Domiracer rockers and eccentric adjusters.

Purity Vendetta

Purity Vendetta

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Jul 14, 2014
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I'm sure that this is an enormously long shot but was wondering if anyone has any information/drawings regarding these two extremely rare components? I am told that G12 eccentric adjusters can be used but haven't had chance to look at a set yet.
I have often wondered if any of the works drawings still exist and would be very interested if anyone has any leads.
 
In short the answer is no. I looked into this myself,
The rockers are too short as are the spindles.
 
Oddly enough I have just today received a very interesting local lead on this. I guess it's one of the few advantages of living near to the West Midlands. As I'm in a position to actually manufacture the components the lead I have may prove to be very useful. You'd be surprised at what and who people know ;)
 
If going to eccentric adjusters, I take it you will fit four rocker feed pipes as per 500 Domiracer :?:
 
It would seem that, by the nature of the eccentric adjuster spindle design, the four pipe feed system would be the easiest route if a little untidy. I do rather favour the setup illustrated in the Motorcycle News, June 1961. It not only looks good but it looks a far better solution to the issue of incorporating any necessary reducing jets. Sorry I have no idea how to upload pictures and computers aren't really my thing. I've had a go at posting a link to an online source below...

http://www.etmoteur.fr/images/domiracer_head_lub.jpg

I'm planning to go to forced cam oiling using a 6 start pump and an oilway running through the cam and exiting on the rising side of the lobes.

I do have the illustration by Bill Bennett pubilshed in Motorcycle Racing of the Domiracer motor. I'm not sure of the date but judging by the title, 'Why the Domi-Racer dream ended', I guess it's probably a mid 60's article. Very interesting but obviously lacking the fine detail necessary. Short of a miracle I will be using an 88SS crank (with a modification of my own) as the 1.6" big end cranks are obviously as rare as hens teeth and the con rods even rarer, neither of which I have the means to produce. I have exciting some about barrels but I can say no more... As for a set of GP carbs I will have to save up and call in some contacts as I don't believe that the correct bore size is produced new any more. I suppose a set of new 1 1/2" carbs could be sleeved down. My motor currently runs a set of 1 1/8" handed monoblocs and does fuel very well.

I'm very grateful for the help I've already received from some generous and interesting people who've stepped in with their help and knowledge. Without them and one person in particular I wouldn't even be able to consider a project like this.

That said I'm still interested in any and all Domiracer information anyone has lurking as I think this was a very underrated project which, as has been said elsewhere, could have been far more successful if it had been allowed to continue. Their also seems to have been rather a lot of versions of what I would recognise as Domiracers (Lowboy frame, Manx wheels and forks etc) as well as Manx and wideline framed bikes built after the Bracebridge St race shop closed in 62. I suppose with the project being so short lived it's not really surprising there is so little reliable information. I am going over to the VMCC library at Allen House but I've been told that they might not have much information either. Anything is worth a try.
 
Rex Butcher who rode the Dunstall bikes and I think worked for Paul will be at the Surrey NOC Evening Dinner meeting , It may be possible to pre -ask a few Questions to be put to him. Contact one of the Surrey NOC guys .It happens very soon.
 
Hi Bernhard, I had read the thread you pointed out but there was rather too much assumption and speculation before it all got a little argumentative and spiralled a bit off topic. I'm not saying it wasn't an interesting read but not really the precise information I'm after. Other sources have been quite helpful in offering some solutions regarding details for re-manufacturing my own parts.
 
Thanks Norton Bob, that's a great lead. I'll try to contact the Surrey NOC guys and see if some sort of dialogue can be set up. Thanks again.
 
Purity Vendetta said:
Oddly enough I have just today received a very interesting local lead on this. I guess it's one of the few advantages of living near to the West Midlands. As I'm in a position to actually manufacture the components the lead I have may prove to be very useful. You'd be surprised at what and who people know ;)
Click to expand...
Hello P.V also a devotee of the 500 domiracers 50+ years ,collected every publication I could get my hands on . You can also find more on this forum e.g the works barrels with completely different cam followers. Picture can be worth a thousand words. From what I read in the mags there was a mark 1 and mark 2 versions , Mk 1 being closer to the std 88ss. Of the many topics mentioned I am surprised no one as mentioned the flanged manx type main bearings , I have made do with the Dunstall upgrade flogged in the late '60s i.e 10 ball caged type. I did contact John Hudson some years ago and will gladly pass this on to you but I think his memory may have faded in his latter years. Roger Moss built a version but always seemed busy with Scotts m/cs. One nice mod was the split bearing on the camshaft and bored for end feed. The nearest I got to one of the P.D 500 was when Ken Redfern joined the team and brought it to Croft Autodrome. Seeing those alloy barrels had me drooling having bought a 1965 88ss in '67. On that subject a few years back I got an alloy casting from Ed Shoobridge who apparently supplied the 650 set Norman White sold. When they arrived , rather than expecting the bores to be semi finished for the intent of direct coated bores they are bored for liners. I may enquiry as to having alloy liners fitted by the same firm that were involved with the works machines , Laystall I believe are on your doorstep. I bought a set of Maney cr/cases also a few years ago and had a local machinist finish the mouth to suit . Not having the funds in case of any costly mistake, progress is at a standstill. I only wish I had the bucks to buy the stuff Herb Becker makes. I'm sure, had Doug Hele carried on he would have made the same upgrades. Hoping to have further discussions with you. Bo NORTON Malton nth yorks
 
Barry Smith sold me this photo a while back - you might like it ?

Domiracer rockers and eccentric adjusters.
 
Always amused me as to the works Norton Domiracer got away with using elastic straps to hold the rear of the meggers :!: :shock:
 
Hi PV, making the eccentric rockers is a simple engineering project all you need is some suitable flat steel drilled out at an angle to weld onto the rocker shafts and the rocker ball fixed at one end. The radius of the valve end is a rather more difficult and complex.
My question to you is will you be making the bucket cam followers that the original 500 Domiracer came with as designed by Dog Helne
 
An article written by Steve Robinson, first published in 1972, about tuning of the Norton twins, had a section devoted to the Domiracer engine, and carried details of the eccentric rocker adjusters, together with other details relating to how the Domiracer engine differed in a number of ways to the production engines.
Those interested should be able to find it at http://www.lansdowneclassic.co.uk/tuning-norton-twin/
 
Thanks Snotzo
I have an earlier edition with only the first eleven chapters
Good to have the additional info
Cheers
Rob
 
Purity Vendetta said:
It would seem that, by the nature of the eccentric adjuster spindle design, the four pipe feed system would be the easiest route if a little untidy. I do rather favour the setup illustrated in the Motorcycle News, June 1961. It not only looks good but it looks a far better solution to the issue of incorporating any necessary reducing jets. Sorry I have no idea how to upload pictures and computers aren't really my thing. I've had a go at posting a link to an online source below...

http://www.etmoteur.fr/images/domiracer_head_lub.jpg

I'm planning to go to forced cam oiling using a 6 start pump and an oilway running through the cam and exiting on the rising side of the lobes.

I do have the illustration by Bill Bennett pubilshed in Motorcycle Racing of the Domiracer motor. I'm not sure of the date but judging by the title, 'Why the Domi-Racer dream ended', I guess it's probably a mid 60's article. Very interesting but obviously lacking the fine detail necessary. Short of a miracle I will be using an 88SS crank (with a modification of my own) as the 1.6" big end cranks are obviously as rare as hens teeth and the con rods even rarer, neither of which I have the means to produce. I have exciting some about barrels but I can say no more... As for a set of GP carbs I will have to save up and call in some contacts as I don't believe that the correct bore size is produced new any more. I suppose a set of new 1 1/2" carbs could be sleeved down. My motor currently runs a set of 1 1/8" handed monoblocs and does fuel very well.

I'm very grateful for the help I've already received from some generous and interesting people who've stepped in with their help and knowledge. Without them and one person in particular I wouldn't even be able to consider a project like this.

That said I'm still interested in any and all Domiracer information anyone has lurking as I think this was a very underrated project which, as has been said elsewhere, could have been far more successful if it had been allowed to continue. Their also seems to have been rather a lot of versions of what I would recognise as Domiracers (Lowboy frame, Manx wheels and forks etc) as well as Manx and wideline framed bikes built after the Bracebridge St race shop closed in 62. I suppose with the project being so short lived it's not really surprising there is so little reliable information. I am going over to the VMCC library at Allen House but I've been told that they might not have much information either. Anything is worth a try.
Click to expand...


To bad Heinz has passed away. He was a fountain of knowledge on Domiracers he owned and raced one from new until just before he passed away. I have wondered who got his bike and parts. I do know he was looking into oiling the lifters through the cam from the breather hole and a drilling through the cam to the lobes. Not sure he ever finished that project.

John in Texas
 
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