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Post by prodigit on Jul 7, 2013 4:34:44 GMT -5
I'm thinking of putting a performance exhaust on my EVO150. The current muffler muffles very well, but I think it still has too much back pressure. On a cold engine it goes only 50MPH, on a hot engine 60. I think, but am not sure, that the engine is actually running a bit on the rich side; as BP Premium gasoline does not give a significant performance boost over regular on this bike. A bit yes, but not much. I want a cheap exhaust (I found $75 exhausts, not sure if they would fit though), preferably one with little chrome or metallic parts that can rust, that would fit the bike. www.amazon.com/150cc-Scooter-Performance-Exhaust-Black/dp/B005M30IUCWhich exhaust should I get? |
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Post by tinman7809 on Jul 7, 2013 6:31:27 GMT -5
If you go with the amazon one just make sure to use a blue loctite on all the bolts. You can try to take yours at part, if it uses rivets drill them out and you can take out any restriction and repackage it with a muffler packing. Any motorcycle shop that sells dirt bikes should have it. Then just re assemble with new rivets or self tapping screws.
It's a cheap mod.
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Post by oldchopperguy on Jul 7, 2013 11:32:21 GMT -5
Prodigit,
I've been "on a mission" to improve my stock exhaust now for several months, and learned quite a lot. While there are NUMEROUS aftermarket MUFFLERS available (and most will run fine) the REAL problem with restriction in the exhaust is RIGHT AT THE HEAD itself... Every stock GY6 150 I've yet seen, has a 3/4" inside-diameter exhaust header. BUT, the exhaust port in the head is a full 1" diameter. So, even if you run NO muffler at all, your exhaust is ALREADY major-restricted just a fraction of an inch from the exhaust valve itself, RIGHT WHERE IT WILL DO THE MOST HARM to your performance. Here's picture showing a stock header and one I made from a John Deere generator header for comparison... screenshot by lightshotHere's a picture of a GY6 150 head, and my header, showing the 1" diameter of the port and the header... screen shotsFor a muffler, I used an expansion-chamber setup for a 50cc GY6 which I already had on hand. However, after working on this for a while, I'm convinced that most ANY "performance" muffler would run fine, and even the stock, somewhat short-lived factory mufflers are not excessively restrictive. And they can be gutted and reassembled for even less restriction. If you look around, you CAN find ready-made exhaust systems which incorporate a full, one-inch inside-diameter header. The increase in overall performance, idle, carb-tuning, consistent smooth power from idle to WOT and such, was impressive on my Xingyue 150 after fitting the one-inch head-pipe. While a performance muffler is always a good idea, I'm FIRMLY-CONVINCED that a full-size header is MUCH more important to performance and engine cooling than ANY muffler. Without a full-diameter header, you're "shooting yourself in the foot" before the exhaust ever reaches the muffler.My home-brewed exhaust wouldn't bolt up to my scooter whatsoever, so, since I had to make a mounting system anyway, it was about as easy to just make my own header... But, if you want to go with mostly ready-made parts, you CAN find a 1" header AND performance muffler available as a set. I think "Jeepsteve" just put such a system on his ride, and made a post.I've seen a chrome 1" header on eBay for around $50 and it is long, and has no fittings at the the muffler end, so you can adapt any muffler you wish, or purchase the header/muffler as a set. No matter what system you decide on, it is VERY unlikely to simply "bolt on" to your particular scooter. However, with only a little effort and a piece of aluminum or steel bar-stock, you can usually adapt any system to any scooter. I even was able to "repurpose" my original muffler strap-clamps and rubbers to my unorthadox tapered cone-shape chamber. With any muffler that is a plain cylinder-shape like a stock unit, making a mounting setup is usually fairly easy. I've got 500 happy miles on my new exhaust, and am very impressed with the improved performance. And, I'm convinced that the increase is due mostly to the large-diameter header, rather than my choice of muffler. (Past experience has shown me that 2-stroke style chamber pipes DO run great on 4-strokes too). I do recommend a full-one-inch header as your very first upgrade to the exhaust, regardless of what muffler you decide on. Hope this may be of help,Leo in Texas
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Post by jerseyboy on Jul 7, 2013 12:50:11 GMT -5
P&P,,on ebay,,I had to cut one bracket off but other than that it works great!!!
Zoom in on my avatar pic...its 125 shipped,,maybe too much for ya?
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Post by justin010304 on Jul 7, 2013 14:30:00 GMT -5
I've always said the issue is the header. Everybody thinks that putting holes in the muffler is going to make it flow better, but the real restriction is the header.
As far as a the mount not being correct on a eBay exhaust, well you can only expect so much when there are so many different bodies with the same motor.
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Post by prodigit on Jul 7, 2013 19:20:54 GMT -5
That's what I'm worried about, if the pipe will fit on the bike.
The diameter of the exhaust pipe is purposely made smaller, because the exhaust gasses would flow faster that way, causing a better vacuum suction, resulting in improved performance.
One of the reasons why on motorcycles they don't equip them with full 2in diameter exhaust pipes.
They use only tiny pipes, because exhaust gasses go faster through them and increase MPG (as slower moving gasses cause less of a vacuum, necessary for the cylinder to exit the exhaust gasses better.
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Post by jeffery5568 on Jul 7, 2013 21:46:55 GMT -5
Where do you find a 1" header or better yet the parts you used to make yours.
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Post by oldchopperguy on Jul 7, 2013 22:14:10 GMT -5
That's what I'm worried about, if the pipe will fit on the bike. The diameter of the exhaust pipe is purposely made smaller, because the exhaust gasses would flow faster that way, causing a better vacuum suction, resulting in improved performance. One of the reasons why on motorcycles they don't equip them with full 2in diameter exhaust pipes. They use only tiny pipes, because exhaust gasses go faster through them and increase MPG (as slower moving gasses cause less of a vacuum, necessary for the cylinder to exit the exhaust gasses better. True, BUT if the pipe is to be smaller than the exhaust port, it should be done AFTER the exhaust port (and tapered) to create the reverse-venturi's suction effect you describe. Blasting 1" of 1,500-degree exhaust right out of the combustion-chamber into a 3/4" hole is just NOT a good idea. Witness the fact that my oil-temperature dropped 20-degrees with the 1-incher. I shudder to think what my head temp once was... LOL! I achieved the suction effect with the expansion chamber, but it's only slight... I doubt that a regular muffler would run noticeably less "strong". After building Harleys, Triumphs and V8 car engines long ago, I found most engines except for the lowest-compression utility motors, still run best with the pipe fully the same size as the exhaust port. These little GY6's are actually fairly high-compression performance designs. All I can say is that my own Xingyue 150 really came alive with the larger-diameter header, much like our hot-rod Harleys, Brit bikes, Fords and Chevies did in the sixties. The best aftermarket exhaust kits for the GY6's today do feature the 1"inch headers. Not saying you're wrong, just that we differ on ideas on how to achieve the end result... Certainly no offense meant for sure.Leo in Texas |
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Post by justin010304 on Jul 7, 2013 22:14:59 GMT -5
You can find flanges on eBay from time to time, or pick them up on other forums. Pick up stainless pipe from an online supplier like aces stainless supply.
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Post by oldchopperguy on Jul 7, 2013 23:00:10 GMT -5
Where do you find a 1" header or better yet the parts you used to make yours.
Here are some possibilities...SCOOTER 125CC 150CC GY6 RACING HIGH PERFORMANCE SHORT EXHAUST BLACK eBay item #181160168201 This one looks VERY promising, complete with muffler and clamp for $  and FREE shipping! SCOOTER 125CC 150CC GY6 RACING HIGH PERFORMANCE SHORT EXHAUST CHROME eBay item #171061664829 Same seller, same price, looks GREAT! The last two are from the seller gy6racingteam whom I've bought both disk-brake calipers and master-cylinders from. I've been satisfied with their quality and shipping time. Since GY6 heads DO differ slightly in the angle of the exhaust-port, you probably can lay your old header down, take a digital photo of the bolt-on-flange, and compare it to pix in the eBay listing well enough to be sure it will line up with your head. While I did make my own head-pipe, from a used John Deere generator header, it took some notching, welding and fitting. Not hard, but if I do it again, I'll spend a few bucks and just buy a ready-made header. If you search eBay under "GY6 150 exhaust" you'll find a BUNCH of choices, from affordable, to quite pricey. It just isn't NEARLY as daunting as it looks, to fab up mounts and strap on a system to your scoot... Especially if your ride uses the wrap-around clamps with rubber insulators. Please feel free to PM me any time if you have specific questions... It's good to post here in public forum though, so others can learn from our successes... OR our mistakes! LOL! I'll post pix of my mods here as a reference... They can apply to most any exhaust replacement mounting.Here are the old John Deere header stubs (I cut off the tops which originally inserted into the flathead motor.) The port and bolt-spacing is perfect for the 150 GY6, but the bends are NOT nearly tight enough to run the header between the engine and frame as the stock pipe. You can't run it BELOW the frame as I'd like to, because it would be the lowest part of the scooter, and would hit obstructions, damaging the engine  free jpeg imagesHere's the John Deere header cut and bent to fit the frame. I had a shop weld the cut closed, and used 1 1/8" aluminized flex-exhaust-tubing for RV use, mated to the steel flange with "INFERNO" sealant. then I heat-wrapped the tubing as it runs CLOSE to the engine and frame. image hosting imgurHere's the "muffler" with the simple flat bar-stock mount. The muffler-clamps bolt to the bar, and the bar bolts to the scooter. With a traditional straight, round muffler, you might be able to bolt the clamps right to the scooter. screenshot greenHere are all the "bits and pieces" before final assembly... how to take screenshotsAnd here's the system as it runs today... 500 miles so far... Solid as a rock, and runs like a bear! lightshot free downloadSorry to make this so long, but a few pix are worth a thousand words... I think that after just a few years of riding, the originals rot, and a better exhaust is pretty much a "given" with these. I'm old, tired, and have no fancy tools... So if I can do this kind of mod, ANYBODY probably can... LOL! Any help I can be, just let me know.Leo in Texas PS: If you DO decide to make your own header, and use flex-exhaust tubing, it's hard to find. One eBay seller has it for RV/implement exhausts. It's 1 1/8" I.D. which fits over the steel header perfectly. |
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Post by prodigit on Jul 7, 2013 23:04:38 GMT -5
The exhaust tip of the stock muffler of the 150 on mine is <1/2 in in diameter. It's too much back pressure. Perhaps drilling it out will help somewhat.
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Post by oldchopperguy on Jul 7, 2013 23:17:28 GMT -5
The exhaust tip of the stock muffler of the 150 on mine is <1/2 in in diameter. It's too much back pressure. Perhaps drilling it out will help somewhat. That far back I'm not sure they are too much of a problem, but many riders HAVE obtained increased performance by opening up the stock muffler. If you do want to improve your factory system, I'd highly recommend that along with gutting the muffler, remove the header, and, "chamfer" the header "hole" at the flange, just to "ease" the transition from the exhaust port to the smaller header flange. Others have found this to be of some help in freeing up the exhaust's breathing. Little things can make some big differences!Leo |
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Post by prodigit on Jul 8, 2013 0:17:22 GMT -5
I think most of the exhaust system is pretty ok. The muffler works so good, because it's so huge, and the tip is so small.
I wouldn't mind having a bit louder sound, but also a bit better performance; running a bit leaner.
The exhaust tip is restricting the muffler, and causing exhaust gasses to go back to the exhaust valves, causing lower MPG and lower performance.
Though I have no complaints about performance, 65MPG is a bit on the low side for a 150.
I should at least be able to get 75-80MPG out of it, and a bit tuned it should get ~90MPG, not 65; that's only 2/3rd as efficient as it should be.
I just wanted to know if the exhaust tip (yes I got the angled one), is a pipe that goes in the muffler, or just a tip only on the outside of the muffler?
If it's only a tip, I can drill it out, but if it's a pipe, I'll have to find a larger diameter pipe, and won't be able to drill it out.
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Post by scootnwinn on Jul 8, 2013 0:26:50 GMT -5
Just start drilling trust your instincts and drill
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Post by oldchopperguy on Jul 9, 2013 12:11:48 GMT -5
I've always said the issue is the header. Everybody thinks that putting holes in the muffler is going to make it flow better, but the real restriction is the header. As far as a the mount not being correct on a eBay exhaust, well you can only expect so much when there are so many different bodies with the same motor. Most of my own building involved Harleys, Brit bikes and Chevy cars... and that was a full half-century ago. Whew, time FLIES! I wondered if my past experience was outdated, but it seems not. We always used a full-diameter header back then, and it always seemed to work best. The most expensive, name-brand headers were always made with tubing as large as the exhaust ports, and even the better headers for our little GY6's are still made that way. You can always adjust for back-pressure (or the need for expansion of the gases for scavenging on an individual engine) at the muffler. That's where the old megaphone-tips came from, but they were mighty LOUD! The BIG problem I find with these scooters' headers is the abrupt size-reduction DIRECTLY from the exhaust-port to the header... It's the reverse of putting an intake manifold on your engine with the intake larger than the port in the head. Everything hits a solid wall right at the head... Bad enough with the intake, but with the exhaust gas hitting that "wall" right at the valve, it must create some turbulence right at the combustion-chamber, while trapping 2,000-degree exhaust right at the valve... I personally think that if one absolutely MUST use a stock header, it should at least be chamfered at the flange to ease the transition of the exhaust from the head to the header... You can live with a smaller pipe, but the transition from the large port should be gradual, and augmented by an area of expansion somewhere "down-stream" to create the suction/scavenging effect if desired. Witness the fact that with my own setup, using the 1" header and a 2-stroke expansion chamber, I got an instant increase in smoothness, consistent idle, ease of carb-adjusting and acceleration. AND... Get this now, a 20-degree lowering of my oil-temperature, AND a slight RICHENING of the fuel mix. With the stock exhaust, my oil temp was running around 220 to 230 degrees after a hard run on a 100-degree day. Now, it's running around 200 to 204-degrees... Can you IMAGINE what my head-temperature must have been with that 2,000-degree flame trying to get through that 3/4" hole in the flange?It's most common to have a free-flowing exhaust LEAN out the mix, but my formerly tan/brown plug now reads just a tad sooty-black. That scavenging effect is pulling some extra fuel into the chamber! The valve-timing on this little "hemi" must have a slight overlap, leaving BIOTH valves slightly open for a nano-second... Hmmm... I can see some REAL potential for the serious tuner here. Not me though! At my age, I want to ride more than wrench... LOL!With temps around my area running right at 100-degrees and more, I can live with a little "rich" so long as it's not "slobbering-rich"... LOL! Enjoy the ride!Leo in Texas |
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