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1974 Ty250 Engine Mods


twinshocker
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I have a 1974 yamaha ty250 . Does anyone know of anything to make it more snappy and powerful..It's on it's 2 nd overbore. I already has boysen reeds and a reed spacer .I also added a Sammy Miller silencer.It is already pretty good ,But i rode a ty at a trials and was amazed.in the difference in mine and the other one.The owner said he bought it that way. Anything will help Thanks :thumbup:

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More snappy: lighten the flywheel

More powerful: source a later model cylinder and head. The TY250B (1975 model 434), C and D model (493 model) TY250s are noticably more powerful than the TY250 (1974 model 434) in standard trim.

More powerful: Big bore it to 320cc (DT360 piston, new sleeve, welding and machining). Not cheap but works

More powerful: fit an ignition that has an advance curve

More powerful: raise the compression ratio

More powerful: fit an expansion chamber

Talk to Bob Ginder at B&J Racing

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  • 2 weeks later...
 
  • 12 years later...
On 7/19/2006 at 8:32 PM, rock hopper said:

I have a stock ty250 with the exception of a Kehin pe 28 mm carburetor,rides like a modern bike!!!!If you want to find out more about jetting for it send me a e-mail

Rock hopper,

  A new carb would be the next thing that my bike needs. I still have the old TK on it.  So if you still have the information ( I know it's an old thread)  That would be much appreciated!

Thanks!

 

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  • 7 months later...
On 7/19/2006 at 8:32 PM, rock hopper said:

I have a stock ty250 with the exception of a Kehin pe 28 mm carburetor,rides like a modern bike!!!!If you want to find out more about jetting for it send me a e-mail

rock hopper, I saw your good comment on changing out the stock TK carb for the Kehin pe28.  Can you give me some details as to how much money and rework this would entail? my TK is about on it's last legs.

Thanks in advance!

Tillerman6

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Get hold of mid-atlantic trials, they sell ready to go OKO D-slide carbs for a good price. I'd suggest getting the 26mm kit, you need to heat up & stretch the airbox boot to fit over the carb 

I have seen the kits on eBay from them before but being in the US it would be easier to buy direct

http://www.mid-atlantictrials.com/TY-Yamaha.html

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