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Discussion Starter #1
So, I've owned my first RC for almost a year now. One of the first things I learned was how on/off the bike is at slower speeds just as you crack open the throttle. Bike is always "chomping at the bit" as someone else put it. What has been bothering me however is the large amount of slack in the driveline, which is really adding to the herky jerky-ness of slow speed riding. What I mean is this: when I have the bike on a rear stand and in gear, I can move the rear tire forward and backward a couple inches before it stops. There seems to be alot of play somewhere, and it seems like its within the transmission. The cush drive seems tight, the sprockets aren't excessively worn, the chain is brand new. When I'm riding and I go from deceleration to acceleration, the bike jerks forward a little due to the free play. Is this normal? Should I be concerned? What steps can I take to minimize this issue?
 

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Do you have your chain properly adjusted?
It should be around 25-35mm at the mid-point.
If there is too much slack, it will allow too much movement along with poor shifting.
The reason for that is extra slack will allow extra chain whip, causing the output shaft to rotate back and forth causing missed alignment with engagement dogs, and possible missed shifts or false neutrals.

It should also not be too tight. That puts tremendous strain on the chain and sprockets, plus all bearings in the path.
Better to run too loose than too tight.

While there is some gear lash in the drive train, from the the crankshaft to the the output shaft, there's nothing that can be done about it, short of redesigning the engine.
The RC51 does have an abrupt throttle, and the combination of greater rotating mass from the two pistons and flywheel over a 4 cylinder does compound the problem.

Most of the complaints about this behavior is during low speed operation, where the engine is below 3500 RPM and in lower gears, such as 1st through 3rd in slow traffic.
I've found the best way around this is to try and keep the engine around 4000 RPM and make smooth throttle gestures.
It also helps to cover the clutch lever with your hand, so you can disengage and reengage the clutch if traffic forces throttle action to induce the bike into jerky movement.
 

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if you can move the rear tire/wheel forward and back in the swinger you dont have your axle nut tight! regardless of anything else, if your wheel is moving forward and backwards isnt that all it could be?
 

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if you can move the rear tire/wheel forward and back in the swinger you dont have your axle nut tight! regardless of anything else, if your wheel is moving forward and backwards isnt that all it could be?
The same initial thought occurred to me as well.
But I figured he meant rotating the wheel back and forth, I hope...
 

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This bike as most know was designed for the track, not the street. Which is why there are many issues: Abrupt throttle, rough running at low idle etc...

The explanation of the wheel movement is strange too....running your bike on a stand means the wheel/suspension is not loaded and wheel will hop along with the drive train lash.

I would avoid doing that because the drive train is meant to be loaded when the gears are engaged.

Maybe some illustrations are due?
 

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The same initial thought occurred to me as well.
But I figured he meant rotating the wheel back and forth, I hope...
after rereading it i agree. first thing that popped in my mind. sometimes putting it in lamens terms is exactly what you need lol! you can definitly over think this stuff sometimes. it is pretty normal for the wheel to move while roatating it in gear with engine off back and forth...

hey these things have pretty abrupt throttle response and mine definitly feels the same way and its probably just the nature of the beast
 

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I agree with "the nature of the beast" spot on comment. If chain tension is correct maybe just learning to "feather" the clutch more will smooth things out. You're not going to hurt it, stock rc's are bullet proof as long as the shiney side is up.
 

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Its also a twin, so you have less pulses at lower rpm (or any rpm) than a 4-cylinder. And those pulses hit with alot more thump than one of the 4-cylinders. Just try to keep it a little above idle and it helps quite a bit I've found.
 

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Discussion Starter #9
Yeah, I was definitely talking about ROTATING the wheel forward and backward, not actually sliding it back and forth in the swingarm. I appreciate the responses. Turned out to be a non-issue I guess, but I just wanted to double check here in case it was an indication of some sort of excessive wear somewhere. The reason I ask is probably because I have been using the bike more and more for commuting, and in slow speed city traffic, it can get to be a bit of a headache with all the driveline "lash"<-----(there's the word I was originally looking for!). I guess I could slip the clutch a little more but I worry about premature clutch wear.
 
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