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Old 06-18-2019, 09:29 AM
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Default Quieting down the Predator 420

Hey guys. I recently put a Stage 1 kit on my kart for the Predator 420 and its awesome and a big improvement but Id like to do something quieter. The quieter the better honestly, but I don't want to sacrifice too much performance. that means a straight through design.

The problem is finding something with a Pipe ID relatively close to the 1"-1-1/4" of the aftermarket pipe. Currently I rigged up a cheap tractor muffler from the local TSC and its definitely better then a straight pipe, but I need something better so I can putz around with my 2 year old without hearing protection. I was thinking a slip on or dirt bike muffler.



*Yes I know I should brace the pipe, this was right after I did it and tested it. Once I have the final design done I will brace it up.

What have you all found?
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Old 06-19-2019, 05:37 PM
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Ha ha, well that seems to be the trend lately: Quieter.

Everyone seems to want loud and proud but I tell you, being as close as we are to a straight pipe (compared to a car etc) on a kart or minibike, it gets taxing.


So you're saying that giant muffler doesn't do much?

Here's a recent thread that might shine more light on the issue:
http://www.diygokarts.com/vb/showthread.php?t=41365

I don't think we know very much about less-restrictive sound deadening at this point.
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Old 06-19-2019, 06:05 PM
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Yep, I started that thread and still haven’t made a choice. I might go down to the scrapyard with wrecked bikes and see what mufflers they have, it would probably be cheaper than buying even a used one off eBay

If this helps any, kartfab has used a Honda grom muffler and said it works very well
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Old 06-19-2019, 06:37 PM
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I'm in the same situation. I looked at kartfab's suggestions the other day and it seemed pretty pricey. Do we have a direct link to something moderate? Perhaps a scrapyard is the best plan as you said.
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Old 06-19-2019, 06:42 PM
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Everything I have looked at is out of budget, so either scrapyard or maybe somone is parting out a bike in craigslist would sell for cheap
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Old 06-19-2019, 07:09 PM
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Another thread I found while browsing on the interwebz:

http://www.diygokarts.com/vb/showthread.php?t=11757

Still reading....
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Old 06-20-2019, 06:09 AM
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Quote:
Originally Posted by Hellion View Post
Ha ha, well that seems to be the trend lately: Quieter.

Everyone seems to want loud and proud but I tell you, being as close as we are to a straight pipe (compared to a car etc) on a kart or minibike, it gets taxing.


So you're saying that giant muffler doesn't do much?

Here's a recent thread that might shine more light on the issue:
http://www.diygokarts.com/vb/showthread.php?t=41365

I don't think we know very much about less-restrictive sound deadening at this point.

Yeah its just a tube with some baffles basically. I dont think there is any packing material.

I come from the high HP car world and there is so many options for mufflers/resonators but they are all at minimum 2" diameter. I wonder if something like that would be as effective with such a step up in diameter
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Old 06-20-2019, 11:41 AM
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the ebay slip on dirt bike mufflers are almost as loud as no muffler at all.

honda grom muffler is too small for a 420.

Any sort of stock bullet bike muffler you can find good deals on. I want to say i paid $12 fro TWO Yamaha R1 mufflers on ebay. I found one for $26 here
https://www.ebay.com/itm/09-14-Yamah...Condition=3000

Only problem I ran into is that the muffler is really high quality so if you plan on chopping the tube up to the muffler to make it shorter, you will need to TIG weld it with a piece of the muffler pipe used as filler rod. It is made of titanium. I used some sort of stepped flange to step from the pipe to the muffler. They are super cheap as well.


good luck. A single yamaha R1 muffler will give you all the quietness you need and all the performance you want.

If you look at some of my go kart MIDAS videos before the wreck, you can see how i did the muffler. Tucks in nicely under the bore and rear of the block. yyou can probably just keep the same angle you have right now and fab up some sort of brace to hold it.
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  #9  
Old 06-20-2019, 12:27 PM
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Quote:
Originally Posted by KartFab View Post
the ebay slip on dirt bike mufflers are almost as loud as no muffler at all.

honda grom muffler is too small for a 420.

Any sort of stock bullet bike muffler you can find good deals on. I want to say i paid $12 fro TWO Yamaha R1 mufflers on ebay. I found one for $26 here
https://www.ebay.com/itm/09-14-Yamah...Condition=3000

Only problem I ran into is that the muffler is really high quality so if you plan on chopping the tube up to the muffler to make it shorter, you will need to TIG weld it with a piece of the muffler pipe used as filler rod. It is made of titanium. I used some sort of stepped flange to step from the pipe to the muffler. They are super cheap as well.


good luck. A single yamaha R1 muffler will give you all the quietness you need and all the performance you want.

If you look at some of my go kart MIDAS videos before the wreck, you can see how i did the muffler. Tucks in nicely under the bore and rear of the block. yyou can probably just keep the same angle you have right now and fab up some sort of brace to hold it.
You remember what the diameters of the inlet is? In your experience this type of muffler is better for a stage 1 and beyond setup than say a RLV?
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Old 06-20-2019, 01:15 PM
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Mufflers are only as tricky as you make them out too be.

Most times i find it too be more difficult too fit a item specifically made for another application onto another and have it look and function well...most times.

Heres the exhaust i built for the 12hp briggs on my t555.

After running it with just a short curved open pipe for some time i liked the performance but not the noise so i came up with a mini version of a glass pack.

The 1 3/8" goes straight through the 2 1/4" with about 100 cross drilled holes in it that is wrapped in woven fiber glass mat so it is open pipe all the way through.
I mounted it all to one of the extra frame slots for adjusting the motor and made a clamp from the same tubing just in case i didnt like the performance and wanted to slip the open pipe back on.

Simple easy an the only cost was the mat i already had an i still would like some exhaust wrap.

It is as quite as any factory atv until under load at about half throttle.
Personally i feel it runs and performs way better than the open pipe that i did the spray paint tuning trick too.

I pull the yard wagon around loaded with kids so pointing the pipe down was crucial to me.

This design can be made to work with any size tubing, and fitted too just about any application as quite as you wanna make it.

Tubing can be cut many differnt ways an if you dont have one im sure you know someone with a welder.
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  #11  
Old 06-20-2019, 03:18 PM
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Quote:
Originally Posted by kayde View Post
Mufflers are only as tricky as you make them out too be.

Most times i find it too be more difficult too fit a item specifically made for another application onto another and have it look and function well...most times.

Heres the exhaust i built for the 12hp briggs on my t555.

After running it with just a short curved open pipe for some time i liked the performance but not the noise so i came up with a mini version of a glass pack.

The 1 3/8" goes straight through the 2 1/4" with about 100 cross drilled holes in it that is wrapped in woven fiber glass mat so it is open pipe all the way through.
I mounted it all to one of the extra frame slots for adjusting the motor and made a clamp from the same tubing just in case i didnt like the performance and wanted to slip the open pipe back on.

Simple easy an the only cost was the mat i already had an i still would like some exhaust wrap.

It is as quite as any factory atv until under load at about half throttle.
Personally i feel it runs and performs way better than the open pipe that i did the spray paint tuning trick too.

I pull the yard wagon around loaded with kids so pointing the pipe down was crucial to me.

This design can be made to work with any size tubing, and fitted too just about any application as quite as you wanna make it.

Tubing can be cut many differnt ways an if you dont have one im sure you know someone with a welder.
Good stuff didn't think about sliding a muffler over the pipe with holes. I've got all the fab tools necessary (tig and all) so I think I'll try this route...
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Old 06-20-2019, 09:44 PM
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In my experience RLV mufflers rob about 0.5 hp from a 212cc predator with stage 1 mods. Results may vary depending on what cam profile you choose. I don’t want to get into why and what but some cam profiles with a pipe that isn’t tuned could benefit from an RLV muffler and others perform worse. I have no testing to prove this, just what I have heard some people mention. The only testing with RLV I’ve done is stage 1, stage 3, and stage 4. They all had about 0.5 hp loss vs open header.

The Yamaha r1 mufflers are for a bike that revs over 10k rpm and makes 150 hp. They are probably overkill and I doubt would cause any losses like the RLV mufflers do.
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Old 07-01-2019, 09:38 PM
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Have you looked into SuperTrapp? For the 420cc, probably the 5S with tri-tube resonator and fewer discs (over the smaller 3S with more discs). It's not cheap, but if you put a dollar amount on your time, you might end up saving money by simply buying something (unless you already know exactly what to do and how to do it).

I found a video of the 5S taking a 105dB generator down to 90dB. Might not sound like a lot, but perceived loudness supposedly doubles with every 6dB, meaning a reduction of 15 dB is about 1/6 the loudness of no muffler. That said, my 196cc clone went from 82 dB idle @ 1' / 75 dB idle @ 15' / 88 dB full rev @ 1' with a stock muffler.....to only 2 dB louder across the board with a loop header and 3S SuperTrapp w/ Muffler and 3 discs. Seems to be about the same loudness to my ears though.

https://photos.app.goo.gl/PzjUt3fPNT1gpYx37

There are of course other things you can do, as in being aware that much of the perceived noise is what's being reflected off of other objects, and so pointing the exhaust into the sky to minimize that can help. Additionally, other noise comes from other parts of the engine, so having a sound deadening box /panels that absorb and/or redirect noise can help, if you can figure out how to do it.

There's lots to be found if you research how to quiet a generator.
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Old 11-08-2019, 03:26 PM
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Back from the dead....
A stock sport bike muffler would be perfect. I was looking at using a gen 1 Hayabusa 99-07 muffler on my golf cart swap.
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Old 11-08-2019, 06:38 PM
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It would be perfect but you haven't tried it?

A note on SuperTrapps: they are one of the few ways to get a universal USFS-approved spark arrester. The rub is that they don't flow well until you put a heap of discs on and that in turn makes them very loud.
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