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Post by katt on Aug 30, 2018 20:52:55 GMT -5
My exhaust opening where it connects to muffler is 16.5mm is this a restriction?
Whats the diameter of exhaust pipe inner and outer i need to have when installing 70-80cc mod?
Tried riding with muffler off still same power as before no changes.
Is this backfire between 4000-6000 RPM when i close throttle?
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Post by lostforawhile on Aug 31, 2018 11:21:03 GMT -5
That's a restriction
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Post by 90GTVert on Aug 31, 2018 14:08:29 GMT -5
You could try to grind it so it's a circle instead of the shape left by the weld, or grind till you don't feel a lip. If you do much grinding, you will have to be careful not to go all the way through the pipe or welds and make a permanent leak. Wouldn't matter much with a bare header, but it would if you ever attach a muffler again. I don't really know that it's a big restriction, but I'd probably at least try making it a more even circle; unless whatever will bolt to it is smaller anyway and then it won't matter.
The backfire could be from running a little lean, possibly because of the open pipe.
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ratdog
Scoot Enthusiast
Posts: 342
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Post by ratdog on Aug 31, 2018 16:01:16 GMT -5
Pull your plug and let us see a closeup of the “white part” inside the plug. My first thought is that you are running lean and would benefit from going to a larger jet. Getting a look at the plug is the best way to “see” inside the engine
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Post by katt on Sept 1, 2018 19:32:04 GMT -5
Okay i did open it up to 19mm ID not seeing much difference though.  |
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Post by katt on Sept 27, 2018 22:43:30 GMT -5
Is stock exhaust pipe from 150cc has wider inner diameter will it fit on qmb139?
What you think about installing aftermarket 150cc exhaust pipe + muffler on 80cc qmb139?
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Post by scooterpimp on Sept 27, 2018 23:34:01 GMT -5
Wont fit
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Post by katt on Sept 27, 2018 23:50:26 GMT -5
You mean in the mounting where it bolts on the engine or in what way?
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Post by scooterpimp on Sept 28, 2018 12:54:43 GMT -5
Different bends etc.
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Post by katt on Sept 28, 2018 13:22:01 GMT -5
I thought bend could be wrong, but i have pipe bender perhaps i can change the direction. Is it actually bigger inner diameter?
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Post by scooterpimp on Sept 28, 2018 15:27:41 GMT -5
Pretty sure flange at head is different too. , i had a couple old 150 pipes i was going to try in the past , but wasnt worth the headache. Cutting & reshaping .No real gains from larger pipe. Found most1 piece exaust systems flow best. As in muffler & pipe 1 piece. Imo.
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Post by katt on Sept 28, 2018 21:54:40 GMT -5
Can you recommend any cheap but not obstruction muffler or system, $50 bucks price tag?
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Post by scooterpimp on Sept 28, 2018 22:41:40 GMT -5
Maybe check ebay?
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Post by katt on Sept 29, 2018 1:44:01 GMT -5
Which one is sufficient for 80cc "not obstruction" there's many different ones, do you have experience with any particular one?
Another option i have is to buy stock muffler for QMj157 (150cc) that is longer, but have same mount (i guess) for about $30 is it better than stock muffler on QMB139?  |
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Post by katt on Sept 29, 2018 15:18:11 GMT -5
I am dying to spend my money (while i still have them) someone please advice what should i get.
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