Clack clack clack!

Questions regarding the DR800

Clack clack clack!

Postby Hann » Wed Aug 01, 2018 10:34 pm

Hi there,

DR800, SR42A.
I`ve got a very ominous sound to my engine when starting...

If the motor is cold i`ll pull in the manual decomp lever and thumb the start button.
The engine spins over fine with just the normal engine cranking sounds.
When the engine has spun over for a second or two at a nice`n`quick speed i dump the decomp lever where at the correct point in the cycle the decomp mechanism is released and the handle lever returns to the `off` position - at this point while still cranking but before the engine fires i get an horrendous-sounding CLACK noise which seemingly occurs once per revolution. It sounds like someone sharply tapping the crankcase with a pin hammer. :shock:
Once the engine fires into life and the starter button is released the noise is not heard again.

When the motor is warm i carry out the same start technique but the motor fires almost instantly and i get one `clack`.

Is this anything ominous going on here or `do they all do that, mate`?!

As far as i can tell through a very short test ride there is nothing seriously amiss with crankshaft/rod/bearings etc.

Cheers, Hann.
Hann
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Re: Clack clack clack!

Postby BigBob » Thu Aug 02, 2018 7:57 am

The noise you hear is from the starter clutch. This is a common problem.
There have been plenty of posts about this problem so I suggest you search for them as I don`t feel like repeating myself at length for the umpteenth time.
Do not hold the decomp lever down or you`ll bend valves.
Just pull it in and it should stay there until the engine turns and it releases automatically
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Re: Clack clack clack!

Postby Hann » Thu Aug 02, 2018 11:39 am

Cheers Bob, i`ve already read all about the starter clutch - and the cost to fix...............

Is the `reversing the pins` trick worth trying?

On other bikes i`ve had a failing starter clutch usually manifests itself as a whirring starter motor but no drive to the crank.
On these DR`s is the building compression on each stroke causing the starter clutch to receive a momentary turning force in the opposite direction to which the starter gears/clutch are turning, hence the noise? CX650`s are well known to suffer from this and i know a lot about those...

Surely adequate clearance has been designed in to prevent piston/valve interace if the decomp lever is pulled in during cranking or at idle speeds - that`s the recommended method to stop these engines i`ve read?



****edit*****
just to be clear the noise i here is not a graunching, grinding noise as if the starter clutch is slipping on the drive gear/crank, it`s just one err, clack. The engine cranks fine.
Still starter clutch?
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Re: Clack clack clack!

Postby nug » Fri Aug 03, 2018 10:45 pm

May just be the backlash in the starter gears between compression strokes.
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Re: Clack clack clack!

Postby Hann » Sat Aug 11, 2018 3:00 pm

Further investigations have revealed that the starter clutch drive gear is locked on - where it should rotate one way (to crank the engine) and freewheel in the opposite direction it is not rotating freely and is driving all the starter gear train and spinning the starter motor when the crank is rotated in both directions...
With the drive train gears removed the starter clutch drive gear is immovable..

The crank bolt was removed easily enough through the use of my CX650 rotor holder which luckily fitted the DR;

Image

Image

A rotor removal tool was acquired and is now in situ under load for a few days - they`re tight, arn`t they?

Image


The starter motor drive gear shafts are also a little sloppy in their casing holes...
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Re: Clack clack clack!

Postby Hann » Sun Aug 26, 2018 9:11 am

The new starter clutch has been installed and the noise has gone and the engine starts very well.
Rotor removal tool - £30, starter clutch - £180.
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Re: Clack clack clack!

Postby BigBob » Sun Aug 26, 2018 12:58 pm

:tup:
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