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Yamaha Ty250 Modifications


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#1 mattylad

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Posted 10 November 2005 - 10:11 AM

What have you been doing to prepare a standard machine for trials.
My only mod to date is to lower and move rearwards the footrests.
What else is worth doing?

Do the wiseco pistons for yz/dt/it fit the ty what code number do I look for?
Do Boysen have reeds for the ty if so what is the code?
What gearing are you using.
What carb jetting for a standard engine.
Many thanks for youb help


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#2 amos

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Posted 11 November 2005 - 02:09 AM

On my 74 TY
I use boysen reeds, good change,
removed head gasket, used hi temp rtv to seal,
ported cylinder and modified head
removed the ring on the flywheel,
moved the pegs down and back
Suzuki front wheel
gearing 42x10
Use at times Yamaha rear hub with a Fantic
tubeless rim
modified upper triple tree to use pro taper bars
bars moved forward
Gas Gas Dellorto carbs, 25 or 26mm
jetting for 5,000 ft altitude
fork tubes 1/2 inch above the top triple tree
makes noticeable differance in turning
Bultaco muffler and stock rear

#3 dman

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Posted 11 November 2005 - 05:20 AM

Definatly get the sammy miller TY footpegs. Those stock ones are just useless!
Other than that, I think the TY came with reeds anyways. Put a good carb on it and put modern trials tires on it. Also remove the oil tank under the seat and make it so you just premix your fuel to save some lbs...

Other than that, well it prolly gets a big more expensive. But I like the stuff that amos did to his. Sounds like an awesome bike, but really modern. Does it meet vintage rules?


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Bultaco muffler

Gawd, I hope you aren't using that club foot silencer on it, please tell me your talking about the header/midmuffler... :ph34r:
"Give 'er some korn!"
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#4 mattylad

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Posted 11 November 2005 - 08:25 AM

Thanks for the info,
What did you do on the porting front and head mods?
I am looking for a more modern power delivery not the slow old girl of yesteryear.
Where your changes required as a result of altitude we are nearer 500mm above sea level.

#5 amos

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Posted 19 November 2005 - 03:30 AM

Here's pictures of my bike
Fred's bike

One thing that help's, is to remove the head gasket, clean the
surfaces, and use high temp silicone, torque and let sit 24 hours
before starting.
I machined the head, moved the squish band closer to the piston.
Cleaned up the ports, raised the exhaust about 1mm, knife edged
the transfer port lower edge from the crankcase.
Removing the band on the flywheel helps the motor rev quicker.
Boysen reeds really help.

Fred

#6 mattylad

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Posted 24 November 2005 - 10:28 AM

Ok,
Lowered the footrests,
removed head gasket,
machined half the flywheel weight off,
narrowed the side cover after removing the oil tank,
put on a modified tailbox with same internal design as a shirty mono,
28mm dellorto.
stiffened forks by removing tight would coils by 3" or so.
It certainly is a lot friskyer now only needs some Boyesens.
Does any one have a code number for the late post 1975 engine.
I have bought a cheap culinder off of a DT 250 i will fit this in a few weeks to see the difference.
Thanks for your help.

#7 amos

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Posted 27 November 2005 - 07:09 PM

Did you check the port timing/heights (dt250) against the ty cylinder?

On my TY I moved the pegs down and back, also I modified the upper
triple clamps to use Gas Gas handle bar stands, the bars mount forward
about 1.25 in.

I've been using either a 25 or 26mm dellorto, been playing with slides,
won't run clean with a "40" cut away, using 60 or 70 cut aways.

Using a Uni filter, done away with the stock air filter box.

What kind of modification to the clutch side cover have you done?

Anyone know of aftermarket triple clamps for the TY?

Next on the list is electronic ignition, and then a big bore kit.

Fred
Wyoming homepage

#8 mattylad

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Posted 29 November 2005 - 09:54 AM

For the side cover I just made sure it followed the line of the frame on left hand side.
I cut an alloy plate to use as a seat with a 2mm foam top. I.e as narrow and low as possible.
I have not yet got the barrel it is still at my fathers, the specs give 22bhp as a pose to 16 for TY so it will be more powerful, wether the bottom end goes only time will tell.
There is a big bore kit on ebay at the moment.
The clutch side cover is just cut away to leave the circular flywheel cover so that it does not trap mud.




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