Gearing.
Without doubt, Honda got the gearing just right with the TL. 1st 2nd and 3rd are very low and close for off road work, 5th is as long as could be accommodated in the space available and 4th just bridges the gap. Unfortunately, they had to change the order of the gears in the cluster and reduce the size of one of the flywheels to cram it all in. Any long stroke crank mods will foul 5th gear. For a pure off-roader, the lack of a suitable gear for road work is not a problem, but if you want to do any more than pop to the shops, it’s a real pain. Because the gears are reordered, it isn’t possible to mix and match gears, except in very limited ways. The whole cluster must be replaced as a unit.
| CG/CB100 | TL125 | XL185 | |
| Primary | 4.055 | 4.055 | 3.333 |
| 1st | 2.769 | 2.769 | 2.769 |
| 2nd | 1.882 | 2.125 | 1.722 |
| 3rd | 1.450 | 1.450 | 1.272 |
| 4th | 1.173 | 1.000 | 1.000 |
| 5th | 1.000 | 0.724 | 0.777 |
The above table shows all the combinations of primary and internal ratios that I have found, and that are readily available. The TL and CG type clusters will not interchange with the later XL125/185/200 5 or 6 speed internals without major work. The only viable way to use these is to build the motor with the later cases as well, if this option is open to you.
The lowest primary gearing fitted to this family of engines is the 4.055 ratio in the TL, and I think this is the best to use off-road, although the 3.333 may be better for a dual-purpose machine. If you decide to do a swap, you must replace the clutch basket, primary gear and oil pump drive gear as one unit, to ensure that the teeth mesh fully. All clutch baskets are interchangeable, even though there are different methods of fixing these to the mainshft. Some shafts are fitted with a circlip and others with a castle nut. The clutch lifter plate must match the mainshaft and the clutch outer cover to operate properly.
I finally settled upon using the CB100/CG125 cluster with the 2nd gear set from the TL, and the TL primarys. This gives the same nice bottom 3 gears as a TL, but with 5th gear where 4th would have been. This is the best compromise that I could come up with.
| Fitted | |
| Primary | 4.055 |
| 1st | 2.769 |
| 2nd | 2.125 |
| 3rd | 1.450 |
| 4th | 1.173 |
| 5th | 1.000 |
Final gearing was easy. 15T gearbox, 60T rear wheel. (Biggest I could find!)
Gasses in - Gasses out.
I'll do this section in reverse order, for no good reason. The exhaust was built from scratch because I had no suitable system available to use and the chassis mods precluded the fitting of any alternatives without modification. The system is made in one piece from the header to the silencer. I used a pipe from a Kawasaki ATV, cut and shut in various places. I had to do this as I have no access to tube bending facilities. The silencer is a Yamaha ATV spark arrester with modded internals. The system turned out to be very light and have a lovely note. With a standard frame, the Sammy Miller system is now available again and takes a lot of beating.
Sorting the carburation took up more time than any other part. The standard TL carb would probably be the best choice in most cases. Early ones with the clip-on float bowl make jetting much easier. Its small bore keeps gas speed up. The only problem with these units is the near non-availability of jets. Very few sizes seem to exist. I used the CG carb because I had one! It also takes the standard Keihen jets of which I had a good selection. All the carbs from this family of engines will fit with the matching manifolds. Head port and carb bore sizes vary and should be smoothed to suit each other.
I had no suitable airbox, so I used a K&N filter on an extension to clear the frame. This meant that the standard jetting was miles out. It took ages to get right. I went up and down through the range of available main jets, not really getting anywhere until I went to a much, much, bigger jet. More on this subject later.
Chassis.
Riding the thing.
Conclusions .