Big sprocket equals more speed? Maybe

Want to make your Royal Enfield Bullet go faster? Why not just increase the size of the front sprocket? That means that, without increasing engine rotations per minute, the rear wheel will turn faster. And away we go! Maybe.

"Andy" in Callahan Florida happens to be selling a 2002 Royal Enfield and notes in his ad that it has a 22-tooth front sprocket. That's the biggest they make. I asked him what it's like.

"I find the 22-tooth is better for the top end (but) you have to rev up a little more to start off. I have no power problems 'at all,' possibly since Florida is flat.

"I still have the same problem as before though: it only revs so high with the stock carb so top speed is still limited but about at 77 mph instead of 68ish. I weigh 190 lbs and I usually carry about 5 to 10 pounds in my side bags. As far as shifting down (for hills, in traffic), no! It didn't make that much of a difference. It made a difference but not a considerable amount.

"I actually wish it did take me to the point where third was more cruisable but I still pass it by and ride in fourth going 40ish and it pulls real good and maybe even better than the stock gear when riding with the big dogs; they actually can't pull away from me 'til I top out, then I am toast."

He adds:

"If they made a 25 or 26 tooth I would buy it to try out and cruise third on the steep bridges and hit forth on the down hills and flats to push 85-90."

Like many owners of original Bullets, I have increased the size of my own front sprocket.

My 1999 Bullet 500 came with a 17-tooth front sprocket and 38-tooth rear. Using the Dropbears.com Sprocket Ratio Chart, my original ratio was 2.24. The change to an 18-tooth front sprocket brought the ratio down to 2.11. That's a change of just about 6 per cent. Sounds modest.

My wife added the discarded 17-tooth sprocket to a very nice shadow box she made for me.

On the road, the improvement was phenomenal. There was no noticeable difference in the way the motorcycle accelerated from a standing stop. Presumably, my educated left fist was smart enough to release the clutch just the right amount to compensate.

What was different was that I no longer needed to shift to second half way through the intersection. I could actually hold first long enough to get across, building up some real speed. The time saved by not having to shift gave me a bit of a jump on traffic.

Second lasted longer, too, and third, previously a milquetoast gear, was now a tiger, good for all sorts of situations that previously would have had me lumping along in fourth. The 18-tooth front sprocket was such a good idea, and so popular, that Royal Enfield eventually made it standard on the 500.

The only problem in the old four-speed bike was the huge jump up to fourth, which now felt like overdrive. This is where you confront the fact that you don't really have much power. Fourth was a real show stopper for my unmodified Bullet but — oh well — it was good for cruising.

"Top Speed" on my Enfield is a concept more influenced by wind direction than gearing. But I will say that casual cruising speed seemed to bump up a bit, from 38 mph (indicated) to 41 mph.

Now let's use the Dropbears chart to try out a 22-tooth front sprocket. The ratio is now 1.73! That's a 23 per cent change from my original 17-tooth wheel and fully 18 per cent from even my upgraded 18-tooth sprocket.

It's hard to imagine. But I would love to give it a try.