This is a very mechanically novice question so I apologize in advance.

IF (because I don't know) my bike (a 97 softail heritage classic) is revving at (say) 2000 RPM's @ 60 MPH now in it's stock configuration, if I increased the power of the bike would that mean that increase in power would lower the rev's from 2000 RPM's @ 60 MPH to (say) 1800 RPM's @ 60 MPH?

If not, is there a way to do that, decrease the RPM's for a given speed?

As said, sorry for the mechanically novice question if this is a pretty basic principle.

 

To decrease rpm's for a given speed you need to change the gearing.

The cheapest way to do this is to change pulleys. Going up or down on the tooth count will alter the rpm for the speed. This is essentially the same as changing the gear ratio in the differential of a car.

Another way to do it iif you have deep pockets is to add a sixth, overdrive, gear to your transmission. You can buy replacement gear sets for this or buy a complete six speed transmission.

By changing pulleys, you will lose some of your get up and go since all gears are effectively higher. You can compensate for this by increasing your engine's power.

By going the sixth gear route, you avoid losing the get up and go since it is only the top gear that is higher. You still want to increase your engine's power though because a stock 80" Evo will be marginal in sixth gear.

Now for my story.

I started out wanting to lower my rpm's on the interstate because my engine felt like it was screaming and vibrating a lot past 60 or 65 mph and it just was not fun to ride at 70 mph.

I concluded that whatever I would do, I would need to increase my engine's power regardless. I went with an EV13 cam and a handful of parts to support it including fresh rings. I also had my heads milled slightly since Evo's respond well to increased compression. Manufacturing tolerance was sloppy when these bikes were built and you could have a significant variance in combustion chamber volume. By having my heads milled, the volumes were reduced to be the same for both heads. As a result, besides my engine making great power right where I need it, it also runs extremely smooth for a Softail Evo. I ended up not adding a sixth gear or changing pulleys because my bike runs so much smoother and is no longer screaming on the interstate, I now have problems where I lose track of speed and have gone past 100 mph while still accelerating but decided to back off.

 

Thanks mate for the detailed and clear explanation.

I started out wanting to lower my rpm's on the interstate because my engine felt like it was screaming and vibrating a lot past 60 or 65 mph and it just was not fun to ride at 70 mph.

This is exactly what I am experiencing as well and want to stop. At the moment I am looking at putting in an Andrews 27 Cam with Wesico Pistons, an S&S Super E kit and S&S ignition. From what you have said, that should fix the issue with the screaming and vibrating above 60 MPH.

 

When Harley switched to the N grind cam, power went from marginal to atrocious.

It's not really the rpm that makes the high speed riding miserable, it's the fact that the power is nearly maxed out.

The EV27 will benefit from an increase in compression. Go with a .030" head gasket. Stock head gasket is .040"

Change the cam bearing to a new Torrington bearing. New lifters would not be a bad idea. Screaming eagle or other free flowing air cleaner. A drop in k&n into the stock sir box is not going to be sufficient. I tried that and it hurt the upper rpm a lot. A dynatek ignition provides a slightly better curve and raises the rev limiter a tad.

Rejet the carburetor. I went with the dyno jet kit because of the replacement slide, spring, new gaskets etc. Dyno jet makes a few different kits, so read carefully if you go that route.

The CV carburetor is fine. The old style carburetor is junk. Mikuni makes a great carburetor but it is somewhat harder to dial in perfectly. The S&S carburetor is popular because it is very easy to tune. Best bang for the buck is if you already have a cv carburetor, dyno jet kit or simple rejet it.

My bike probably doesn't make big numbers but what it does do is run really well and feels like it pulls hard right where I want it to. It is amusing to watch watch late model TC103's disappear in my mirrors.

Now if I could just feel good enough to ride. I have been having a hard time with my health for a while.

 

Thanks Prot appreciate the "parts list" and the reasoning behind them. At the end of the day though, I will be getting Hillside to do the work so am sure they will match everything appropriately.

Hope your health improves so you can get back on the bike as well, can't imagine the frustration at not being able to do something you love due to health issues.

 

If your going to Have Scott do the work just go with the Woods W6 cam. Hands down the best performer in an evo. set comp to 10.2 with stage II heads and the S&S carb, this set up will yield High 80's tq and mid to upper 80's hp.. I know cause I had it. AND.... the best thing about this build is the gas mileage, 45+......

My 96" Evo is there now.......

 

Just a question about using a. 30 headgasket instead of a stock one.

when installing adjustable pushrods, do you simply deduct 0.10 from their length or do you get to replace the springs?
might be something for my next project

 

No you don't have to replace the springs to use the adjustable pushrods. But to keep things quiet you should set preload to .130"-.140"

 

Sounds good and I'll talk with Scott about having what you had done. Scott actually mentioned the Woods cam as well.

 

You will like that W6 cam. Pulls hard from 2000-6000 rpm's. Nice fat powerband.