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Offline chay

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Massive clunk going into 1st
« on: 03 October, 2019, 07:59:17 PM »
Hi guys.

Well I swapped the front cog to a Renthal 17 tooth on my Mk2 - using the excellent instructions on this forum . Many thank Art, RichardCBF, Robo, Bifferman et al.

I haven't noticed any reduction in the hooligan element !!

Before I did it, the clunk going into 1st was fine - just a noticeable nudge.

Now though, it's an unacceptable "thunk" with the bike taking a lurch forward.

I'm sure it will lead to damage long term.

The clutch is obviously dragging. With the bike on the centrestand, when I select 1st (with said thunk) and let the clutch out, the rear wheel revolves as expected. But when I pull the clutch lever in , the rear wheel continues to be driven. If I snick it into neutral, the wheel comes to a halt as expected.

I've replaced the clutch fluid (which was clear with no bubbles), cleaned the bit of corrosion from the rod as experienced by others.

I've tried the chain over a range of adjustments but to no avail.

I think my next option is to remove rear wheel again and refit - with someone on my shoulder checking my work.

Any advice or pointers would be be welcome.
Full luggage, Metzeler Z8s (lots of tread left but squared off after 5k miles).

Offline chubbleybear

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Re: Massive clunk going into 1st
« Reply #1 on: 03 October, 2019, 08:25:27 PM »
What you describe happened with both my MkI and MkII CBF, together with almost every other bike I've ever owned, when the engine and gearbox are stone cold. This due to the drag caused by the oil in the engine/gearbox. It shouldn't happen at normal running temps when the oil thins off....does yours?
No good deed goes unpunished.

Offline NJD

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Re: Massive clunk going into 1st
« Reply #2 on: 03 October, 2019, 11:56:44 PM »
I'd leave the rear wheel and chain adjustment alone. So long as the rear wheel spins in 1st on the centre stand without the chain so loose it hits the swingarm or so tight it makes a noise from the front sprocket area (very bad sign) then that's fine. You wanting to adjust these just sounds like one of them problems you can't put your finger on so run around in circles and end up in a panic.

As above common issue on many bikes. My chinese 125 a few years ago was as bad as this and sometimes would lurch forward and cut out during winter. Kawasaki probably did it but don't have any horror memories. CBF does it now but not that bad after the very first time after starting the bike for the first time from cold that day. Sometimes the CBF makes a noise like its going in and out of gear like a ping pong game for a moment and then works fine.

Just playing with your head. Give it a good kick rather than a gentle tap.

There's probably an old age trick or two some of the older folk will remember to remedy the severity of the clunk.

So yeah; overall I wouldn't really worry about it.

Check the torque setting on the front sprocket and make sure there's enough clearance around the sprocket for the chain to run without hitting the casing. Make sure nothings wobbling inside the sprocket cover. Get someone to put it into first from cold and you watch what happens.

Offline chay

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Re: Massive clunk going into 1st
« Reply #3 on: 04 October, 2019, 07:24:16 AM »
Thanks  for the quick responses.

It happens even when I've been out on a 20 mile run. It was perfectly ok before.

I think you're probably right NJD - the issue is at the front end.

I'll double check that area and give it a go. Be the weekend now !!

Will let you know how I get on.

Full luggage, Metzeler Z8s (lots of tread left but squared off after 5k miles).

Offline Art

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Re: Massive clunk going into 1st
« Reply #4 on: 04 October, 2019, 07:42:12 AM »
Sounds more like a clutch issue than chain and sprockets.

Offline NJD

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Re: Massive clunk going into 1st
« Reply #5 on: 04 October, 2019, 11:05:17 AM »
After a 20 mile ride isn't normal: the bike should be well up to temp by then and running smoothly.

I'd dump the oil (use 10w30 or 10w40) and perhaps check the clutch plates. My initial reaction was that they're sticking together. Removing them and soaking them in oil may help (alongside a visual inspection).

Offline chay

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Re: Massive clunk going into 1st
« Reply #6 on: 04 October, 2019, 11:52:01 AM »
I agree it sounds like a clutch issue.

I wonder what I've done because it was okay before I started fiddling - so I must've caused it !!

I changed the oil about 3 months ago (10W40).

I'll need to research how to check the clutch.

Busy weekend I think.
Full luggage, Metzeler Z8s (lots of tread left but squared off after 5k miles).

Offline Art

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Re: Massive clunk going into 1st
« Reply #7 on: 04 October, 2019, 01:53:18 PM »
Since you've had the slave cylinder off and the clutch push rod out it might be an idea to start right there! The problem is something to do with the clutch and in all probability something that you've touched. Check you've assembled it all correctly, hard to see where you might not have but hey ho its a logical place to start. Also check that the slave cylinder internals (spring, piston, 'O' rings & oil seal) have not been disturbed.

Re-bleed the clutch using the flush method. Don't drain the fluid but flush 200 to 250 ml of fresh fluid through the system using the fresh fluid to push the old fluid out through the slave cylinder bleed nipple.
« Last Edit: 04 October, 2019, 01:57:11 PM by Art »

Offline Fair Weather rider

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Re: Massive clunk going into 1st
« Reply #8 on: 12 October, 2019, 09:43:54 PM »
Only had my Biffer a week and I noticed a massive clunk, going into first gear, and then I read on this forum, to pull clutch in and hold for 5 seconds and then select gear...………………. it works. :046: :046: :046: No clunk. :028:


Offline raYzerman

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Re: Massive clunk going into 1st
« Reply #9 on: 13 October, 2019, 01:35:14 PM »
Some bikes with wet clutches suffer from not getting enough oil, sometimes just a splash or the oil gallery feeding the first couple of plates.  Sticking plates, especially cold, can be caused by a few things.... any one of these can be an issue, if you can resolve it by the first three, you're good to go.
The brass bushing in the clutch lever may be worn/scored/out of round.
Lever adjustment (if equipped) to ensure full travel of the slave cylilnder
The hydraulic system needs bleeding
The clutch plates could do with a "soak"... essentially, disassemble the clutch plates, clean as necessary (check for wear), liberally coat with engine oil for a few minutes, reinstall....