Open exhaust header, and rejetting carbs?

[dj820621]

Hey I'm wondering if there is a general rule of thumb concerning how many steps up on pilots and mains one should go if running open header?
Also, if anyone has had any problems with doing so.

Yes, I know of the SUPPOSED problems of burning/warping valves.

Any info from some of you guru's would be greatly appreciated!
Thanks a ton!

[dj820621]

Anyone?

[thatkid]

Haha, "SUPPOSED". Open headers are a dumb idea. A) It's loud and pisses people off. If you believe that loud pipes save lives you should take a science class on sound waves. B) There goes any back pressure you had. Now you bike runs like crap. Rejet all you want. It isn't going to fix it.

[DonTZ125]

The pipe, exhaust port, intake port, intake tract (including carb and boots) and airbox is designed to operate with a muffler on the very end. Take out the muffler / baffles, and you're on your own for determining the operating characteristics. Hopefully you won't damage your engine too badly before a nice police officer persuades you to perform a cranio-rectal inversion.

[dj820621]

The muffler I plan on putting on has a small baffle, but not enough of one to cause any measurable back pressure.
It won't be nearly as loud as many of the Harleys in town, nor will it be as loud as my xj1100 with these same mufflers (basically open header).
Never had any problems with the Police to date (for a motorcycle).

I am definitely not one who agrees with the argument that loud noise saves lives.
Sounds preposterous, that's actually the first time someone has mentioned that idea to me.

Grew up in the shop, have always, and still do work on old muscle cars.
That being said, I prefer the open header sound.
Whether it is detrimental to performance slightly or not, it's just a silly preference which I acknowledge as such.

Also, I've had open headers, and basically open headers (small "moto-gp" style muffler)
for years and years, ride the shit out of my bikes, and have never had any problems with warped, and/or burnt valves.

Now, the only common problem is, the bike becomes harder to tune. Not impossible, but harder.
I can usually get all lost power back with rejetting.

Yes, the bike needs bigger jets to run more fuel due to the increased air flow.
Yes it contributes to slightly poorer fuel mileage.
No, I don't care.

I was just curious if anyone had an open header and a good place for me to start concerning pilots/mains.

[pefrey]

I don't have anything to add, but I have to know if you are running open headers on the street or on a track? Also, if it's on the street, do you wear hearing protection?

By open headers you mean headers connected to nothing on the exhaust side, simply connected to the engine and a straight pipe to the exit? I just can't believe that's allowed to run anywere street or track.

[dj820621]

As I said earlier, I run these small "moto gp" style mufflers, which have a thin baffle, And quiet things down some but not a ton.

[DonTZ125]

Not quite 'open headers' then, is it?

[dj820621]

Nope, but equal flow. So the jets used for an open header (singular) would apply.

[dj820621]

Alllriiiight, so no one has any input that could be potentially beneficial to me?

[pefrey]

Alllriiiight, so no one has any input that could be potentially beneficial to me?

Looks like two people posted that you should not run open headers. That sounds beneficial. It's not the answer you want to hear, but that does not mean it is not beneficial.

Nobody here runs their bike in the condition that you choose to run yours, therefore you are on unchartered territory and will have to figure it out. When you do, post up your results just in case somebody else wants to do the same thing.

[reelrazor]

es, the bike needs bigger jets to run more fuel due to the increased air flow.

Bullshit, let me say that again... BULLSHIT.


Increased airflow from running almost NO muffler/stinger section of pipe behind the collector? Ahem, Bullshit.

In a purely static flow bench situation, you may find that you can find a flow rate and velocity that will back that up.

Very much research has been done since the 19 teens proving that a properly 'tuned' length and 'depth' of backpressure will do huge amounts of good in dynamic flow.

I'm pretty sure that if you have never cooked valves it is because you have never come near stoichiometric from the fat side for a large enough RPM range to matter.

Just 'cause your throwing fuel down it's throat doesn't mean it is badass.

A good pipe setup(including muffler with baffle) will ALWAYS make more power. It has been proven over and over that the baffle also gives 'depth' to the rebounding negative pulse that helps scavenge.

Your bike, your neighbors, run it like you like.

I guarantee mine will blow your ass off the road at any rev range with it's 4-2-1 straight baffle Kerker.

And, I'll add: in the days when they ran no muffler/baffle on racebikes they found that 'reverse megaphones' did the same thing...gave 'depth' to the scavenging wave

[dj820621]

Didn't say i was trying to make it faster did I?
No, just run, rev, and idle properly.

jesus christ, are the only people in this forum that reply to threat pricks that always feel the need to be a dick and say how wrong you are?

[DonTZ125]

In your first post, you asked for info, and you asked for problems that others have run into. Why then are you rejecting the info and comments on problems that your proposed mods have caused in the past? In this particular case, the people who are responding are the ones who are telling you how wrong you are because in their experience, what you are proposing is wrong. If you are wondering why no-one is chiming in to tell you about their success stories, it may very well be because no-one has had any success with what you are proposing.

When three mods and an experienced regular tell you you're wrong, calling them pricks who feel the need to be dicks and say how wrong you are is not the way to make yourself welcome. Sort yourself out.

[Mikey]

Didn't say i was trying to make it faster did I?
No, just run, rev, and idle properly.

jesus christ, are the only people in this forum that reply to threat pricks that always feel the need to be a dick and say how wrong you are?

You obviously didn't get the advice you wanted. Have you ever given your Daughter or Son Driving lessons? I have. When a very loud bike overtakes them, they panic and don't know what to do. On one driving lesson a VERY loud (possibly with an illegal exhaust like the ones you use) bike over took my Daughter. She froze swerved and almost hit the loud bike, I grabbed the wheel and averted an accident that may of cost that biker his life not to mention the innocent on coming drivers that may also have been involved!

It's your bike and your life. If you prefer to put others lives in danger...........