Hoghead
Not a Total Newb
- Location
- Chiangmai and Vancouver
Super Meteor 650 belt drive kit is finished in two final drive ratios, and I am trying to get feedback on what gear ratios are preferred - stock or the 38T rear/16T front mod.
My thoughts on SM 650 gearing:
Gearing is a bit confusing with a larger number being "lower" geared – IE the SM 650 stock sprocket ratio at 2.6:1 is lower than the Interceptor stock ratio at 2.5:1
A lower gear ratio (2.6) will accelerate quicker, but top speed will be lower. At highway speeds the engine will be spinning at a higher speed, and depending how fast you are riding, you may not want to work the engine that hard for very long.
A higher gear ratio (2.5) will accelerate slower, but top speed will be higher, IF you have the HP to pull the higher gearing. Top speed on a SM is usually not a consideration, however some riders, myself included, would prefer lower engine speed on the highway. When higher geared, cruising speed rpm will be lower, and in the meat of the TQ band.
While not an engineering law by any means, and there are a lot of variables, (with notable exceptions like the new Ducati single); a rule of thumb for long engine life, is that you want to keep long term RPM under a piston speed of 2500 Ft/min – not to say that you cannot spin it up to redline – just do not hold it there while cruising if you intend to achieve long life.
2500 ft/min on a RE 650 = 5619 rpm
Noteworthy that the SM does not have a tach. Using the SM stock gearing, 120-140 kph calculates to 5170 - 6050 rpm, not accounting for the bike weight, your weight, rolling resistance, or drag from panniers and a windscreen - measured rpm will be higher than this calculated engine speed. 5170-6050 rpm is past the engine torque peak of 5150, and pushing the long term piston speed into the rule of thumb range for a shortened life span.
Carrol Shelby famously said “horsepower sells cars, and torque wins races”. RE Street riding is mainly in the engine torque band, I try to match gearing to my riding style. Having a cruising rpm in 6th in the meat of the torque band, and not flogging the engine, works best for me.
The Enfield 650 engine has modest torque and horsepower, so gearing becomes a compromise between acceptable performance, the ability to pull a higher gear, with ones tolerance for wringing its neck to keep up with motorway speeds in some countries.
Horses for courses depending on your riding style and location.
Which ratio do you prefer?
Pic of the RSTech Interceptor belt drive for attention, and I will post a SM pic when the pullies are back from anodizing/heat treating
My thoughts on SM 650 gearing:
Gearing is a bit confusing with a larger number being "lower" geared – IE the SM 650 stock sprocket ratio at 2.6:1 is lower than the Interceptor stock ratio at 2.5:1
A lower gear ratio (2.6) will accelerate quicker, but top speed will be lower. At highway speeds the engine will be spinning at a higher speed, and depending how fast you are riding, you may not want to work the engine that hard for very long.
A higher gear ratio (2.5) will accelerate slower, but top speed will be higher, IF you have the HP to pull the higher gearing. Top speed on a SM is usually not a consideration, however some riders, myself included, would prefer lower engine speed on the highway. When higher geared, cruising speed rpm will be lower, and in the meat of the TQ band.
While not an engineering law by any means, and there are a lot of variables, (with notable exceptions like the new Ducati single); a rule of thumb for long engine life, is that you want to keep long term RPM under a piston speed of 2500 Ft/min – not to say that you cannot spin it up to redline – just do not hold it there while cruising if you intend to achieve long life.
2500 ft/min on a RE 650 = 5619 rpm
Noteworthy that the SM does not have a tach. Using the SM stock gearing, 120-140 kph calculates to 5170 - 6050 rpm, not accounting for the bike weight, your weight, rolling resistance, or drag from panniers and a windscreen - measured rpm will be higher than this calculated engine speed. 5170-6050 rpm is past the engine torque peak of 5150, and pushing the long term piston speed into the rule of thumb range for a shortened life span.
Carrol Shelby famously said “horsepower sells cars, and torque wins races”. RE Street riding is mainly in the engine torque band, I try to match gearing to my riding style. Having a cruising rpm in 6th in the meat of the torque band, and not flogging the engine, works best for me.
The Enfield 650 engine has modest torque and horsepower, so gearing becomes a compromise between acceptable performance, the ability to pull a higher gear, with ones tolerance for wringing its neck to keep up with motorway speeds in some countries.
Horses for courses depending on your riding style and location.
Which ratio do you prefer?
Pic of the RSTech Interceptor belt drive for attention, and I will post a SM pic when the pullies are back from anodizing/heat treating
My understanding is that new header pipes are lighter than stock so all good. Though see #2. OTOH, from what I can tell, only S&S makes add-on muffler/silencer that has a catalytic converter in it. Not sure if that's correct, but it's my current understanding. In any case, seems like a mix and match of Hitchcock's header pipes and S&S muffler/silencer would be the way to go.
