Project WR
Right, last year, I got my hands on a WR200 motor. Now some of you may be thinking, “Err, doesn’t he mean the DT?” Indeed I don’t, Yamaha did in fact manufacture a WR200 between 1991 and 1995 or so.
So what’s special about it and how is it different to the DT? Well think of it as the 4th generation of the 2 stroke 200cc Yamaha built for their dirt bikes and quads. We start our lineage with the popular IT175 in the 70’s which featured the 66mm bore, characteristic of this lineage, it’s sort of like their family trait! The stroke however was 50mm. Throw in a 34mm Mikuni and you had 14.5 horses under the tank. From there, the IT200 was introduced which had more displacement courtesy of a 56mm stroke and essentially was the same motor as the 175, but with a whopping 26.6HP. Yamaha then took the IT200, tamed it down a bit added an oil injection system, increased the stroke to 57mm and through it into a Yamaha Blaster fame we all know and love on this site. The Blaster was developed to be an “Entry Level Sport Quad” and with all of 18HP to haul itself around with. It served a big sector of the market well, but the eagle eye rider would have noticed a marked power disadvantage between his Blaster and his mates IT200. Yamaha achieved the “Tractable” power by restricting the intake to a 26mm Mikuni carb and fiddling with the port timing and combustion chamber design. Soon afterwards, the DT200 was developed. This was a big step forward with its water cooling and Yamaha Power valve System being the major development and sales points. This all made the DT, faster, cooler and more reliable. Strangely, a 28mm carb was all that was needed to produce a monster, 33HP from this machine. They also started fiddling with the gearbox and gave the DT longer legs than previous variants of this engine.
In the early 90’s work began to enhance this motor even further. New design principles were implemented and developed to produce a 199cc WR200 (Wide Ratio). The new features included a direct crankcase fed induction system, a 30mm Mikuni TM carb, bigger reed cage, better port timing, even longer gearing as well as a nikisil lined cylinder with a slightly bigger bore at 66.8mm. Although Power is rated as being less than the DT at 27.6HP, the torque is notably higher. With the WR’s purpose as a trails bike in mind, the developers opted for torque over power for those technical sections were too much power is your worst enemy.
No further development was carried out after the WR200, and so it is fair to say that the WR200 is the pinnacle of the 200cc from Yamaha. Its direct competitor was the KDX from Kawasaki and the two are for all intent and purposes, very well matched.
http://www.motorcyclespecs.co.za/model/yamaha/yamaha_wr200r 93.htm
So the idea of fitting the WR to the Blaster is indeed a case of giving the Blaster what we all knew it always deserved, a real deal, “let me show you a thing or two” 200cc engine!
I started when I got the engine, I immediately plonked it on the workbench and gave it a good look. I then compared the bottom end from my spare blaster engine with the WR, there are a few obvious differences.
On the whole however, things look promising, I have already made peace with the fact that a few frame mods will be needed to get this to work properly, but on the whole, and it should be a neat fit!
Recently, I burnt a hole through the top of my piston while doing 30km of flat out WOT gravel riding, on a perfectly sealed, standard bore, 330 main jetted carb with mild porting. I couldn’t figure out why this had happened, until I pulled the head off. I noticed the head gasket had started leaking and hence drawing air. This must have happened while riding at high rpm or something. So as you know, airleaks once again proved themselves to be the ultimate silent killer. Later, I began thinking about the limitations of an air-cooled motor. I couldn’t help but wonder that had a head gasket gone on a water-cooled motor, the effects would surely not have been as detrimental. A bit of water loss and bad compression, that’s about it until you spotted it after the ride. I would surely buy you time and allow you to spot the problem before it blows up in your face.
After this episode, I decided that instead of rebuilding the YFS for the Umteenth time, I would fast track the Project. Why not!?
And so began the stripping process. I pulled the motor apart and found a few interesting things. How exactly do you shear off the primary drive shaft?!
Anyway, after finding the service manual and reading through some specs, I realised this motor could not be more different yet more alike to the Blaster.
The main differences lie in the following points:
· Cylinder angle
· Crank shaft length
· Shift drum length
· Shift star
· Gear Shifter length
· Magneto
· Cylinder
· Hear
· Water cooling
· Clutch pushrod
· Primary drive gears
· Balancer shafts
· Gears sizes (Teeth/Ratio)
· Water pump
· Crankcase induction
· Port timing
· Cylinder
The similarities between the YFS and WR are as follows:
· Clutch boss
· Clutch basket
· Clutch plates and disks
· Clutch springs
· Conrod
· Kicker mechanism
· Idle gears
· Balance gears
· Crankcase volume
· Crank bearings
· Transmission bearings
· Gear shafts
I will get into more detail on all of these points as I go along and figure out compatibility with various components.
In the meantime, I have myself a 3mm stroker and Mikuni 34mm carb which should add some spice to the mix once things are rolling!
Stay tuned and Il keep you posted!
Right, last year, I got my hands on a WR200 motor. Now some of you may be thinking, “Err, doesn’t he mean the DT?” Indeed I don’t, Yamaha did in fact manufacture a WR200 between 1991 and 1995 or so.
So what’s special about it and how is it different to the DT? Well think of it as the 4th generation of the 2 stroke 200cc Yamaha built for their dirt bikes and quads. We start our lineage with the popular IT175 in the 70’s which featured the 66mm bore, characteristic of this lineage, it’s sort of like their family trait! The stroke however was 50mm. Throw in a 34mm Mikuni and you had 14.5 horses under the tank. From there, the IT200 was introduced which had more displacement courtesy of a 56mm stroke and essentially was the same motor as the 175, but with a whopping 26.6HP. Yamaha then took the IT200, tamed it down a bit added an oil injection system, increased the stroke to 57mm and through it into a Yamaha Blaster fame we all know and love on this site. The Blaster was developed to be an “Entry Level Sport Quad” and with all of 18HP to haul itself around with. It served a big sector of the market well, but the eagle eye rider would have noticed a marked power disadvantage between his Blaster and his mates IT200. Yamaha achieved the “Tractable” power by restricting the intake to a 26mm Mikuni carb and fiddling with the port timing and combustion chamber design. Soon afterwards, the DT200 was developed. This was a big step forward with its water cooling and Yamaha Power valve System being the major development and sales points. This all made the DT, faster, cooler and more reliable. Strangely, a 28mm carb was all that was needed to produce a monster, 33HP from this machine. They also started fiddling with the gearbox and gave the DT longer legs than previous variants of this engine.
In the early 90’s work began to enhance this motor even further. New design principles were implemented and developed to produce a 199cc WR200 (Wide Ratio). The new features included a direct crankcase fed induction system, a 30mm Mikuni TM carb, bigger reed cage, better port timing, even longer gearing as well as a nikisil lined cylinder with a slightly bigger bore at 66.8mm. Although Power is rated as being less than the DT at 27.6HP, the torque is notably higher. With the WR’s purpose as a trails bike in mind, the developers opted for torque over power for those technical sections were too much power is your worst enemy.
No further development was carried out after the WR200, and so it is fair to say that the WR200 is the pinnacle of the 200cc from Yamaha. Its direct competitor was the KDX from Kawasaki and the two are for all intent and purposes, very well matched.
http://www.motorcyclespecs.co.za/model/yamaha/yamaha_wr200r 93.htm
So the idea of fitting the WR to the Blaster is indeed a case of giving the Blaster what we all knew it always deserved, a real deal, “let me show you a thing or two” 200cc engine!
I started when I got the engine, I immediately plonked it on the workbench and gave it a good look. I then compared the bottom end from my spare blaster engine with the WR, there are a few obvious differences.
On the whole however, things look promising, I have already made peace with the fact that a few frame mods will be needed to get this to work properly, but on the whole, and it should be a neat fit!
Recently, I burnt a hole through the top of my piston while doing 30km of flat out WOT gravel riding, on a perfectly sealed, standard bore, 330 main jetted carb with mild porting. I couldn’t figure out why this had happened, until I pulled the head off. I noticed the head gasket had started leaking and hence drawing air. This must have happened while riding at high rpm or something. So as you know, airleaks once again proved themselves to be the ultimate silent killer. Later, I began thinking about the limitations of an air-cooled motor. I couldn’t help but wonder that had a head gasket gone on a water-cooled motor, the effects would surely not have been as detrimental. A bit of water loss and bad compression, that’s about it until you spotted it after the ride. I would surely buy you time and allow you to spot the problem before it blows up in your face.
After this episode, I decided that instead of rebuilding the YFS for the Umteenth time, I would fast track the Project. Why not!?
And so began the stripping process. I pulled the motor apart and found a few interesting things. How exactly do you shear off the primary drive shaft?!
Anyway, after finding the service manual and reading through some specs, I realised this motor could not be more different yet more alike to the Blaster.
The main differences lie in the following points:
· Cylinder angle
· Crank shaft length
· Shift drum length
· Shift star
· Gear Shifter length
· Magneto
· Cylinder
· Hear
· Water cooling
· Clutch pushrod
· Primary drive gears
· Balancer shafts
· Gears sizes (Teeth/Ratio)
· Water pump
· Crankcase induction
· Port timing
· Cylinder
The similarities between the YFS and WR are as follows:
· Clutch boss
· Clutch basket
· Clutch plates and disks
· Clutch springs
· Conrod
· Kicker mechanism
· Idle gears
· Balance gears
· Crankcase volume
· Crank bearings
· Transmission bearings
· Gear shafts
I will get into more detail on all of these points as I go along and figure out compatibility with various components.
In the meantime, I have myself a 3mm stroker and Mikuni 34mm carb which should add some spice to the mix once things are rolling!
Stay tuned and Il keep you posted!
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