Difference tzr125 and dt125
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@calum it must be accomplishable to port a 4DL to perform like the SP right?
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@irongamer727 No mate, the port timings are completely different. The transfers, the fact it has auxiliary ports.
Just good TZR SP barrel and compare it to your stock DTR barrel, then you'll know what I mean.
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@calum sounds like one nice cylinder.
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@calum going a bit off topic now but what would you say makes the enduro 125's cylinder's produce so much power?
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@irongamer727 Higher compression, more aggressive port timings, bigger transfer ports, cleaner transfers, bigger boost ports. Auxilary boost ports. More spark advance. Increased squish clearance. Better designed crank journal spaced for increased fuel atomisation. Smoother inlet tracts. No emission laws to adhere to. Smaller piston to wall tolerances. Less blow by, single rings... The list goes on.
If you're really interested then I'd recommend reading a book on a the subject as it's not something I am going to describe in a sentence or two...
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@irongamer727 I'd recommend Tuning For Speed By Phil Irving PDF available online
http://tuningforspeed.com/files/Tuning_for_Speed.pdf
As a start
Then have a read of Graham Bell's Two Stroke Performance Tuning
Then Graham Bells Engine Performance TuningYou always want to read in Chronological order. Phil's book was written several decades ago, Grahams during the late 80's.
Irvin was way ahead of the curve and received the highest engineering award they have in Australia. Named after him called the Irving award. The guy is a genius.
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@calum I have Graham 2 stroke at home. First time I read it I didn't understand much. Perhaps time to do it again.
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@irongamer727 I refer you to my previous statement.
Start in chronological order. Ready Phil Irvins book first. As this will introduce to the concepts at the time, which are assumed or taken for granted in later books.
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@declan The barrels are cast with only so much metal in them. It's not a case of inside liner. The walls are only so thick and can only be ported so much.
You could spend thousands and thousands porting the barrel, and the result is ultimately worse than a £60 RS barrel. It's cost vs Reward.
If I was going to spend X amount of money for maximum bang for buck, do an engine swap. It'll be cheaper and better.
So I'd rather swap the DTR engine out for a 2RK engine out of the UK spec TZR. Or better still Rotax 122 engine, or a YZ engine or anything else.
By all means, mildly port and tune the DTR engine, but accept that there are limitations. Ensure that what you spend, is less than what it would have to have simply swapped the engine.
That accounts for time as well as money. An engine may cost less than a decent port, but if it takes a year to fit then it's cost you time.
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The DT is still pleanty fast for what it is, a road going bike developed for teens on L plates, it's a damn site quicker than any of the 4t 125 bikes around, and they get incredible reliability when right. I plan on doing a lot of miles with long runs this year, so simply a road going mx would not work.
