The Spares Company
Club Shop/Regalia
Parent Website
Contact Officials
Machine Registrar
Club Secretary
Membership Secretaries
MPH Editor and Forum Administrator.
Section Newsletters
Technical Databases
Photos
Home
What's new
Latest activity
Forums
New posts
What's new
New posts
Latest activity
Information
Bike Modifications
Machine Data Services
Manufacturers Manuals
Spare Parts Listings
Technical Diagrams
Whitakerpedia (Vincent Wiki)
The Club
MPH Material Archive
Flogger's Corner
Obituaries
VOC Sections
Local Sections
Local Section Newsletters
Miscellaneous
Club Assets
Club History
Club Rules
Machine Data Services
Meeting Documents
Miscellaneous
Essential Reading
Magazine/Newspaper Articles/Letters
Adverts and Sales Brochures
The Mighty Garage Videos
Bikes For Sale (Spares Company)
Log in
Register
What's new
New posts
Menu
Log in
Register
Install the app
Install
Home
Forums
Forums: Public Access
Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Twin Valve Timing
JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding.
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an
alternative browser
.
Reply to thread
Message
<blockquote data-quote="timetraveller" data-source="post: 55884" data-attributes="member: 456"><p>Yes, I think that is the one. I bought the cams on the understanding that they were Picador cams but was told later that Tom Somerton had copied the cams using a slightly non accurate diameter on the cam follower. Whatever, they timed up nicely and the bike did 135 mph at the end of a standing start half mile, having been ridden to the meeting and then ridden home again. The figure of 135 came from the rev counter which was at 7,000 rpm as I crossed the line and working back through the gearing. As the chronometric rev counters lag a bit it is possible it was a bit more but I was certainly surprised. The MPH article was done when I was designing some new cams which were eventually made but when I came to fit them the front exhaust lower valve guide was missing and several other things needed doing and then my personal circumstances changed and I took on more projects than was comfortable so the bike and cams have still to be tried in anger. To give some idea the new cams, with ratioed rockers, will give up to 0.45 lift, with Mk I (that does say <strong><u>one</u></strong>) timing and yet nowhere does the acceleration exceed that of a Mk I or III. This means that if one wants to get more air/fuel into the cylinder than standard there is only the Mk I duration to do it in so we will have to see what will happen. I've bought 32 mm Mikunis and opened up the ports so I have to get round to it at some stage.</p><p>Incidentally, mentioning Mk IIIs, I have yet so see any evidence of 'quieting ramps' on any Mk IIIs that I have measured so whether modern copies are incorrect or whether it was hype at the time I do not know. The story was that they had underground the base circle by twenty thou and then blended that into the original profile over tens of degrees. It might sound like a good idea but when you get involved in cam design it does not look to me as though that would do what was required.</p></blockquote><p></p>
[QUOTE="timetraveller, post: 55884, member: 456"] Yes, I think that is the one. I bought the cams on the understanding that they were Picador cams but was told later that Tom Somerton had copied the cams using a slightly non accurate diameter on the cam follower. Whatever, they timed up nicely and the bike did 135 mph at the end of a standing start half mile, having been ridden to the meeting and then ridden home again. The figure of 135 came from the rev counter which was at 7,000 rpm as I crossed the line and working back through the gearing. As the chronometric rev counters lag a bit it is possible it was a bit more but I was certainly surprised. The MPH article was done when I was designing some new cams which were eventually made but when I came to fit them the front exhaust lower valve guide was missing and several other things needed doing and then my personal circumstances changed and I took on more projects than was comfortable so the bike and cams have still to be tried in anger. To give some idea the new cams, with ratioed rockers, will give up to 0.45 lift, with Mk I (that does say [B][U]one[/U][/B]) timing and yet nowhere does the acceleration exceed that of a Mk I or III. This means that if one wants to get more air/fuel into the cylinder than standard there is only the Mk I duration to do it in so we will have to see what will happen. I've bought 32 mm Mikunis and opened up the ports so I have to get round to it at some stage. Incidentally, mentioning Mk IIIs, I have yet so see any evidence of 'quieting ramps' on any Mk IIIs that I have measured so whether modern copies are incorrect or whether it was hype at the time I do not know. The story was that they had underground the base circle by twenty thou and then blended that into the original profile over tens of degrees. It might sound like a good idea but when you get involved in cam design it does not look to me as though that would do what was required. [/QUOTE]
Insert quotes…
Verification
What was Mr Irving's Christian Name?
Post reply
Home
Forums
Forums: Public Access
Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Twin Valve Timing
This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
By continuing to use this site, you are consenting to our use of cookies.
Accept
Learn more…
Top