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 'A' 500cc/1000cc Bikes
Series A single cam.
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="A_HRD" data-source="post: 104046" data-attributes="member: 49"><p>Andy,</p><p>In reply, perhaps the best thing I can do is quote from the Late Great Bob Stafford's "Ab Initio". It covers the cams, the pinion and the cam bushes - your early meteor bushes might be different to later ones (ie without the 3/16 dia peg??):</p><p></p><p>Three patterns of cam pinion were used, the standard plain gear, the lightened, recessed and polished</p><p>one on the specials and T.T.Rs. and the recessed and slotted type on the front camshaft of the Twins. The</p><p>interference fit of the shaft in the pinion is 0.001” to 0.0015” and theoretically any of the cams can be fitted</p><p>into any of the pinions and the same timing marks (if any) can be used. It should be mentioned that originally</p><p>no timing marks were used on the T.T.Rs, and where replacement gears have been fitted it is likely that they</p><p>too will be unmarked.</p><p></p><p>The camshaft bearings are merely iron or bronze rings, 1.126” OD with a 3⁄4” bore. Originally these</p><p>bearings were just trapped in a housing when the cambox cover was clamped down, later a 3⁄16” diameter</p><p>peg projecting 1⁄8” was fitted into the OD of the bearing, this peg being threaded either 2 BA or 3⁄16” BSF,</p><p>and it is to ensure that should the bearing ever come loose it will not rotate in the housing. Nevertheless,</p><p>if a seizure does occur the bearing does sometimes move and on rare occasions has been known to cause a</p><p>fair amount of damage. The inner bearings (ie. next to the barrel) are always iron as oil only reaches them</p><p>through a catchment on the cambox wall. The outer bearings can be iron or bronze as the oil supply to the</p><p>rockers runs by these bearings and some is diverted to the camshaft under pressure. It should be noted that</p><p>the outer bearing of the front camshaft of the Twins is always of bronze as this has also to withstand the</p><p>drive to the mag-dyno. The inner bearings have an oil hole in the top to line up with the catchment hole, the</p><p>outer bearings have a 1⁄8” wide 5 1⁄16” deep groove around the OD to pass oil to the rocker feed pipes and a</p><p>1⁄16” diameter hole drilled into the bearing to feed the camshaft.</p><p></p><p>The Series ‘A’ cams were known as 2X, 4X and 5X; timing figures approximate closely to Mk. I and Mk.</p><p>II post-war cams although the actual form is different, 2X were original equipment in Meteors, 4X in Comets</p><p>and 5X in Specials and T.T.Rs. Rapides were fitted with either 2X or 4X. The cam form is identical for all, that is the same shape on the rise and fall but the actual theoretical lift varies as follows: 2X — 0.320” lift inlet and</p><p>exhaust, 4X — 0.331 lift inlet and 0.333 lift exhaust, 5X — 0.333” lift inlet and exhaust: these differences in</p><p>lift are negligible but because of the variations in radii used on the various cams the valve timing is altered</p><p>appreciably, incidentally the radial relationship between inlet and exhaust cams is 172degrees (or 188degrees, depends which way round you go); on the Series ‘A’ models the cam nearest to the cylinder operates the exhaust valve.</p><p></p><p>Now to the theoretical timing of the cams which is as follows:</p><p></p><p>I.O. I.C. E.O. E.C.</p><p>2X: 40 BTDC 52 ABDC 65 BBDC 33 ATDC</p><p>4X: 44 BTDC 56 ABDC 68 BBDC 38 ATDC</p><p>5X: 48 BTDC 60 ABDC 71 BBDC 42 ATDC</p><p></p><p>Obviously it will be almost impossible to obtain these settings on worn components so my own method</p><p>is to use a degree plate and to set the inlet valve opening at its correct position then take a note of the actual</p><p>opening and closing points as they occur, the engine then has to be run to observe the performance.....</p><p></p><p>Peter B</p></blockquote><p></p>
[QUOTE="A_HRD, post: 104046, member: 49"] Andy, In reply, perhaps the best thing I can do is quote from the Late Great Bob Stafford's "Ab Initio". It covers the cams, the pinion and the cam bushes - your early meteor bushes might be different to later ones (ie without the 3/16 dia peg??): Three patterns of cam pinion were used, the standard plain gear, the lightened, recessed and polished one on the specials and T.T.Rs. and the recessed and slotted type on the front camshaft of the Twins. The interference fit of the shaft in the pinion is 0.001” to 0.0015” and theoretically any of the cams can be fitted into any of the pinions and the same timing marks (if any) can be used. It should be mentioned that originally no timing marks were used on the T.T.Rs, and where replacement gears have been fitted it is likely that they too will be unmarked. The camshaft bearings are merely iron or bronze rings, 1.126” OD with a 3⁄4” bore. Originally these bearings were just trapped in a housing when the cambox cover was clamped down, later a 3⁄16” diameter peg projecting 1⁄8” was fitted into the OD of the bearing, this peg being threaded either 2 BA or 3⁄16” BSF, and it is to ensure that should the bearing ever come loose it will not rotate in the housing. Nevertheless, if a seizure does occur the bearing does sometimes move and on rare occasions has been known to cause a fair amount of damage. The inner bearings (ie. next to the barrel) are always iron as oil only reaches them through a catchment on the cambox wall. The outer bearings can be iron or bronze as the oil supply to the rockers runs by these bearings and some is diverted to the camshaft under pressure. It should be noted that the outer bearing of the front camshaft of the Twins is always of bronze as this has also to withstand the drive to the mag-dyno. The inner bearings have an oil hole in the top to line up with the catchment hole, the outer bearings have a 1⁄8” wide 5 1⁄16” deep groove around the OD to pass oil to the rocker feed pipes and a 1⁄16” diameter hole drilled into the bearing to feed the camshaft. The Series ‘A’ cams were known as 2X, 4X and 5X; timing figures approximate closely to Mk. I and Mk. II post-war cams although the actual form is different, 2X were original equipment in Meteors, 4X in Comets and 5X in Specials and T.T.Rs. Rapides were fitted with either 2X or 4X. The cam form is identical for all, that is the same shape on the rise and fall but the actual theoretical lift varies as follows: 2X — 0.320” lift inlet and exhaust, 4X — 0.331 lift inlet and 0.333 lift exhaust, 5X — 0.333” lift inlet and exhaust: these differences in lift are negligible but because of the variations in radii used on the various cams the valve timing is altered appreciably, incidentally the radial relationship between inlet and exhaust cams is 172degrees (or 188degrees, depends which way round you go); on the Series ‘A’ models the cam nearest to the cylinder operates the exhaust valve. Now to the theoretical timing of the cams which is as follows: I.O. I.C. E.O. E.C. 2X: 40 BTDC 52 ABDC 65 BBDC 33 ATDC 4X: 44 BTDC 56 ABDC 68 BBDC 38 ATDC 5X: 48 BTDC 60 ABDC 71 BBDC 42 ATDC Obviously it will be almost impossible to obtain these settings on worn components so my own method is to use a degree plate and to set the inlet valve opening at its correct position then take a note of the actual opening and closing points as they occur, the engine then has to be run to observe the performance..... Peter B [/QUOTE]
Insert quotes…
Verification
The Series 'A' Rapide was known as the '********' Nightmare?
Post reply
Home
Forums
Forums: Public Access
Tech. Advice: Series 'A' 500cc/1000cc Bikes
Series A single cam.
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