Reduce Exhaust Noise 4rt

[munch]

dixie ,im afraid your wrong mate ,who said the restrictors are welded in?

[dixie]

munch

look at rabids picture

thats what i am going on,a small expansion box with a outlet pipe at 30?% to the main body and it looks to be welded in,cant remember from the dirt bike show,

have you seen an 07 in action??

[munch]

still the same restrictors ,front pipe ,middle box and end cap.

yes im sat looking at one now. the silencer is a big improvement ,a deeper sound

[mattylad]

Dixie, I do'nt think I made my point clear. It is no use producing a bike to comply with legislation which does not work for it's intended purpose. If it is necessary to remove restrictors to achieve full power then the design is rubbish! I maintain that Honda could and should do a better job at noise restriction for the lifetime of the bike not just to pass type approval. We will lose more land to noisy bikes than quite ones.

[baldilocks]

:agree: cant beleive the might of Honda cant make that thing quiet.

I like this idea that the restrictors dont need to be removed, if thats true :

1) why make them removable ?

2) why does everyone seem to do it ?

Edited December 22, 2006 by Baldilocks

[02-apr]

Whether removable or not surely the concept of washers stuffed up the pipe in a (vain) attempt to silence a bike belongs in the middle of the last century and not on a machine that is supposedly at the cutting edge of technology in 2007?

[munch]

what a load of B*****ks! all the bikes cheat by using smaller jets /restrictive front pipes etc ect , all the stuff put in a bag at pdi and never used again.

[rapid roy]

i

[baldilocks]

Yes munch I agree but you can put all the restrictors in a bag after pdi on any bike without waking up the local village 2 miles away ....except a 4rt. The point I was making is why is it so loud when its supposedly more advanced than anything else ???

I'd leave testicles, cream crackers and boll ox out of it as I dont think its relevant

[jezza]

Interesting thread. Just off at a slight tangent, when the first revamped modern 4-stroke motocrossers emerged, the Yamaha YZ400 followed by the likes of the Honda CRF, one of the big selling points was supposedly low emissions.

Turns out that they were also easier to ride for the average Joe compared to a fiery 2-stroke and so grew in popularity, that and the natural urge to want the 'latest thing'.

The bike buying public didnt seem to be put off by the extra cost/weight/complexity of rebuilds and they soon became the main stream new bike.

However, when fitted with an aftermarket silencer, to alledgedly unleash more power, boy were they loud.

LOUD=SOUND POLLUTION=COMPLAINTS=LOSS OF LAND FOR RIDING.

Hence the governing bodies ACU,FIM and the like are implementing a rolling sound reduction scheme, ACU 96Db for MX 2006&2007 reducing to 94Db for 2008 in line with FIM regs.

The reality here is that most MX riders on a standard production machine would reduce their lap times by holding the throttle on longer, using the brakes harder and increasing their fitness/skill levels. Forget the louder after market silencer.

Cant help but see some comparisons emerging here, as the trials manufacturers go 4-stroke, it is likely that sound issues will start to creep into trials as they have in motocross if the bikes are substantially louder or made louder than standard by their owners.

Although the bark of a 4-stroke is music to our ears, not everyone else would agree.

Time will tell I guess

[monty-python]

When the subject of noise & 4rt's first came up, shortly after release, i seem to remember that

Caroline sandiford had one noise tested by an ACU official, and it came in under the 95db limit.

Don't see what all the fuss is about, a 2 stroke, revving its t*ts off is probably louder!

I like the noise of them, and removal of the tailpipe restrictor doesn't make it as loud as you average 4t motocrosser.

[baldilocks]

Just an example and I'm not anti montesa , i'm giving thought to buying one for the ssdt.

I was having breakfast one morning at last years ssdt in the West End Hotel. As I watched the bikes going up the achintore road out of Fort William the only one I could hear through the closed window was the 4rt.

I dont doubt they pass the ACU test, its done just above tickover and the bike will have had the restrictors in. But wind the throttle up with the restrictors out and it is considerably louder than any other bike on the market. I dont think anyone disputes that ?

[neonsurge]

I dont doubt they pass the ACU test, its done just above tickover and the bike will have had the restrictors in. But wind the throttle up with the restrictors out and it is considerably louder than any other bike on the market. I dont think anyone disputes that ?

I HATE sitting behind a 4RT in a queue at a section for that very reason. They're almost inaudible at tickover then the rider starts to blip the throttle and BLAAAAAAAART!!!!!!

The problem with noise tests is that they only measure the volume at close distance and the real issue is that the lower-pitched exhaust note of a 4-stroke travels much further than 2-stroke engine noise due to the longer wavelength. The fact that the 4RT has passed all ACU noise tests means absolutely nothing and does not acknowlege or address the real problem of perceived noise levels when the listener is physically distant.

The Beta 270 is considered to be a "loud" bike but put it next to a 4RT and rev both bikes' nuts off and although many people will say that the Beta is louder (which it may well be perceived to be due to the higher pitch cutting through the lower frequencies coming from the 4RT), it'll be the 4RT not the Beta that you'll hear from half a mile away. THAT'S the real problem.

Ye cannae change the laws of physics.

[dixie]

same old rubbish this year then...

just go and listen to a pre 65 trials bike if you want to hear loud.

and why is it the observers cant hear my 4rt waiting at there section???i am forever having to shout.

and the reply is sorry mate did not hear you.

most trials i go to you could let a bomb off and no one would hear it.