Vintage Project - Yamaha DS7 - 250

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raYzerman
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Re: Vintage Project - RD250

Post by raYzerman »

Ah yes, but to do it right you have to put a Triumph seal in an ES first, then replace with the correct ES seal..... in your case, have the RD seals ready but also a set for the DRZ... we'll get it right eventually.
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Re: Vintage Project - RD250

Post by bungie4 »

extrememarine wrote: Thu Oct 25, 2018 5:46 pm If Ray helps me put it back together, the fork seals will get flipped and end up right side up then.

I plan on running these tires - just going to add some gorilla tape to the inside to keep them together about 90...
wheatonFJR wrote: Wed Oct 24, 2018 9:35 pm Looking good, cept mebbe that crack in your front tar...that you were replacing when the other stuff gets done.

I'm not sure, but from here it looks like the fork seals are installed upside down.
Black shoe polish on the outside of the tars. That theirs a tip from Burt Munro. How could it be bad advice?!
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Re: Vintage Project - RD250

Post by kliembiddle »

Black shoe polish on the outside of the tars.

You are from West Virginia.....?
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Re: Vintage Project - RD250

Post by extrememarine »

Progress update - 2/10/19.

No where to go but up from there...

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Re: Vintage Project - RD250

Post by wheatonFJR »

Nice clean lines...
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Re: Vintage Project - RD250

Post by philharmonic »

I guess you already know this, but this is not an RD it is a YDS7.
Last edited by philharmonic on Thu Feb 14, 2019 8:34 am, edited 1 time in total.
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Re: Vintage Project - RD250

Post by extrememarine »

My historical education on this is still in it's infancy. Now I realize why there was some confusion when I said earlier there were not reeds - RD250 in '73 had reeds, the DS7 (250) had piston port induction. This little snipet below says this bike put out 30hp at 7500rpm - holy cow - that's like two complete DR650's!!
philharmonic wrote: Mon Feb 11, 2019 9:56 am I guess you already know this, but this not an RD it is a YDS7.
From wiki link:

The Yamaha DS7 motorcycle was made in 1972 for one year. It was a 250cc twin two-stroke that made 30 hp @ 7,500 rpm. Top speed was 93 mph. 12v battery ignition. five-speed gearbox. 1/4 mile in 14.8 seconds.

The DS7 was the initial forerunner of the Yamaha RD series of motorcycles started in 1973. The major difference between the 250 cc DS7 and 350 cc R5 of 1972 and the 1973 RD250 and RD350 was that the DS7 and R5 utilized piston-port induction, whereas the RDs were introduced with reed valve induction. The 250 was "oil injected" meaning that although the 250 was a 2 stroke or (2 cycle engine) there was no need to premix the gas and oil. The gas tank only contained gas but the oil was injected from an oil tank beneath the seat.
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Re: Vintage Project - Yamaha DS7 - 250

Post by Bust »

I have a 28 horse Kohler V twin on the shelf. I bet with all the brain power on tech day we could mount it in there.
Now how to couple it with a baker 6 speed.
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Re: Vintage Project - Yamaha DS7 - 250

Post by extrememarine »

The fact that the stock motor is advertised with 30hp is nutz - I'll bet that Kohler weights 40lbs more than the 2 stroke!!

Baker 6speed - hmmm....
Bust wrote: Tue Feb 12, 2019 10:53 am I have a 28 horse Kohler V twin on the shelf. I bet with all the brain power on tech day we could mount it in there.
Now how to couple it with a baker 6 speed.
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Re: Vintage Project - Yamaha DS7 - 250

Post by mi_pjk »

Bust wrote: Tue Feb 12, 2019 10:53 am I bet with all the brain power on tech day
Is that what you call one of those : "Oxy-Morons" ?

:stickpoke:
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Re: Vintage Project - Yamaha DS7 - 250

Post by raYzerman »

Dayum.... the Kohler V-Twin in my tractor is only 23 horse...... hmmm, trailer or truck..... hmmmm.
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Re: Vintage Project - Yamaha DS7 - 250

Post by MindWebs »

93mph.. that's it?

My 75 Kawy s1 250 is good for 115.

But a little port'n polish job helps ALOT.

So consider it, porting and polishing should help it breath another 10 HP. Maybe? Maybe not that much...

At least it would accelerate faster :twisted:

Because that 2 stroke smoking screamer needs faster power band hits, right?

Then you can honestly say some joker put a spare tire on the front of your uni-cycle.

(Factory rating for the kawy is around that 95mph range)
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