Making my 4 wheeler quieter

[Blr243]

16 yrs old 250 cc runs very well ., nothing wrong with the existing muffler. I have never thought of it as noisy. But I have recently discovered I can make it quieter. Do I replace the muffler , or add a muffler silencer or have two mufflers one after the other. Or add a big car muffler. I’m handy with metal work, sheet bending and welding I don’t Care what it costs I don’t care what it looks like. I just want my thermal hunting at night to be more sneaky .....calling all rev heads for advice.....what would you do ? .......nb ..... this is not for poaching I just want to be able to see animals in my binos before they can hear me. Then partially approach on bike , then final stalk on foot

[Tiger650]

Air cooled ?
If so you could look at additional fin blocks, these are basically hard plastic blocks fitted tight between cooling fins to dampen mechanical noise, used to see them on aircooled Yamaha 2 strokes and such.
Exhausts are engineering for Engineers and Juju for ordinary blokes, high frequency can be attenuated fairly easily with straight through glass pack mufflers [hot dogs] but low frequency needs the science.
Wizardry apparently involves a dead end tee off the pipe of such a length that energy pulse diverted down that branch bounces back out of phase with natural exhaust frequency, ie rebounds back into the main exhaust between exhaust gas discharge cycles.
Good theory for diesel generators and such that run at constant RPMs but NFI if it would work through the rev range of your engine.
Silicone tube [high quality engine coolant hose] will handle hot exhaust after a muffler [not straight off the exhaust port] and may deaden things.
You could try sparging water spray into the exhaust, water absorbs heat [energy] as it vapourises.
Or you could rat a muffler off a small late model car at the Wreckers and try adding that, may work miracles and may not.
I was looking at quietening a 5.5 KVA diesel genny a few years back, Exhaust Control Industries in Melbourne quoted $1300.00 odd for a super critical residential muffler, that for a 190cc Yanmar.

[ZaineB]

turn it into a tesla lol

[Blr243]

Yes tiger it’s air cooled. And thanks for the ideas, very technicaj info/ knowledge

[Oldbloke]

I think an additional sausage dog might be a good option.
Too much back pressure will likely lower performance.

[Skinna]

Im tempted to say leave it switched off & push it...but that would be silly because your huffing puffing & swearing at me would probably make more noise than the bike...

[Oldbloke]

Push bike.

[Blr243]

I have condsidered an electric bike or tricycle , I once had a pushbike on top of my Ute as I sat on the edge of a paddock thermal scanning .......normally I would just walk from there once a mob was spotted. ..the idea was if I spotted A mob in a different location ( wind direction wise) I could jump on the bike and madly pedal along the track and cover ground so much quicker with less effort. It worked once so the idea was not a complete failure ...

[brinny]

My new Polaris buggy is super noisey, so i did this to try and quieten it down....
I added a baffled hot dog to it....does cut the bark down a bit but still up there with being to loud....

[GQshayne]

I have given this a lot of thought over the years. In my experience, the worst culprits are 4 stroke engines, either single or twin cylinder. The obvious example is that a bike or quad is noisier than a 4wd. We have all experienced that. Without question, in my experience a nicely muffled two stroke engine is much better for hunting.

Out in the field I have seen numerous instances of a two stroke engine that I could see approaching but not hear, and yet a four stroke was easily heard. As mentioned above, it is the frequency of the sound that makes the difference. A four stroke single or twin is hard to make quiet.

I have been hunting with a mate on a YZ125, and another on an XR Honda. The difference in noise heard when you cannot see them was simply amazing. The Honda was easy to pinpoint from somewhere out of sight. The YZ could be coming right at you and yet you could not hear it.

As for the 4 stroke problem, on a twin I would be looking at the collector to try and change the phasing. Forget performance if you are more concerned with noise. If it is a single, which as a 250 is likely, then a bigger muffler will help, but it will be an uphill battle I think.

[Blr243]

Lots of research I think, and listening to different peoples opinions , hopefully at the end of the day I’ll b able to make a successful decision

[Oldbloke]

Come to think of it, postie bikes are pretty quiet. Four stroke I think?

[on_one_wheel]

Come to think of it, postie bikes are pretty quiet. Four stroke I think?

Honda CT 110,

[cz515]

When I was younger, some adventurous people with very loud exhausts would get EPA noise notices.

The options were go back to stock muffler, put an additional hotdog muffler or stuff the exhaust with steel wool. All worked pretty well to bring noise back to legal levels.

Let me know if the steel wool works on your 250cc single cylinder

[8x57]

I put a silent rider on my Yamaha kodiak 450 reasonable easy to attach, seems to be working well able to lurk up a bit closer to the beasties

[bigpete]

Weld a washer over the end

[Oldbloke]

Weld a washer over the end

That will help. Worth a try but increasing back pressure will likely effect performance. How much? Who knows.

[womble]

A new 250 street bike is pretty quiet. Has to be for them to sell them and meet epa standards. Bikes like 250 ninjas, those green ones, Kawasaki’s. I think they’re a single.
So all the kids who buy them, learner riders, take the original muffler of and put something noisier on there. Little gayass fake carbon fibre wrapped cans.
I’d be looking for the original mufflers on late model 250-500 street bikes. Gumtree perhaps. They won’t be expensive because who buys them. Factory, stock, oem muffler.
(This is going to look totally ridiculous btw and we will need photos)

That would be a dramatic improvement for a 16 year old thumper, don’t think theres much else you can do.
Possibly wrap manifold and pipe in exhaust heat wrap. Some guys with big air cooled cruisers do that to stop burning their legs because of course they ride in shorts.
I’m thinking in your area that would trap damp and cause rust pretty quickly though.

[womble]

Something like this https://www.gumtree.com.au/s-ad/boronia-heights/motorcycle-scooter-parts/honda-2012-250-factory-muffler-789-new-my-good-2nd-hand-one-now-75/1271437307

Offer him 20 bucks. Not like anyone is going to buy it ever.

[bigpete]

Weld a washer over the end

That will help. Worth a try but increasing back pressure will likely effect performance. How much? Who knows.

It DOES work....

[Blr243]

Big Pete do u mean fit a washer with smaller diameter than existing hole at end of my exhaust?

[Tiger650]

Do not like the washer idea, excessive back pressure is never a good thing, can coke up plugs and also cause hot running.

[Die Judicii]

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I made my own 2nd muffler as per pics,, and added it to the existing one.
It is packed from one end to the other with fine stainless steel mesh, that is folded zig zag fashion and slid/pushed into the RHS.
Being a 650 yamaha Grizzly it originally had quite a thumping sound to it,,, but now is much quieter.
Added benefit is definitely no chance of a spark to start a bushfire anymore.

[Blr243]

Dj. Steel rhs 75 by 75. 89 by 89. Or 100 by 100 ?

[Die Judicii]

Dj. Steel rhs 75 by 75. 89 by 89. Or 100 by 100 ?

Doesn't really matter what size Mate.
Whatever you can get hold of,,,, and find room for it to fit etc.
The bigger and longer, and number of baffles or (folds) the better.
I think by memory I squeezed about 4 or 5 meters of mesh into the RHS.

[Die Judicii]

Dj. Steel rhs 75 by 75. 89 by 89. Or 100 by 100 ?

Doesn't really matter what size Mate.
Whatever you can get hold of,,,, and find room for it to fit etc.
The bigger and longer, and number of baffles or (folds) the better.
I think by memory I squeezed about 4 or 5 meters of mesh into the RHS.

[Die Judicii]

Mind,,,,,,,,, if you over do it with baffles etc and create too much back pressure,,, you'll soon know about it.

[bigpete]

Big Pete do u mean fit a washer with smaller diameter than existing hole at end of my exhaust?

Yup

[Oldbloke]

The idea is to:
Cool & slow down the exhaust

Giving it a box to expand in and forcing it to change direction helps to achieve that. Baffles force it to change direction, therefore slow down.

[Oldbloke]

You get the idea.

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