Chain and Sprocket Orientation

| 6/15/2016 12:00:00 AM

Motorcycle Classics tech expert Keith Fellenstein

Editor’s note: If you’re having trouble with that old Suzuki, BSA or BMW, Keith Fellenstein is your guy. From motorcycle tuning tips to detailed motorcycle engine repair, he can draw from a wealth of experience to help guide you to success. Send questions to: Keith’s Garage, Motorcycle Classics, 1503 SW 42nd St., Topeka, KS 66609, or send an e-mail with “Keith’s Garage” as the subject.

Chain and sprocket orientation

Q: I have several Japanese 2-strokes from the late 1960s and early 1970s and have an issue that has plagued me on countless motorcycles, both new and old, over the decades. I’ve never received an explanation that would seem to justify the sheer volume of instances I have run into.

 Every time I align a chain and front and rear sprockets, I find the chain will almost never run centered over the sprockets. Now, I’ve known for over 45 years that the little factory indents/alignment marks on the swingarm are generally useless for alignment purposes, so I have used all the alignment methods I have ever seen, from name-brand alignment tools (which work great, by the way) to measuring and equalizing the distance between the swingarm pivot and the axle shaft, the string method, etc. I always check the sprockets themselves to ensure they are flat as a pancake and not tweaked. Most recently, I had a piece of steel machined to be exactly straight and laid it up against the two sprockets of my current project, finding they were misaligned by 1.65mm. I then removed 1.65mm from the countershaft sprocket spacer as there was more than adequate clearance and got those two sprockets aligned within a gnat’s behind, but to no avail. For clarification, the sprockets and chain are new and correct factory OEM parts. The result is always the same: The right inner link of the chain rides up against the right outside edge of the sprocket. Thus, the chain is slightly to the left of center. I always make sure I have the correct play in the chain measuring it multiple ways, including with the shocks removed and the countershaft, swingarm shaft and rear axle all in the same plane.

Of course I am also aware that frames and mounting points, etc., were not always perfectly in alignment from the factory 40-plus years ago and can get out of whack from living a hard life over the years. Therefore I also do my best to ensure the frame is not tweaked before I ever start on a project and rectify any noted problems I find.

Out of curiosity, I recently visited my local multi-brand dealership and I nosed around the street bikes checking the chain alignment on every brand new street bike on the showroom floor. Every single bike I looked at but one had the exact same issue. The chain was to the left of center and riding on the right inner edge. Even the used bikes I looked at had the same issue. The only bikes in the dealership that didn’t have the issue were the dirt bikes. I’ve often wondered if the issue was that the front and rear sprockets were not vertically parallel and I don’t know how to check that. But after seeing all the new bikes with the exact same issue, well, I give. Chuck Floyd/via email

Guzzi Mutt
10/15/2020 4:53:11 PM

...and is this normal? or should things be adjusted to account for the flex in the output shaft?

The sound and the fury: celebrate the machines that changed the world!

Motorcycle Classics JulAug 16Motorcycle Classics is America's premier magazine for collectors and enthusiasts, dreamers and restorers, newcomers and life long motorheads who love the sound and the beauty of classic bikes. Every issue  delivers exciting and evocative articles and photographs of the most brilliant, unusual and popular motorcycles ever made!

Save Even More Money with our RALLY-RATE plan!

Pay now with a credit card and take advantage of our RALLY-RATE automatic renewal savings plan. You save an additional $5.00 and get 6 issues of Motorcycle Classics for only $29.95 (USA only).

Or, Bill Me Later and I'll pay just $34.95 for a one year subscription!

Facebook Pinterest Instagram YouTube Twitter