1972, 4 Speed, Engine, Engine Rebuild, Fix, Made In England, OIF, Repair, Tiger, TR6, Triumph, Triumph Engine Rebuilding, Triumph Mechanic, Triumph Motorcycles, Vintage -

1972 Triumph Tiger (650) Full Engine Rebuild

Here we have a 1972 Triumph TR6R in for a full engine rebuild! Everything will have to be completely dissembled and thoroughly cleaned and checked. The Main Roller bearing is suspect to be the problem. As most engine rebuilds go, you always find (and see) little corners that the previous owner(s) "cut". Initially the bike ran great but started to develop a bottom end rumble. Very unfortunate as it was a very sweet runner. Follow this blog as we will update it weekly!


Cylinder head from 1971-1972 have many differences from the previous and earlier years. Studs with Allen heads can be seen to securely fasten the cylinder head down with adequate torque.

Cylinder head & Barrel look to be in great shape. Behind the right cylinder on the case there appears to be what we thought was a surface crack but is indeed a crack, but nothing severe. Sometime in the Tigers life it threw a rod and luckily the intake cam took most of the damage saving the case. The case will have to be repaired especially on the inside as the previous owner/mechanic decided to use J.B. Weld rather than having it welded. Little particles of J.B. Weld & gasket sealer floating around in the crank is not a good thing! One of the corners "cut" I was referring to earlier.

Notice the timing gear thread size on the wheel as they are different from the earlier years. A special tool or puller must be used.

The Tiger appears to have new +.020 JCC Pistons & valve guides previously installed. Gasket sealer was improperly used all over this engine! Various oil seals look to be completely dipped in red sealant. In the crank, oil seals, sump filter, push-rod tubes and the list goes on! It will be very interesting to see whats in the sludge trap. We have completely striped every nut and bolt off the cases to be ready for a deep cleaning. The drive side roller bearing was the cause of the problem as we earlier predicted. The journal's where surprisingly still STD but with much wear they will have to be reground to .010. Our main goal at this point is to carefully inspect all parts to see if it can be machined, replaced, or fixed. So far so good.
The RHP MRJA 1 1/8" roller bearing inner race appears to have much wear.

Cleaning the cases we simply used a brass brush and allowed the cases to sit in a tank cleaner. There are many options to clean cases such as vapour blasting, sand blasting or soda blasting. I highly recommend vapour blasting over sand or soda blasting as vapour blasting is non-abrasive and keeps the original texture of the cases. Using a soft brass brush is an excellent non-abrasive alternative (affordable) to clean it up without any damage.




  • August Tiberio

    While cleaning out a shed on my newly purchased property, I discovered a milk box filled with parts that I believe make up an old Triumph motorcycle engine. Can you give me some advise on how to determine if I have a Triumph and what the engine might be worth. Thanks.

  • john paulson

    hello i have a 1968 TR6 my center stand hits the muffler has anyone had this problem?

  • ed smith

    JB weld has it’s place but not in a engine ! I like the 72 build I have one and did a rebuild a few years ago if I remember the 2 cank bearings different , mine didn’t have studs either ? over 50yrs being a mechanic and a backyard mech keeps the parts guys in business .

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