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Post by lain on May 18, 2015 14:59:32 GMT -5
My muffler is in pretty bad shape after my friend crashed my scoot. I have a muffler from an old 2 stroke, looks the same size hole for the exhaust port but the angle is different. If I mounted it it would be aiming about 30 degrees off to the side from the back.
Is there any difference between mufflers for 2 strokes and 4 strokes? Can I bend the muffler tube to be the correct angle to mount properly to use it?
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Post by ramblinman on May 18, 2015 15:02:08 GMT -5
iicr i think Leo put a 2-stroke pipe on his old 4-stroke. get some info from him imo.
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Post by lain on May 18, 2015 15:06:56 GMT -5
iicr i think Leo put a 2-stroke pipe on his old 4-stroke. get some info from him imo. Did you do this too? Are you still using it? I am thinking there is not much differences, but maybe difference in how much air they let pass? Like different exhaust compression? |
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Post by ramblinman on May 18, 2015 15:13:37 GMT -5
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Post by lain on May 18, 2015 16:15:47 GMT -5
Well I'm not talking about a muffler with expansion chamber, but just a muffler/tube welded together type factory style muffler that is currently rusting on a 2 stroke hopeless engine I have in the corner of my yard. My current muffler is literally falling apart and being held together with some weird muffler repair kit stuff I got months ago. Still holding after the fall surprisingly.
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Post by ramblinman on May 18, 2015 16:26:35 GMT -5
idk lain, thought that was what you were referring too.  |
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Post by oldchopperguy on May 19, 2015 10:42:57 GMT -5
OK, guz and galz... The 2-stroke "chamber" pipe on a 4-stroke engine has been one of my favorite "tweaks" ever since my 2-stroke kart days in the sixties. I rode my Xingyue 150 with the chamber pipe for a season before trading it on my current used Kymco 250. It was SWEET!
On my particular Chinese GY6 150 my original factory muffler was also "done for". I had the chamber pipe on-hand and figured it was time to use it. In actual use, the chamber effect is minimal on a 4-stroke, but IS noticeable. The chamber allows the exhaust to rapidly expand, helping scavenge it more efficiently than a straight-pipe. On a 4-stroke, the chamber is simply an expedient to scavenge the exhaust, while on a 2-stroke, it's a "whole nuther thing"... LOL! The chamber must be tuned to the 2-stroke engine, but when done right, it not only pulls the exhaust out, but pulls in a larger air-fuel charge, clear through the combustion-chamber and then rams it back in, for a true supercharging effect, sometimes nearly DOUBLING the hp at a given rpm.
I feel the MOST important aspect of stock muffler replacement is to also replace the HEADER with a full, ONE-INCH tube. Every factory 150 GY6 header I've seen is considerably SMALLER inside diameter than the exhaust port. THAT is BAD! It chokes the engine right at the port.
You can now buy professionally made full-diameter headers on eBay or from other vendors for around $50 and I'd consider that a good investment. No matter WHAT muffler you use, that 1" I.D. header will liven up the engine, and make for easier carb-adjustment and offer better overall performance.
The muffler off the old 2-stroke mentioned should work OK even without the benefit of a chamber. Even the much maligned factory muffs are not all THAT restrictive. The engine needs at least a little backpressure to run right. That's why a short straight-pipe often cuts a little performance compared to a muffled exhaust. It's the undersized HEADER that is the culprit. Even if you don't wish to replace the factory header, you can "chamfer" or bevel it at the port to ease the exhaust-flow from the port to the header. This simple mod to the original header will often make a noticeable improvement in drivability.
Most any muffler from a large Briggs & Stratton stationary engine type, to a small automotive glasspack, to Japanese baffled car exhaust "tip" should run fine with little or no carb-jet changes. It just happens that the old-school 2-stroke chamber pipe runs just a tad "better"... LOL!
Hope this info helps,
Leo in Texas
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Post by oldchopperguy on May 19, 2015 10:58:37 GMT -5
My muffler is in pretty bad shape after my friend crashed my scoot. I have a muffler from an old 2 stroke, looks the same size hole for the exhaust port but the angle is different. If I mounted it it would be aiming about 30 degrees off to the side from the back. Is there any difference between mufflers for 2 strokes and 4 strokes? Can I bend the muffler tube to be the correct angle to mount properly to use it? There's little difference in "utility" mufflers on 2-stroke and 4-stroke engines. On performance 2-strokes however, a properly designed chamber pipe can nearly double the hp at a given rpm. A chamber exhaust on a 4-stroke, simply aids in scavenging... Not the monumental improvement like with a racing 2-stroke, but still, a noticeable improvement.
You should be able to bend your muffler tube, or header to better align it with the exhaust port. If it's steel tubing, and you can find a suitable "fixture" to wedge it in, you might be able to carefully bend it by hand. If you have access to a welding torch, heating it red will aid in bending. You also might get a local muffler shop to put a bend or two in it for a few bucks.
If the headpipe is smaller inside-diameter than your exhaust-port, I would at least chamfer or bevel the inside a little with a drill and ball-shaped stone to ease the exhaust passage from the head to the pipe.
Please take pix and let us see how it works out.
Ride safe,
Leo in Texas
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