[Manatoc fox]

With the advent of the stage 1 performance increase, the option of an x-ring chain and some super sweet batteries, most of the replacement maintenance issues on our RE seem to have a modern answer.  The question I have now is how to increase top speed so it can run 70-75 without a problem. 

After reading the threads here I had an idea, but was wondering what the gear heads think.  I know that adjusting the front sprocket (up or down, I can't remember) will lower bottom end power but lower the RPM at any given speed which should theoretically give a higher cruising speed.  To make up for the power loss then add the PC5 and the exhaust.  Would this work to make this bike something that could handle freeways a bit better?  I know it's never going to be a superslab cruiser but I'd like to be able to comfortably take it on a freeway for an hour or so without worrying that the engine is going to crap out.  Right now I just don't have that confidence.

[ace.cafe]

Okay, as a combination of those things, it may get closer to your goal. It wouldn't hurt.

But you really cannot do it with just the gear alone. That will lower the cruising rpm, but the hp necessary to cruise faster will still be required, and so it will need to have the throttle opened further, or have some mods as you outlined.

The power mods AND taller gear in combination will definitely assist in getting faster cruising with the right approach. Whether it will get you all the way to the 75mph cruise goal, I don't know. Maybe it might.

The taller gear is good for about 4mph faster road speed at the same rpm as before. So, if you cruised at 62mph in top gear at 4000 rpm before, you'll cruise at about 66 mph at 4000 rpm after the change.
The power mods should help the bike to produce a little more torque(and hp) at those rpms, so that hopefully you can use nearly the same throttle position as before too.

So, I think you have the right idea to move in the general direction you want to go.

[Manatoc fox]

Ok, then if a taller gear is good for 4mph the max cruising speed would be around 70 (65 is rated as the top all day without a problem speed).  The stage 1 performance is good for another 4hp (20% higher output).  How will the higher output affect the RPM at speed?  Will it lower the RPM needed to go at a certain speed because there is more oomph?  I'm not looking for something to set the world on fire here, but I'd like to be comfortable cruising at 70 if possible.

[ace.cafe]

Ok, then if a taller gear is good for 4mph the max cruising speed would be around 70 (65 is rated as the top all day without a problem speed).  The stage 1 performance is good for another 4hp (20% higher output).  How will the higher output affect the RPM at speed?  Will it lower the RPM needed to go at a certain speed because there is more oomph?  I'm not looking for something to set the world on fire here, but I'd like to be comfortable cruising at 70 if possible.

The performance kit should give general power increase. It is not really related to changing rpms, other than possibly giving more power at somewhat higher rpm.
It can help you to  more easily cruise at any rpms to reach your goals. But the rpms at road speeds are fixed by the gear train, so using the combination as you outlined would address both halves of the equation.
Reduce rpms with taller gearing.
Make power mods to produce higher hp at lower rpms to help the engine cope with the gearing change.
Free-flow the intake/exhaust to help the engine breathe easier to make more power in the higher rpms, so that it can rev higher with less effort.

The Stage 1 kit, as I understand it, makes some necessary steps in this direction, and so does the 1-tooth larger sprocket. These are modest changes, but will be helpful to move toward your goal, and this combination is a sound approach.
I think cruising speed of 70 mph is more probable than 75 mph with this package..

[Vince]

     By its very nature, any single cylinder engine is inherently out of balance. The stress this puts on the engine is exacerbated by high speed and extended runs at a constant RPM.
     Engines such as the Kawasaki KLR 650 and the Suzuki Savage 650 have a engine balancing system to reduce felt vibrations. These systems do not affect the stresses put on the piston and crank by its single cylinder configuration.
     My shop sees a lot of these kinds of bikes. I can always tell which ones see a lot of freeway use because these are the ones that smoke and rattle by around 15,000 miles.
     The point to this is that the Enfield is not a freeway bike. No matter what you do to it, riding it in the manner I infer from your goals will at best cause significantly increased wear and maintenance issues.
     Occasional freeway use is OK. Even stock, they'll do 70MPH for a few exits with no hassle. But if you are talking twice daily 20 mile commutes you should seriously consider a more suitable mount.

[John20121978]

I have a 2012 c5 with the power commander v, k&n filter, and the cocktail shaker silencer fitted. Stock chain and gears. My commute is 40 miles round trip, 26 miles on interstate. I am running at 65 to 75 mph indicated on the speedometer. To me in the stock form the bike was very happy at 50-60 mph. Now it feels happy at the 60-70 mph range.

[johno]

My b5 is similar except it now runs with K&N, 1 tooth larger sprocket on the drive and shorty silencer. After chain issues, I have now fitted a DID530nz chain but not ridden with it yet so can't say if it makes a difference.
With my setup without a power commander my B5 will cruise at 70mph with occasional spurts to 80mph for overtakes (on the speedometer) and that's for 55 miles of my 100 mile journey's, apart from a poor chain I have had no other mechanical worries or issues.(so far)

[wildbill]

I often think the speedometer is a lot faster than the bike...lol