Athena 170
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@bananper Without a Dyno Graph it's hard to tell. But due to the port timings being way out, once you start climbing through the revs, the opportunity for the power to be made starts diminishing.
Hence why at low RPM's you have the extra CC's to help deliver more low down grunt, but the power tapers off and the gap between a stock barrel and Athena barrel starts to thin out. You definitely lose overrev with the big bore, so the stock barrel will continue to rev out further, allow you to zap out a few extra ponies with the help of porting.
Two strokes in general don't love over square engines, the fact that the big bore kit widens the bore whilst maintaining the stroke exacerbates this. A longer stroke is ideal for this kit. There is the potential then, for the longer stroke to correct the port timings, out by 3mm I'm led to believe, to actually correct the issues with the barrel.
But by the time you've done all that, you may as well have just thrown a 3XP0 cylinder and crank and be done with it.
I haven't the expertise or experience to really comment on how any of this translates. But it's just what I've read from various sites.
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I believe the dt200r is a 3ET barrel. Dt200wr and wr200 share the same 3xp cylinder which is nickasil plated but you can buy steel sleeves for them. I believe the dt200wr is autolube and has a tachometer at generator different dor the electrics
Also the dt230 cylinder and crank is a possibility
never seen this one done. -
Best option is to get your standard 125 barrel re-sleeved to 66mm then fit a Wiseco Forged Yamaha BLASTER YFS 200 Piston Kit 66mm. Piston gudgeon pin and small end bearing same size as dt 125, you will also need your head machining to suit. Kpm or Pjme will re-sleeve the barrel to 66mm and machine the head to match and also works out including forged piston kit and work to barrel and head less than half the price of the Athena kit. Also having a steel liner gives you the option of several rebores. https://www.ebay.com/itm/Wiseco-Yamaha-BLASTER-YFS-200-Piston-Kit-Top-End-Bearing-66mm-Std-Bore-1988-06-/173027889008?fits=Make%3AYamaha
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@2stroketerry very cool I love all the little Frankenstein things you can do to engines
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Wossner do a forged piston kit for the dt 125 that is 61mm and the absolute maximum can bore a dt barrel to. Gives around 146cc. https://www.ebay.co.uk/itm/Wossner-Piston-Kit-KTM-LC2-1991-2006-Yamaha-DT125-Over-Bore-61mm/371410153446?hash=item5679c52fe6:g:YI8AAOSwHnFVyn8J
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@2stroketerry what gains should I expect from doing the overbore and porting
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Hi, If you get Karl at Kpmotosolutions to re-sleeve the cylinder to 66mm to suit Forged Wiseco blaster piston and machine the head to new bore size and alter squish and compression to suit. He will also fully port the re-sleeved barrel to suit your driving style, some people want a really high reving max horsepower top end like a YZ 125 for example. He can also bore out the standard Mikuni 28 TM carb to 30mm but will need to enlarge your inlet manifold to 30mm and sort your own jetting out.
With the price of the forged piston kit, Karl re-sleeving and porting the barrel and head plus the price for boring out the carb, it will all add up to less than the Athena 170cc kit. When bored out to suit 66mm Wiseco piston the engine will be 176cc.
With a decent exhaust on it will be over 30 bhp at the rear wheel, have to fit set of stronger clutch springs too. With all the mods done and the carb setup spot on will do 115 mph and wheelie in every gear. http://www.kpmotosolutions.com/ -
@2stroketerry said in Athena 170:
Best option is to get your standard 125 barrel re-sleeved to 66mm then fit a Wiseco Forged Yamaha BLASTER YFS 200 Piston Kit 66mm. Piston gudgeon pin and small end bearing same size as dt 125, you will also need your head machining to suit. Kpm or Pjme will re-sleeve the barrel to 66mm and machine the head to match and also works out including forged piston kit and work to barrel and head less than half the price of the Athena kit. Also having a steel liner gives you the option of several rebores. https://www.ebay.com/itm/Wiseco-Yamaha-BLASTER-YFS-200-Piston-Kit-Top-End-Bearing-66mm-Std-Bore-1988-06-/173027889008?fits=Make%3AYamaha
Do the windows in the skirt effect it? The blaster 200 isn't crank induction I think
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Hi @Louis-James . no the windoes in the skirt don't matter and don,t affect the running at all even though dt has case induction, if anthing add slightly to the power as some 2 stroke tuners add windows to piston skirts. Strenth wise pistons are ok too
with windows in the skirt and being forged makes them a lot stronger than cast pistons, also a superior alloy is used in forged pistons. -
So what's the crack with the 3bn cylinders and the tzr 2RH?
Been a while since talking about 125 cylinders I need a refresher.
How many different genuine Yamaha cylinders fit the DT?Does the one of the tzr 250 cylinders fit?
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@louis-james Don't know about TZR cylinders.
But
3MB
3MBP
4FU
Are bolt ons.The 3BN has a slightly bigger bore, so shorter stroke, as a result, a 3MB con rod will bit too long.
