exhaust nuts

lasttry · Jul 20, 2011

is there any kind of fix foe when the exhaust nuts won't tighten due to the threads in the head becoming worn out.one of the nuts is fine the othe gets tight then slips back to loose...thanks

platinumsmith · Jul 21, 2011

If there is a fix, you're gonna find it here!

cameron forbes · Jul 21, 2011

hi
i have seen a fix where a brass insert is fitted,
think ex port has to be machined bigger, then head heated
up to allow insert to drop in, whan head cools it should hold
insert in place, not sure how good it is tho.

Josh Cox · Jul 21, 2011

I've heard of several suggestions on this website:

* Drilling a hole in each nut and lock wiring together,
* Loctite, tried it, did not work too well,
* using the lock tabs on ebay ( http://www.ebay.com.au/itm/Norton-Comma ... 3f0c060701 )

Or what I am presently trying, putting high temp silicone on the threads and all over the sealing washers, then tightening up normally, seems to be working thus far.........

L.A.B. · Jul 21, 2011

cameron forbes said:
i have seen a fix where a brass insert is fitted,
think ex port has to be machined bigger, then head heated
up to allow insert to drop in, whan head cools it should hold
insert in place, not sure how good it is tho.

Usually it's a welded-in alloy insert. My Commando's cylinder head was repaired with welded alloy inserts (by Norvil) although some repairers fit helicoils.

Foxy · Jul 21, 2011

Pity you cant buy slightly oversize nuts for a bit more bite in the thread?

gtsun · Jul 21, 2011

Sorry to hear your threads are stripped lasttry, do a search of this topic and you will find that Jim Comstock talked about a way to get by with a temporary fix for a season or so and how he fixes them correctly. If I was in need of this I would send the head to him to be repaired the right way. Do some research & learn what NOT to do as well. This is a common problem.

travelerjerry · Jul 21, 2011

lasttry said:
is there any kind of fix foe when the exhaust nuts won't tighten due to the threads in the head becoming worn out.one of the nuts is fine the othe gets tight then slips back to loose...thanks

Here is a billet exhaust repair kit that I bought 3 years ago on E-Bay in event my threads get stripped. Old threads get bored out to diameter of repair piece and pressed in. Once in, hole gets grounded to match existing port. Outer edge of billet piece gets staked as you would a bearing. (Per instruction sheet)

If these are not available, I should have these reproduced. Or someone with a lathe could make them. Seems this is a common problem.

swooshdave · Jul 21, 2011

lasttry said:
is there any kind of fix foe when the exhaust nuts won't tighten due to the threads in the head becoming worn out.one of the nuts is fine the othe gets tight then slips back to loose...thanks

Where in the world are you? That would help direct you to the nearest resource.

Flo · Jul 21, 2011

Personally I would go for the helicoil type inserts. Used a head with them in for years & never had a problem.

grandpaul · Jul 21, 2011

If the threads are shot, no amount of silicone will fix them, nor will beer can shims and the like.

Phil at Fair Spares in California has fixed several heads for me.

RennieK · Jul 21, 2011

IMHO the lock tabs like on ebay should be outlawed and are the cause of many worn heads. Tab washers don't keep the nut tight, they only stop them from backing out after the compression washers heaat up, soften up and flatten out and the nuts loosen. Sure they prevent the nut from backing right out when you're riding but then when you stop you think "well, they're too hot to touch right now I'll tighten em later. They can't fall off on the road with those tab washers heh heh.". You ride some more and remember "oh yeah, gotta tighten those" all the while the loose nuts are vibrating away, eroding the threads.

Tighten them on install then after a while when the pressed ring gasket gets soft tighten some more. Tighten them when the motor is real hot and you won't have these problems.

Josh Cox · Jul 21, 2011

Grandpaul,

Am not using silicone to fix them, am using silicone to stop the vibration, heating a cooling from them loosening themselves, it appears to be working thus far ( my threads are OK, and they will still come loose ).

DogT · Jul 21, 2011

Josh,
Get a 3' extension on your exhaust 'nolts' wrench (spanner) and tighten them properly. They won't come loose.

Dave
69S

Josh Cox · Jul 21, 2011

Sorry DogT, it probably has more to do with me being a limp wrist.....

swooshdave · Jul 21, 2011

DogT said:
Josh,
Get a 3' extension on your exhaust 'nolts' wrench (spanner) and tighten them properly. They won't come loose.

Dave
69S

Get the engine hot then tighten, no need for the "grandpa bar". :mrgreen:

lasttry · Jul 21, 2011

thanks to all that answered.by the way i live in canada near toronto ontario,thanks for asking...

rvich · Jul 21, 2011

Comnoz does a hardened bronze insert, whereby the exhaust ports are bored oversized, threaded and a bronze insert threaded in. I am planning on having him do my head.

Russ

WEAL Norton · Jul 22, 2011

I make my own alu inserts. The old thread gets milled out of the head, the insert is made oversize and shrunk in then the outer edge gets welded to the head all around. When its all dressed up and blasted you can´t see a difference to the original thread.
Mike your exhaust nuts - they have all slight differences - thatswhy I make each insert suitable for the nut that should fit it...

Rich_j · Jul 22, 2011

cameron forbes said:
hi
i have seen a fix where a brass insert is fitted,
think ex port has to be machined bigger, then head heated
up to allow insert to drop in, whan head cools it should hold
insert in place, not sure how good it is tho.

This type of insert was fitted my head when I first bought the bike. Problem is a lack of meat in the head making the material too thin around the insert to hold an interference fit.
One of my inserts came out while still fitted to the header. Small cracks had formed in the head around both the inserts.

Of the repair options all the rest seem pretty good - welded aluminium/threaded aluminium/threaded bronze/helicoil.

My head was welded up and threaded aluminium inserts fitted and pinned - held up well for a lot of years now.

exhaust nuts

lasttry

platinumsmith

cameron forbes

Josh Cox

L.A.B.

Moderator

Foxy

gtsun

travelerjerry

swooshdave

Flo

grandpaul

RennieK

Josh Cox

DogT

Josh Cox

swooshdave

lasttry

rvich

WEAL Norton

Rich_j

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