excessive exhaust noise

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excessive exhaust noise

Post by Malkypaul » Mon Jul 22, 2019 11:22 am

Hi Everybody
I do a lot of horse events on my MT350e and it has been commented that my bike is rather "noisy" is there any method of packing/repacking the silencer/muffler with more sound absorbing material, and what's in the silencer? I would like a drawing before I start cutting steel? can anyone help?
Also on the last MOT the rear brake light was reluctant to come on on I really really stomped on the foot brake this would probably lock up the back wheel (not ideal when you're green laneing is there a modification? I would like to fit a spring operated switch (as per honda) has anyone done this before, any pitfalls?
I also had to adjust the idle speed and mixture settings after a carb rebuild, I now notice that there is a lot of noise coming from the top of the engine, when I last had the cam belt cover off i noticed that the top pulley had come loose and had marked the inside of the cam belt cover, is there a permanent fix for this?
many thanks Mal Phillips
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Re: excessive exhaust noise

Post by Wirralman » Mon Jul 22, 2019 1:45 pm

Re silencer, some years ago Arceye cut a silencer, painted the various parts and posted the details on this forum. If you Search hard enough you may find his post

Have you got a standard silencer ? The OEM system is quite quiet , a small carb mod makes no difference in noise if you have the standard carb

Rear brake light- go through the system, strip and clean master cylinder and adjust correctly. Clean all electrical connections.

If you really want to soften the rear brake for off reading, fit a 500 rear wheel

Induction noise- has anyone in their 'wisdom' cut holes in the side of the airbox or cut the trumpets off ?

Noise from top of engine? Tappets?

Your cambelt pullies should have loctite to stop them backing off. Check the depth of the external teeth, if worn you need to renew. If the internal teeth are worn scrap it.If the spines themselves are excessively worn, that's a bigger job altogether

Permanent fix ? Maintain bike as per manual and they give trouble free service
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Re: excessive exhaust noise

Post by MTBrown » Mon Jul 22, 2019 1:52 pm

If you have the original silencer fitted then because it's for a military vehicle it was designed to be quiet. I would have thought it more likely that the silencer is blowing because it has a hole in it. Check around the bottom of the silencer near the front end where it normally rusts through first and also check under the front mounting bracket where mud usually collect and again where it can rust through. The silencer will have internal sound deadening baffles fitted but I doubt that these would fall apart and stop working due to rust before this happens to the outside of the silencer.

The standard back brake on my MT500's is a bit marginal and requires the spring that connects the switch to the brake pedal to be carefully adjusted. In the past I've had to bend the spring to shorten it to get the back brake working reliably.

You need to make sure the cam pulley splines are a tight fit on the end of the cam shaft before tightening up the bolt. If not, no amount of retaining fluid will keep it in place when the bolt is done up. If the splines are worn too much, you'll need to replace the pulley.
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Re: excessive exhaust noise

Post by Minter » Tue Jul 23, 2019 10:23 pm

Many 'standard' exhausts had big drills or punches made to the baffle plates inside via the silencer exit hole.. Made them noisier but no quicker!

Maybe you have one a these as a standard un molested silencer is quiet..
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Re: excessive exhaust noise

Post by mycatisbjork » Thu Dec 12, 2019 1:58 pm

I'm still looking at MT350s for sale. I want the exhaust to be as quiet as possible so would prefer the original system, but realise that's asking a lot. So how much louder are the stainless replacements please?
One of the reasons is I sometimes leave for work at 02.30 hrs from our quiet village and I much prefer to sneak out unnoticed and all stealthy like ;) plus as an occasional greenlaner I don't want to let the ramblers know I'm there till I'm on top of them. The conversations always go better if they haven't been wound up for 15 mins before you arrive. OK some of them are already in a wound up state but...
Any advice would be welcomed, thanks. Steve
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Re: excessive exhaust noise

Post by TJRL » Fri Dec 13, 2019 12:30 pm


I do not think the OEM stainless steel silencers are any different in noise to the plain steel ones. I too wanted to make my MTs quieter and for me the route was to get the Sportax Racing large bore end can but that was because my MTs were fitted with 500cc and 600cc engines.

I have a little used OEM stainless steel exhaust here in Reading taken off my 500cc bike (when I fitted the Sportax one) which you are welcome to try if you want, PM if interested.

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Re: excessive exhaust noise

Post by arceye » Fri Dec 13, 2019 3:07 pm

Most standard exhaust silencers will fit with a link pipe available from Sportax. So I would find an after market silencer with stated decibels and removable baffle. Or you can buy decibel eliminators separately. Although the more you restrict the exhaust gases it will effect the running and performance. Then you will need to adjust carb.
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