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cams.... and more cams......

charles d cannon jr

Active Forum Website User
VOC Member
Still working on my 1950 Shadow and placed an order several mos ago for new cams as the originals were pretty worn. Mark 1's would seem to be the appropriate type should I still adhere to original fitment. However, there has not been availability within the spares co for Mark 1's as of yet and "there are some Mark 2's on the shelf". Comments and recommendations as to what to use would be appreciated. I've heard the Mark 1's are a little more fierce in opening and thus a little more powerful (and noisy) Thanks in advance for your individual thoughts.
 

timetraveller

Well Known and Active Forum Website User
VOC Member
You will find several people on this forum, including me, who have used MkIIs on the road for years. However, they were intended for racing and the overlap is such that you will get significant blow back from the carburettors below about 4,000 rpm. I used to get 55 - 60 mpg with MkIs and I am lucky to get 40 mpg with MkIIs. They were also intended to run with an open exhaust system!! Either MkIs or MkIII are suitable for normal road use and will give a more tractable engine. The MkIIIs were intended to have quitening ramps to cut down some of the noise but I have never measured a set which had what I would call a 'quieting ramp'. The acceleration, which is what would generate noise, is not very different between these cams. I think that I posted some graphs of the relevant figures on this forum some years ago. Gary Robinson, on the Isleof Wight, makes these cams for the spares company, and assuming that he is still alive and well would probably deal with you direct.
 

roy the mechanic

Well Known and Active Forum Website User
VOC Member
Mk 1,s went in rapides, good mk 1,s went in shadows, mk2.s went in lightnings, mk3's had "quietening" ramps. Having inspected all standard cams I came to the conclusion that they are all, basically ,"a peice of junk" Depends how fast you want to go. Andrews made the first cams to go in Big Sid's Vincati, read the report, immediately phoned them, only to be told, we don't do them any more, phone megacycle. The numbers suggest re-made mk2's. Finally went to Terry Prince for mk4's! It has yet to run but I have a good feeling for them.
 

Bill Thomas

Well Known and Active Forum Website User
VOC Member
Hello Charles, I run mk 2s on my bikes and they are fine, As Norman says they do like an open exhaust, I get 50 to the uk gallon easy, The twin now comes down to 35 mph in top but if you want a very slow tickover, It will have to be mk1 or 3s. Good luck Bill.
 

Bill Thomas

Well Known and Active Forum Website User
VOC Member
Morning Charles, BIG PROBLEM !! I hope you know that if you fit Mk2s you have to take the cylinder heads off , To shorten the top of the lower valve guides, Sorry, shoud have told you befor, Cheers Bill.
 

davidd

Well Known and Active Forum Website User
VOC Member
Morning Charles, BIG PROBLEM !! I hope you know that if you fit Mk2s you have to take the cylinder heads off , To shorten the top of the lower valve guides, Sorry, shoud have told you befor, Cheers Bill.


Bill's point cannot be overstated as you can ruin some very expensive parts very quickly. This should also apply to the "105" cams as Bill Easter found out after running his bike for a few revolutions. When installing any new cam it is worth making many careful checks while the cover is off to see that everything is working properly.

David
 
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