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montesamadness

MH349 Noisy WES Exhaust- Is This Normal?!

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Better do some proper welding, very easy work with MIG or TIG equipment. If you try to open and pack the WES box, of course you need a TIG. The rivet and silicon solution could work on any box, but is a more provisional repair (if I may say so...).

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Yes, Sir! But welding is nice therapy. You feel better and the bike look better afterwards, too. Then, the next re-packing is easy using the old welds as a template when cutting the box open. TIG re-welding, a little grinding and it's almost invisible....

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Right then, time for an update. Having spent several hours performing keyhole surgery on the front pipe, pulling the old wire wool out and replacing it with glass fibre wool then patching it back up I can report a small improvement....but not much. In desperation I wrapped the front box in exhaust wrap externally as well to try and add a bit more sound insulation. I also re-packed the (brand new) WES rear silencer. Overall, this catalogue of exhaust surgery has quietened the bike down marginally but I'm still not totally happy.

Turbo, you're right - TIG would have been nice and neat. Only problem is I haven't got a TIG welder. And my MIG welding usually ends up looking like pigeon $hit! So I went for the easy (and easily removed) option and riveted the cover plate on with lots of messy silicone - no leaks there!

Next stage is I'm going to try and knock up some sort of baffle insert (a bit like the FMF quiet inserts for four-strokes) and stuff that in the end of the pipe. Anyone got any thoughts / experience of doing this?

Thanks everyone for your help so far....

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OK I'm going to ask a silly question. Is it possible that your other big 2 strokes have been water cooled? The 348/349 motor is well-known for having significant piston rattle and if you are not used to the sound of a noisy air-cooled motor the noise you are having trouble eliminating might be piston noise (not being deadened by the water jacket)

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In answer to your question about the tailpipe insert. Don't do anything to the exhaust that will change the backpressure because it is fairly critical for how well the motor runs. Too little and the low end response will be poor. Too much and the motor may develop detonation problems when it is hot

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Feetup - interesting point- thank you. Yes all my previous strokers have been water-cooled. One thing I've noticed though, is that the motor is actually quite quiet if I put a glove over the tailpipe, which suggests that my re-packing of the front box may have had more of an effect than I initially thought. Not sure the glove is a permanent solution though!

Good point about the back-pressure. I'll have a bit more of a tinker with the WES tailpipe, but I won't do anything too drastic. If I can't get satisfactory results then I might go for a secondhand original tailpipe as Cleanorbust previously suggested, although the bike already owes me nearly 500 quid in parts so I don't want to just keep chucking money at it.

One thing I hadn't considered is how two-stroke noise travels through the air. Although they seem very noisy close up, the noise never seems to travel as far as four-stroke noise. The nearest house to where I ride is a good 300 yards away, and the nearest footpath is approx 80 yards away so I'm hoping that the (marginal) success that I've had in quietening it down might be enough.

I'm wondering if I'm suffering from noise paranoia!

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I'm like that with the noise level too. I've a nice practice area at home but there are houses within 50 metres, so I have been quite persistent in getting my bikes as quiet as I can so I can practice without annoying people. One of my bikes is a Cota 348 with standard (repacked) exhaust system and it is blissfully quiet to ride. Late model Bultaco trials bikes are also amazingly quiet with the standard exhaust. With a bit of work you can even make Japanese two stroke trials bikes quiet.

One thing I noticed about a WES muffler I have on a TY250 Yamaha with standard main chamber. It is nice and quiet both through the walls and at the muffler exit, but if I put the same WES end-muffler on my KT250 (also with standard main chamber), there is a lot of noise at the exhaust exit of the KT. Because of this I have re-modelled the internals of the standard KT250 end mufler to make it quiet enough to ride at home (and so I can hear the whining primary drive gears better)

One of my TY175s is a Whitehawk with a standard Yamaha front exhaust section and the end muffler is from the super-quiet TY175JC that was fully road registerable after the noise-limiting Aussie vehicle design standards came out in 1976. The TY175JC also had a rubber snorkel on the inlet of the airbox which further quietens this bike. The engine in this bike has just been restored so there is no mechanical noise to speak of and overall it is a very stealthy bike.

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Feetupfun,

Is the Wes muffler on your TY250 a good deal quieter than the standard TY muffler? 

I have the same issues  when I practice in my yard and the TY is louder than my Sherpa T 199A.I did cook the TY main pipe last year on the burn pile which did seem to make it run a little better,but it does seem a bit louder now.

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Cheers Feetupfun

You sound like you've got a lot of bikes....excellent work!

You say you re-modelled the internals of the KT250 exhaust to make it quieter- what specifically did you do to achieve this?

Interesting you say about you using the TY175JC silencer. I did wonder about trying to put a KTM 2-stroke enduro silencer on my Cota.These are really quiet, and seem to sell for next to nothing on ebay, unlike the standard Cota 349 silencers which seem to cost a fortune.

 

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9 hours ago, scot taco said:

Feetupfun,

Is the Wes muffler on your TY250 a good deal quieter than the standard TY muffler? 

I have the same issues  when I practice in my yard and the TY is louder than my Sherpa T 199A.I did cook the TY main pipe last year on the burn pile which did seem to make it run a little better,but it does seem a bit louder now.

Yes the WES is noticably quieter than the standard TY250 muffler, and it is a much more pleasant tone as well to many people's ears.

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8 hours ago, montesamadness said:

Cheers Feetupfun

You sound like you've got a lot of bikes....excellent work!

You say you re-modelled the internals of the KT250 exhaust to make it quieter- what specifically did you do to achieve this?

Interesting you say about you using the TY175JC silencer. I did wonder about trying to put a KTM 2-stroke enduro silencer on my Cota.These are really quiet, and seem to sell for next to nothing on ebay, unlike the standard Cota 349 silencers which seem to cost a fortune.

 

The KT end muffler now has a perforated tube that runs the full length of the casing with loose wool packing attached to the tube with steel wire and has a long radius 90 degree bend of the same diameter as the perforated tube welded to the outlet, pointing downwards. The perforated tube was cut from a 2 stroke go kart muffler core.

Edited by feetupfun

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Thanks David,

I might have to look into one of those.A more pleasant tone would be an added benefit.The exhaust note doesn,t sound near as good as the Sherpa T.

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Some of the ringy dings of air cooled two strokes can also be from the barrel n head fins. Are all the rubber blocks in between the fins still there 

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After a bit more tinkering over the weekend, I thought I'd give you all an update, as I'm sure you've been waiting excitedly for the next installment....or not!

I took a bit of inspiration from your KT silencer mods Feetupfun, and had a nose inside the WES tailpipe. I found that the part of the silencer that has packing in it only extends about two thirds of the full length of the tailpipe. The first third (furthest away from the tailpipe exit) is an empty chamber and the only silencing in this section is the fact that the inlet to the chamber is at the bottom, and the outlet (the perforated tube that runs through the rest of the silencer) is in the middle. In other words, the inlet and outlet don't line up which (I assume) is intended to block the passage of sound.

As an expirement, I extended the perforated tube all the way through the silencer and into this first chamber also. I then re-packed the main chamber with silencer packing, but much tighter.

Amazingly this inspired engineering (or bodging as most people would call it) seems to have worked, and the bike is a fair bit quieter. I was riding with a guy on a TY250 mono at the weekend and my Montesa didn't seem any noisier than that. I don't know if that's a particularly good benchmark, but it's good enough for now.

Moving foward, I might try angling the tailpipe downwards and maybe even putting exhaust wrap round the silencer if I'm really desperate (to look ridiculous), but now it's time to move onto the next job....fork oil seals.

Just a final note to say a massive THANK YOU to everyone who has contributed in trying to help with my little silencing challenge. I'm sure I'll be back with another head scratcher soon....!

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