Need Help .. Exhaust Question

Hey, I just bought a yz426 hybrid and it has a Supertrapp exhaust on it. I think this exhaust looks goofy because of the cap it has on the end. I took this cap off today to see how it would sound(i didnt want to run it very long because i was pretty sure with its removal that it would lean it out) It sounded really nice, but will this decrease my horsepower with not running the end cap and the rings? Or will it increase? I sure love the sound with out it on, but with it on it is still very very loud. (the sound doesnt seem to be muffled much even when it is on) So basically I am saying i like the new look...but should i chance it? It runs great as it is with a lot of power. I dont want to lose power or blow the engine up. Let me know your guys' thoughts...good idea/bad idea.

Thanks

Here is the endcap i removed.

[prepracing]

that end cap and disc are designed to tune your engine, I forget which way but its like less disc give more bottom end and more disc give more top end.....something like that. But running no cap disc should not hurt your engine in anyway, its just like running a normal open ended exhaust.

ya you are right...less rings more bottom end, more rings more top end. Do you think i will gain any power? Will i lose some bottom end? because bottom end is what i do not want to give up.

[pit/wood]

I have an sparks x-6 with the same type of spark-arrester.supertrapp has been around since the 60s I believe.there are several types of endcaps out there,you just have to look around.less rings/less noise=more backpressure=less high rpm airflow=less topend.More rings/more noise=more airflow at high rpms=more topend.More airflow needs more fuel,less airflow needs less fuel.If you want to run it open at home but still be able to close it up and take it where there are decibil requirments,just rejet for the number of discs you are using at the time.make a chart,12 discs=170 main jet for hittin the dunes,no discs=175 main for rippin around the house.I know appletree automotive up at silverlake uses supertrapps on alot of the sandrails they build.they have the discs in stock,along with different endcaps.Thats where I bought more discs and screws for mine.check your local sandmachine shop.

Im racing outdoors in iowa and there are no decible requirements. my hybrid has a 444cc bore kit. when i rejet it will i see more power than as of right now witht he endcap on?


p.s. what is your recemended jet size?

[bwamos]

Not necessiraly. The power curve will just shift ever so slightly, and perhaps give you a very tiny amount of additional HP (like 0.25hp, but you may loose some as well.. it's all about tuning. It will be a higher rpm power curve.. whereas an 8 disk setup will run a lower rpm power curve, giving you a little more torque at the bottom.

You're not going to really "feel" the difference up top. You'll probably just be louder. You also dont have any spark arresting device on there with the disks off.

[pit/wood]

you just have to work out the proper jetting for your machine.I dont have any experiance with that engine.As for what power increase you will see it is hard to tell.depends on the complete package and what you are trying to do with it.I would say that all jetting is application specific,any recomendations you get will only be ball-park a closest.IMO

I think since it is jetted fine right now and runs great that i just keep it the way it is. what do you think?

[2muchquad]

i have run a similar setup on my yz426,i had to go up 1 size on the main when i had no disc on,you'll also have to open your fuel screw a hald turn or so or it will pop on deceleration.the motor already has gobs of power so you wont notice any lowend loss really;) otherwise just leave it as is

i have run a similar setup on my yz426,i had to go up 1 size on the main when i had no disc on,you'll also have to open your fuel screw a hald turn or so or it will pop on deceleration.the motor already has gobs of power so you wont notice any lowend loss really otherwise just leave it as is


So you have ran this exhaust without the endcap and went up a main jet size and it ran alrite?