Athena 125 with Athena pipe on dyno
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Those 19 hp - are they on the back wheel or crankshaft?
Original spec is 23 hp (crank), so if 19 hp is wheel then that would suggest 21% loss in transmission which sounds a bit high for a motorbike.
Of course a 35 year old bike is expected to lose some, I'm just wondering.
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The 170 kit on my setup is bloody awesome! I love it so much I bought 2.
Is it as fast as my RS or Cagiva... No. But I learnt long ago that the DT just isn't that type of bike. I have had my Athena ported and the bikes tuned and it rides just lovely. Pulls really well and is so much fun to ride!
With regards to vibrations, yeah that could do with dialing out. After long rides it feels like I have haptic feedback on my phone switched on. But I ride invariably so it's something I can live with.
I will get my bike dyno'd this year and post up the results...
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Piston and crankshaft counterweight should match each other. Increase the mass on one keeping the other the same causes more vibrations.
In fact, there are two optimums regarding the counterweight - one gives the least vibrations but a bit more bearing load, the other the least bearing load but a bit more vibrations.
Extra balance shafts are typically removing secondary vibrations from the conrod, so if the mass of those is the same they should still be right.
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Interesting, I would love to be able to dial away some of the vibration. It’s such a high frequency it sets my bones on edge sometimes…
I had a really strange thing happen a couple weeks ago. I was waiting on a roundabout to pull away and a car came by towing a huge caravan. It had the absolute worst squealing brakes that I’ve ever heard! The strange thing is my bike seemed to ‘pick up’ the frequency! The rest of the ride home my engine & expansion chamber was ‘ringing’ with weird harmonics! I Shit you not! 🫤
It sounded kinda like an overhead camshaft that was lacking oil! WTF?!… -
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I have the Dellorto VHSA 32mm Carburettor as found on the Rotax series of engines. I originally source a 4DL carburettor and saw another VHSA on eBay. I made a very good one from both of them, thinking at the time they were the same. They were not and therefore jetting on my DTR is WAAAAYYY different to that of the 4DL VHSA.
All I will say is, jet to suit, what works for my setup (bearing in mind how unique my setup is) may not be good for you.
But in essence, it's like a 140 main jet with a U13 needle (IIRC) But I bought the whole range. I don't run oil pump and have advanced the ignition + ported barrel with VForce4 Reeds and airbox delete with an underslung pipe. All of those will have factors on jetting so kinda take my setup with a pinch of salt.
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