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What makes the factory bike sound?
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Posted by: Studboy---------------------
I've always wondered what makes the factory bikes sound the way they do.
Is it the fuel? The tuning? The silencers? Or just the fact that those guys hold them WFO the hold time 
?
Help me out here because I've been puzzled over how their bikes sound totally different than any others I've heard.
Now for the freestyle sound...we all know that they all just have a straight tube instead of a perforated one inside their silencers... 
Posted by: marcusgunby---------------------
I would love to know as well.
Posted by: ononewheel---------------------
i think its a combination of high performance ****e.
I.e race fuel, race porting, race exhaust, not sure what they do with silencer, etc?? would like to know for definate though.
Posted by: marcusgunby---------------------
I asked KP this question and he confirmed what ononewheel said, its mainly that they are tuned to work well at high rpms-not the lower ones the std ones run at, so the porting, pipe, reeds, head etc all work at higher revs, this gives them the distintive sound-also having sharp jetting helps alot.
Also he said those same engines that bark when you blip the throttle are horrible to ride, no roll on power or bottom end, just lots of top end and overrev.
Posted by: Studboy---------------------
Cool...so what theoretically would it take for someone to make a std. bike sound like that?
Mid/Top race porting, Mid/Top pipe, CF reeds, ignition?
What else?
Posted by: Studboy---------------------
Oh...and how much HP difference is there between a bike like that and a well tuned Std. bike on top?
Posted by: mxer842---------------------
Marcus, I always thought that the stock 250/450's already had close to enough peak power for those guys, and the engine work was usually based on making the powerband as broad as possible. The mechanics always say that 55hp is the threshold where more power hurts, most of the 450's and 250's are just 5 to 6 hp short of that and they focus more on broad and usable than sheer peak.
Maybe this all top nothing else type of powerband is common in the 125's but i just can't see K-dub always running 13k on his crf450.
Posted by: ononewheel---------------------
Stock bikes are no way near top performance available. There are so many better parts (forgive me for saying better as they are probably not) they are more powerfull should we say.
Also the parts that the pros have on their bike from my knowledge I'd say you ain't got a chance of getting any of them bits, or bits of that quality.
Pipes that you buy in shops etc are nothing on the direct race track parts you see the pros use.
PS Also parts can be custom I.E custom exhaust etc that you just wont be able to get.
Quote
Cool...so what theoretically would it take for someone to make a std. bike sound like that?
Mid/Top race porting, Mid/Top pipe, CF reeds, ignition?
EVERYTHING!!! A FAT BUNDLE OF CASH AND A 2 STROKE TUNER/ MECHANIC
PS Im just about to get a road bike I was going to get the Honda RVF 400 cc as I dont want anything bigger as they are to heavy and powerfull, this is 60BHP but I then see that the 2 stroke Aprilia 250 has got 70bhp and beats 400's standard and also I can work on it BONUS!!
Cant wait
PS thats 20 bhp standard more than my favourite 2 stroke crosser (I have not got a favourite four stroke cos I donr really like em) the honda CR500.
Looks like I is going to be doing rolling burnouts/ wheelies on road soon baby!!!
The insurance is going to be a bitch though something like 2000£ as im only 18.
Posted by: dubious---------------------
The distinct sound of a an all out race bike is due to the porting and pipe configuration.The resonance of a pipe designeed for high flow and top end power; scavenges the exhaust out of the cylinder at a higher rate at any rpm,thus the pipe does not provide enough resonance to prevent the exhaust from exiting into the pipe at low rpm, effectively and indirectly increasing duration. The mixture is still burning as it leaves the exhaust port
The porting will be modified and designed for more peak high rpm power too. This means more port duration and area, as well as pipe that will flow more at high rpm.
Think of a top fuel dragster with a huge cam and open exhaust. The idle is very rough (sounds wicked) and lumpy.
The same idea for a high HP peaky engine the pro MX would use.
The pro's for the most part keep the throttle pinned, and use the clutch to control traction, and power to the ground.Therefor the bike is kept on the pipe! or power curve(band).
Although these engines sound wicked, they are real handfull to ride and keep on the pipe. Not for novices and trailriders as they are dead on bottom end and hit abruptly. 
Posted by: Timr---------------------
What makes the factory bike sound?
The factory rider holding the throttle wide open!! 
Posted by: jumpingjoe628---------------------
I am fortunate enough to have a great mechanic blessed with the ability to build an engine like you guys are talking about. I have been told many times that my exhaust note resembles that of a factory bike. Basically he modified the intake port timing, transfer ports and a little on the exhaust side. That along with polishing the entire exhaust port with a 4mm spacer. A Vertex single ring race piston with bulsified teflon baked into the piston skirt and a ceramic coated head. The RAD3 intake valve and a pro-circut pipe and shorty silencer. The Nology Hotwire works good too. The jets are changed to match track and weather conditions so the engine performs the same every time. At the pace I ride at and the amount of time I put on it, I change the piston at least 3 times a year. To tell you the truth there is no economic reason for a weekend rider to do this to their bike for after like the 5th or 6th hard, long ride you can hear the exhaust note getting tamer and tamer. This type of engine has to be meticulously maintained to be at 100% for that factory sound. So what you get is a very abrupt powerband that screams to the heavens. This kind of power is not for a regular guy who wants a cool sounding bike at the local races, they will NOT like it on technical mx or sx tracks. Only at wide open sand pits will they be satisfied. It's funny when I let a novice or intermediate ride it at the track, they come in after a lap and say " I don't know how you ride this thing so fast without flipping over !!!"
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