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Tech Corner

Technical Q and A for classic motorcycle maintenance and repair.

Triumph 650 Engines Head/Cylinder Compatibility


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, 1503 SW 42nd St., Topeka, KS 66609, or send an e-mail with “Keith’s Garage” as your subject. 

Triumph 650 Engines Head/Cylinder Compatibility 

In the May/June 2012 issue, I answered a question about head/cylinder compatibility between model years of Triumph 650 engines. The answer I gave was correct, but as always, the devil is in the details. Careful attention must be paid to matching the pushrod tubes when mating different year parts. Jon Berglund of Countryside Cycle Shop in Tallahassee, Fla., provides the details:

“The basic idea that all 9-bolt heads will bolt to any 9-bolt cylinder is correct. However, the tappet guide blocks, pushrod tubes and cylinder heads MUST be matched completely.

• 1963-1965, first series: Any cylinder head from 1963-1968 is correct because of shallow machining at the upper pushrod tube position.
• 1966-1968 second series: Any cylinder head from 1963-1968 is correct.
• 1969 through last production in 1972, third series: No cylinder head application to earlier series pushrod tubes and tappet blocs. This is because of deeper machining at the upper pushrod tube position to any earlier series of tappet guide blocs and pushrod tubes. If a 1969 or later cylinder head is used, same year pushrod tubes and tappet guide blocs must also be used. All 1963-68 engines must have a thin gasket under the pushrod seal cup at the bottom of the pushrod tube. Rocker boxes interchange to all 650s from 1963 through 1970. 1971-1972 rocker boxes must be used with 1971-1972 cylinder heads because of the locating pins between the cylinder head and rocker boxes. All 650 cylinders have 26 TPI Whitworth threads. All four outer cylinder head bolts interchange with all Triumph 650 engines. Center head bolts are all the same. Inner bolts are all the same from 1963-1970. Inner bolts from 1971-1972 must be used with 1971-1972 rocker boxes.”

Thanks Jon, for the important details. MC