Exhaust Upgrade Theory

[Zapkin]

Originally Posted by chiefmeat68

I hate loud annoying bikes... unless it's mine!!!

When I was driving my typical junk cars, which I've had my entire life, it used to annoy me that the cops would pull over cars with loud exhaust but let some incredibly loud motorcycles get away with it. But then I realized why. Usually, a loud car exhaust is due to a failure that could leak carbon monoxide into the interior, and I have, in fact, suffered from that when I was driving one. I'd get home after a long drive, and have a headache. That might be why half of my brain has atrophied!

[Zapkin]

okay so I had to try it anyway. I took out the baffle and it made the bike louder and also screwed up the throttle response..immediately. so back in it went. sometimes you just have to learn the hard way. i still have stock carb so maybe it got even leaner?

[Bill Hilly]

Originally Posted by Zapkin

okay so I had to try it anyway. I took out the baffle and it made the bike louder and also screwed up the throttle response..immediately. so back in it went. sometimes you just have to learn the hard way. i still have stock carb so maybe it got even leaner?

I'm not surprised that removing the baffle made it some louder, but I'm surprised that it was restricted enough to cause any tuning issue. The screen on the baffle is so fine that it's possibly more restricted than the baffle itself. I think you said that you ordered a PE28FL, so after you get that properly jetted, and on you won't have to be so lean that simply removing the baffle throws the tune off like that. I would say that your stock jetting is so lean now that the removal of the baffle was just the straw that broke the camel's back. When you increase flow by changing, or modification of exhaust, or pod filter ( which I remember you ordering), then up jetting is necessary, but that's good, because you know you have freed up some corked up power.

[Megadan]

Stock carb = Too lean to begin with.

Stock carb with any exhaust mods = way too lean.

You need to jet the carb or wait until the nibbi comes in.

[Oldenslow]

All admirably packed with self-delusional pseudo-science...

Quite entertaining, while remaining minimally informative.

[Bill Hilly]

Originally Posted by Oldenslow

All admirably packed with self-delusional pseudo-science...

Quite entertaining, while remaining minimally informative.

We're all ears Professor. Will you please educate us , and explain to us , the hard, genuine science of the matter. I assume that all who may feel any improvement of performance after replacing, or de-restricting the exhaust on a Hawk, are confusing actual performance gains with wishful thinking.

[Thumper]

As Dan describes, deleting the cat is the single most effective one thing to do for performance enhancements. Here is what I did on my Storm.

https://www.chinariders.net/showthre...ighlight=storm

Then you need to rejet, and there are various ways to increase exhaust flow. Drilling is the least technical and can give you a clue about whether or not it will help to open up the exhaust.

Then head work (porting) and a performance cam are the next steps, which usually require rejetting.

Originally Posted by chiefmeat68

It seems everybody claims a significant boost in power by upgrading their exhaust. I believe these claims. I understand a higher flow less restrictive exhaust will give a performance boost.

What is not obvious is why many of the aftermarket exhaust setups I see suggested would be any less restrictive than the stock exhaust?

Like this one I am considering... suggested by moto taco... for the Hawk 250 as an example...
https://www.amazon.com/dp/B07GYSLJMD...roduct_details

It apears to be the same tube diameter and still has a cat... how does it make such a difference?

Is it actually bigger ID diameter? Smother on the inside? Less bends? Is the cat less restrictive somehow? Is the baffle/muffler the key?

Would it be better to keep the stock exhaust and remove the cat or would an aftermarket one with a cat still be better? Any suggestions for an aftermarket that comes without a cat?

Maybe it exists... but if not it seems someone could make some money selling just a straight pipe "header" that mates with the stock mufflers!!

[Zapkin]

Originally Posted by Bill Hilly

I'm not surprised that removing the baffle made it some louder, but I'm surprised that it was restricted enough to cause any tuning issue. The screen on the baffle is so fine that it's possibly more restricted than the baffle itself. I think you said that you ordered a PE28FL, so after you get that properly jetted, and on you won't have to be so lean that simply removing the baffle throws the tune off like that. I would say that your stock jetting is so lean now that the removal of the baffle was just the straw that broke the camel's back. When you increase flow by changing, or modification of exhaust, or pod filter ( which I remember you ordering), then up jetting is necessary, but that's good, because you know you have freed up some corked up power.

I had to put off the new carb until next month, so I am running what I have for now. I already have the Nibbi filter. I figure when I throw the smaller sprocket on the back (already did the 17 up front), I will install the new carb and then take it from there. I am learning. I know I ask some stupid, redundant questions sometimes, but the search function on this site leaves something to be desired (or else I am not using it properly).

[Thumper]

I used to think the search function was useless, until I looked more closely at it:

-use the advanced search instead
-if you can limit to a specific forum section, like "Video and pics" or "Dual sport/enduro" which simplifies the results
-select Show results as "posts". This is an important limit-really helps because otherwise you have to search through the entire thread!

I haven't used search by Tag, but I think that this is for a specific complete text string, like "cat delete" or "cg clone valve adjustment". I think that the exact text in that order must be present, so if you want to search for something very specific, results could be only one post!

[JerryHawk250]

Originally Posted by Zapkin

I had to put off the new carb until next month, so I am running what I have for now. I already have the Nibbi filter. I figure when I throw the smaller sprocket on the back (already did the 17 up front), I will install the new carb and then take it from there. I am learning. I know I ask some stupid, redundant questions sometimes, but the search function on this site leaves something to be desired (or else I am not using it properly).

You don't need to upgrade the carb. A inexpensive jet kit for your stock carb will get your Hawk running much better.

[Bill Hilly]

Originally Posted by Zapkin

I had to put off the new carb until next month, so I am running what I have for now. I already have the Nibbi filter. I figure when I throw the smaller sprocket on the back (already did the 17 up front), I will install the new carb and then take it from there. I am learning. I know I ask some stupid, redundant questions sometimes, but the search function on this site leaves something to be desired (or else I am not using it properly).

I realize that money can get tight, and it's easy to read post , especially on the Facebook China bike sights, of people having "miracle results" by installing the PE28, but even though it's a good carb, and has an easy to reach idle mixture screw, it's not going to make your otherwise stock bike run any better than a properly jetted VM26 clone, or the stock PZ30 carb. You could just put a 110 main jet in the stock carb, and with the factory pilot, have a perfectly adequate carb. I would not spend much money on one, but I have replaced the bowl screws with hex head, but that's just a few bucks, and not necessary,if you do a neat job of slotting the smooth headed bowl screws. I will gladly send you a 105, and a 110 main if you do want to run the stock carb. If you do still decide you want to buy a Nibbi, I will mention that you don't have to get buy the black, and red one. You can get the basic PE28FL, for far less, especially if you look under "today's deals", and "all discounts" on Amazon. That's what I did, and I think I ended up paying around $50 or so . One good thing about the Nibbi is that it comes with an assortment of commonly used jets. If you want me to send you a couple of jets, let me know in a message, and were to mail them..

[Megadan]

Hell, I probably have 2 or 3 105 and 110 jets just sitting around doing nothing. I will happily mail one or two away to somebody that can use them.

As for the PE28FL. Nibbi mails them with a range of main jets from 110 to 125, which is all you really need for a bike with an exhaust upgrade. Mine came with a 35 and 40 pilot jet, but I ended up needing a 38. Others said theirs came with a 38, so you may or may not need to buy a pilot jet for it.

[Zapkin]

well I already invested in the Nibbi filter. I think 48mm. Is there an easy way to match that to the stock carb? layer after layer of duct tape? (mcgyver anyone)

[Bill Hilly]

Originally Posted by Zapkin

well I already invested in the Nibbi filter. I think 48mm. Is there an easy way to match that to the stock carb? layer after layer of duct tape? (mcgyver anyone)

I was running a foam filter that was for the 49-50 mm carbs, on a VM26,and I cut the end off of a stock airbox hose, just were it slips over the carb, and it was a perfect adapter, but I had two space hoses. If you do that, then you won't be able to use the airbox hose again. I can probably still find the piece that I used, and if you want the jets, I can send that as well, or if you want, assuming that you bought the filter from Amazon, return it, and either buy a 42mm pod filter, or just use the stock airbox, and save about $15.00 bucks. This fits the stock carb, and VM26... https://www.amazon.com/gp/aw/d/B09W2...b_b_asin_title

[Zapkin]

well i lost my dang idle adjustment tool. had it in my pocket and must have pulled it out with my phone. major brain farts today.

I am not messing with anything until I have the resources available to correct it immediately if I screw it up. at the moment the bike is doing just what I bought it for, they say dont fix what isn't broke.