Technical Articles

Changing Triumph 650 4-Speed to a 5-Speed

Update To A 5-Speed Gearbox

There have been many iterations of the Triumph 5-Speed transmission.

Not all 5-Speeds gear sets are the same. The early gear sets first offered in the 1971 model year turned out to be problematic. If used hard they would break. This wasn’t discovered during testing, but only after the bikes were in the field. When used hard, like when doing wheelies or drag starts, they would fail often breaking the crankcase in the process.

After a long wait for spare parts to repair all of the broken motorcycles sitting in dealer workshops, Triumph supplied an updated gear set under their part number CP-1000. The kit consisted of:

  1. 57-4661 Layshaft Dog
  2. 57-4654 Layshaft First Gear
  3. 57-4660 Layshaft Shift Fork
  4. 57-4653 Mainshaft First-Second Gear
  5. 57-4657 Layshaft Second Gear
  6. 57-4647 Layshaft Third Gear

Improved five speed new

There are still some early 5-Speed gear sets in 1971-1972 bikes that were never used hard and that are being used today. Just be aware that they still could cause problems. The gears included in the CP-1000 kit were finally incorporated in the 1973 model year production.


This is a picture of typical of the damage caused when the early gear set fails. I have seen much worse.

Tech Note: If a transmission gear includes a bushing the part number for the pair will be one number different than the number stamped on the gear.

Update Shift Quadrant and Plungers for a 5-Speed

When changing from a 4-Speed to a 5-Speed gear set there are a couple things you must remember to do. The gear selector quadrant in the outer cover and the index fingers must be changed to the 5-Speed parts. Also you need to enlarge the casting at each end of the mainshaft to allow mainshaft first and mainshaft high gear to clear.


The 5-Speed Quadrant pictured above right is wider limiting travel.


The plunger on left is an original 5-Speed plunger. Note the i.d. groove on the shaft. The 4-Speed plunger is on the right.


Again the 5-Speed plunger is on the left. This is an aftermarket plunger. Note: To make it interesting it does not have the i.d. groove. The 4-Speed plunger is on the right.

The 5-Speed Gear Set Assembly

Fig 5

Tech Note: There are several reason one or both of the shafts can be bent. A bent shaft will hamper the shifting. Also examine the gear dogs for wear. 5-Speed gear dogs are “back cut.” This means the more torque that is applied the tighter the gears pull together. It is normal for the leading edge of the dog to show a little wear. Excessive wear is a sign that something is wrong.

Tech Note: In the early layshaft the fixed high gear is just pressed on to the splines on the layshaft. This fixed gear has been known to move further onto the shaft locking the freely to rotate gear adjacent to it to the layshaft . This effectively puts the bike into two gears at once. As you would expect it starts to heat things up. The symptom is a difficulty to shift from gear to gear. The last iteration of the layshaft uses a circlip to retain the layshaft high gear in place.

Fig 4

Tech Note: There have been two iterations of the 5-Speed layshaft 1st shift fork. They are not interchangeable. The shift fork pins ride in the camplate grooves and are subject to wear. Also the forks themselves can be bent. If a fork is blued from heat where it rides in a gear it is a sign that the fork is bent, or the bike has been trying to jump out of gear. The gear and the fork should be examined and replaced as necessary.


Tech Note: There have been two iterations of the 5-Speed camplate. The one on the left is the will see most often while the one on the right is from a T160. The standard camplate can only be removed or installed after the mainshaft high gear is removed. The T160 camplate can be removed and replaced with the high gear in place. Because the T160 camplate is expensive, many technicians modify the early camplate to the T160 condition by grinding away a part of the camplate. When using the “full” round camplate you want to use the pointed plunger (57-7020 plunger, 57-4459 spring and 57-4400 housing). When using the lightened camplate you should use the rounded nose plunger (57-4226 plunger, 57-4459 spring and 57-4227 housing) from the T160. The T160 camplate has an ear that operates the neutral switch and might require attention to clearance when fitting.

Improved layshaft pg 23

Tech Note: The early layshaft high gear was prone to breaking. The gear was also noted for moving inward and keeping the adjacent 4th gear from rotating freely. The last iteration had the high gear widened and included a circlip to positively locate the high gear.


There have been several iterations of the high gear and its roller bearing. The first supplied under part number 57-4782 came as an assembly with Hoffman RL11V3M roller bearing. The high gear can be identified by the width of the roller race on the gear (see arrow above). It is 0.348″ wide and the rollers in the bearing are 0.345″ wide. Neither the gear or the bearing are available as replacement parts.

All of the later iterations of this gear use an RHP RJ009 roller bearing supplied under part number 60-4100. The race on the gear is 0.318″ wide and the roller is 0.3125″ wide. You cannot mix gears or bearings!! The last iteration of the gear is illustrated above with the “O” ring/lock tab groove at the end of the threads.

Tech Note: Even with the “O” ring in place gearbox oil can leak through the splines. Clean the splines with alcohol and apply your favorite sealant to seal the splines.


Don’t forget that you will have to enlarge the opening the bearing shield to 1 11/16″, or a bit more, where the 5-Speed high speed gear passes through the case. You will also have to enlarge the same shield behind the mainshaft bearing on the inner transmission cover to 1 1/8″. This allow the shoulder of the first/second gear cluster to clear the cover.


The last job is to replace the 4-Speed quadrant and replace it with the 5-Speed shown above. It will only go in one way and have the cotter pins line up. The teeth on the left engage the camplate and the notches on the right are used by the quadrant plungers to change gears.

German 6 Tr1 VB6

Tech Note: 5-Speed mainshafts have been known to break. This is especially true for after market shafts. They typically break at the clutch end. Used on the street, the after market main shafts work fine. At the moment the only after market mainshaft that is avaiable it the last iteration and is made in Taiwan. But when setting up a bike for competition I always seek out a donor that was made at the Triumph factory.

Important Tech Note: There are two basic iterations of the mainshaft:
The early shaft (57-4432) used 9/16-18 tpi threads on the clutch side and 9/16-20 tpi on the kick starter side. These shafts proved to be very reliable both for the street and competition (especially the clutch nut, normally torqued to 70 foot pound is torqued up to 90 foot pounds). They work best when the taper is NOT lapped and the nut retained with Loctite.
The later shaft, first used in the TSS (57-7077), had larger threaded ends, but that said the only ones available are made in Taiwan. They have 5/8 – 18tpi threads on both ends. But here’s the catch: the depth of the 18 tpi thread on the kick starter end is so close to the cavity that retains the clutch rod bushing that it is very easy to break off the threaded end of the shaft. I still use 70 pounds on the clutch nut, but while 45 foot pounds is shown for the kick starter end nut, I prefer to under tighten it (30-35 foot pounds) and rely on the one place I would use red Loctite on a Triumph to retain the mainshaft kick starter nut. While perfectly OK for the street, I personally would not use one of these shafts on a competition machine. I would search out a donor factory 5-Speed shaft.

Indexing the Quadrant




You are are looking into the inside of the gearbox at the back of the camplate. The crankcase has been cutaway to provide this view. Note that the quadrant is indexed with the camplate’s teeth so the gear set will be in high gear. Look at this picture carefully because it is at the heart of understanding how to index the camplate and quadrant quickly and accurately. Notice that the quadrant is about one tooth away from hitting the top of the gearbox

The quadrant being one tooth away from being properly indexed is what you use as an aid to index the transmission first time, every time.

Assemble the gear set so that it is in 5th gear. Offer the inner cover with your thumb situated so you can push down on the quadrant. Once the inner portion of the quadrant clears the outer edge of the gearbox gasket surface push down with your thumb until the top edge of the quadrant is hitting the roof of the gearbox. Slide the outer cover assembly in until the two sets of teeth just begin to touch. To do this as I offer the inner cover I intermittently release the thumb pressure on the quadrant a little bit letting it start to fall. When it stops falling the teeth are just starting to touch. All you need to do now is to back the inner cover assembly just a bit which will allow the quadrant to fall. Then drop it one tooth and the gearbox is indexed.

How do I know it has dropped one tooth? When keeping a bit on inward pressure on the cover, as you lower the quadrant away from the roof of the gearbox tops of teeth are hitting each other which prevents the cover from going in. When the next set of teeth align the resistance pressure felt is gone you can now push the inner cover in place. The gearbox is indexed!

Quadrant in Fifth Gear

index 5th

With the camplate rotated so the gear set is in 5th gear this is what you will see from the outside. Notice relationship of arrow to the quadrant’s teeth! So with some feel and the visual alignment of the quadrant’s teeth with the bushing you will index the transmission first time, every time.

Quadrant in 1st Gear

index 1st

There are times when you want to index the gearbox with the gearset in 1st. This is especially true when indexing a transmission that has a leaf spring detent. The relationship of the quadrant and the floor of the gearbox casing is the same as with indexing in 5th gear. The proper alignment of the teeth is one tooth away from the bottom.

When indexing a leaf spring gearbox place the camplate and gearset in 1st gear. Then rotate the camplate counter clockwise past 1st gear so the 1st gear camplate indent is facing out at about the same level as the leading edge of the leaf spring. Offer the inner cover lifting the quadrant with your thumb it so it clears the gasket surface. Then let the quadrant drop to the bottom of the gearbox. As you slide the inner cover into place the tip of the leaf spring will engage the camplate indent and rotate the camplate into the proper 1st gear position. Do the opposite of what you did when you were in 5th. You are one tooth away and you need to raise the quadrant the one tooth.

Copyright John Healy 2015