Right hand to left hand shift change time frame

Why in the world would Yamaha build a bike with a six speed trans and sell it in some market(s) (U.K.) and block off the top gear? The two RD350s I had, had the slickest shifting trans of any bike I've had.
 
If I remember correctly I think it was UK Motorcycle Mechanics magazine that did an article on how to convert the gearbox to 6-speed. I believe it was then necessary to take care not to change from 6th to 1st.
 
" Early production models were supplied with five-speed gearboxes, but owners soon discovered the box in fact contained six sets of cogs, with sixth gear blanked off with a stopper on the selector mechanism. Modifying the gearbox to gain the extra gear involved not only removing the stop plate but also fitting a revised pawl plate."
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Buying Guide: Yamaha RD250 | Classic Motorcycle Mechanics Magazine

Yamaha RD250 Yamaha launched its first 247cc two-stroke twin, the YD1, in 1957. Following a series of piston port YDS models, the RD250 (for ‘race dev ...
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The RD250 was the more popular model in the UK as it was possible to ride up to 250cc on a learner licence at the time.
 
L.A.B. said:
" Early production models were supplied with five-speed gearboxes, but owners soon discovered the box in fact contained six sets of cogs, with sixth gear blanked off with a stopper on the selector mechanism. Modifying the gearbox to gain the extra gear involved not only removing the stop plate but also fitting a revised pawl plate."
www.classicmechanics.com

Buying Guide: Yamaha RD250 | Classic Motorcycle Mechanics Magazine

Yamaha RD250 Yamaha launched its first 247cc two-stroke twin, the YD1, in 1957. Following a series of piston port YDS models, the RD250 (for ‘race dev ...
www.classicmechanics.com www.classicmechanics.com

The RD250 was the more popular model in the UK as it was possible to ride up to 250cc on a learner licence at the time.
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Yep, that was me, and I bought one of the first 5 imported. It wasn't in UK showrooms until at least July '73. I ran mine out of the dealers with a brand new 'M' registration on the 1st August '73. I asked the salesman how many gears it had, he had to change up and down the box a couple of times to find out!

In MCN reports at the time that stopper was called a dingus! The 5th gear ratio was plenty high enough, you would have to have changed the final drive ratio to make 6th worthwhile.

Within a month, I had passed my test on it! Bugger! A year later I bought a Commando, right foot gear change!
 
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quawk said:
Why in the world would Yamaha build a bike with a six speed trans and sell it in some market(s) (U.K.) and block off the top gear? The two RD350s I had, had the slickest shifting trans of any bike I've had.
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Because when they sold it in the US with access to all 6 gears, they ended up getting sued by the family of a deceased rider!

It was indeed a great gearbox and pretty much what went into the TZ250/350 race bikes.
 
acotrel said:
So what happens when you are speeding down a long straight stretch of road and change up one time too many and get a neutral ? Do you hit it again and get first gear, our do you try to change from neutral back into top ? Top gear might be turning relatively slowly ? If you went from top to neutral to first, it might become interesting.
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I never rode a bike that had that issue.

I did, however, race Jeff Moyer's H1R Replica in AHRMA's Formula 500 class and was ever mindful to make sure I counted every gear so as not to fly off the track in neutral instead of engine braking in 1st gear! Totally foreign bike with on/of switch for a throttle, no rear brakes to speak of, and could flip backwards if the clutch wasn't properly released on launch. Left foot shift bike with a right foot shifting rider, but I never screwed up once in 8 races on 4 different tracks. Never put a tire off the track proper, and finished 3rd in the F500 championship out of 29 riders in the class. Now THAT was a hoot! (pardon non-Norton content, but the topic was opened previously)
...age 51 at the time...

barber06.jpg
 
SteveA said:
Because when they sold it in the US with access to all 6 gears, they ended up getting sued by the family of a deceased rider!
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Not to try to understand the legal issue, and it's irrelevant, but how can having an additional gear in the trans be cause for someone's death. The RD350s certainly weren't or aren't the only bikes with a 6 speed trans. Sounds like another example of ambulance chasing lawyers and law firms looking for another pay day.
 
quawk said:
Not to try to understand the legal issue, and it's irrelevant, but how can having an additional gear in the trans be cause for someone's death. The RD350s certainly weren't or aren't the only bikes with a 6 speed trans. Sounds like another example of ambulance chasing lawyers and law firms looking for another pay day.
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You said it - It can be cause for death because lawyers exist .
I was recently at an open house at a small local airport. The Civil Air Patrol was there with a brand new Cessna 172 . The guy told me that nearly 25% of the total cost - $ 350 - 400 k ? - was a premium to cover manufacturer’s liability.
 
L.A.B. said:
If I remember correctly I think it was UK Motorcycle Mechanics magazine that did an article on how to convert the gearbox to 6-speed. I believe it was then necessary to take care not to change from 6th to 1st.
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Yep there was an article
I have it somewhere
 
baz said:
Yep there was an article
I have it somewhere
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A shift from 6th to first at speed would almost certainly crash a bike. A change in the wrong direction between lower gears, can be bad enough to destroy a motor. I did not know that unlocking 6th in the Yamaha box, enabled a shift into 1st. The RD400 box was closer ratio than the RD350. I gave one to my mate's son - he was playing with that stuff. In its year the TR250 Suzuki was better than the Yamaha 250. The porting concept was different. The T250 Suzuki racer I built was extremely fast. I think the velocities of the gases in the Suzuki transfer ports must be much higher than in the Yamaha. Some guys have tried using Yamaha port timings in Suzuki motors. It does not work.
 
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