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Intake & Exhaust The ins and outs - carburetors, manifolds, mufflers, expansion chambers and more to keep your engine running the way you like

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  #11  
Old 11-04-2011, 12:23 PM
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Ernst Ernst is offline
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Default Re: Drilling into muffler cup

Expansion by SBP and Stinger is a hot water flexi pipe and the muffler is a tractor supply 3/4 inch off the shelf.

I have great power for the weight the bike carries.

The engine noise and the exhaust noise are separated for me.

When the bike is running at 28mph which is my highway speed there is a satisfying balance of running noise.
At 2 am or so it will not make any friends but the sound is relative to the small engine it is.

I wouldn't drill holes in the muffler myself. I went with a better exhaust,
Again separating the engine sounds from the exhaust sound made a difference in my enjoyment of riding my MaB

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  #12  
Old 11-04-2011, 01:14 PM
geoldr geoldr is offline
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Default Re: Drilling into muffler cup

Ah ok. This post was a while ago, and I have had a SBP x chamber for a while now. Really like it!
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  #13  
Old 11-09-2011, 04:02 AM
Mozenrath Mozenrath is offline
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Default Re: Drilling into muffler cup

I'm not much of an motorized bicycle expert, to be honest, but I'll contribute my opinion.

When I ran my engine for the first time, I my muffler didn't fit on yet, but I was eager to ride so I went without it. In comparison to having the muffler on it, it was DEFINATELY faster to some degree across the whole power band. I know one could say that it's a placebo due to the increased sound, but there seriously was a major difference.

That being said, somehow I doubt that a small hole would make much of a difference, both as far as power and sound go. You would have to remove a lot more of the back pressure to make a difference to justify the increase in noise. I remember somebody made a modification where the end cap could be actuated with a lever; that way if the rider was going up a steep hill, the end cap could be pushed away from the muffler and cause the engine to run leaner and have a little extra speed. Unfortunately I don't remember where I saw it, but that sounds like a better mod for speed because you could still run the engine at the proper richness and dynamically lean it out when it's necessary. Not sure how safe that is, though.

My replacement end cap that I made has no baffle tube, and it only sounds a tad bit louder IMO. In fact, a few people have asked me if I made my bike quieter, so nobody has noticed the difference. I have noticed though that the engine runs a little better. Not by much, but it seems to be breathing a little better. The baffle tube hardly does anything, so if you want to do everything possible to maximize performance, cutting off that baffle tube can't possibly hurt.
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  #14  
Old 01-26-2013, 01:38 PM
locutus_1 locutus_1 is offline
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Default Re: Drilling into muffler cup

all of you guys have to learn these little bitty engines arent made for performance.. its not worth the .3 hp your going to get.. 2 or 3 hp then you notice.. but all these little things do nothing.. its just to take your money to spend on carbs and etc.. you want power you get a morini motor or dirt bike 125 motor and install it in your bike.
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  #15  
Old 01-27-2013, 07:07 PM
geoldr geoldr is offline
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Default Re: Drilling into muffler cup

Quote:
Originally Posted by locutus_1 View Post
all of you guys have to learn these little bitty engines arent made for performance.. its not worth the .3 hp your going to get.. 2 or 3 hp then you notice.. but all these little things do nothing.. its just to take your money to spend on carbs and etc.. you want power you get a morini motor or dirt bike 125 motor and install it in your bike.
The fun of it is in the tinkering around. Your suggestion of buying a dirt bike motor and putting it on your bicycle is probably the worst suggestion you can give. Our bicycles were never meant to go that fast. If you will be spending the money to get a morini or anything else that is that expensive, you might as well just save up a bit more and get a motorcycle. A used Kawi Ninja 250 goes for very little. And its a lot better than a bicycle.

And you should read the thread first. It well agreed upon that drilling into muffler cup is not worth it.

Thanks.
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  #16  
Old 09-14-2014, 09:01 PM
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electron electron is offline
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Default Re: Drilling into muffler cup

Might keep this 1 going...
After reading about drillin holes, etc i decided i would change the flow, but not the backpressure, so i cut off the removable tube section and drilled through the remaining inside section keeping the external piece and weld, of course. This made a smooth exit. On the 80cc(66) it sounded a fair bit louder and more agressive/ dirt "bikier" and with the carby ground out another 2mm diameter resulted in heaps more torque and response, but not change in top speed on the flat. This mod helps up hills and attract jusr enough attention so people know i'm commin'.

Last edited by electron; 09-14-2014 at 09:06 PM.
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  #17  
Old 11-17-2014, 10:57 PM
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G3R0N1M0 G3R0N1M0 is offline
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Default Re: Drilling into muffler cup

I removed my cap and the difference greatly noticeable. It could easily do a burnout (in dirt). The climbing power was increased,plus more throttle response. The only down side was how loud it was. Now its crazy loud. But at least people know I'm coming.

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  #18  
Old 11-18-2014, 11:30 AM
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2door 2door is offline
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Default Re: Drilling into muffler cup

Quote:
Originally Posted by G3R0N1M0 View Post
I removed my cap and the difference greatly noticeable. It could easily do a burnout (in dirt). The climbing power was increased,plus more throttle response. The only down side was how loud it was. Now its crazy loud. But at least people know I'm coming.

You're not doing the hobby any favors. Negative attention we don't need. Your power increase is negligible and mostly in your head. If it's louder, it must be faster. Not true. There are exhaust modifications that will increase performance. Removing the cap from the muffler isn't one of them. Put the cap back on.

Tom
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  #19  
Old 11-18-2014, 08:37 PM
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Allen_Wrench Allen_Wrench is offline
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Default Re: Drilling into muffler cup

I have to agree with Tom here. The only thing I could add is that you may want to also check what a lack of calculated back pressure will do to the way the two-stroke engine uses fuel. An expansion chamber is generally a better choice. And I think you may end up finding out whether there is a maximum permissible decibel level in your area; some cop may come and talk to you about that. There are headaches that can come with making the decision to de-cap-itate your muffler. The previous posts in this thread cover more detail.
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  #20  
Old 11-20-2014, 01:39 AM
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G3R0N1M0 G3R0N1M0 is offline
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Default Re: Drilling into muffler cup

I will put the cap on it. It seems to drink a lot more gas with no cap. Probably the lack of back pressure. But i have to buy a new one the old one got bent and broke. So time for that great 3-5 day waiting period we all love so
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