Is the ty a reed valve ? Surly exhaust resonance has no effect beyond that ?

Hi, guys,

here's the airbox I've built for my 250 twinshock (from fiberglass and epoxy resin). The filter comes from a cota 315 :

Very tidy, is it riveted & sealed to the inner guard like on the 250?

Thank's for the replies!

And the airboxes from post #5 and #17 look very professional.

@zuma:

Have you done a model first? (out of styrofoam f. e.?)

@jc2:

It was only a calculation for illustrating what is going one inside the intake, (idid mention this in my post).

This is and was far away from any calculation of the airbox size, the airbox size as rule of a thump should

be around 6 - 8 times of the capacity of the motor, More sience in english here: http://www.ten-tenths.com/forum/showthread.php?t=76195 if someone is interested.

Anyway:

I will as an first step clear out the standard airbox from the inside, then cladd the inside with deadening foam (5mm) to reduce roaring sound and the airfilterfoam will be imposed over the top, well we will see how good this work ...

If not as good as I aspect ... a custom made airfilter will be taken in consideration. the fiberglass variant is very nice and light ...

The engine can only draw as much air as it needs and if the stock airbox doesn't stop it drawing that air it's difficult to see how a bigger one will make any difference - like the 300 Fantic example, or my 320 Majesty?

Not really, there's a lot of science goes in to creating the right size still air box on a modern road bike. The principle is the same but at the power levels of a trials bike less noticeable except in extremes.

To add more oil to the fire. The size of the size of a air box is only as good as the air flow that it will let pass through it. The stock air box and carb to air box pipe are not the best. The intake pipe has to turn the flowing air 90

Hi everybody,

@tony27 :

my bike IS a 250...

@pschrauber :

yes, I've used styrofoam, shaped to use the maximum of space in the frame (with the possibility to remove the assembly airbox/inner guard without removing the shocks and/or the exhaust), then it has been recovered with fiber glass and epoxy resin, painted, sealed and riveted to the inner guard.

i've also made a heat shieldbetween airbox and exhaust :

Please note that i've got a dellorto (28) and a WES exhaust system. the genuine airbox was definitively too small for well breathing...

Edited April 5, 201313 yr by zuma

I think bestrcpilot comment is probably the one that is the most important, in it he mentioned '' flow bench '' now we are talking. Every time I make a change on my TY 250, WOW what an improvement !! But when I ride a stock one after a few hour on mine often I have to confess that my WOW was for the gallery.. A flow bench for the development and a dyno to confirm that it change the power band is the only way to go. And yes when you alter the intake, the carb as to be adjusted and you have to make sure your exhaust can take the increase flow.

Guy

Per recommendations from Bob at B&J Racing, I made my own fiberglass airbox so that I could use a K&N air filter. I have a 24mm Oko carb, and the throttle response is absolutely perfect! I'm still using the stock Yamaha boot between the carb and airbox. The round hole on the left side is so that I can get to the hose clamp. The reason for the angle that is cut on the left side is so that I could get the side panel to fit. Since the side panel covers that whole side of the airbox, I don't have to worry about water getting splashed in. This was my first ever attempt at making an airbox from scratch, and I know that it looks ugly, but it works.

Gary

Very well done Gary what is the model number of the K&N filter ? From experience an oiled K&N as better flow than oiled foan. I want one for my 250.

Guy

guy53,

Thanks for the complement. The part number I used is RD-0450, but it was too tall. I had to cut off the lower end cap, cut 25mm off of the filter, and then reglue the end cap back on. When I decided to make this airbox, I went to my local bike shop and they had this one in stock, so I built the airbox around it. There may be a filter available that may be a better fit, but I didn't have a problem modifying this one so that's what I did.

Gary