Tech Tip: (Late) Singles Cam Follower Orientation

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 


Early & Late Singles 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


Cam Follower Details


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 

Service bulletin 


BSA Service Bulletin - Victor 441 Tappet Orientation

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Here are some part numbers (and superseded numbers) for the late style tappets as shown above:

  • 41-0668
  • 41-668
  • 70-7739
  • E7739




Cam Follower Direction Installed


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 


Cam Follower 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 


Thanks for reading today's new Tech Tip post 

For more tech like this one, please click here to view our index for your reading pleasure 

Have something to say? - drop us a comment in the comment section below 

Ride safe! - CBS


  • steve smith

    good info and don’t forget the “correct” timing mark on the gear

  • John corven

    I have never noticed this on my b44ss, but now I will have to pull it down and check!

  • Geoff Ahrens

    Great info !!! I have a 69 B-44VS since 1981. Bought it real cheap!! It was running but with a piston rattle. The kid that had it bought from the orig. owner in 1980. I was fortunate to have met a former dealer that moved to Fl. when BSA folded. He owned House Of BEEZA in Lockport N.Y. He helped me with the top end tear down. We found the piston cracked from the top of the pin to the oil ring groove. Lucky me, it was caught in time before it went boom. Beno Rodi in GA. had a .010 piston & ring set. Dave Pras @ Tri-County Cycles in Brooksville Fl. made the hole the correct size and I ran a .312 knurler through the guides, and lapped in the valves. Here I am 39 yrs. later still have it,& runs great still. Bottom end never been touched, has a BB ign. Tympanium R/R and 30mm R-S Kuni. Last Nov. it quit charging and need a time tested stator. (I use YTX-4 gel electrolite batt.) Holds up real good from the vibration. Just a big fun old Brit thumper. I ride it regular along with my 64 A-65 SF-Hornet street tracker mutt.
    Here is some useless trivia. Michael the promotor of the Woodstock Festival used a VS to run all round on Max Yeagers farm. Watch the movie sometime if you have not already. Cheers Geoff!!

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