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
General Chat (Vincent Related)
Vincent Comet 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: 5970" data-attributes="member: 456"><p>If when you road test the bike you are happy with the performance then leave well alone. If not then do the job properly. Assuming that you have either MkI or Mk III cams then you can check for wear as the lift on both inlet and exhaust should be about 330 - 340 thou. Significantly less than this and the cams are worn. Then as to the timing. You do need to ascertain TDC properly, not just 'about'. Accuracy of one degree is quite reasonable. Then, at TDC, there should be more lift on the inlet than on the exhaust. The reason for this is that the 'degrees of inlet opening should be greater than the degrees of exhasut closing'. It says so in the book. Depending upon the cams and whether the followers are still flat or have worn concave you should have 10 - 20 thou more lift on the inlet than on the exhasut at TDC. The correct way to do all this is to remove the oil tank and front end and then use the DTI on the top of the valves and then take a reading all the way round each lift profile at 10 degrees of engine rotationi .e. 5 degrees of cam rotation. Check the base circles first by nipping up the tappets by about 20 thou and leave the tappets tight for doing the lift profiles. When you have the measurements plot them on a graph, a spread sheet makes it easy, and then draw a line at 5 thou lift. That is the figure at which Vincent valve timing is given. Work out what is the best compromise for your particular cam profiles as many Vincent cams are of really poor quality when it comes to the profiles. Your cam and follower hardening must have been right for them to have lasted so long. Pain in the posterior I know to have to do all this but if you are proper engineer the you know that you have to do things correctly otherwise your customers come back with the items you have made and threaten to use them as suppositories on you. Good luck.</p></blockquote><p></p>
[QUOTE="timetraveller, post: 5970, member: 456"] If when you road test the bike you are happy with the performance then leave well alone. If not then do the job properly. Assuming that you have either MkI or Mk III cams then you can check for wear as the lift on both inlet and exhaust should be about 330 - 340 thou. Significantly less than this and the cams are worn. Then as to the timing. You do need to ascertain TDC properly, not just 'about'. Accuracy of one degree is quite reasonable. Then, at TDC, there should be more lift on the inlet than on the exhaust. The reason for this is that the 'degrees of inlet opening should be greater than the degrees of exhasut closing'. It says so in the book. Depending upon the cams and whether the followers are still flat or have worn concave you should have 10 - 20 thou more lift on the inlet than on the exhasut at TDC. The correct way to do all this is to remove the oil tank and front end and then use the DTI on the top of the valves and then take a reading all the way round each lift profile at 10 degrees of engine rotationi .e. 5 degrees of cam rotation. Check the base circles first by nipping up the tappets by about 20 thou and leave the tappets tight for doing the lift profiles. When you have the measurements plot them on a graph, a spread sheet makes it easy, and then draw a line at 5 thou lift. That is the figure at which Vincent valve timing is given. Work out what is the best compromise for your particular cam profiles as many Vincent cams are of really poor quality when it comes to the profiles. Your cam and follower hardening must have been right for them to have lasted so long. Pain in the posterior I know to have to do all this but if you are proper engineer the you know that you have to do things correctly otherwise your customers come back with the items you have made and threaten to use them as suppositories on you. Good luck. [/QUOTE]
Insert quotes…
Verification
The Series 'A' Rapide was known as the '********' Nightmare?
Post reply
Home
Forums
Forums: Public Access
General Chat (Vincent Related)
Vincent Comet 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