One of the best free mods you can do.

[mjc85]

Port out the carby end of your intake manifold to make it the same size as the carby outlet. The manifold is a few mm smaller all the way around which in turn increases the amount of turbulence, as the air hits this lip of the manifold it bounces back towards the incoming air creating turbulence and disrupts airflow.

Use a rounded file until you get the right size and then sand it smooth, i started with 80 grit paper and went right up to 2000 grit for a smooth finish.

I was riding on tuesday at a place near where i live and there was 3 other standard orion's, a couple of times they tried to race me and my bike pulled away steadily from them along the straights, i also have a uni filter.

 

[Dilox-125cc]

nice m8 nice i might try that thanks for that

 

[mjc85]

There was also a provert and a thumpstar that turned up later, they were hardly faster along the straights, just a little but then on the bumps they took off obviously because they have much better suspension.

 

[user 2364]

t

 

[mjc85]

hey mate so what your saying is: open up the part of the manifold that connects with the air filter? does it give alot of top end speed? what mods have you done to ur bike compared to the standard orions you raced? and were u roughly the same wieght

Take the carby and manifold off your motor, then take the carby off the manifold and remember which way it goes back on as the two flanges on the manifold are different.

Then take the plastic spacer that has the seal on it (the one inbetween the carb and manifold and line the holes up with the holes on the carby end of the manifold and get a pencil and draw a circle around the inside of that. This is where you wanna file the manifold out to (this line). Then sand smooth once you have filed out to this point.

 

[RabidDog12345]

thanks for that tip, im gunna do that tomorrow when i get home from work, have you taken the choke out aswell?

 

[user 2364]

t

 

[mjc85]

does it give alot of top end speed? what mods have you done to ur bike compared to the standard orions you raced? and were u roughly the same wieght

Just better acceleration. The only other mod i have done is a uni filter. I would've been heavier, im 20 years old and 83kg 6'2". The guys that were there would've been 15-16 yo and like 60-65kg i would say.

ok so the plastic spacer that is between the manifold and the engine is a smaller hole than the manifold, so i sand it back until it is the same size?

No, the plastic spacer is the same size as the carby outlet, you are filing the manifold out to be the same size as the spacer and the carby.

have you taken the choke out aswell?

Nope, i don't see how this would improve performance on a slide carburettor such as the 25mm mikuni, i can see how it works on the butterfly choke carbys though.

 

[mjc85]

Here is a diagram, sorry for my crap drawing.

 

[user 2364]

t

 

[LOL]

Here is a diagram, sorry for my crap drawing.

i like the look of your engine :lol: , to be honest though, i did do this mod aswell, and yes its well worth it, just make sure you clean up the ports otherwise you will have well crap :roll: in your engine, i did it to the other end aswell, i know it wouldn't have done anything but yeah....hey does anyone know, will i get any performance if i removed the plastic spacer?

 

[mjc85]

Make sure you use a round file and don't file to much. You could file the engine side as well, but i'm not sure it will make much a difference.

I am going to get rid of this standard manifold soon anyway, but this is a good mod if you don't have money or resources make a new manifold.

For the new manifold i am going to cut the flanges off the standard manifold and get a 1 inch 90 degree mandrel bend and weld the flanges onto it. A mandrel bend pipe is a pipe that does not change size throughout the bend unlike the standard one which gets smaller in the middle by a fraction.

 

[Dilox-125cc]

awsome thanks for that im going to remove the choke and do that naifold thing tomoz awsome great good work

 

[user 2364]

t

 

[RabidDog12345]

i was thinking these mikuni were the butterfly choke... but they arnt so if you have the mikuni 25mm you cant remove the choke hey MJ did you cut the gasket to match the size of the engine because on mine the gasket on the engine head... is actually about 4 mm smaller than the engine hole.

 

[user 2364]

t

 

[Dirt Bikez & Pocket B]

hey guys, instead of modyfing the spacer y dont you just remove it completly i have done it after i saw that no-fear did it on his thump, better throttle response and acceleration, verry good cheap mod to do 8)

 

[mjc85]

hey guys, instead of modyfing the spacer y dont you just remove it completly i have done it after i saw that no-fear did it on his thump, better throttle response and acceleration, verry good cheap mod to do 8)

We aren't modifying the spacer, but the carburettor end of the intake manifold to make it the same size as the carby. When you removed the spacer did you just make a gasket yourself ?

 

[user 2364]

t

 

[Dirt Bikez & Pocket B]

yes i made a gasket out of policarbonate (SOFT PLASTIC) i dont know if thats how you spell it. but yeh its been all good since then. 8)