Exhaust Pipes for 99

I presume you have released the junction with the LH pipe and the silencer mounting before tightening the rose nut?.this will make a difference. The smallbore siamese was always said to improve the motor. It maybe an older RGM system ,they don't fit very well.The siamese does give good access to the primary area , a weight reduction and a longer life to the silencer through less condensation.

hello well after forty od year owning Norton,s all this about siamese exhaust make dose not a jot of difference the your performance overhaul , but this is up to the owner I have twin exhausts but not the silencers type you have fitted these were only made for one model and for a short time, now like hens teeth and Armours have never reproduce any, they never seen one, but their music on a Norton 650 twin and I find that full bore 1.5/8ths are better then the reduced bore but this is the owns preference yours anna j

The siamesed system does leave the primary side clear but it can be troublesome to fit and remove. I reverted to twin pipes for that very reason.

The siamese system was tested on the 88/99 bikes and found by Norton to improve the acceleration ,as were are considering those motors then the later 650 with a different cam is not relevent. I fitted my siamese 20 + years ago and its not needed to come off. So can't comment. The big bore pipes on the Atlas are a right pain as they jam in the Rose nuts.I would swop them for small bore if possible.

My siamesed system (from Armours in 2001) fits well and isn't hard to remove and replace. Its has two main drawbacks. One is that it is not technically possible to get as good a thickness of plating between two diverging surfaces, so the chrome has deteriorated between the pipes where they come together. The other is the internal connection is not as smooth as it should be and I'm sure that restricts the gas flow.

On the road I can't say that I feel any performance benefit. I do get the impression that it is a bit more vibratory. I see in my 2001 notes "seems significantly improved mid range acceleration but maybe a bit less at the top end". I also see 85mph mentioned, but I haven't been there for some time. I also see that I fitted two copper crush washers - but I'm pretty sure there is only one in place now.

I think for an old bike it is largely up to you and which you prefer the looks of. I think more people like the look of twin pipes, and I think they are easier to polish and stay looking polished, but the siamesed is a bit more unusual. Whichever you choose, all the books say the smaller pipe diameter is preferable for performance, and the smaller size was standard for 88SS, 650SS etc. Don't know about 99 a year or two earlier.

If you buy new pipes, you also need to decide on the rose nut material. Shiny polished bronze seems to be fashionable today. One is swaged permanently to one leg of the siamesed pipes, so if you want to re-use yours you'll have to go to the supplier! Armour didn't have chrome when I bought mine - but that's a long time ago now.

You need Bacon's 'Norton Twins Restoration'. Andover Norton had it last time I looked.

And welcome to the club!

Thats good to hear Bert, Just don't expect me to get it right all of the time,none of us know everything,many of the real experts have passed on, but on this forum we usually do have a friendly (sort of!) kick about and someone will come up trumps. The dommy is mostly repairable ,the main areas of concern seem to be very scarce Barrels and awkward to repair rocker supports in ally heads. My 99 is favorite and everyone who rides it are surprised by its "all togetherness* and good handling.

Previously Bert Powell wrote:

Well I must say that I have been knocked over by the number of your replies, and thank you to all. You certainly have given me lots to think about. You certainly are a friendly crowd.

My 99 is the first Norton I have owned and I am so pleased that I managed to get my hands on her. Apparently she has been in one family for about 50 years and the logbook only shows one previous owner, and the clock shows an indicated mileage of some 48,000 miles, so needs a bit of recommissioning and TLC.

Anyway, thanks to Robert Tuck, my leaky right-hand exhaust port seems to be cured, although as my wife is on night shift, I haven't managed to fire up the engine to check, but it certainly seems a much better fit, and I have managed to fit a couple of thin collets which have allowed the rose nut a better grip.

As quite a few other things need refurbishing and replacing, including carbs and cables, I'm going to keep the siameze for the time being and see how it goes.

Looking forward to getting out on the road and doing some miles!

Many Thanks

Bert Powell

Hello, best rose nuts are RGM own in bronze they do not come undone and the 1.5/8ths bore is best as the presser waves have more chance of doing there job of make the engine breath that bit better and you all can fit the inlet rocker cover breather banjo for that bit extra air around your motor Has they were first fitted to the 650Manxman for November 1960

The quality and fit of new pipes can vary a lot and those big bore pipes on our atlas are a really tight fit in the rose nuts making it difficult to get the seal,would NOT recommend that. The small bore siamese I bought many years ago from RGM is not much better,perhaps they have improved. IF you think about it ,the Armors 88/99 pipes are the same part (they told me) yet the 99 barrels are longer than the 88,can't both be right. Thats how things are ,not quite right.

Back when I first restored my 99 I wrote to the Norton factory and had many helpful responses. (From John Hudson I think) One was that the 99 performed better with siamese pipes. Mine was fitted with them when i bought it but then - the previous (sole) owner had fitted a sidecar - to a bike which he had paid extra for all the bells and whistles from new! Chromed guards, twin carbs etc. I guess Mr Stork had eventually come calling so his hot bike had to be detuned!

Previously robert_tuck wrote:

The quality and fit of new pipes can vary a lot and those big bore pipes on our atlas are a really tight fit in the rose nuts making it difficult to get the seal,would NOT recommend that. The small bore siamese I bought many years ago from RGM is not much better,perhaps they have improved. IF you think about it ,the Armors 88/99 pipes are the same part (they told me) yet the 99 barrels are longer than the 88,can't both be right. Thats how things are ,not quite right.

Hello Rob well my 650 Manxman has 1.5/8ths pipes and I do not find this jamming problem on the Rose Nuts your talking about but these pipes are made specially for this bike along with its own set of silencer witch you cannot buy at Armores or anywhere else for that matter And over the years I have found after market pipes and silencers are made incorrectly and Armours are the ones doing this along with otherssome are copies of copies and do Not fit to the bike right the bends are not in the right places and do not follow the frame tubing has the originals did, has for Dominator silencers the originals were made in house at Norton workshops Bracebridge street by their own crafts men and then out shopped to other makers yours anna j

In the real world ,as it is now, you can't buy pipes made for a production line machine and therefore tried and tested by the assembly worker and rejected if necessary till the subcontractor does the job properly. Thats why so many parts fit so poorly and don't ever get better. Imagine getting a delivery of 500 pipes returned with the message Remake again a bit thinner so they fit the exhaust nuts!!, that would focus the minds.

Previously robert_tuck wrote:

In the real world ,as it is now, you can't buy pipes made for a production line machine and therefore tried and tested by the assembly worker and rejected if necessary till the subcontractor does the job properly. Thats why so many parts fit so poorly and don't ever get better. Imagine getting a delivery of 500 pipes returned with the message Remake again a bit thinner so they fit the exhaust nuts!!, that would focus the minds.

hello all Norton Manxman 650 exhaust parts were made in house and no one has made them since Not even Armours exhausts and most of Armours exhausts there stuff is not correct ether take a 1951 Triumph 650 alternator model and do not say there is not one made may friends have rebuilt them these were export models and Armours did even know triumph had made them and lot of other bike to like racing pipes for a Plus 90 Douglas some prise Armours like they were gods or something well there far for being gods yours anna j

John Hudson told me when I was first fettling my '99' that siamese pipes did seem to benefit its performance. In those days (1965/66) we could write to the factory for advice.

Previously robert_tuck wrote:

I presume you have released the junction with the LH pipe and the silencer mounting before tightening the rose nut?.this will make a difference. The smallbore siamese was always said to improve the motor. It maybe an older RGM system ,they don't fit very well.The siamese does give good access to the primary area , a weight reduction and a longer life to the silencer through less condensation.