UK Monster Owners Club Forum » .: Technical :. » Engines, Clutch, Gears » Transmission slack?

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Old 05-08-2020, 07:28 PM   #1
Mr Gazza
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Transmission slack?

Ever since I rode that ultra smooth electric bike I've thought my Monster was a bit harsh.

I would have thought I would have gotten over the electric bike by now and settled back into what was always one of my smoother motorbikes, but I think there is definitely something different going on?

It feels like a chain so slack that it's about to fall off the sprockets. (Please don't ask me how I know what that feels like it was a very long time ago!)
I've checked the tension on the chain and lubed it since the electric ride.

The worst time is between power on and power off, particularly at a fairly neutral throttle with the power not really on or off.

Obviously I'm very familiar with large L twin power delivery, it's not like I've just jumped of a UJM.

Gear changes seem to have become a little harder to get smooth, going up and more so going down.

The clutch is a 48 tooth with a small amount of wear. There is negligible play in the sprocket cush drive.

When in gear I can roll the bike back and forth 70mm measured on the ground, before meeting resistance. it doesn't matter which gear. I measured this with a square off the back tyre onto my level floor.

That seems like a lot of free play to me? Is it excessive? If so where can the play be? I wouldn't have thought it was the gears, but I am wondering if it might be the primary gears?
Maybe just cumulative wear in everything after more than 40,000 spirited miles?
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Old 06-08-2020, 07:44 AM   #2
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Have you checked how much rotation you are getting at the sprocket relative to the rear wheel? If the cush drive rubbers are “tired” that allows quite a lot of slop.
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Old 06-08-2020, 08:36 AM   #3
Mr Gazza
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Thanks Darkness.
Yes there is "detectable play" in the sprocket, but virtually un-measurable. It certainly does not account for 70mm peripheral movement at the tyre.
This will probably prompt a bush and pin change this winter anyway.

The irony is that I was so pleased at how smooth the bike was after changing the belts for Exactfit this spring and checking the clutch for wear. I coated the drums with Graphite too and thought that the bike was generally smoother and quieter. The clutch rattle is certainly back with vengeance now though and there does seem to be more play in the tangs.

I always did think that there was a lot of play in the transmission train as a whole, maybe it's just my altering sensitivities? Maybe she's just not as young as she was and doesn't like those hard spankings anymore?
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Old 06-08-2020, 12:17 PM   #4
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This is quite interesting to read as I too have some movement in the rear wheel Cush drive and plan to refresh them soonish.

But like you I feel the motor and gearbox generally pretty smooth- snicking into first without a clonk and easily finding neutral at a standstill so tomorrow afternoon I will measure any ‘slop’ in the same way you have for a comparison.

Just for fun I will also do the same measurement on my similarly aged Yamaha Thundercat which has less than a third of the miles that of my Monster but always has its signature ‘clonk’ into first gear despite its featherlight clutch and very Japanesely smooth four cylinders.
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Old 06-08-2020, 12:53 PM   #5
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Thanks Flip, That will be an interesting comparison.
I just put it in gear and pushed forward until it hit resistance, rested it on the side stand and marked down on the floor with a roofing square off the back tyre, then same again pulling it back.

I've just had a 60 mile ride on mixed roads, concentrating on my gearchanges a bit more than normal.. To be honest it all feels perfectly normal again!
I have an MOT booked for the morning, so I will give the old girl it's annual little once over.
I will also, if I can get them finished, pop my new silencers on and change the spark plugs.

At the moment I am running the cored cans that have been on there since shortly after I bought it. I have had a running battle over the years trying to keep the "baffles" in. The last time the left hand one blew I just gave up and ran it till there was nothing left inside!
So it's reasonable to assume that it's not running at it's best and sounds awful!
I usually change the spark plugs @ 6k but have let these ones sail on past that because they seem to still be working fine. I do find that old plugs affect the slow running.

So tomorrow we will see if it was just that electric bike that spoiled me?
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Old 06-08-2020, 01:23 PM   #6
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For a comparison, I just put my Monster in first gear with engine stopped on a paddock stand and rotated the rear wheel by hand.

I went as far clockwise as possible without turning the engine and marked the tyre with a biro at the Tip of the hugger.
I then rotated anti-clockwise as far as possible and made another biro mark.
The two biro marks are 63mm apart.
There is a pronounced click from the clutch area as the movement stops, but with 8000 miles on the clock the clutch shouldn’t be worn out yet.
It’s rotation that is cumulative at each connection, so the distance moved at the cush drive rubbers, drive sprocket splines and clutch tabs wouldn’t have to be huge to add up to the 11.5 degrees of rotation equivalent to the 63mm that was measured.
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Old 06-08-2020, 01:45 PM   #7
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Thanks for doing that Darkness. Very interesting. I think that will be equivalent to how I measured my backlash as it equates to distance travelled by the tyre. I seem to remember measuring about 50mm using your method, some years ago, the last time I had a little worry about this.


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Originally Posted by Darkness View Post
It’s rotation that is cumulative at each connection, so the distance moved at the cush drive rubbers, drive sprocket splines and clutch tabs wouldn’t have to be huge to add up to the 11.5 degrees of rotation equivalent to the 63mm that was measured.
I would agree. It should be possible to work out how much the clutch rotates in relation to the wheel via the gearing. (gear commander perhaps?) So clutch wear will have an exaggerated effect on the rear wheel backlash including everything in between.
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Old 06-08-2020, 01:48 PM   #8
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There are probably 35 pins between the drive sprocket and the trailing tooth on top of the rear sprocket, even a fairly new chain would account for a few mm of movement, similarly, any slight rock on the front sprocket, multiplied by the front/rear sprocket ratio and then by the difference in the radius between the rear sprocket and the tyre contact patch could be a large contributor.
The most likely "culprit " will be any slack in the driven plates to the clutch basket. This obviously has the same multiplier as the front sprocket.
If the primary drive was worn I suspect it would make a dreadful noise
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Old 06-08-2020, 04:08 PM   #9
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I have always thought that both my Ducatis have a lot of lash in the drive train but I didn't think there's anything wrong and that it was just a Ducati 'thing'?

Certainly more play (from memory) than other bikes I've had and, as a comparison quite a bit more than my 40 yr old Guzzi although, being shaft drive eliminates any chain lash.

Mine are noticeably more in higher gears though and both about the same amount.

There is also a cush drive setup in the clutch which could be worn? That said my 916 doesn't have the clutch cush as it has a one-piece billet hub and there's no less lash in that than the Monster.
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Old 06-08-2020, 05:01 PM   #10
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The Numbers are.......

1996 Yamaha Thundercat at 13122 miles- 31mm

1997 Ducati Monster at 33422 miles- 40mm

Not too much of a difference on paper there then although the Monster does ‘feel’ looser pushing it between resistance points.
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Old 06-08-2020, 06:30 PM   #11
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If you need uprated cush drives, i’ve had some Afam poly rubbers fitted for a few years. Similar to these.
https://sprocketcenter.com/superlite...piece-set.html

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Old 06-08-2020, 06:38 PM   #12
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Thanks for measuring Flip.

Yours is tighter than mine. But you've got less miles on the clock.

Damien, I would have polyurethane bushes in an instant, but I don't think they are available for the earlier hub? I have 6 silent block type bushes in the hub, with steel pins on the sprocket.

Ha! You edited while I was posting and added the link. Yes those ones won't fit my bike.
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Old 06-08-2020, 08:34 PM   #13
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interesting thread. There are a lot of variables in effect here though, most compounded through various factors, gearing ratios/clutch. Surely the biggest ones are the chain and sprockets wear, then the rear wheel cush. i wouldn't be overly concerned. But saying that I might check what mine is like anyway!
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Old 06-08-2020, 10:10 PM   #14
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This really is interesting. I've been concerned about the amount of play I notice on my own bike but can't find a reason for it. Having replaced my clutch friction and steel plates over the winter, new chain & sprockets and checked cush drive rubbers were OK I still have what I think is more play than there should be. I've put it down as normal but will follow this if it develops with interest.
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