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  #1  
Old 05-14-2010
hugoender hugoender is offline
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How to Silence Pocket Bike

I know 2 stroke engines are inherently loud but if I wanted to silence my pocket bike (GP MTX) as much as possible, what could I do?

What can be done on the exhaust?
Will lining the inside of the fairing with foam help any?

These are the types of suggestions I am looking for.
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  #2  
Old 05-14-2010
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Kieran Kieran is offline
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Re: How to Silence Pocket Bike

the bigger muffler, tip of the exhaust, the quiter it will be.
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  #3  
Old 05-14-2010
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Re: How to Silence Pocket Bike

What about something else that does not have to do with the exhaust? Is there any other way of quieting the bike?

I am planning on removing the muffler and drilling more holes into the exhaust and then packing the muffler with fiberglass muffler packing material.
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  #4  
Old 05-14-2010
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Re: How to Silence Pocket Bike

none that i really know of, unless you put the engine on rubbers to get rid of the sound travelling through the frame.

Why drill holes?
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  #5  
Old 05-14-2010
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Re: How to Silence Pocket Bike

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Originally Posted by Kieran View Post
Why drill holes?
Well from experience with weapon barrels, the less porting a barrel has, the louder it is. I figured this probably applied to an exhaust pipe as well since they are both essentially pipes that are guiding the engine/weapon sound out.

Am I wrong? Would drilling holes in the exhaust pipe (where the muffler covers it) not do anything? Will it damage or negatively affect my bike?
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  #6  
Old 05-14-2010
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Re: How to Silence Pocket Bike

once you dont drill holes in the actual part of the exhaust where the back-pressure is needed.

Never heard of that before but experience is better than knowledge so il take your word for it.
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  #7  
Old 05-14-2010
hugoender hugoender is offline
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Re: How to Silence Pocket Bike

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Originally Posted by Kieran View Post
once you dont drill holes in the actual part of the exhaust where the back-pressure is needed.
I am having trouble understanding what you typed here. Can you please retype this?

Also, what part of the exhaust creates the back-pressure?
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  #8  
Old 05-14-2010
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Re: How to Silence Pocket Bike

There should be plenty of holes drilled in the pipe underneath the muffler already. I think it should be okay, as long as you don't drill anywhere that the muffler doesn't cover. The back-pressure is caused by the expansion chamber (I think).

You can do the spraycan mod for the muffler, like I did. <-- The rubber washers underneath the engine really damp down the vibration on the bike, too. As for lining the fairings with foam .... never heard of that one, but if it works, let us know, okay?
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  #9  
Old 05-14-2010
hugoender hugoender is offline
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Re: How to Silence Pocket Bike

Quote:
Originally Posted by SpyGuy View Post
There should be plenty of holes drilled in the pipe underneath the muffler already. I think it should be okay, as long as you don't drill anywhere that the muffler doesn't cover. The back-pressure is caused by the expansion chamber (I think).

You can do the spraycan mod for the muffler, like I did. <-- The rubber washers underneath the engine really damp down the vibration on the bike, too. As for lining the fairings with foam .... never heard of that one, but if it works, let us know, okay?
I just re-packed the muffler with some fiberglass packing material and noticed that indeed the exhaust pipe already has a bunch of holes drilled. The bike is a little less loud now that I used better packing and packed it throughout the whole muffler (the stock packing only covered half the length).

I will eventually do the spray can mod but I have no spray can much less an empty one.

I will try the rubber washers when I take my bike apart to try and fix my bogging down issue.

As for the foam lining, I have to see if I can find a bunch of foam and then I will temporarily tape it to the inside of the fairing to see if it makes a difference before I commit and glue it in there.
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  #10  
Old 05-14-2010
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Re: How to Silence Pocket Bike

Okay, sounds good. In the spraycan mod, I used #3 coarse steel wool - didn't have any fiberglass packing - and it helped quet things down, too.

Do the rubber washer mod when you go to swap out all the cheap Chinese bolts for good quality stainless or hardened ones. Since you'll have them all out, anyway .....
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  #11  
Old 05-15-2010
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Re: How to Silence Pocket Bike

just dont drill any holes in the actual exhaust, but you probally know that anyway. Sorry about my typing.
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  #12  
Old 05-15-2010
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Re: How to Silence Pocket Bike

I used up a can of carburetor cleaner (it was a really nice extra big can) but unfortunately it was too long and so it would not fit. Oh well. Will have to find another spray can.

Yeah I am not going to drill any holes in the exhaust. I thought the exhaust end where the muffler is was a solid piece with no holes but when I removed the muffler I saw that is has plenty of holes.

I also went to Home Depot today to get the bolts and washers and turns out they had no metric bolts or washers. TOTAL BS! So now I have to find another place that might have them. Any suggestions?

Oh and I took my whole bike apart and put it back together after cleaning carb but I forgot a small oring on the bottom part of the petcock (it fell out and I didn't realize it) and so it leaks like crazy. Needless to say I am ****ed that now I have to take the bike apart again since there is no easy way of removing that part of the petcock without have to remove the engine.
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  #13  
Old 05-16-2010
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Re: How to Silence Pocket Bike

Just a regular spraycan will work, like a WD-40 or paint can. I've also heard someone used a can from Bush's Baked Beans - those things are big enough to stick your fist through!

ACE Hardware, or any regular hardware store chain, not the big box stores. I don't like Home Depot for getting my bolts, because I occasionally have to check bolt and nut sizes .... kind of hard to do when everything HD sells is wrapped up in plastic bags!

You can just take off the carburetor by unbolting it from the back of the engine, just pull the rear wheel off. Unscrew the air cleaner, then undo the carburetor. That o-ring can also be found at the hardware store - might want to buy a few of them, as they do break or get lost now and then.
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  #14  
Old 05-16-2010
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Re: How to Silence Pocket Bike

Quote:
Originally Posted by SpyGuy View Post
Just a regular spraycan will work, like a WD-40 or paint can. I've also heard someone used a can from Bush's Baked Beans - those things are big enough to stick your fist through!

ACE Hardware, or any regular hardware store chain, not the big box stores. I don't like Home Depot for getting my bolts, because I ocasionally have to check bolt and nut sizes .... kind of hard to do when everything HD sells is wrapped up in plastic bags!

You can just take off the carburetor by unbolting it from the back of the engine, just pull the rear wheel off. Unscrew the air cleaner, then undo the carburetor. That o-ring can also be found at the hardware store - might want to buy a few of them, as they do break or get lost now and then.
Yeah, Home Depot was garbage.

My problem is that I have a tank and fuel line full of gas so removing the carburetor is not my first choice since it would get messy. I want to instead move the whole engine a little so I can access the phillips head screws that hold the petcock encasement onto the carb. This way, no fuel is spilled.

I did not lose the o-ring though. Luckily, I looked down at the floor and saw it there before putting my bike back together but wasn't sure where it belonged (or if the o-ring was even part of the bike since I use those small o-rings on my paintball guns and so I thought it might be from that). I stored the small o-ring in a bag anyways, just incase and good thing I did. As soon as the gas started leaking I knew what it was. Had I not found the o-ring on the floor I would have had no clue as to why my petcock was leaking.

I took a bunch of pictures and actually recorded a video of me taking the bike apart. I will figure out the best way of posting it all in the most organized fashion possible although the videos are way too long and boring to post anywhere.
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  #15  
Old 05-16-2010
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Re: How to Silence Pocket Bike

Clamp off the fuel line with a pair of vise grips. I use the spade-style ones for welding (well, since I weld anyway, I DO have them available!). Then you can remove the carburetor if need be. Otherwise, just drain your tank into an available can - makes it easier to work on the bike. I use a gallon gas can for the fuel, and any I have in the bikes gets drained into there before I start working on them.

Hardware: go to the Air-Cooled section, and at the top of the page is the "Air-Cooled Mods" subsection. Go in there, and look for the "Hardware Shopping List" - that tells you all the major bolts you need for your bike.
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  #16  
Old 05-16-2010
hugoender hugoender is offline
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Re: How to Silence Pocket Bike

Quote:
Originally Posted by SpyGuy View Post
Clamp off the fuel line with a pair of vise grips. I use the spade-style ones for welding (well, since I weld anyway, I DO have them available!). Then you can remove the carburetor if need be. Otherwise, just drain your tank into an available can - makes it easier to work on the bike. I use a gallon gas can for the fuel, and any I have in the bikes gets drained into there before I start working on them.

Hardware: go to the Air-Cooled section, and at the top of the page is the "Air-Cooled Mods" subsection. Go in there, and look for the "Hardware Shopping List" - that tells you all the major bolts you need for your bike.
Unfortunately, I do not have any of these vice grips. How do you recommend draining the tank without making a mess?

I went to the hardware section and looked up the list you mentioned on my iPhone while I was at Home Depot but they just didn't have ANY metric nuts/bolts/washers. I actually put all the bolts in labeled zip-loc bags and took them all to Home Depot to make sure I got the correct bolts. To be honest though, the bolts that came with my bike seem pretty solid. Maybe some bikes are coming with good bolts just how my bike came with an inline fuel filter when other bikes don't? What I really wanted to go to Home Depot for was the half rubber washers to dampen the engine vibrations but no luck.

Let's see if I can find an ACE Hardware store somewhere.
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  #17  
Old 05-16-2010
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Re: How to Silence Pocket Bike

Ace, OSH, a local small hardware store ... those big-box places are NOT gonna help you out much.

On the gas line, you just need some kind of clamp to crimp it closed. I happened to have the spade grips, since I weld, but aregular set of vise-grips will do. Once you get the line off the petcock, angle it down over the side of the pullstart and into a catch-can. Alternately, you can open the drain plug on the bottom of the carburetor while the bike is on its stand, and put the can underneath. Takes a little while longer, but it works ....
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  #18  
Old 05-16-2010
hugoender hugoender is offline
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Re: How to Silence Pocket Bike

Quote:
Originally Posted by SpyGuy View Post
Ace, OSH, a local small hardware store ... those big-box places are NOT gonna help you out much.

On the gas line, you just need some kind of clamp to crimp it closed. I happened to have the spade grips, since I weld, but aregular set of vise-grips will do. Once you get the line off the petcock, angle it down over the side of the pullstart and into a catch-can. Alternately, you can open the drain plug on the bottom of the carburetor while the bike is on its stand, and put the can underneath. Takes a little while longer, but it works ....
I am kind of putting information in this thread that belongs in my "GP MTX Bogging Down" thread so I will just stop and go back on topic...

Today it rained so I did not have time to go to ACE or any other store to look for the rubber washers. Maybe later this weekend or next weekend. I will also see if I can use up my spray can so that I can do the muffler mod. I peeled off the sticker on the can and it has a nice chrome finish so I will not be painting it. Looks nice as it is

Will post back with pictures once I do this.
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  #19  
Old 05-16-2010
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Re: How to Silence Pocket Bike

Nothing wrong with chrome, amigo .... And you don't always need to quote everything everyone says ... just enter your ext down in the box at the end of the thread and hit "Post Quick Reply."
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  #20  
Old 05-17-2010
hugoender hugoender is offline
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Re: How to Silence Pocket Bike

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Nothing wrong with chrome, amigo .... And you don't always need to quote everything everyone says ... just enter your ext down in the box at the end of the thread and hit "Post Quick Reply."
I only quote when I am responding to something specific that someone said. That way, the reader does not have to scroll back up to see what it is that I am responding to.

For example now, I am responding to what you said about me not having to quote what someone says so I quoted what you said as this post is a reply to that

Just the way that I forum. Sometimes I get lazy and quote the whole post and not just the section that I am responding to so if that is what you are complaining about then I apologize.
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