Cams

[Roy]

Bonjour

So, having just completed one majour overhaul (cosmetic) of my streetbob, I am now planning the next.

What I would like to do is cruise at my usual 'cruising speed' while not thrashing the engine so much, so preserving fuel economy etc.

Acceleration I am really happy with, so would not want it to diminish, so its more top end and keep the bottom end the same.

'Engine mods' thus far extend to a PCIII USB, Big Shots and an S&S air filter. Given my objectives above, what is the next stage? Cams? If so, which ones? Be interested in hearing from Devon John also on the changes from fitting a carb


Cheers, Roy

[simonDyna]

Roy,
what engine do you have at the moment?
1450? 1550? 1580?

I know you have a six speed gearbox but what primary drive do you have? The older one or the newer one with different primary ratios?

The only way to change rpm at any given mph is to alter the gearing. It wont matter if you have a stock build or a monster build, 3000 rpm will still give the same mph unless the gearing has altered.

By modifying the engine you will get the ability to accelerate quicker. This new ability can be used in different ways. You can have a bike that accelerates very quickly or you can offset the newer pulling power against, for example, a 34t front pulley which hopefully will give the desired cruising rpm but use the additional pulling power to keep acceleration as it was.


Simon

[simonDyna]

Forgot to add, that what you have stated as a desired result would be targetting a cam that delivers more torque/power below 4000-4500rpm rather than top end, if coupled with a 34t pulley.

There are plenty of people on here far better qualified than I am to give opinions on the various SE cams but something like a SE203 or SE211 would be a good starting point if you want to keep the cam chain arrangement.

This is only really relevant if you have the 1450/1550 engine and "normal primary" as a starting point. If you have the later primary, then I am not really in a position to add much more. I know the primary ratios changed completely to make more use of the stock engines torque delivery. But, I dont know what the new ratios are and thus, can only give generic information rather than specific. Potentially there may be gearing gains to be had by changing primary ratios.

Finally, the cam that helps deliver all the torque AND all the power in all the revs doesnt exist. Hence so many different cam profiles being available. With camshafts, there will always be a compromise.

Let us know what your engine build is at the moment and then we can point you in the right direction.

[MadMax]

Are you planning to move up to 95 or stay at 88 inch? This question could go on forever depending on how far you want to go with your upgrade. The Andrews 21H is designed to work well with stock compression in an 88, I've fitted a few of these cams into otherwise stock motors & they always put a smile on the owner's face. the Andrews 26 is also a good cam, they just come on a little later but also last longer up to about 5200 rpm. As Simon says, the SE 203 would work, the 211 requires more compression - about 10.5:1 static CR. As you're running fuel injection whatever grind you choose will require a tune on a dyno to get the best out of it. Good headwork will optimise the cam characteristics, you should at least have your chamber volumes equalized and compression set to what the cam dictates. If you're staying at 88 inch and only looking at a cam change then I would recommend the Andrews 21, if going to 95 inch then the 26 with chamber equalization. The Andrews 37 is an excellent performing cam for a 95 inch motor but then you're getting into head machining and porting work to really pull the package together. Your stock throttle body will be fine with any of these choices, the exhaust is also a major factor to consider.

[Roy]

Wow!

Okay .. lot of information. I do have a 1450 and was planning to keep it as such if possible. My only desired outcome here is to be able to cruise at my normal speed and lower fuel consumption.

So, a combination of a 34T front pulley and a Andrews 21 sounds like a good way to go.

Would it pay to have the chamber equalisation done anyway, or would this be not so effective with my current setup?

The other thing I'd also like to look at is making throttle response a bit sharper. Any hints or tips on this would also be appreciated.

Cheers, Roy

[Scotty]

Like Simon says, need more info as to what your motor is now.
But either way from what i think you want, higher compression and cams should do the trick.....
And if its an 88" motor, take it out to 95" up the compression and change cams, but as has been said their are a million and one different cams.

If you want to go all the way stick some decent heads on it as well, their are gonna be a set on e-bay soon
And maybe a set of geardriven cams toooooo, all brand new

[Ukkid76]

One thing you won’t get is the same fuel consumption, if you up the cams, heads and bore size it will affect how much fuel you use,

I know cos I have been there!! I have it all (as you want) on a standard crank,

I needed to take it to Rodgers at full bore the other day for some work and after they took it out for a road test they commented on how lively it was,

So it really does work!!

It has been sat on a Dyno many times to try to get it exactly right, I even have a 34T front sprocket, this reduced the cruise by about 160rpm, so my 80 mph was about 3400 rpm it is now 3240 ish ,

All the above is very positive, but the down side is the fuel consumption if I push it I can empty the tank in no time, (less that 100 miles) taking it steady gives me about 6 miles to a litre that equates to 28 miles to an old fashioned gallon,

I have a Mikuni carb and I think yours is injection so you should fair a little better than me, however I have been told that if you just fit a powercommander and a balanced exhaust system dyno tune it all together and your bike will perform much much better,

It should be the first thing you do anyway, no matter what you do you’ll have to re map it and the standard Harley set up can’t be altered the way you,ll need it,

So get this done first cost would be about £1000 to £1200isk ride it for a few months and see how you get on,

Good luck

[Ming the Merciless]

Roy, just a reality check from me. I am certain that this...

Originally Posted by Roy

The other thing I'd also like to look at is making throttle response a bit sharper.

is achievable, but I am NOT confident that this...

Originally Posted by Roy

My only desired outcome here is to be able to cruise at my normal speed and lower fuel consumption.

can be done at the same time. The extra surge comes from bigger bangs, which is the output from burning more fuel more efficiently. Are you really chasing more 'go' or less fuel consumption?

If it is the latter, then don't spend big bucks on engine work, as you would have to do a load of miles to ever get get money back.

[Scotty]

Originally Posted by Ukkid76

All the above is very positive, but the down side is the fuel consumption if I push it I can empty the tank in no time, (less that 100 miles) taking it steady gives me about 6 miles to a litre that equates to 28 miles to an old fashioned gallon,

Now then.

I have a 1550 kit 10.5/1, Headquarters heads, HQ33 cams, AR100 pipes, Twintec ignition and S&S Super E carb with Yost Powertube and i get around 40 to the gallon, more on the motorway and a bit less if i give it loads of stick, so i aint sure whats going on there.

Its putting out around 110 bhp and 115 ft/lb of torque.

[simonDyna]

Originally Posted by Scotty

Now then.

I have a 1550 kit 10.5/1, Headquarters heads, HQ33 cams, AR100 pipes, Twintec ignition and S&S Super E carb with Yost Powertube and i get around 40 to the gallon, more on the motorway and a bit less if i give it loads of stick, so i aint sure whats going on there.

Its putting out around 110 bhp and 115 ft/lb of torque.

Agree with the mpg figures.

In a previous bike I had a 1550 kit, 42mm Mikuni, SE heads, SE257 cams and SE mufflers. That one dyno'd at 108ft/lb torque and 106hp. It ran at 45mpg unless ridden over 3200rpm where it would drop to 35-38mpg.