TY250 / DT250 ENGINE SWAP

[owen]

HELLO

Is a TY250 twinshock engine the same as a DT250 engine, if not what is the difference?

So if not, what other bikes have the same engine as the TY or a engine that will fit (different cc etc)

thanks

Owen

[monty_jon]

HELLO

Is a TY250 twinshock engine the same as a DT250 engine, if not what is the difference?

So if not, what other bikes have the same engine as the TY or a engine that will fit (different cc etc)

thanks

Owen

Im not 100% sure but I would guess the gearing & cylinder porting is different

I would think the DT is closer to the early YZ rather than the TY

Edited February 9, 2011 by Monty_Jon

[old trials fanatic]

A DT engined TY just sold on flea bay. Wonder if the buyer knew what they were buying???

[owen]

So save me the mistake and explain.. whats the difference between the DT and TY engine? help

Edited February 10, 2011 by Andy
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[02-apr]

So save me the mistake and explain.. whats the difference between the DT and TY engine? help

About 30mph probably. I'm not taking the P but that seems the easiest way to sum up the various differences in tuning, gearing, expansion chamber, carb size etc that would render the DT hopeless for trials use.

[feetupfun]

maybe you are asking which parts are interchangable?

Unfortunately for would-be parts swappers, Yamaha made quite a few changes to their 250cc dirt bike engines during the time frame that they were producing the TY250 motor, so your question would have to take into account which DT250/DT2/DT3 motor and which TY250 motor you are referring to. Many parts are interchangable but also many are not.

As far as performance-oriented design differences, the TY250 motor has a much heavier magneto flywheel, similar port timing, closer gear ratios for 1,2 and 3 gears, lower compression ratio, smaller carby and very different exhaust pipe design to what was used on the DT2, DT3 and DT250ABCDEFG motors.

[mattylad]

If you are talking about twin shock then the crankcases and covers are all different. Some internal parts fit

[jc2]

There are 4 different sets of crankcases, each with diff engine mounts & diff non-interchangeable clutch covers:

1) DT1/2/3, YZ A/B,

2) DT A/B (& perhaps C)

3) TY

4) DT D etc (eng mounts are close to DT A/B but slightly diff

DT A/B/C/D cases are about 1" longer than TY cases, so its not a straight forward engine transplant, but I did read of somebody (foolishly, IMHO) putting a DT400 engine in a TY in USA (where else?) I think.

TY stud spacing on barrel & head is same as DT250 A/B/C/D, & interchange, but diff porting, Comp Ratio

Some internal cluth/primary gear/g'box parts exchange, but not all.

IIRC TY A & DT A use keyed primary gear; B/C/D models for ea use splines (or vice versa)

DT C/D gears were diff (wider) to DT A/B IIRC but not sure if the whole set will interchange.

Don't know if shifting forks & drums are diff/same

Edited February 12, 2011 by JC2