Knackered threads - exhaust nuts

fritz · May 6, 2006

Having returned from our little adventures and taken the ol’ bike for MOT I was a bit disappointed to get a fail :confused:

(first ever). The front nearside head was blowing on the exhaust and needed a bit of fiddling to seal and get the pass

.
The upshot of all this is that the retaining nut has threaded the threads on the head

, something I’m always meticulous about, but there you go.
So the question
Is the only way forward to send the head to Motobins and get it alloy welded up and have the threads re-cut ? Can’t think of any alternatives ?
It ran virtually 5 months on the trip chipping away as the gases blew past with no ill effect as I knew disturbing it would be a disaster (thank goodness I did leave it !)
Head is off ready for repairing – is the build up alloy weld and re-thread the only option ? Are Motobins the only people to do it ? (Don’t want another head as only changed the valve seals before we left). Comments welcomed

Kenny · May 6, 2006

Looks like the only course for a repair

Just got my re-built bevel drive back from 'Roger Bennett Engineering'
(tel no 01422 835566 ) and he did the seal and helecoil etc etc.

A top bloke and well recommended...give him a bell..he repairs the exhaust port threads and is a VERY competetive price.

Cheers kenny, Wirral

Paul Rochdale · May 7, 2006

Jim Cray in Sittingbourne also carries out repairs on damaged exhaust port threads. I think he cuts off the stub and adds a steel threaded tube in it's place - but then again, I may be talking bollocks.

I've two Boxers and remove the exhaust rings once a year. clean up the threads and Copaslip them. Never had any problems even though all four had to be cut off originally.

Kenny · May 7, 2006

That's a good tip for all airhead users Paul...I do the same myself !!! Incidently as well as obviously soaking the blighters overnight/few days before etc etc with plusgas...also try pouring boiling water over the exhaust flanges immediately before undoing them

Big Jets · May 7, 2006

i broke an old r80 during the winter. It had a brand new stainless system so care was required.I poured several kettles of water to heat the exhaustnuts and with my exhaust spanner had a go.a couple of tries and with a peice of scaffold tube over spanner they would not budge and to my dismay my mates ex spanner twisted like it was made to chocolate.in the end the butcher in me succsseeded with a blunt chisel chapping them round .the threads on the head where ok and copper slip is the answer to keep them from seizing .I then had to cut the engine out of the frame as the mounting bolts where seized beyond beleif .any body got out of that one id love to know.

fritz · May 7, 2006

Cheers folks. I need some other bits so may send to MotoBins providing they still do the job. Cray sounds interesting too though - think HPN do some mod also. Rest assured the damage wasn't done by your humble scribe, I'm a twice a year copper slip man meself

cookie · May 7, 2006

when it's sorted: grey optimol paste from motobins is the way to go IMO.

my experience is that copperslip vapourises in that sort of location.

edit: optimol does well on oilhead exhaust studs too

MikeP · May 7, 2006

cookie said:
when it's sorted: grey optimol paste from motobins is the way to go IMO.

my experience is that copperslip vapourises in that sort of location.

edit: optimol does well on oilhead exhaust studs too

Cookie,

Will that stuff work for the headguard studs on my 1150?

(They're a bugger for needing some heat to loosen up when a service comes around).

cookie · May 7, 2006

MikeP said:
Cookie,

Will that stuff work for the headguard studs on my 1150?

(They're a bugger for needing some heat to loosen up when a service comes around).

i would think so. do you copperslip them at the moment and they still seize?

got to say i'm very impressed with optimol's ability to stay put.

MikeP · May 7, 2006

cookie said:
i would think so. do you copperslip them at the moment?

I did but as you said it just boils away.

cookie · May 7, 2006

i'd give motobins a ring. i don't know if anyone else sells it.

there's grey for heat apps & white for splines.

MikeP · May 7, 2006

cookie said:
i'd give motobins a ring. i don't know if anyone else sells it.

there's grey for heat apps & white for splines.

Ta, Grey it is then.

Steptoe · May 7, 2006

BLR engineering will fit a phospher bronze replacement exhaust thread, inserted and pinned , last one i had done cost £50 per head . But that was a while ago -

Paul Rochdale · May 7, 2006

"my experience is that copperslip vapourises in that sort of location"

....and in my twelve years of owning Boxers, it doesn't.

cookie · May 7, 2006

Paul Rochdale said:
"my experience is that copperslip vapourises in that sort of location"

....and in my twelve years of owning Boxers, it doesn't.

fair enough, that's about 3 x more years than i've had experience of boxers.

comment based on my 30+ years experience of exhaust fittings of other vehicles

fritz · May 8, 2006

Cheers all, head on way to Motobins as needed other bits too. Will try the Optimate as Copperslip does and doesn't work :confused:

Cheers for helpful responses

Bezzler · May 8, 2006

Knackered threads

Do heli-coil still exist, these were used a hell of a lot for exhaust threads in alliminium.
All you had to do was tap the hole out bigger and screw in what looked like a spring with an internal and external thread.
This also meant you did'nt have to have the head off.

Paul Rochdale · May 8, 2006

The exhaust thread on a Boxer engine is a MALE thread and not a female one so a Helicoil (which still exist) would not apply. On mine, after cutting off the old alloy retaining 'nuts', I cleaned up the corroded stubs as best as I could then got a hacksaw blade and ground a knife edge on it. I then used that to clean up the manky thread until it was useable. With new 'nuts' and Copaslip, I never again had a problem with them. The use of the correct bronze spanner is important too.

chiefrider · May 9, 2006

After you get this work done, invest in an exhaust nut wrench, or find a buddy who has one, and ANNUALLY loosen the nut & expose the threads and apply a high temp antiseize.

Here's Snowbums writeup on this:

http://pweb.jps.net/~snowbum/exhaustnuts.htm

Tom

fritz · May 10, 2006

Thanks for the link, don't worry I'm an intensive regreaser

Knackered threads - exhaust nuts

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