Clinician
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Post by cbb on Mar 19, 2012 12:01:29 GMT -6
Replaced the stock muffler on a 150cc with a performance muffler which is a straight pipe type. Runs fine but sucking gas (only 20 mpg) and small blue fireball on throttle down. Muffler gets HOT. My guess is I need to adjust the mixture on the carb way down? Other ideas? I was going to re gap the valves as well.
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Post by Bashan on Mar 19, 2012 12:09:43 GMT -6
What air filter and jet are you running? It sounds like you're way too rich and you're going to need to downsize on the main jet. I don't think the A/F screw will make much of a difference with what you have going on. Rich
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Scooter Doc
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Post by sprocket on Mar 19, 2012 12:41:10 GMT -6
Could also be the muffler many of them are just glass packs with a perorated pipe down the middle...
But I agree with Rich.. main jet...
You odometer may be in Kilometers if it is a mechanical type..so the gas mileage could be even worse...
it could be in kilometers
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Post by cbb on Mar 19, 2012 13:58:21 GMT -6
Miles per gallon... It is actually doing fine on speed. It went 20 miles on one gallon of gas vs. 60 previously. And yes, it is glass pack with a straight pipe.
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Post by sprocket on Mar 19, 2012 14:11:09 GMT -6
You have measured the odometer on a known mile?  Most odometers are in kilometers even if the Speedo is in MPH or MPH/kms. Electronic odometers can be switched from MPH to KMS.. depends on what it was set at in the factory... Anyway... You are simply pouring fuel into the engine... because you have lost the back pressure of the muffler... I would try a UNI or K&N air filter to get more air flow... then you may have to try doing with a smaller jet... Frankly the rule of thumb is you go UP 2 jet sizes for the muffler and 2 for a UNI or K&N...so the engine must be way out of balance... Yeah... the glass packs run very hot... |
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Post by cbb on Mar 19, 2012 15:16:59 GMT -6
Yes we took it to a known 10 mile marker (we have used it before for this purpose) and 10 miles back and the tank was all but empty. So we are very sure of it sucking gas. The jet is the stock jet that came on it not sure of size. I have read these are usually very small already but we will see tonight.
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Post by felliott on Mar 19, 2012 16:50:09 GMT -6
Check the vacuum fuel shut off. Could be leaking fuel in vacuum line and sucking fuel in the intake by passing the carburetor
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Post by sprocket on Mar 19, 2012 16:56:07 GMT -6
Very true felliott...very true...
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Post by roketafan on Mar 19, 2012 19:42:07 GMT -6
I have the same type muffler and it gets as hot as a stck 1 does i use a uni and jetted carb just recently put mine on i see a really dff in rpm about 1000 rpms higher wow what should i do next lol
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Post by cbb on Mar 19, 2012 21:19:07 GMT -6
The muffler that came on it was a dual muffler so I'm sure it had a lot of back pressure. I sure wish I could just find an exact replacement.
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Post by roketafan on Mar 19, 2012 21:24:59 GMT -6
Dual ? What the model scoot you have
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Post by cbb on Mar 19, 2012 21:48:42 GMT -6
Massimo MSM-150-26 is the make and model.
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Post by Bashan on Mar 20, 2012 2:39:39 GMT -6
Well sure enough, the OEM bike has a dual muffler, very cool:
The stock jets are usually 104 so I don't think that's the problem. Felliot hit on a great point that I think we overlook a lot, thanks man. The fact that you're getting a blue flash from the exhaust says there's a boatload of unburnt fuel getting through. Sucking it through the vac would explain everything except why it still runs OK. That's a fuel injection system you don't need.  Rich
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Rich