Many Thanks David, But my tuning days are over, As long as I can keep my bikes running, Thats enough for me, All The Best, Bill.
Lindsay Kyle Racer
- Thread starter davidd
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Back in the 50s my pal Mac built up a nice Shadow with two rear heads , wanted the front head for another project . Took a special inlet manifold up front to position the carburetor where the original one went . Ran well . In fact I ended up with it ! Pulled like a brute .
I have heard that the rear head actually pulls more power , it's inlet port actually in a better position re swirl and tumble . Sid .
I have heard that the rear head actually pulls more power , it's inlet port actually in a better position re swirl and tumble . Sid .
Sid here . On carb size chosen , it's again horses for courses . Too large , say 1/12 inch and you lose low through mid range torque , most important if road racing on a twisty course , and for street and road work . This size loses velocity through its choke down low , falling on its face as its called where a little smaller size , I used 1& 3/8s GP2s , pulls harder right through the full range .
I actually wrote to the Amal Competition Dept and discussed this subject and was advised just this way . And decades earlier I was often with the great Gold Star racer Tommy McDermott who warned of going too large . In later years I asked Dick Mann who concurred .
A new BSA Gold Star comes with a 1&1/2 inch TT but has a step down of 33 thou where the manifold meets the inlet port , Mann stated that it was fastest over a road course with this sharp step left in place tho many removed it thinking it would increase power .
Wrong . It did possibly pull a few more revs if this were done BUT only on very long pulls , but was slower over a twisty course , so losing races in most instances . This advice right from Mann , a prolific winner on Gold Stars . Bill Hoddinott was right beside me when Dick told me this golden nugget .
An interesting point , having a sharp edge where the manifold flange bolts to the head itself boosts torque . Experimented with this myself . I believe it skims the droplets off the manifold wall and knocks them into the center of the air column . Sid .
I actually wrote to the Amal Competition Dept and discussed this subject and was advised just this way . And decades earlier I was often with the great Gold Star racer Tommy McDermott who warned of going too large . In later years I asked Dick Mann who concurred .
A new BSA Gold Star comes with a 1&1/2 inch TT but has a step down of 33 thou where the manifold meets the inlet port , Mann stated that it was fastest over a road course with this sharp step left in place tho many removed it thinking it would increase power .
Wrong . It did possibly pull a few more revs if this were done BUT only on very long pulls , but was slower over a twisty course , so losing races in most instances . This advice right from Mann , a prolific winner on Gold Stars . Bill Hoddinott was right beside me when Dick told me this golden nugget .
An interesting point , having a sharp edge where the manifold flange bolts to the head itself boosts torque . Experimented with this myself . I believe it skims the droplets off the manifold wall and knocks them into the center of the air column . Sid .
I was surprised, How well my old L/ning, Now a road bike, Goes with 28mm mk 1 Concentrics, I thought I would be, "Round to the stop" All the time, But it does 80mph on 1/4 Throttle, I think now, It would have gone better on short tracks like we have in UK with smaller carbs, Or am I just getting Old !! Cheers Bill.
It's all torque development , good cylinder pressure stems from the compression ratio and cams , and porting of course . If these factors are working for you it doesn't take a wide throttle to cruse fast . Full power development demands greater air flow , ie bigger carbs wide open , and certainly velocity or ram tubes really enhance both torque and full power with open pipes . Well chosen these two work in concert . Sid .
More on such things as cams and the way she runs , and FEELS while doing it . I first went to Mk 2s in the mid 50s , WOW they were more sexy , pulled harder above 80 , all the good stuff . Ran them for a couple years beating me pals . Then one day I cleaned up a rusty set of old Mk 1s and popped em in , nothing else changed just to see the effect . Immediately I felt the change in running style . It was more forceful right off idle and zippier at town speeds , needed less gear swapping , tick tocked along in top smoothly at speeds as low as 18mph and happy to pull right up to road speed with out a gear change . It was really sweeter , easier to live with .
Sure it lacked strong pulling the equal of Mk2s beyond that but it suddenly seemed not to matter as much . I had matured a bit , gotten wiser anyway as far as this cam deal went . It was a worthwhile consideration to make , horses for courses yet again . Sid .
Oo
Sure it lacked strong pulling the equal of Mk2s beyond that but it suddenly seemed not to matter as much . I had matured a bit , gotten wiser anyway as far as this cam deal went . It was a worthwhile consideration to make , horses for courses yet again . Sid .
Oo
More . It's surprising the effect on bottom end torque just swapping the old carb end bells for a pair of good ram tubes makes .
Not those with wire screens in them , these defeat much of the effect . The old John Player Norton type work super good . Sid .
Not those with wire screens in them , these defeat much of the effect . The old John Player Norton type work super good . Sid .