Hello i was wondering if the N4 cams and the dyno slip-ons and a rejet of carb would give me more midrange? I am not really into max hp, I would just like more response when rolling on the throttle to pass someone. I sometimes ride 2-up with the wife also. I have a 2003 xlh1200.

Thank you...Tom

N2 cams are great for bottom end / midrange power. But they are no good for the upper RPMs. N4s are more geared toward the upper RPM range. Slip on mufflers will certainly help. Do the Stage I mods with a nice set of slip ons and see what you think of that combo before you make any other changes.

Hey guys. While we are on this topic, I was thinking of putting a set of cames in. Have a 95 Hugger with 1200 conversion, SE II slipons, Hypercharger, some carb work done but unknown. Can't afford to do the planned headwork and cams. Was thinking of going with a set of Andrew's N8's. Suggestiions would greatly help with delema. Want to keep cost to a min.

Bob

As I've said so often... cam changes are fine as long as you know what to expect and pair it up with what you want. Change for change sake alone is pointless and can get expensive. Folks like crim, stevo and others are always ready to help in that area.

Woody, for an 883 conversion, I'd go for the head work over cams any day. Massaged 883 heads are great for making low and midrange power. Stock cams are actually pretty decent for an everyday ride.

The spec that has the greatest impact on the rpm range of the cams is the intake close point. It's critical because it's the point where you decide to stop trying to fill the cylinder and instead seal it up and start compressing the intake charge.

The intake valve closes as the piston is on it's way up on the compression stroke. The reason it's not closed until then is that the incoming intake charge has inertia. Close the valve too early and you slam the door while the cylinder is still filling. Close it too late and you push back some of the intake charge.

So what determines the inertia of the incoming fuel? The velocity of the intake charge. And rpm has a huge effect on that.

So look first at the intake close point. Keep in mind though that it's not a linear scale, i.e. the amount of piston movement per degree of crank rotation varies depending on where in the stroke you are. It doesn't hardly move at all for the first 10 degrees, for example. Stock "D" cams have a .053 close point of 40 degrees. N4's are 46-48 degrees depending on whether you believe HD's numbers or Andrews' numbers. N2's are thirty something if I remember right.

If your heads are stock, you're stuck in the bolt-on world. If the springs & guides have been upgraded, you can go with something higher lift, and if the ports have been worked appropriately, you can gain quite a bit of cylinder fill this way. A port that works above .500 lift (stock ones don't) coupled with a high lift, narrow grind (like the "E" cams, RS 567's, Wood W8S, Carl's CM580) is a good way to build power without having to turn a lot of rpm.

But cams & ports aren't the only things that affect cylinder fill, not by a long shot. Another very rpm sensitive influence is the exhaust system. During that window of time while the exhaust valve is almost closed and the intake valve is just starting to open ("overlap"), the intake and exhaust are essentially connected together. This gives the exhaust system an opportunity to directly affect intake flow. The piston is passing through TDC during overlap and it hasn't really started pulling on the intake tract yet. If the exhaust system pulls right then, it'll get the intake charge moving before the piston even starts pulling on it, and this can really help the cylinder fill. Likewise, if the exhaust pushes back right then, it shoves that next intake charge back out the carb, really screwing up the cylinder fill. You see this as a fog of fuel out the mouth of the carb (aka "stand-off") and a corresponding rich spot in the a/f curve (because the charge gets triple carbureted, it got pulled in, pushed back out, and then pulled in again).

The more overlap in the cams (intake open point + exhaust close point), the bigger the exhaust system's influence on the powerband.

Exhaust systems work on pressure waves. I really don't want to get into the details of it right now, but bottom line, think of the pressure waves like what happens when you toss a rock into a pond (thanks Doug). The waves travel outward, hit the shore, reflect back, etc. Well, if a positive pressure wave arrives at the chamber during overlap, you'll get a stand-off and a dip in the torque curve (the shape of your torque curve is a map of your cylinder fill). But if a negative pressure wave arrives during overlap, you'll draw on the intake and get a bump in the torque curve.

The big problem here is that the waves travel in the exhaust system at about the same speed (the speed of sound) regardless of the rpm of the motor. So if you have a nice negative wave that's timed perfectly to arrive during that sliver of time called overlap, well, move 2000 rpm away and it won't be timed right anymore. In fact, you may have a positive wave there instead!

That's more or less what happens in a drag pipe. The outlet generates one strong, narrow wave that only works at one rpm, and at the typical pipe lengths that look nice on a bike, it tends to be something of a high rpm, and therefore a couple thousand rpm below that, they're pushing back, causing poor cylinder fill, richness, and resultant poor performance. People tend to chalk it up to a lack of "back pressure", but in reality, it's a wave timing thing. Hell, I can show you zero back pressure pipes that make a ton of low end power, they just have to be designed for it. What a baffle really does is alters the wave timing and shape, making a weaker, broader wave that therefore works over a wider rpm range. The back pressure is actually a bad side effect that causes pumping losses. Diffuse and broaden the wave with a device that doesn't cause back pressure (for example, a megaphone) and it'll make even more power. But I digress.

The point here is that if you put some overlap into your cams (so that the exhaust system has more influence), and then set the exhaust up correctly, you can really boost the torque at whatever rpm you're targeting. It's a major opportunity to improve cylinder fill and one that we fully exploit on the race motors, but it can be done on street motors as well.

Stock "D" cams have a whopping 4 degrees of overlap, so the pipe gets largely taken out of the equation. They do that specifically because they know that have to ship the bike with a poor exhaust system and they're mitigating it's effect on the motor.

In the race motors, we often run 66 degrees of overlap or even more. Numbers in the 30-50 range are common on street performance motors.

A formula you'll never go too wrong with: put enough overlap into the cams to give the exhaust system some influence, and pair that with an exhaust system that pulls during overlap at the same rpm that your intake close point & ports are optimized for. That's called a happy marriage between the pipes and the cams.

Sorry to be so long winded, but honestly, this is still just a gloss-over. A whole bunch of things are going on that we're not even touching on.

WOW and thanks a ton. I just learned far more than I'll be able to repeat (just like school) but I'm a whole lot more informed about cam choices. We're priveleged to have your expertise on board.

That was a great explanation on cams. Now which one do we use again ? just kidding. !!!!! You need to put that somewhere on the site for others to see, in a how to or tech section.

and here in lies the problem guys......

the more questions you ask the more questions there are.....

As Aaron has just said many things will have an effect on where the power occurs.... and the first thing you need to determine is this..

WHERE DO YOU WANT THE POWER??????????????

I see it too many times where guys over cam and over carb their engines in a effort to make more power .... only to push the torque curve so far up the rev range that they never see the torque peak on the road...

To Tom's origional question ...

"..Hello i was wondering if the N4 cams and the dyno slip-ons and a rejet of carb would give me more midrange? I am not really into max hp, I would just like more response when rolling on the throttle to pass someone. I sometimes ride 2-up with the wife also. I have a 2003 xlh1200."

A few key points in his question.... I would just like more response when rolling on the throttle to pass..and ride 2 -up...I read that as someone who doesn't drop down a gear to overtake so we are looking for more punch around 2500 - 3000..
As Crim said a set of N2's would be as far as you would want to go with a set of slip ons for that range....

To go with the N4's ...as Aaron said a larger overlap allows you to take advantage with different exhausts.. But with this we are moving the VE point or torque peak further up the rev range and it will get too high for where Tom's going to use it.

Personally Tom...If ya wish a bit more in that range I'd send ya heads off to Nallins and get 'em to breathe on 'em gently instead of spending $$ on cams.... and/or complement them with a set of "W" grind cams if ya really wanna go with cams..... :tour

Stevo,
What are the specs for "W" cams, are they the ones in the 1200S?

Yup.. they're the twin plug 1200S ones and also standard in the '04 - '05 sporties

Still at the end of the day they give a good mid range and will happily rev if ya get some head work done.........

I see alot of talk about what the N2, N4 and SE bolt in's will do to your power band but I seldom see anything on the N8. What I have read about this grind is that in regards to lift and intake duration, it falls between the N2 and N4 thereby still giving decent torque in the low to midrange. However, I truly don't know because I haven't seen a whole lot of conversation on it. So, my question is to anyone who knows and is willing to answer: What will N8 cams do for ported Thunderstorm heads, 2 into 1 exhaust (or dual slip-ons cause I have those too), and a CV40 carb? Judging by most of the posts I have read, it seems to me that alot of us are searching for the same thing: a 1200cc (or 1250) Sportster engine that delivers the most power possible at the top end without sacrificing anything down low. I like my torquey stock cams because its fun to ride but I like to go fast too. Is there an option for better cams that will not sacrifice the low end? If not, I'll stick with the stockers.

Thanks for any input.

G'day BD


Basicly from small to large ... N2 , N4 and SE bolt ins, N8 , SE 0.536"

For most street riding with a 1200 I'd tend to use around a W grind or N2 to N4's

Although personally I'm not a fan of N2's as I don't think the increase is worth the $$$$ over stock cams, they do however allow the exhaust to have more of an effect on the power.

If you like to rev it and do very little 2 up and maybe race it then an N8 or SE 0.536"
My '98 S has 0.536's and runs 11's BUT it's not got much under 2700 and it doesn't like runnin under 2250 as it tends to "cam" along..


Cam basics

For all things being equal (which of course they never are :shhhh )
An increase in lift will increase cylinder fill as the valve curtain is open further
An increase in duration will tend to move the VE (volumetric efficiency )point further up the rev range
The VE point is the point in the rev range where the cylinders are being filled the most.... this is the torque peak...
The later the inlet close the more static compression you can run and will need to run to gain lost dynamic compression at lower rpm.
Due to the fact HP=(torque * rpm)/5252 if you can make the same torque peak at a higher rpm you will make more HP
HOWEVER it's no good making 50% more power past 4500 if you've lost 10% below 3000 and you rarely rev it past 3500 ...you've just spent a lot of $$$ for nothing more than bragging riights at the pub.

cam .............. intake close .........duration...........overlap...........lift
stock D............41.......................223/223..........4.....................458/.458
N2................. .38...................... 240/244..........40...................465/.440
W....................38.......................223/240..........19...................476/.476
E '04-'05...........44...................... 249/249..........35...................551/.551
N4................. .46...................... 256/256..........54...................490/.490
SE bolt-ins .......48...................... 256/256..........52...................497/.497
N8...................44...................... 256/263..........60...................490/.490
SE .536"...........50...................... 256/265..........56...................536/.536


A set of N8's with your T/storm stage 1's and a set of 2-1 would give you a good mid to top bike that wouldn't really come alive untill after 3000 rpm...


Hope this helps .... :D :tour


Just added E type cam spec ... these things are torque monsters... short duration/high lift

W grinds are the 1200S cams. They and N2s close the intake at 38 but the N2s open it much sooner. This results in more overlap (40 vs. 19.) And if I've studied my ASW cam lessons correctly, the greater overlap of the N2s would allow a tuner to adjust the power delivery with different exhaust set ups to a greater degree than with the W grind.

But from what I recall, N2 cams are only good for mid to low end power on a stock engine. Start porting heads and raising compression and they're not so great.

A set of N8's with your T/storm stage 1's and a set of 2-1 would give you a good mid to top bike that wouldn't really come alive untill after 3000 rpm...


Hope this helps .... :D :tour

When there's a so big lost of power at the low revs I think it's time to correct the gear ratio.
1 tooth less on the front sprocket (pulley?) or 3 teeth at the rear pulley.

--
Mr. Mechano
'04 XL1200C red/silver
Kawasaki ZRX1200

883 front pulley is 27 .... 1200 is 29

I run a 27 for racin and in the twisties ....

27 front lets me go thru the traps at around 6500 in 4th

yeah I'm not a fan of N2's

Hardly worth the effort....

If ya gonna spend $$$$ on cams then IMO ya should get the heads done anyway...

A decent set of heads with stock cams would be all most people would be after...

If ya wanna make power then I reckon ya need ta start at N4's and for most of the "power" guys stop there..'specially with a 1200


For the stupid ones like us that can't leave well enough alone....... well 88" and N9's for starters :) and I'll see if I want anymore cam after that ;) DUH of course :)

Here are the 04-05 specific SE cam specs to add to Stevo's list: (same specs as the Buell XB-12 cams)
P/N 25197-04

DURATION: 249 / 249
LIFT: .551" / .551"

TIMING:
Intake opens: 25 degrees
Intake closes: 44 degrees

Exhaust opens: 59 degrees
Exhaust closes: 10 degrees
________________________________________

Here is how they compare to the stock "W" cams found in the 04-05 XL 1200

DURATION: 223 / 240
LIFT: .476" / .476"

TIMING:
Intake opens: 05 degrees
Intake closes: 38 degrees

Exhaust opens: 46 degrees
Exhaust closes: 14 degrees
________________________________________

Thanks for the info Stevo.

A decent set of heads with stock cams would be all most people would be after...

That's me!

So, if I wanted to keep my stock cams and pistons ('97 1200), would I just send my stock 1200 heads to Nallin for a Stage 1 port job, or would I want to buy a set of aftermarket heads? In other words, what is my best choice in heads or head work if I want to stay stock with cams and pistons?

Porting your stock 1200 heads would be a pretty cost effective way to gain HP.

That was a great explanation on cams. Now which one do we use again ? just kidding. !!!!! You need to put that somewhere on the site for others to see, in a how to or tech section.
I agree completely. add stevos response #13 to the stickey and you got most of the info you need on cam choices and spec.

Stevo has a very good point! You can throw a flatslide at the motor, and over carb it, or you can put a .575 in there, and over cam it. If you plan on saving money, and want to do a cam, you better do adjustables, or you are paying labor to pull the heads. If you are pulling the heads, why not have them worked? You need to sit down with a knowledgeable tech and decide exactly what you want to achieve. A lot of the time, you can roll on the throttle and pass if you kick it down a gear!

igot n8's in my motor when i had the vanceand hinse drags ontheir with baffles itdid ok forlow end... withthe bafflesout a moped could take me off the line. but at mid range on up she was gone.. now i switched to bassani pro streets and i am thinking this fall a good p&p and the motor will be toped out short of mikuni 42 and adjustable ignition and xb heads...

Hello i was wondering if the N4 cams and the dyno slip-ons and a rejet of carb would give me more midrange? I am not really into max hp, I would just like more response when rolling on the throttle to pass someone. I sometimes ride 2-up with the wife also. I have a 2003 xlh1200.

Thank you...Tom


Tom, how stock is your bike? Have you done anything to help the bike breath better?

Depending on where you are now and how much more mid-range power you want a good free flowing intake, including carb mods/change and exhaust will do wonders for your throttle response without a cam change.

igot n8's in my motor when i had the vanceand hinse drags ontheir with baffles itdid ok forlow end... withthe bafflesout a moped could take me off the line....
Dude
You're not texting, you're on the real thing.
You have plenty of characters available here.
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