has anyone fitted a 5 speed gear box to a road going Dominator 88 , if so what’s the verdict, are the ratios good for road use?
Most 5-speeders I know of has a higher 1st than the standard gearbox. Makes it a bit more impractical in traffic. What you really want is a wide ratio gearbox that gives you a low first for slow going and a tall fifth for keeping revs down when cruising. Sadly I don't know of anyone. My only experience is of TTI and Quaife for racing. There they makes it easier to keep the engine in its narrow power band.
it was my suspicion that the box done by Mick Hemings was designed more for racing than road going.. I guess I will persist with my box repairs which seem to be going badly, only two gears at the moment!!!!
If we were to get a 5Th speed would it be direct drive? , this would mean that most of the riding would be in an indirect 4th with the subsequent heavy wear on the sleeve gear?? And the need to fit a bigger box sprocket to get an overdrive effect ,which would mean all the gears ratios would then be raised, or need to be lowered to compensate?. Not simple.
No idea how a Quaiffe cluster would go on an 88 but when looking at a full gearbox refurb on my Mk 3 850, decided instead on a 5 speed from Mick Hemmings. This was around 20,000 miles ago and I would never refit the 4 speed despite many comments on various forums about there being no need for more than 4 gears. The torque doesn,t compensate for the gaps between the gears from my experience and that same torque with decent ratios is way better.
I kept the standard 4.38 gearing and it,s one of my best mods for riding enjoyment on my bike with no problems. I use the standard type mineral oil recommended by Mick at the time and change it every 2 years although probably not needed. First gear is higher but hardly a problem and certainly doesn,t make riding in traffic more difficult.
You should have a word with Mick Hemmings if he,s still available, or do a bit of research to check the 88 first gear and compare it to the available Quaffe ratio with a kickstart. That would be the only consideration apart from price, but I suspect it would make riding your own bike a much nicer prospect especially if you enjoy riding roads with many corners.
Top gear is direct so that will be the same as standard assuming you have the original sprocket and tyre sizes, no need to overgear if you are happy as it is, or worry about sleeve gears!
i have finally decided to fit a 5 speed unit and am in the process of ordering from Mick Hemings.i will strip the bike yet again in preparation ready to slot one in upon arrival!.
regards to all.
I can see that a closer ratio box would make an 850 a pleasant ride and it would pull the higher first gear no problem . It already has a fairly high top so maybe does not need a cruise 5th anyway and with the Isos does not vibrate at 75mph.. The 88 will struggle with a higher first but can cruise at 75 as its a smoother motor . The 99/650/Atlas are the ones that really need an overdrive 5th to allow comfy 75 mph cruise as the vibrations are greater. A close ratio box will not do the job.
you should also get the improved layshaft bearing with the kit. I,m pretty sure I had to reverse the camplate because of the Mk3 lefthand gearshift but your kit should be a straightforward fit.
Because it was my first Britbike gearbox rebuild, I found the Old Brits Commando gearbox tech notes below very helpful along with the workshop manual and Hemmings instructions. I also replaced all bearings seals, springs etc.