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Post by magoconnor on Feb 6, 2018 15:29:11 GMT -5
Hello. Will it hurt the engine if I just ran a straight pipe and left the muffler off ?
Any ideas for a silencer/baffle that will make it a little more quiet, but still keep the straight pipe look? Diameter the size of pipe or smaller to fit inside.
139qmb
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Post by magoconnor on Feb 6, 2018 15:30:25 GMT -5
Anyone tried the lollipop mod?
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Post by jeff84 on Feb 6, 2018 17:48:12 GMT -5
so long as you get your a/f ratio dialed in it wont hurt anything, other than your ears
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Post by greginisn on Feb 8, 2018 1:14:23 GMT -5
I don't suppose you remember but the old, 1964 era Honda 250 / 305 scrambler had a straight pipe looking exhaust. It wasn't loud or nasty but did have a unique pleasant sound due to some sort of in pipe diffuser system.
I don't know how it worked but it did and sounds to my much like what you're looking for. Google Honda CL 77.
good luck, Greg
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Post by 90GTVert on Feb 8, 2018 8:37:40 GMT -5
Any ideas for a silencer/baffle that will make it a little more quiet, but still keep the straight pipe look? Diameter the size of pipe or smaller to fit inside. 139qmb If you're using a stock 139QMB header, I don't think it would be a good idea to try to cram anything in there and reduce the size. Don't know that you have to worry about finding a silencer insert of any sort that small anyway. If you want it to look like a straight pipe, you'll probably need to run a bigger pipe. You could use larger pipe for a little more distance to try to camouflage it. If you look up something like "pipe insert muffler" or baffle, you can find some ideas. Most of the stuff is for much larger pipes that wouldn't be good for the scoot, but the basic designs aren't so complex that they couldn't be copied if you really wanted to go this route.
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Post by dexameth on Mar 7, 2018 12:08:07 GMT -5
I run a straight pipe most of the time on my built 50. Neighbors do hate it, so I push it out of the trailer park just to be nice. Doesn't hurt a thing. I have tried different headers with different IDs and my current one is 28mm ID and I love how it's deeper and less "raspy". I'm going to be trying to get a megaphone style straight pipe soon.
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Post by benji on Mar 7, 2018 13:24:14 GMT -5
I run a straight pipe most of the time on my built 50. Neighbors do hate it, so I push it out of the trailer park just to be nice. Doesn't hurt a thing. I have tried different headers with different IDs and my current one is 28mm ID and I love how it's deeper and less "raspy". I'm going to be trying to get a megaphone style straight pipe soon. Did you need to reset? Exhaust changes always need a rejet on 2t, but I don't know bout 4t.
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Post by dexameth on Mar 7, 2018 14:44:51 GMT -5
I run a straight pipe most of the time on my built 50. Neighbors do hate it, so I push it out of the trailer park just to be nice. Doesn't hurt a thing. I have tried different headers with different IDs and my current one is 28mm ID and I love how it's deeper and less "raspy". I'm going to be trying to get a megaphone style straight pipe soon. Did you need to reset? Exhaust changes always need a rejet on 2t, but I don't know bout 4t. No, I have a 24mm carb on my 88cc build, have had a 107 jet it in for a while now. When going from a stock muffler to an aftermarket exhaust or open header then yes, you should upjet because now the motor can breath a little better.
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Post by ruckus60 on Aug 4, 2018 13:17:15 GMT -5
If you run a straight pipe that doesn't give any back pressure, you are in danger of a loose flame front burning your exhaust valve. Just sayin' Not recommended.
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ratdog
Scoot Enthusiast
Posts: 342
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Post by ratdog on Aug 4, 2018 21:41:10 GMT -5
The single most important thing when you go to a stright pipe is to check your jetting. You should get a new plug and do some WOT plug chops to see where you are
I remember well the Honda “scramblers”. I has a 305 super hawk, but hated the gas tank and pipes on it. So I got a 250 scrambler tank and upswept pipes for it. This was mefore Honda came out with the 305 scrambler. Any way the deal we had was like a washer that just fit inside the pipe. It was on a shaft the stuck out the pipe with a knob on it. Most of the time, I just turned the “washer” so it was like a wide open butterfly valve. But I could turn it so the much smaller hole in the center of the washer was the only outlet. That made the exaust much quieter for “ in town” driving. Sounded very “tinty” but at least I could drive by the cops.
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Post by GrumpyUnk on Aug 6, 2018 13:59:10 GMT -5
I wonder why the sound of the 305 scrambler was so well received. It was the best sounding small machine of its time, IMO. I drooled over them on my way to class whenever I saw one. I bet they still command a pretty good penny, even though they date back to the late 1960's. Almost 50 year. Oh boy, makes me think I am old. tom
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ratdog
Scoot Enthusiast
Posts: 342
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Post by ratdog on Aug 6, 2018 15:42:46 GMT -5
You think you feel old? I had one when I was 14. Less then a year old at the time. I drove it on my “scooter” tag, even though it was a little more the 50cc (G). I rode it to school and there where 4 other “scramblers” in the lot almost every day. The others were 250s. Mine was the only one with electric start. “Real” scramblers did not have electric start. I had the fastest bike in school that year. When I turned 16, I got a 750 Norton, that later became the dark bike “who’s chicken”
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Post by jackrides on Aug 6, 2018 16:05:10 GMT -5
Ah yes, the famous "Snuff-or-Not".
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Post by diynuke on Aug 6, 2018 16:20:24 GMT -5
If you run a straight pipe that doesn't give any back pressure, you are in danger of a loose flame front burning your exhaust valve. Just sayin' Not recommended. i don't believe in this.. when you hit your rev limiter a constant flame is burning in your exhaust no matter if you have back pressure or not. the air and the fuel is there so it will burn. and the exhaust valve's are kind of made for it they disapate heat just as well on the back as on the front. unless you rev like 12.000rpm but then any valve would get hot in that situation no matter what you do to the exhaust
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Post by jeff84 on Aug 6, 2018 17:28:52 GMT -5
most race vehicles run straight pipes, many street bikes run straight pipes, most off road vehicles run straight pipes. there is no need for a muffler other than simply to make the engine quieter. the pipe needs to be long enough to evacuate the gasses and keep the pulse from backing up to the valve faster than it can close, that is all. backpressure is much more important in a 2 stroke application than it is in a 4 stroke
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