Derestricted jetting

Zack Guiliano /

On tomos mopeds when you remove the airbox their is a tube restrictor on the intake. If i file it off to get more airflow and more power will i have to change jetting and if so will i have to get a higher or lower jet.

Re: Derestricted jetting

Do you have good reason to focus on intake and jetting?

Increasing the potential flow rate of the fuel/air mix will not increase power unless your engine can trap and burn a larger amount of it than it did before.

So, unless the engine is now fuel-starved, the change will have no positive effect on power output.

The trick is to find out what will make the engine trap and burn more fuel, not to simply make more fuel available.

Lets say there is a lot of exhaust gasses in the combustion chamber when the exhaust port closes. These gasses don't burn and simply occupy space that could be filled with fresh fuel mix. How can you get these dead exhaust gasses out? Modified porting? A better tuned expansion chamber?

Re: Derestricted jetting

Zack Guiliano /

i jus wanna do it for more power or speed, its restrictive.

Re: Derestricted jetting

Zack Guiliano /

you do know im not talking about upping the jet jus for the sake of gettin more fuel but because im going to take off the restrictor plate in the airbox right? it has a 12mm tube for the air to enter but the hole has a plastic plate restricting air flow, so if i remove it will i have to adjust jetting is what im asking.

i know if i jus up the jet it wont make it go faster.

Re: Derestricted jetting

sure.. it's "restrictive". There is something on every engine that is restrictive. The fastest engine in the world is restricted somehow or it would be even faster.

The question is this: Right now, on your engine, is that intake restriction preventing higher power or is something else preventing more power?

Go ahead and remove the intake restriction, test the power output, try rejetting if you think that may be a factor. Find out if that modification helps or not.

This is the soul of performance tuning.. think and study and calculate and experiment. Sometimes you are right and sometimes you are wrong.. but you always learn.

Re: Derestricted jetting

Yes, You MUST upjet (bigger)... But it wont do you any good unless you at least buy a preformance exahust.

Alan

Re: Derestricted jetting

Stefan Chivu /

See attach.

This is a drawing of my air filter, i'll probably post tomorrow a photo, I think it's restricting the air flow, because the diameter of the tube is about 1 or 2cm.

1087586691_airfilter01.jpg

Re: Derestricted jetting

Stefan Chivu /

This is my exhaust, it already gave me a 5kph boost, without rejetting, so a larger main jet and a bigger air flow will help in my case ?

1087587440_10027007.jpg

Re: Derestricted jetting

Zack Guiliano /

definately styx. thats a crazy exhaust whered you get it?

Re: Derestricted jetting

Danny Emerson /

on the older tomos peds DO NOT DRILL OUT THE THE JET SCREW my dumb@ss did that and am still currently paying for it.......just a helpful hint dont try to give it more fuel the mixture is set perfectly stock...any attempt to give it more power by messing with the jets will kill it

Re: Derestricted jetting

Hmmm... Looks like there would be no backpressure... Not good.

Alan

Re: Derestricted jetting

That exhaust is not tuned in any way from the looks of it. So any performance gain from it would only be from the increased amount of flow it allows. And Alan's right, no back pressure so low end would probably take a hit. I wonder if it was designed for a four-stroke?

Tuned pipes use reflected pressure waves to act as a type of exhaust valve. You would get the same benefit from this pipe as running no exhaust at all. And watch that you don't seize your engine with it.

Re: Derestricted jetting

Stefan Chivu /

It's not a performance exhaust (I think), but It's not like running without an exhaust, because I think most of you know the sound made by a moped running only with the exhaust pipe, and with this exhaust I get a cool, relative silent, low pitched sound like one of those harley, and I've done some tweaking inside the exhaust too...please see the attachment.

1087635150_myexhaust01.jpg

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