Carb jetting question

M

mathd

Member

Oct 11, 2008

208

0

• Mar 21, 2009

• #1

Ok,
There we go, i got a yz125 1998
Stock jetting is
MAIN...350
PILOT...45

And i have a spare yz125 2001 carb with stock jetting too but different
450 main
25 pilot

What happen if i take the jet(and needle) of the 2001 carb and set them to my 1998 carb, considering these are stock value same carb and same engine?

 

Last edited: Mar 21, 2009

J

_JOE_

~SPONSOR~

May 10, 2007

4,697

3

• Mar 21, 2009

• #2

Why in the heck would you want to do that?

 

I

inotocracy

Member

Apr 22, 2008

208

1

• Mar 21, 2009

• #3

^ Makes it go faster, like putting racing stripes on a car gives it 25 extra HP.

 

M

mathd

Member

Oct 11, 2008

208

0

• Mar 21, 2009

• Thread starter
• #4

_JOE_ said:

Why in the heck would you want to do that?

Click to expand...

Thats the same question i asked really.
If i do it, will it do change something or not. Its the same bike but 3 year newer i cant get it why the factory jetting is different. maby it is better or there is just no reason for the manufacturer and they did it anyhow.

 

J

_JOE_

~SPONSOR~

May 10, 2007

4,697

3

• Mar 21, 2009

• #5

If the carb bodies are exactly the same and you do as you say, it wouold be pretty stubborn to start if it would start at all and probly run like crap/foul plugs while riding. I can't really even believe you would consider this?!

 

2

2stroker_88

Member

Jan 3, 2009

11

0

• Mar 21, 2009

• #6

The carb on the 2001 model is different. A 38mm carb to be exact.

 

whenfoxforks-ruled

Old MX Racer

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Oct 19, 2006

8,129

2

Merrillville,Indiana

• Mar 21, 2009

• #7

2stroker_88 said:

The carb on the 2001 model is different. A 38mm carb to be exact.

Click to expand...

And the engine needs are different. Whats wrong with the stock carb? Replace the float valve and seat and jet that bike! You will not be able to want it faster on a track, maybe you faster?

 

M

mathd

Member

Oct 11, 2008

208

0

• Mar 21, 2009

• Thread starter
• #8

Thanks for the answer.
I said, IF i do it but didnt really consider doing. i just whanted to understand why/what was different.
Thanks you again i know these are different carb size/engine need.

 

R

rmc_olderthandirt

~SPONSOR~

Apr 18, 2006

1,533

8

• Mar 23, 2009

• #9

Being stock does not make the jetting "right". I suspect that Yamaha jets their bikes rich from the factory to cut down on engine failures. Taking the bike to a different altitude will usually require different jetting. Changing the pipe can often require different jetting.

There are ways to establish if your jetting is correct or not. Follow the procedure and do it right. A quick search on "jetting" on this message board will get you to some great links.

Rod