Small exhaust retaining nut (rear)

[yeadon_m]

Chaps,
You may find from time to time your rear small pipes or the whole large/small mountings coming loose.
If so it may mean that that welded / kept nut on the small pipe bracket has a failing thread. There's not much you can really do about that without some proper engineering.
This happened to me a few times before I twigged - last time was saturday.
So I have fitted those slim half-nuts on the inside end of the long bolt that goes through the silent block and large pipe bracket then into the knackered kept nut.
The ones that fit nicely are the same nuts as hold the rear sprocket onto its carrier. They even look 'right'. I've put one on each side and nipped them up with a drop of loctite.
Might be of help to someone noticing a clanking from behind on the over-run!!
Cheers,
Mike
ps: whatever you do, its vital to ensure the whole exhaust assembly is free to wobble on its rubbers....or it will soon crack the small pipe bracket!

[SmokingBiker]

Mike the threads on the exhaust hangers should be from new 10 mm x a finer than normal pitch think its 1.0mm pitch the ones on the sprocket i think should be standard pitch
(might be wrong)

[Waterbuffalo]

Mike are you referring to the nuts welded to the hanger bracket on the inner pipes? If so then why not just tap out the damaged threads and use a helicoil. Normally any clanking on overrun is usually a slack chain hitting the pipes, but if your pipes are falling off then you will hear that as a clanking too.

[yeadon_m]

WB - yes, spot on. Good idea re helicoiling. Meanwhile though I am fine with the slim extra nut!

You know, I do get an intermittent 'clack....clack' occasionally even a steady, small throttle opening, which seems to come from the left rear area, and goes away when opened up harder, but when I sight along the chain from the rear, I can't see that it could be clipping anything. Might you, the bike is on its mainstand right now. Can the chain hit anything else I should look for as a source of this noise? or any other likely causes.

Cheers,
Mike

[mark.read3]

Helicoiling might be fine in most cases (solid fixings), however as the exhausts tend to have a fair amount of flex and vibration in them i wouldn't recommend the use of these as a permanent long lasting repair that i'd be happy with.
These exhaust bolts need to be pretty tight.
I would use a time-sert personally. Used to use them on the fibreglass bike parts i was making a few years back.

[malky]

Mike- I had that clanking noise on the overun also and it turned out that I had used a slightly too long bolt on the front chaingaurd mounting and the chain would occasionaly clip it hence the noise.
Mal

[Waterbuffalo]

Helicoils are stainless steel which is much stronger than the nut is and so it will outlast the material of the nut. It would be possible to actually rip the newly cut treads out of the nut and take the helicoil with it if you over torqued it to destruction.
The problem with all these mounts I've seen is that they have been either way over torqued or left slack from years of bad adjustment.
The results of this is that the rubber dampers inner collar face cuts down into the outer pipes hangar around the hole and over time solid mounts the whole assembly, as now the frame and outer collars face also hits the hanger and cuts into it further.
This now makes it completely solidly mounted since the rubber mounts floating feature is not in use anymore. What needs to be done is to repair the hanger around the hole and replace the damper if its too badly worn on the inner collars face, then use an appropriate sized wide face flat washer spacer to improve the surface areas contact against the hanger and regain enough clearance so the system can float again.
The end result is that you should have at least 3mm of physical clearance between the frame mount and the hanger face once its mounted and torqued up.
I've been repairing other peoples bad work for over 40 years and in this time I've never had any helicoil fail that I've put in. There is a torque value for the hanger bolt so its should be followed, but seldom is and the results show.