Servo motor issues
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@spookdog I have 3NC-00 on my DTR and is revving a little over 11000rpm with Athena 170 kit when driving,parked and full throttle went up to ~13500rpm.
@MadGyver said in Servo motor issues:
@spookdog I have 3NC-00 on my DTR and is revving a little over 11000rpm with Athena 170 kit when driving,parked and full throttle went up to ~13500rpm.
I gather that the port timing is quite different on the Athena 170?A normal derestricted DT - well, at least the three I have owned - would go decently up to 6-7000 where the torque falters a bit - likely due to YPVS timing because if you pin it open or closed then there is where there is a difference - and then pull well to about 9500 rpm.
Does yours deviate from this substantially? A high-strung porting would probably ruin what little torque there is below the peak power band, I presume.
Asking because I am contemplating an Athena 170 myself.
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@Hark_Ptooie The cylinder is rised 1.1mm,head gasket is custom 0,55mm have a picture on my project thread.
Exhaust port is 199 degrees. Haven't lost torque below power band because of the YPVS and 170ccm. It was cruising with 6th at 80km/h at 4500-5000rpm. I have a 2RH gearbox and 16/46 sprockets. -
I just read your project thread, it is impressive.
So you get normal torque down low, then it goes to 13k? @_@
I understand that raising the cylinder would move the ports up and improve high-end. And the head gasket is thinner than stock, I presume, to maintain compression? That sounds like a hilariously simple way to tune a 2-stroke that I never heard of before!
I sha'nt try it myself, because I don't have the acumen or facilities to make sure the rest of the engine is up to snuff, but I am intrigued.
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I just read your project thread, it is impressive.
So you get normal torque down low, then it goes to 13k? @_@
I understand that raising the cylinder would move the ports up and improve high-end. And the head gasket is thinner than stock, I presume, to maintain compression? That sounds like a hilariously simple way to tune a 2-stroke that I never heard of before!
I sha'nt try it myself, because I don't have the acumen or facilities to make sure the rest of the engine is up to snuff, but I am intrigued.
@Hark_Ptooie The TZR R 4DL Belgarda models ran a slightly modified 3mb with a raised exhaust port. Probably great in the TZR, but in the DTR it just negatively affects the bottom end.
I do rate the 170 kit these days, if you don't mind a drop in overrev for just more cruising power.
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I would actually want more bottom end, for city and trail. Top end is fine for red light dashes.
I won't be taking this on the motorway - thrice I have had piston seizures at flat out top speed and it is no fun. Getting a bigger bike for longer trips next year, this one is more of a nostalgy toy for dorking around.
Apropos red light dashes - I used to race gixxers with my DT back in the day.
Full throttle, "NYANYANYANYANYA", release the clutch with a bang at green. As you jerk your foot up from the ground it is about time to crash it into second gear. As your redline third the GXSYZRRR1750RRR bike would have just reached its power band and come up roaring from behind.
Right as it's time to brake for the next red light, where you end up side by side. Their frustration was delicious.
Also: made me practice drag racing starts with my later CBR929 because I did not want to get shamed the same way myself...
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And apropos racing big bikes - another anecdote:
We had a nice winding road where I grew up, where bikers liked to play around.
I once got there at the same time as two sportsbikes, and we set off. My DT did flat out 120 on the straights, 120 in the curves, because I knew the road and bike like my hand. The big bikes left me on the straights, but I gained in the curves.After a few kilometers I saw how they drove more and more erratically, because they were obviosly furious that they could not shake me off. Many quick glances back under the elbow, and jerking steering.
When we came to a big road they vanished over the horizon like a salary, while I smirked blissfully.
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I don't think I'd get that on my DT, but certainly on the Cagiva/RS vs 400s/600s I reckon I could smoke them in the twisties! Keeping it absolutely gunned the whole way. I was out on a MT700 the other week test riding that, and yeah it's got the grunt, but it was 5k at 70MPH and National Speed limit is 60, so in those tight twisting roads...
I always love watching this little video.
https://www.youtube.com/watch?v=3ajFb3pe-TE
Yeah I'm sure the 600 could have overtaken, but the point is, there is always room for a smoker in your life!
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The thing with 4-cylinder 4-strokes that I think that few know is that they have a quite nontrivial rotational inertia in that transversal crank shaft, resisting angular motion what with the gyroscopic effect. The camshafts and geartrain probably also add to it. So they are quite resistant to flicking around.
I had an RD500 and it was big as a 125er and could be thrown around like a badminton racket. V4 twostroke, not much in terms of long heavy rotating components to cause gyroscopic inertia.
Then I got a CBR929RR and it was like riding a water buffalo. Surely the modern frame added to it - you could not steer it with your butt like a DT, you really had to shove the steering to make it lean over, I nearly traversed a roundabout center the first time I rode it - and at high speed and revs it really did not want to lean over. You had to wrestle it. Doing 250 km/h made the roads really narrow, you'd plan your trajectory well in advance.
So yeah - I rode faster on my 88 hp RD500 than I did on my 152 hp CBR. It'd absolutely outrun the CBR with me in the seat, at least.
It may be one of the reasons why Ducati hung on to the roadracing throne for so long. A V twin doesn't have a fraction of the polar inertia a transversal I4 has.
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1997:
Hilarious thing, but it developed a plenitude of electrical problems that I was to inept to manage, so I sold it cheap. Regrets.
