Tech Tip: (Late) Singles Cam Follower Orientation
The inspiration for today’s Tech Tip blog post was made possible by a BSA Victor (441) we have here at the shop
Since Malcolm happens to be working on getting this BSA Victor road ready again (and for re-sale), he noticed something during the rebuild that shouldn’t be over looked...
Today we will be covering the proper way to install cam followers on late model Triumph and BSA until singles from approx 1966-1973
The models that we will be covering in today's post will include the B25, C25, TR25W, B44 & B50
Here are some points and details that we will also be covering below:
- Early & late cam followers
- Late tappet design
- BSA service bulletin
- Cam follower installation
- Cam follower wear check
Let’s dive in
Early & late cam followers
From approx 1959-1965 BSA C15 and B40 models featured a round or radius style tappet; very typical to British motorcycles
However, in 1966 both Triumph and BSA unit singles (excluding the B40 and C15) changed the tappet design which featured a flat "foot"
Unlike the earlier models where the lifters can be installed in any direction, later models that we are discussing today with the flat "foot" which must be installed in the proper direction that we will showcase later in the post
Late tappet design
Shown above we have a flat "foot" tappet design that features a 1 degree taper on the base of the pad
The pad features the ground taper while the follower is straight and perpendicular
The taper according to BSA (and Triumph) is to allow the followers to stay inline with the cam lobes preventing the followers to shift from "side to side"
You might notice that the followers have no real "guide" on the case to keep the followers in place
Click the image above to enlarge this service bulletin - you can print, save and share...
Dated from 1969, this original BSA service bulletin shows the importance of the proper cam follower instillation
Notice the important details in regards to the tapered pad and instillation tips..
Here are some part numbers (and superseded numbers) for the late style tappets as shown above:
Instillation of the late style cam followers is simple but oftentimes over looked
Here's what happens should you install the followers the wrong way...
- Incorrect cam timing
- Valve colliding with piston
- Longer valve duration
- Premature camshaft wear
With the thinnest portion of the pad facing the front of the engine and the largest taper facing the rear, this is the correct and proper way to install the flat "foot" tapered cam followers
Checking for wear
Beside from installing the cam followers the correct way, checking and addressing wear on the face of the tappets is vital
Due to the flat "foot" design, wear is usually evident on the center of the pad
If your pads happens to be worn or features a groove I recommend having the tappets and camshaft re-ground at the same time
Always use a reliable machine shop to do this job like Megacylce Cams or Web Camshafts
Remember the 1° radius!
Thanks for reading today
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Ride safe! - CBS