will this work?

[JKWGA400EX]

i have a fmf power bomb header,and i made a strait pipe that slips right on to the header.now,would it harm the engine if i ran the strait pipe and rejetted it so it would run nice,or would it ruin the engine,also would i get a bit more power,or just have a VERY VERY loud bike?

-jared

[Quadster450]

that would be one loud mutha! :eek2:
i've heard bad things about doing this on a 4 stroke - valve problems, needing some back pressure to run good, etc.

[JKWGA400EX]

does anyone else have more info?there's something i dont get,why do they call it back pressure when u can see right through the muffler,or does it actually give it back pressure?plus the fmf header thats on there has a part 2-3 in. long and about 1/4 thicker piece of pipe on the header,and it has a little mesh(just like the end muffler)thats suppossed to make it quiter.do u think that could give a little back pressure?



-jared

[Quadster450]

okay,
This is what happens on the exhaust stroke:
- piston travel BDC to TDC
- exhaust valve opens
- intake valve remains closed
- hot exhaust forced past open exhaust valve.
what is called back pressure, is needed to create a small amount of vacuum that helps pull the exhaust out of the cylinder in preparation for the next stroke, or intake. This needs to happen as fast as possible for best performance.
I'm not familiar with the power bomb but the mesh you describe may provide a bit of resistance which could provide a bit or back pressure....

[911]

i don't think u should ever do this for noise reasons only, but, have u ever seen the TC racing muffler for the Yam. it is 6 in long and has like a 3in id. it does nothin but look like somthing is there:D so for a drag quad i think it is feasable:devil:

[JKWGA400EX]

so u dont think it would harm my engine?im not woried about noise that much,ive tried it before with the strait,but i didnt have it jetted right and it boged down easy.so u think it will give it more power?and no i havnt seen that tc pipe,anyone have a pic they could post?

-jared

[JKWGA400EX]

anyone,pics,links or something

-jared

[Quadster450]

http://www.tcracingengines.com/

[JKWGA400EX]

so what should i do?put the strait on,rejet,run it for drag racin,and i should be fine?or will it harm my motor?


-jared

[GPracer2500]

I've never seen anything credible that suggests that staight pipes will burn up your valves or otherwise harm the engine. My guess is that it's an old wives tale started from people cutting up their exhausts causing them to run lean. Running too lean WILL cause burned up engines, but then it's the leanness that's the problem not the exhaust.

Although, I sorta doubt that staight pipes are gonna do any better than a good (non quit cored, non spark arrested) silencer [shrug]. It'll just be obnoxiously loud.

[JKWGA400EX]

so id need to go richer right?ive never rejetted before,so ill probabaly get my friend to help me.any tips to rejet?does anyone know which plastics i have to take off to rejet?i can take the front plastics off because the left hand bolt(that goes into the gas tank)the thread(nut washer,whatever u call it),if u try to loosen the bolt it just turns over with the bolt(the nut thats made in the gas tank)hope that makes sense,if u have info on how to get the bolt out the gas tank id apreciate it.


thanks,
jared

[400exrider707]

The bolt in the gas tank is a big problem and your pretty much stuck with it from what I've seen, I too have one. As far as the exhaust, you will not burn up a valve by doing this, but your probably going to lose power, and it will sound like crap, I have no respect for anyone who tries to make a straight pipe for their quad. Read the posts here.


Originally posted by Quadster450
okay,

what is called back pressure, is needed to create a small amount of vacuum that helps pull the exhaust out of the cylinder in preparation for the next stroke, or intake. This needs to happen as fast as possible for best performance.


Your substantially decreasing your back-pressure. What size tubing are you planning on using here? Those TC pipes although rediculously short, still offer back pressure. I know you can look straight through, but there is the mesh in there with packing. It still offers backpressure. If you have hardly any backpressure you will lose power. Save your money and your ears, and buy an aftermarket exhaust. I've see a few used slip-ons right here on this site in the for sale section go for about $100.

[Flodies400ex]

the friend of mine put my old kasea 250 big gun pipe on the stock header of the 450R and it ran alright but a little loud tho

[JKWGA400EX]

look at my sig.i already have a different exhaust,i would just be cirious,because i love it when its LOUD,the louder the better,sometimes anyway,lol.i already made the pipe it slips right into my fmf header.anyway lets see what i do.

-jared

[TMSmx47]

Significant loss in power! no matter what you do.. jetting or whatever! it needs the muff and back pressure! 2-strokes a different story. that would be faster!

The power bomb on your FMF is called a resonador(cant spell) like on a car. Same thing. Does the same also. it creates a form of resistance to help that back pressure speed up. It helps create that vaccum quicker so the exhaust theroreticaly doesn't have to travel the extra 12inches for that back pressured vaccum to occur. I'm not sure you'd really feel a difference though. If you did, everyone else would be doin the same. Now as for the FMF MEGA bomb, that chit is big as h*ll if you've ever seen that one. Still dont see the reason!

[Thumper13]

you dont need to remove any plastic or even remove carb to rejet all you have to do is at the bottom of the float bowl is a 17mm nut/bolt, reemove it and take a 6mm socket and remove jet