Stage 2

Hey guys ,only new here.Hoping to get some good tips from all you harley heads.
Ive got a 96' 1200 xlh sporty stock with 42mm mikuni carb & N&Kfilter.Im looking for more midrange grunt.Mainly town riding mixed with open hwy .Im thinking N4 cams with port & polish.Can anyone tell me what to expect or can you recommend better.
Rgds Jordie, Sydney Australia

Head work is always good as there's more power to be found in the heads than anywhere else, but N4 cams are certainly not the way to go if you're not willing to give away low-end power. The 42 mm carb hurts low-end power too - you'd do better with a well-tuned stock 40 mm CV, which will handle up to 100 HP on a Sportster. I could give a long engineering dissertation as to why, but here are the basics -

A key to making power is mixture velocity & with a larger carb, ported/polished heads & more lift & duration in the cams, while you get more top-end flow, the speed of the incoming mixture @ lower rpms drops & with it "volumetric efficiency" & useable torque. One reason why an 883>1200 conversion keeping the stock heads has been so popular over the years is with the smaller combustion chambers & valves in the 883 heads, the mixture velocity @ lower rpms is higher, throttle response is better in the low & even mid-range & the conversion is actually quicker stoplight-to-stoplight.

With the new heads that came out in '04, the conversion isn't the deal it once was, but the point is still the same - you must give up something to get something else - i.e., give away low-end torque for top-end HP. The N4's are very similar to the SE .497" cams that came in Buell Thunderstorm engines, which have better heads than Sportster 1200's thru 2003. While those cams will work fine in a Sportster, especially with the larger carb what you'd be gaining in the upper rpm range you'd be losing in the lower. So watch the tach for a while & see what rpm range you actually use most of the time. Are you willing to give away power in the 2000-3500 rpm range to gain it in the 4500-6000 range?

The most popular cam swap for the rpm range most people use has been the N2 cams, which accentuate the lower end, but don't give away the top end. And if you're running the stock ignition module, you can't rev to 6000 rpm anyway. But personally, I like the stock D cams for everyday riding & given the choice of spending $$$ on head work or cams but not both, I'll go for the head work every single time.

But do not polish the ports - that is good for the very top end only & even the ports in the billet heads on my Land-Speed-Record engine aren't polished. A rougher surface (we make a cross-hatch pattern similar to a freshly-honed cylinder) makes the air & fuel mix better & "swirl" into the combustion chambers. Ports opened up as far as they can be & polished to a mirror finish are like open drag pipes - good in only one very narrow rpm range & only @ full throttle - definitely not what you want for daily riding.

If it was me, I'd have the heads cleaned up, the ports matched (not polished), the valves unshrouded in the combustion chambers & then concentrate on tuning the carb & ignition - or go back to the stock CV & get it right. Maybe N2 cams, but probably not & definitely not N4's. And if you've got the stock mufflers on, those would go in favor of quality slip-ons like the older SE's, Cycle shack, etc. - but keeping the stock pipes with crossover. That's the best street/highway exhaust setup there is for a Sportster & that's a proven fact.

hey Art Nj

I am lucky enough to have a father/family owned COMPLETE automotive machine shop and a master welder/machinist/drag racing father. I have P@P-ing since I was ten..no joke... over 30 plus years later still learning.
(so I really get and admire the effort you have shown to accomplish such an event.) Great job!!! We have spent alot of time over the years getting the max flow into the cylinders. Bigger ain't always better for sure. Matching the right parts(bore/stroke/head cc/compression/. Again I looked at the gallery pics of your record ride and wow, awesome effort!!!!

My buddy we call the "Professor" flowed the heads on a HD that held/holds a Bonnie record in the 1000cc class. The man has an uncanny abilitiy to memorize everything he reads but he can also apply it in a mechanical way. You should see some of the doo-dads he has came up with the get more air into his sporty's carb. He actually has a cone-like part the he machined in his shop that hooks into the air cleaner cover and circles the air into the venturi at in a faster way.(one of many hidden gizmmos that he uses on his street spory as well,and some of his friend's rides as well.

Ya ain't gonna get it explained to ya any better than that!!:devil: Congrats on the LSR's Art_NJr

hey Art Nj

I see you're in Ohio, voodoo1 & I think I may know who the "Professor" is, although I've never met him. And with respect to the 1000cc Bonneville Production/Pushrod class, I most assuredly know the owner/builder of "Mystery Evo" that got the record in 2002. Matter of fact I've got a copy of it in my LSR notebook - 2-run average of 143.079 mph - on an 883>995 "Hugger".

You're certainly right about matching parts - I always say "think system" not individual parts - the best parts $$$ can buy aren't worth a flip if they're not designed to work together. And with respect to bigger is not always better, we flow-benched the LSR heads with 3 different sized valves & guess what? The flow actually went down with the largest valves. What we ended up was slightly larger than what the heads originally came with, but not by much & the heads off a 150" 4-cam BT Pro Nitro bike only flowed 1 cfm more !!

And BTW, I must mention that the rider on #506 under construction in my photo gallery is not me - he's a "Buckeye" though & that's where the bike is - I just sent the top end of the engine back up after refurbishing it here in N.C.

And with respect to your comment 30 years & still learning, one thing I've learned is that after you get past the basics of what works, what doesn't & why, getting H-D engines to run their best (especially @ the track) is more "black art" than science ;-)} You'd think that after all the years the basic design has been around, somebody would have figured out the absolute optimum way to get max power, but nobody has & there's always something else to try.

It is fun making 50-year old "odd-fire" engines make more power than the designers ever thought possible though - not much of a challenge with an even-fire, 4-cyl. double-overhead-cam, 4-valve-per-cyl., computerized Japanese engine that you can tune with a laptop computer - but it sure is with a Harley !!

- Art