly the pipe
They claim in the article it was extremely difficult to get good power back in the day, no matter what was done, including fitting older model barrels.
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I had an 83 125 for my son - one of the most impressive bikes I have ridden.
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Engine should make really good power, I would look at the PV opening/pipe /ignition mainly the pipe
They claim in the article it was extremely difficult to get good power back in the day, no matter what was done, including fitting older model barrels.
Well I am very skeptical about analysis from US mx magazines, a similar Yamaha cylinder has no trouble pushing 30hp out even with relatively small 30mm carbies.
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Only one way to settle this then Lozza. We need to find you a YZ125L, to carry out some scientific experiments on.
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yet the it "L" models were good??
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Only one way to settle this then Lozza. We need to find you a YZ125L, to carry out some scientific experiments on.
Shit yeah , if all the cycle parts break after the first meeting I'll count that as a win :D :D
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I had an 83 125 for my son - one of the most impressive bikes I have ridden.
Same here,I had one for years and still believe its the fastest 125 I have ever riden.
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Story claims the '83 was faster than the '84 by a wide margin.
Goes on to say some resorted to fitting '83 cylinders.
It was two steps forward, one back during the steep learning curve of Japanese MX bikes in the crazy rate of development from '73 - '88.
Some would say the '82 RM125 was slower than the "Case Reed" '81. At least it was universally praised as easier to ride. I believe they went back to the Case Reed after two years.
These days it's bold new graphics one year, "revised suspension" settings the next.... Even "total redesigns" are fairly "incremental".
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All depends on who leads development. Yamaha quietly abandoned 5 valves per cylinder after Furusawa-san built a 4 valve cross plane crank engine after Valentino Rossi said that was the engine he wanted to race with. Yamaha used 5 valves on everything since the mid 80's clung to that like a limpet when nobody else in the automotive world used 5 valves.
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1983 YZ125K - Rocketship. I cannot understand how Yamaha got it so wrong in such a short step. I cant say a bad word about the 83 YZ125, such a huge leap from the 82 model which was way too heavy for a 125 and all top heavy to boot.
The 84 model would have been a better bike if Yamaha simply improved the ergos on the K (slimmer tank like the 84/85) and better airbox access like the the L and N models.
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All depends on who leads development. Yamaha quietly abandoned 5 valves per cylinder after Furusawa-san built a 4 valve cross plane crank engine after Valentino Rossi said that was the engine he wanted to race with. Yamaha used 5 valves on everything since the mid 80's clung to that like a limpet when nobody else in the automotive world used 5 valves.
I had an Audi car with 5 valves per cylinder - it didn't seem to go any faster than the previous 4 valve model I had,
I believe Ferrari also built some 5 valve engines for a while, but I don't think either manufacturer builds any today,
an interesting idea , but probably not worth the extra cost
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I had an Audi car with 5 valves per cylinder - it didn't seem to go any faster than the previous 4 valve model I had,
I believe Ferrari also built some 5 valve engines for a while, but I don't think either manufacturer builds any today,
an interesting idea , but probably not worth the extra cost
Shit eh there you go never knew that someone else has tried it. A synopsis I read was about the angle on the rear valve and inlet ports were compromised also some sort of frictional losses from the extra springs
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The big problem with 5V heads is that the flow around the intake valves interferes with each other, so they don't flow any/noticeably more than a good 4V head - a lot of extra complexity for no real gain (apart from in the sales brochure).
There was a version of Toyota's venerable 4AGE that came with a 5V/cylinder head. It made more power than the older 4V version ... because the 5V one was delivered in a much higher state of tune (cams, individual throttle bodies, etc). For a serious race motor, the 16V version beats the 20V hands down.
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That head was done by Yamaha as there was some corporate tie up at the time
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That head was done by Yamaha as there was some corporate tie up at the time
Yamaha have been building some engines for Toyota on and off since the late 1960s,
I read somewhere that they had built 4 stroke engines for Toyota before they had actually built there first 4 stroke bike engine, and supposedly there are some small parts in an early XS1 / XS650 engine which come from an engine they were making for Toyota.
Yamaha are now involved in some of the Ford V8s, cant remember if they make the whole engine or just the castings.
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Apparently the head on the Toyota (2ZZ) motor in the Lotus Exige (before they went to a V6) and Elise is made by (designed by?) Yamaha.
Certainly the Yamaha 5v four strokes were powerful and long lived.
I've had an R1, and 2 250Fs, still have one of the 250fs.
As others have said: there doesn't seem to have been a performance advantage to 5 valves, and definitely extra complexity and cost.
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I love it when these VMX YZ125 posts come up. I raced the F, G, J and K 125's and the K is still the best bike i have ever ridden. And that includes years of MX on CRf450's, YZ250f's, SXF350's and the like.
The K was very light weight, handled brilliantly, was reasonably fast, very reliable, and confidence inspiring.
In fact, i have two now.... and they have only just been finished off.
These will be heading to the dunes, bush and tracks very soon...
(http://i40.photobucket.com/albums/e249/alexbrown64/yz1251_zpskwv7tdxv.jpg) (http://s40.photobucket.com/user/alexbrown64/media/yz1251_zpskwv7tdxv.jpg.html)
(http://i40.photobucket.com/albums/e249/alexbrown64/yz1252_zpsgpgo5pmw.jpg) (http://s40.photobucket.com/user/alexbrown64/media/yz1252_zpsgpgo5pmw.jpg.html)
(http://i40.photobucket.com/albums/e249/alexbrown64/yz1253_zpstwyfodsy.jpg) (http://s40.photobucket.com/user/alexbrown64/media/yz1253_zpstwyfodsy.jpg.html)
Cheers,
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once Yamaha rejigged "monoshock" to a more conventional design, they really picked up their act
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Those are some nice YZs Alex 8)
They are '83 K models?
The article is slagging '84 L models. (As being much slower than the previous year)
Do I have that right?
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That yellow and white K looks so good I can't stop looking.Nice job on both,stunning bikes.
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Yes, the bikes went backwards for a few years after 1983.. The 84's looked good on paper with bigger forks, DLS brakes etc.. but ended up slower and less reliable. Shame really. Both my white and yellow K's are 83, but the U.S one has a lot of fruit on it including DLS brakes, larger carb, porting, PVL ignition, Jemco pipe, RaceTech emulators, gold valves, springs and valving, Takasago rims, aftermarket rads and silicone hoses etc..
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te author=alexbrown64 link=topic=40822.msg390384#msg390384 date=1471174786]
Yes, the bikes went backwards for a few years after 1983.. The 84's looked good on paper with bigger forks, DLS brakes etc.. but ended up slower and less reliable. Shame really. Both my white and yellow K's are 83, but the U.S one has a lot of fruit on it including DLS brakes, larger carb, porting, PVL ignition, Jemco pipe, RaceTech emulators, gold valves, springs and valving, Takasago rims, aftermarket rads and silicone hoses etc..
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Are they DG rad shrouds and side covers?someone had some for sale on facebook but wouldn't list prices.The white looks really good with the yellow.
Is it just the 84 125 that was a flop?my brother bought a 250 new in 84 and still says it was the best 250 ever,he still talks up the double leading front brakes being better than disk,I just think he's stuck in the 80s.
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The YZ250L is/was a great bike.
The same happened in the early 90s, where the YZ125 was a dog but the YZ250 was one of the best.
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James, the white shrouds are DC after i emailed them and got them to customize them in white. The bike is based on Lechiens works OW125 of 1983..
Cheers,
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Yamaha DLS brakes.
I had the first model TT600 brand new. I was disappointed with the front brake, until I fitted a Metzler.
Then I was only disappointed trying to stop rolling backwards on hills.
They were great brakes if maintained and adjusted.