This is the latest report on the ongoing work on my 2021 Royal Enfield Interceptor. I had traded my 2017 Triumph Street Cup with the new water-cooled 900 motor for the new Interceptor following an unscientific drag race with a friend. The Triumph got off to a good start, but once we hit third gear, the Enfield took off and smoked the supposedly more powerful, more refined Triumph. After a few weeks, and learning that my local Triumph dealer, New Mexico Motopia, picked up the Enfield line, I made the switch. I went with the “Mr. Clean” because the badge on the tank is so much better than the lettering on the Continental GT. Here she is on the floor…

I had them tear the awful plastic fender extensions off and install S&S pipes with baffles, and the flyscreen. I added a K&{N air filter and DNA airbox removal next. Stock, these bikes are supposed to make about 47hp and 34ish ft/lbs of torque at sea level, but the gearing overcomes a lot of the supposed anemic power. She certainly was capable of taking on the Triumph. the first few weeks of playing with it, we found she would reliably hit the ton, but just barely, and occasionally could squeak out a titch more. But there was more there, so in a moment of insanity or COVID-restriction induced insanity, i decided to do something I don’t do: we did engine modifications.

The dealer had never done this, of course; they were new to RE and the S&S guys haven’t really thrown a lot into advertising or explaining these modifications. Point of fact, it seems very much like they’re insinuating some of this stuff is plug & play. I bought a 650cc bike and I didn’t want to bore it out. If i wanted an 865cc, I’d have gone and gotten an old air-cooled Triumph Thruxton. So we installed the high power cams and high-compression piston kits. Allegedly, we would be looking at a 14-18% increase in power. Right off the bat, she was torquier, but I was getting serious lean knock on the motor. The dealer had a look and adjusted the timing, which was off almost 4º from the stock. Once corrected, she seemed better, until I really thrashed it on the local mountain road — a 12 mile stretch with 120 turns and an elevation change of over 4000′. That’s a lot of altitude change, and the bike was detonating like crazy! Fuel booster didn’t help. A booster plug to fool the bike into thinking it was cooler to get more fuel didn’t help.

We turned to the folks at Speedin’ up in Farmington, New Mexico — the only guys with a decent dyno setup. Motopia installed a Power Commander V and took her up to Farmington to get dyno’d. This was also not as easy as you might expect. The probes for the 02 sensors were getting a lot of interference and the guys were suprised by the amount they had to enrich the fuel map (upwards of 60% in some places.) The welded in bungs to get the sensors away from the headers and get a cleaner read. Nope — still needed a massive push in some places, but by the time they were done, they had a serious improvement. Here’s the dyno chart from the final run:

That’s a hell of a torque “curve” — a flat line at 42-43 ft/lbs. from 3500 to redline, with a max power of 49.25hp. Now that doesn’t sound like much of an increase ’til you factor in the altitude. Farmington sits at 5,220′ in elevation; about the same as Albuquerque, where I live. Figuring the (altitude in feet/1000)x 0.03 xHP gets you a rough horsepower of 39.7hp for the stock motor. So the jump to 49hp is about 18.5% increase in power! On return, Scott at Motopia took her for a ride and declared in an unqualified success. I was a bit dubious after five months of messing with the bike…but he was right.

The first run up the Crest road had no knock or detonation, although since then I’ve gotten it to mildly knock by whacking the throttle open hard in sixth gear or higher on the highway. Torque and throttle response is fantastic, and she’s a solid match for many of the 600cc sportbikes. Fuel mileage, of course, has been impacted, but nowhere near as much as I feared. I went from high 60mpg (and as high as 72mpg) to the mid-50mpg range…about a 18-20% decrease in fuel mileage. That seems a fair tradeoff for the performance increase.

So was it worth it? The bike was nearly a straight trade for my Triumph, with $600 for the pipes, $100 for the filter/airbox, $1500 for the cams and pistons plus install, and $750 for the PCV and dyno. That’s a total price of around $9000 compared to similar performance out of Triumph’s 900 classics, which are another $2000 or so out the door. Yes, it’s worth it.

If you choose to do this particular set-up, you’ll find that no one else seems to have done it. Big bore kits, sure; not the heavy-piston and cam kit for the 650. You will want to get a PCV for the Royal Enfield, and you will need a tune. DynoJet doesn’t have it, but you can get my map from the guys at Motopia (see link above.)

I also did the usual cosmetic mods expected of people with this sort of bike to “make it my own”: a chrome fneder to match the tank, bar-end mirrors and shorty levers, the proper Interceptor side plate, not the US “INT-650” (up yours, Honda!) and a side panel bag for hat and sunglasses, and the flyscreen.

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