HELP:Vibrations in RTR 160 - Page 3 - xBhp.com : The Global Indian Biking Community

Samarth 619 · 11-14-2008, 07:38 PM

Quote:

Originally Posted by Joel

The vibrations are due to the following reasons,
1. Being a short stroke engine
2. Short gearing. The RTR is the shortest geared bike and hence even at lesser speeds, the engine rpm is high. The engine spins at 83rpm for every 1kmph. As opposed to 75-77 of most other bikes.
3. The grunt produced by the engine, courtesy the ports is higher near the peak torque. Hence u experience the most vibes around 5000-6000rpm.

The RTR is never a bike that will be as smooth as a Zma. A short stroke engine is never super linear. An R15 feels butter smooth coz of its stroking factor, but higher up, it begs for mercy. Also its not even meant to be ridden as a commuter at 60kmph. It was always meant to be threashed and kept at peak revs. You'll enjoy it more than riding it like a 100cc bike at 4000rpm.
The older apache was also short geared. You dont experience vibes on the Fiero coz it has a taller gearing as opposed to the RTR/A150 although the engine is ideally the same.
i have run a taller gearing set-up on my RTR in a modified set-up. It was still faster than a Group D spec RTR and yet smooth. I'm talking about a set-up with a freeflow and full works.
This IS the character of a short stroke engine.

Yes, Exactly what I was suspecting!! I was noticing that these ZMA & Unicorn had less vibrations than Pulsar, Apache, Hunk, etc ... and I was suspecting this Short Size of Stroke for this ... Now, you confirmed it!

Regarding over gearing, you got even more acceleration by the freeflow setup, that's Good!

Quote:

The engine spins at 83rpm for every 1kmph. As opposed to 75-77 of most other bikes.

My question is - this data is based on a gear ratio of 1:1 ... right? Or is there another factor involved? ???

and Top Speed in 1st gear is 41, which is enough I think ...

Joel · 11-14-2008, 07:38 PM

If anybody has ridden anyother short stroke single cylinder, u wont be talking about the vibes on the RTR. Ride a CBR150R, Suzuki FXR150, GF125 etc to know how a short stroke engine feels like. Just ride them and then tell me if they are super linear.
I got a chance to feel the CBR150R and the engine grunt and vibes were really evident. An R15 in comparision feels like a engine running like an electrical motor. Thats long stroke for u.
However in a multicylinder short stroke, the vibes are pretty much ironed out due to even balancing by supporting cylinders.
People used to cry about the vibrations on the GF125. With a stroke of 48.8mm, the vibes are very normal I would say. Max, u can have a balancer shaft to ease things a bit. The CBR and FXR also run balancer shafts to iron out vibes.
The R15 runs a balancer shaft to smoothen the engine further. Hence, it feels like a silent electric motor.
Also consider the fact that the RTR is the only 2-valve short stroke engine. All others in the example are 4-valve.

Joel

Samarth 619 · 11-14-2008, 07:42 PM

Quote:

Originally Posted by Racing Hart

Can u explain what short gearing and tall gearing is....??

Dude, Short gearing is a "Setup" which results in good Acceleration (Pickup) but reduced Top Speed ...

Long gearing is a "Setup" that achieves more Top Speed & even Mileage, at the cost of some acceleration ...

---
@ Joel: Bro, kindly explain that RTR Gearing question I asked ... With a 1st Gear top of 41, it's good enough, right?

Joel · 11-14-2008, 07:46 PM

Quote:

Originally Posted by Samarth 619

ZMA & Unicorn had less vibrations than Pulsar, Apache, Hunk, etc ...

Regarding over gearing, you got even more acceleration by the freeflow setup, that's Good!

My question is - this data is based on a gear ratio of 1:1 ... right? Or is there another factor involved? ???

.

The ZMA is the only long stroke in your examples. Hunk, Apache 150, Unicorn are square engines. Lets not talk about the vibrations of the Pulsars. This topic will head somewhere else then.

I didnt get more acceleration with a freeflow alone, It was a set-up with big valve head, altered ports, higher compression, bigger carb, freeflow filter, fully tuned exhaust etc. Even with a tall gearing, it was faster than any fully light weight Group D spec RTR that too with a light rider. From standstill acceleration to top-end.

The gearing is not 1:1 factor. RTR's 5th gear ratio is 0.88.
Its obtained from various variables. Nothing that we need to discuss about here. It was for reference sake.

sam92 · 11-14-2008, 09:09 PM

[QUOTE=rennycornelius;130784]

Quote:

Originally Posted by onlinesatish

If u ask me the performance increase is negligable....but if u still have that itch...then go ahead

will be puttin it as soon as possible.............

good choice dude

Quote:

Originally Posted by Samarth 619

Dude, Short gearing is a "Setup" which results in good Acceleration (Pickup) but reduced Top Speed ...

Long gearing is a "Setup" that achieves more Top Speed & even Mileage, at the cost of some acceleration ...

---
@ Joel: Bro, kindly explain that RTR Gearing question I asked ... With a 1st Gear top of 41, it's good enough, right?

well said bro .. thank god joel came to rescue

11-14-2008, 07:38 PM	#22 (permalink)
Joel Race Concepts Join Date: Jun 2004 Location: Bangalore Posts: 1,844	If anybody has ridden anyother short stroke single cylinder, u wont be talking about the vibes on the RTR. Ride a CBR150R, Suzuki FXR150, GF125 etc to know how a short stroke engine feels like. Just ride them and then tell me if they are super linear. I got a chance to feel the CBR150R and the engine grunt and vibes were really evident. An R15 in comparision feels like a engine running like an electrical motor. Thats long stroke for u. However in a multicylinder short stroke, the vibes are pretty much ironed out due to even balancing by supporting cylinders. People used to cry about the vibrations on the GF125. With a stroke of 48.8mm, the vibes are very normal I would say. Max, u can have a balancer shaft to ease things a bit. The CBR and FXR also run balancer shafts to iron out vibes. The R15 runs a balancer shaft to smoothen the engine further. Hence, it feels like a silent electric motor. Also consider the fact that the RTR is the only 2-valve short stroke engine. All others in the example are 4-valve. Joel __________________ joel@raceconcepts.in

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