Just taken the Dommie for a short test run after two changes (never change more than one thing at a time...I know...)
Change #1 is replaced the RITA with magneto. So far, it's excellent. No problem starting from cold, restarting from hot, and no performance loss that I can notice.
Change #2 is replaced the siamesed pipes with my old twin pipes. This on 88SS. This is nothing but positive..it feels quicker at all revs (within the limits imposed by the roads we suffer locally)
Has anyone actually noticed a benefit from siamesed pipes? I do know that the joint between the two branches of mine is not as smooth inside as it should be. I suspect that caused power loss and maybe (as someone here suggested) asymmetrical breathing at high revs. I wonder if Norton stopped using them partly because they didn't work very well unless they were expensively fettled inside the joint?
I also wonder if the simple magneto advance curve suits old motorbikes better than a smooth curve? I'm using Esso Synergy plus (at £1.70 per litre...20p extra)
Thanks Al. I need to gain…
Thanks Al. I need to gain confidence in the mag first. It was refurbished some 6 years ago but failed when hot, having had a new capacitor but not a rewind. This time it has had a rewind and the man who did it reported that it had an intermittent fault in the cover (shorting it out) which might have been the problem all along. I've just read his month's Roadholder, with its account of worn cam ring. I did check mine and as nearly as I can measure both sides of the ring are within a degree or so.
I admit I don't really have much confidence in the timing I have achieved to within a degree or so. I should probably check with a strobe. It's not pinking but so far it's only done half a dozen miles and so it hasn't had a really good heat soaking yet. I sometimes wonder how accurately the factory used to set them up.
RITA and its coils and wires are still in place for the time being.
Siamese pipes...
..never fitted to anything I know of for performance. Less bulk/weight for the off road community and improved access to the drive side. I always saw them as a fad that actually save the manufacturers one muffler. A sporting look no doubt but performance enhancement, I'm not so sure.
The Croxford proddy commando with two right side peashooters also an odd modification unless he was counterclock circuit riding??
The reinstatement of the Mag means you wont have to worry about battery level anymore...
How do you find the 88SS Dave; I'm interested in one as a replacement for the 99.
Cheers
Jon
A bit on the side
Siamese pipes are useful for preventing sidecar passengers going completely deaf.
Siamese for a 99
With my first rebuild in 1965 I corresponded frequently with Norton HQ and had great advice from "The Man" - JH. He identified my 1959 99 as a "Special" with optional extras added at the works. Essentially it was an "SS" with twin carbs, large inlet valves, polished head and HC pistons, but with what was then a standard QR camshaft (which I later changed for an SS cam and sold the QR to Barry Lawton for his Domiracer).
In the correspondence he advise that my 99 model performed better with small-bore siamesed pipes and an SS Silencer. I never did find out how different an SS silencer was compared with a standard one but, in any case my poverty budget could only extend to a Gold Star pattern silencer!
I have seen it mentioned elsewhere since that the siamese pipes are best for a 99, but I've not seen any mention of an 88.
Pre SS Specials
I read about these recently in the "Compendium for twins". Seems there was a lot of experimentation before we saw the "650SS".
Small bore higher back pressure, better charge containment according to a little book I have on tuned exhausts.
Funny how the hallowed pattern Gold Star silencer was the go to item in the 60's. My 60 years stored inter had one. When resurrected the internals were found to be completely disintegrated. Now either it was a deliberate ploy by the previous owner, or the ravages of time as it sat in a museum. It neither silences, or twitters (al la G.Star), but it looks the part. Try buying a new one nowadays on a poverty budget!
Cheers Lionel
Jon
siamese pipes
In the '80s, a friend of mine had a siamese pipe on his 99. It was otherwise standard. He was pleased with it, and liked to point out the way it started resonating in mid-range.
At that time, I fitted a siamese pipe and RGS silencer to a Super Rocket. This set-up was allegedly good for an extra 3bhp. I liked it because it tidied the bike up, made chain maintenance a whole lot easier, and gave a lovely exhaust note, but was not loud
I've looked back at my notes…
I've looked back at my notes about fitting siamesed pipes. April 2001, £118 from Armours. Test run; 85mph going to Dorking. "A bit down on top end...improved mid range acceleration". Whether or not I was telling the truth to myself..I don't know. Later that month: A3 London to Guildford. 20 miles at 70 to 80, mostly about 75. "Ran well but seemed to be more vibratory, especially at low revs". (Perhaps the "resonating at mid range"?). Did a plug chop from 80mph(accelerating). Plug looked OK."
Later on I still noted more vibration than with twin pipes.
It was using a single 928 concentric at that time.
The roads I used to use for spot tests now have speed cameras, so I can't repeat the trials. (70 mph up the hill from T road roundabout...allegedly...) But the 88SS should be quick enough on today's sad roads.
Don't use the above notes as evidence...everyone knows we all exaggerate...sometimes...!! I shall deny everything.
Siamese
I have siamese pipes on my 650ss, it goes very well.
Siamese Pipes
Definitely OEM for the single carb 99SS. The press reviews credited the small bore siamese pipes with the significant performance hike over the 99.
There wasn't much else, a slightly warmer cam and a slightly higher compression ratio.
But we were 'appy.
Siamese
My understanding is that (on the 88/99 sports ) the siamese gave a usefull increase to the mid range and with the addition of the 650 silencer a similar top end to the seperate pipe systems. Don't know if they worked on the 650. I do know that my single carb 99 with RGM system got to an indicated 110 ( at least a ton!) chasing Stephen riding my VTR 1000. I think I'm lucky to have my rods still inside the case. Silly sod.
88SS - 500 Class Thruxton…
88SS - 500 Class Thruxton 500 Mile Race Winner in 1960,1961 and 1962 with siamese pipes. Moreover the bike was also second overall in 1961 and 1962 and fifth overall in 1960. Many 88 Specials and early 88SS's had the siamese pipes fitted.
650SS - Unlimited Class Thruxton 500 Mile Race Winner in 1962,1963 and 1964. Fitted with twin pipes.
Moral of this observation - twin pipes better with semi-downdraught heads...... Nuff said, Howard
An interesting swap 'back'. No problem starting from Cold or hot-well there should NOT be, certainly the RITA would not suffer from either unless seriously faulty. The actual spark voltage on the RITA will be greater than a mag. and the actual timing between the cylinders CANNOT vary with a RITA. But it will be interesting to see if the advance curve change improves the road performance of the bike.
If you want the RITA checked before or after you sell it? Then get in touch.