Agricultural clunk

General discussion of the BMW R1200RT/R1250RT
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Beagle
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Re: Agricultural clunk

Post by Beagle »

Blueboy wrote: I found this after a long research on this rainy day here in Montreal...a lot of it makes perfect sense to me...
1) Most motorcycle clutches use multiple plates, which do not free completely (and separate fully from the adjacent plate) because they are contained in an oil bath (the gearbox or engine/gearbox oil).

Consequently there will still be some spinning of the input shaft when the gear selectors select whichever gear is there.

Even dry clutches still do not completely free when pulled in, and you might have to wait for 10 or 20 seconds for the input shaft to slow or stop, before being able to make a noise-free selection.

You could also find, if you do that, that the gear will not actually engage because it has stopped at a point where the engagement "dog" cannot fit into its mating slot(s). That's a little bit like what happens (except in reverse) when you hold the clutch in too long while coasting to a stop, or stop in gear and are unable to select neutral.

The "clunk" is not a sign of a problem, nor is it a problem in itself.


Then changing from 1st to 2nd is also a little rough, but then each gear upwards is fine...
Whats the mechanical reason for this? and is it present in all bikes?
The difference in gear speeds between 1st and 2nd is usually greater at the bottom end of the gearbox, hence there can be more noise because the sliding "dog" has to mesh with another "dog" spinning at a different speed..

However, a skilled rider will compensate for this by preloading the gearchange lever slightly and experimenting until he (or she) finds the correct "speed of lever operation" to make a clean, noise-free change. It's possible.

But once again, this is not really a problem.

Most bikes have this issue, but most good riders learn to change to minimise it. It makes you look better...or sound better.  ;-)

The higher the gear the less difference in speed between components, so that there is less tendency to clunk. However, if you delay the change by holding in the clutch for a few seconds, you should be able to get quite a good clunk.  ;-)


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Very good totally agree.
bandytales
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Re: Agricultural clunk

Post by bandytales »

Zack042 wrote: Just approaching the 600 mile service. When selecting 1st should it still have such an agricultural clunk?

Yes, sadly.
Even the newer gearboxes (2016/2017 onward) are pretty slick in all gears apart from neutral to 1st.
They are often whisper quiet when the engine is cold, but very quickly revert to 'normal' with that embarrassing loud 'crash'
T6pilot
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Re: Agricultural clunk

Post by T6pilot »

On my 15 bike, sitting at a stop or light. I often find it smoother when going from neutral to first to first shift up to second then back down, seems to miminize the clunk
Jim
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Beagle
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Re: Agricultural clunk

Post by Beagle »

T6pilot wrote: On my 15 bike, sitting at a stop or light. I often find it smoother when going from neutral to first to first shift up to second then back down, seems to miminize the clunk

Sounds good ,will try that.  :kacsint2:
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septikangel
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Re: Agricultural clunk

Post by septikangel »

OrangeOkie wrote: Just read where the new R1200RT has the 1st gear "clunk" fixed. Can anyone confirm?
Mine's an '18 model, clunk's there, embarrassingly now and then, though occasionally slick and quiet.
Find pumping lever a couple of times before selection sometimes helps, but not always.
Most bikes do it (don't they?) but best ever for me was an '08 CBR1100 Blackbird... never clunked, ever, so it can be done.

1976 Norton Commando 850MkIII, 1994 Yamaha FZR1000RU, 2019 Honda Goldwing GL1800
guest4915

Re: Agricultural clunk

Post by guest4915 »

kerdoman wrote: My previous 2002 RT1150RT and current 2005 RT1200RT seem to be exactly the same gearbox wise.  As the above post remarks, for this money you'd have thought they could do better. 

My Honda ST1100 also clonked into first sometimes so it's not an unknown issue but if cars can do it properly, why not bikes?

Because motorcycle and car gearboxes are mechanically different. My 18MY RT has actually got better with miles (just coming up to 5000). My Triumph Sprint also makes a clunk when engaging 1st gear - not the end of the world.
Stratman
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Re: Agricultural clunk

Post by Stratman »

I've never had a bike yet that didn't clunk into 1st gear.
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Blueboy
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Re: Agricultural clunk

Post by Blueboy »

T6pilot wrote: On my 15 bike, sitting at a stop or light. I often find it smoother when going from neutral to first to first shift up to second then back down, seems to miminize the clunk
Will try that too, thx.


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Blueboy
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Blueboy
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Re: Agricultural clunk

Post by Blueboy »

Blueboy wrote: Will try that too, thx.


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No difference at all for me.


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Blueboy
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exportman
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Re: Agricultural clunk

Post by exportman »

I find applying the hill start assist  when in neutral then engaging 1st the process is clunk free and virtually silent  Pull the front brake lever again to release the  HSA and you are ready to make a move
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Blueboy
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Re: Agricultural clunk

Post by Blueboy »

exportman wrote: I find applying the hill start assist  when in neutral then engaging 1st the process is clunk free and virtually silent  Pull the front brake lever again to release the  HSA and you are ready to make a move
Wow. Going to try that one this spring , thanks.


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