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RASK CYCLE

FRONT ENDS AND FORK TUBES

PLEASE READ THIS SECTION BEFORE ORDERING FORK TUBES

Front ends are often swapped, motors and frames are occasionally re-stamped, and a lot of times there can be some confusion as to what year the bike really is or if it has the original front end.

The following pictures should help you determine if the frond end of your bike is the right type for the year of the bike. If you find that you have a different type of front end that what was originally installed on your bike, you may want to check and see if it was installed correctly.

Most front ends can be installed on a different model bike, but it is VERY important that it is done correctly. MOST front ends will NOT bolt right on, but can be adapted by fabricating spacers. A quick, easy way to check and see if the guy who installed your front end did it right is to block the bike up with the front wheel off of the ground.... Stand in front of the bike and grab the lower legs. Push and pull the lower legs forward and backwards. There should be NO PLAY...Next center the front wheel. Then gently push it to one side, then re-center it and push it to the other side. It should fall freely to the fork stops on either side just by its own weight. If it binds, the bearings may be worn or too tight. If it slams to the stop they may be too loose. If it tries to stay on center, the bearings are shot. If any of these problems appear, especially on a bike that has a different style front end installed that what originally came from the factory, take the front end off and check everything. Make sure that the bearing races fit snugly in the frame. Check the balls or bearings to make sure that they are not pitted. Check the bearings or race fit on the fork stem. It should be a push fit with no noticeable play.

Before you order fork tubes for fork parts, you must make sure you know what front end you are dealing with. The following pictures should help. This is very general, but should apply in MOST cases. There can always be exceptions and it is possible that what you have was assembled from a couple of different models. You should purchase a parts book ($10.00+shipping) for the type of bike or front end that you are dealing with.

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Pre-Unit Triumph
 
1971-72 650 Triumph
1964-70 Unit Construction Triumph 1973 and up 650/750 Triumph Twins
 


PRE-UNIT TRIUMPH

Very early Pre-unit Triumph front ends can be identified by the lower legs. from the first telescopic to 1956 the axle was pushed through the hole in the bottom of the left leg and screwed into a threaded hole in the bottom of the right leg. The left fork leg was split at the bottom to allow clamping the axle tight. There are lugs for fender mounts on the front and rear of each fork leg. There was a strap around the leg halfway up to bolt the middle fork brace to. 1957 fork legs had the strap for the middle fender brace, but both lower legs had a 2-bolt axle cap. In 1958 the fender strap was replaced by a round lug with a threaded hole welded to the inside of the leg. The two bolt axle caps remained on all twin forks through 1970. Pre-Unit forks all had internal springs and all pre-unit forks used the small (1-7/8 L X 1-3/4 OD) fork seal holders.

There were exceptions especially in the area of the welded leg for the middle fork stay, but generally speaking, if it had internal springs and the small oil seal holders, it came off a pre-unit. One other notable exception is that the first year unit construction 650 (1963) used the older pre-unit front end.

PICTURES OF PRE-UNIT AND UNIT LOWER LEGS.                   CLICK HERE
PICTURES OF PRE-UNIT AND UNIT FORK SEAL HOLDERS   CLICK HERE
PICTURES OF FORK SPRINGS    CLICK HERE
PICTURES OF PRE-1971 INTERNAL DAMPNERS CLICK HERE
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1964-1970  UNIT CONSTRUCTION TRIUMPH

The forks look very similar on all 500 and 600 Twins built between1964 and 1970,but there are some differences. These descriptions are very general and there will be exceptions, but this should be enough information to allow you to get the right fork tubes and seals for the front end that you have.

The lower legs on the 1964-70 are about 10-5/8" long and have a diameter of approximately 1.675 . Earlier Pre-unit lower legs are about the same diameter but measure about 2-3/8" longer. The Pre-Unit and 1964-70 front ends both use the same fork bushings, but they do have different oil seals and seal holders. The seal holders on the Unit front end are much larger than the ones on the pre-units. The unit construction seal holders are about 3-5/8" long by 2-1/8" diameter with a .100 lip at the top for the gaiter. The Unit-Construction Triumphs from 1964-70 all used external springs on their forks. This should be carefully examined before deciding which front end it is that you have, because there were a lot of aftermarket conversions kits on the market years ago. Many unit front ends were converted to internal springs and it was not uncommon to find oil seal holders cut down lengthwise for a cleaner look when the long fork boots were eliminated. As a general rule Pre-Unit (and 1963 unit) forks all used internal springs with an inside dampener rod running the length of the tube. 1964-70 type forks all had external springs. Most models manufactured before 1968 employed a tapered restrictor that was bolted to the bottom of the fork leg. This was changed to an aluminum shuttle valve arrangement for 1968-70. check your parts book to be sure.

The threads in the top of the fork tubes also changed in 1968 from 26TPI to 28TPI. The 650 forks changed from steel to aluminum lower legs in 1971, but the 500 Twins (with the exception of the oil framed TR5T) kept the steel lower legged fork until they ceased production.

The Pre-Unit and 1964-70 unit front ends all rode in ball bearings. If the top tree doesn't have a fork lock built in, the fork was probably made before 1967, if it has a fork lock built in, the fork was probably made from 1967 on. This stem diameter on most pre-1971 fork necks is slightly under 1".

To save you a lot of trouble, Harley fork necks are a few thousands larger and while they are close, they DO NOT BOLT RIGHT ON. If you attempt to run Harley forks with Triumph races, It will not work. Harley front ends CAN be safely adapted, but the proper spacers MUST be fabricated. The same holds true for the later, smaller necked Triumph front ends and oil frames. They can be adapted, but it MUST be done RIGHT.
 

PICTURES OF PRE-UNIT AND UNIT LOWER LEGS. CLICK HERE
PICTURES OF PRE-UNIT AND UNIT FORK SEAL HOLDERS CLICK HERE
PICTURES OF FORK SPRINGS CLICK HERE
PICTURES OF PRE-1971 INTERNAL DAMPNERS CLICK HERE
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1971-72  650 TRIUMPH FRONT ENDS

All 650 Triumph front ends made before 1971 had steel lower legs. All 650/750 Twin Triumph front ends made from 1971 on had aluminum lower legs. 1971-72 were the last of the drum brake front ends. Everything on these front ends was changed from the earlier models. These front ends will not bolt right on to earlier models, but they can be adapted. This MUST be done right or the results could be fatal.

The Pre-1971 front ends had a larger stem size. The 1971-72 front ends had a 3/4" diameter stem. The 1971 fork stem had a course thread. The 1972 fork stem had a fine thread. Both forks are interchangeable as a whole assembly with each other and the later disc types. The four bolt aluminum axle caps are NOT interchangeable between the 1971-72 type and the later disc brake type. These axle caps break VERY EASILY AND GREAT CARE SHOULD BE TAKEN TO TIGHTEN THEM EVENLY.

Do NOT ride a bike with cracked axle caps. 1971-72 front ends are easily identified by the short slotted single hole tab for the brake, the four bolt axle caps, the aluminum legs and the 3/4" diameter fork stems.

PICTURES OF 1971 UP LOWER LEGS CLICK HERE
PICTURES OF FORK SPRINGS CLICK HERE
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1973 AND UP 650/750 TWIN FRONT ENDS

The 1973 and up Disc brake front end looks similar to the 1971-72 drum brake front end, but has a few subtle differences besides the obvious disc brake. On the 1971-72, the axle caps have no fender tab. 1973 up axle caps have a tab cast in to the rear of the cap to carry the fender brace. The right lower leg of 1971-72 front end have a short single bolt tab for the drum brake. The disc front ends have a larger 2-bolt bracket built in to the left lower leg to carry the caliper.

There were also some dual disc models that had the bracket cast into both legs, but they were not very common. Be careful that you don't confuse a triple front end with a Twin-Type. Although they shared some components, there were also some differences. If the stem size doesn't seem right, or if there is a tab welded onto the bottom triple tree between the pinch bolts, it may be a Trident front end. If you have any doubts.............................
CONSULT YOUR PARTS BOOK.
.
.
 IT WILL BE THE BEST $10.00 YOU COULD SPEND ON YOUR BIKE.

PICTURES OF 1971 UP LOWER LEGS CLICK HERE
PICTURES OF FORK SPRINGS CLICK HERE
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