carb comparison question


6 replies to this topic
  • mxmaddman

Posted November 03, 2010 - 05:37 PM

#1

I have an 04 atv carb and a 07 dirt bike carb.

why does the 04 have some type of pilot diaphragm and the 07 doesn't?

Is the 04 supposed to have a hot start plunger? It just has a cap with nothing in the hot start hole.

Its running lean and i found a missing o ring in the diaphragm and no hot start plunger in the hole. I'm thinking its def the problem.

  • grayracer513

Posted November 03, 2010 - 06:27 PM

#2

Yes, there's supposed to be a hot start plunger, and if it's missing, you'll have a huge air leak.

The pilot diaphragm is the same as that on a WR450 carb. It's part of the air cut valve, which is an element of the air injection system.

  • mxmaddman

Posted November 03, 2010 - 08:26 PM

#3

Yes, there's supposed to be a hot start plunger, and if it's missing, you'll have a huge air leak.

The pilot diaphragm is the same as that on a WR450 carb. It's part of the air cut valve, which is an element of the air injection system.


I figured you would know if anyone would. Does the air valve need to be on the carb or can it be removed and blocked off?

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • grayracer513

Posted November 04, 2010 - 06:19 AM

#4

It can be, but there is some compensation that must be made for its absence, and I'm not clear on the details. In a YZ450, air is fed to the pilot circuit through a single jet and passage. In a WR/YFZ, the air passage is forked, with one side bringing air in through a pilot air jet, and the other through the ACV. When the ACV is blocked off, the PAJ needs to be larger. See the WR450 forum for more info.

  • mxmaddman

Posted November 04, 2010 - 07:50 AM

#5

OK thanks gray, Apparently you can flip the diaphragm and block the passage then add a larger paj or maybe smaller PJ.

I know the standard yz passage pulls from the paj, do you know where the second passage draws its air from?

  • grayracer513

Posted November 04, 2010 - 08:13 AM

#6

I could trace it if I had a carb in my hands, but no, I don't.

  • mxmaddman

Posted November 04, 2010 - 02:46 PM

#7

ok, thanks gray.. It looks like it might go up into the top of the carb above the slide...





Related Content

Forums
Photo

Chubby dad, looking at bikes , First trip to the orange/black forum ! by Slow_ride


Dirt Bike   Make / Model Specific   KTM   250-530 EXC/MXC/SXC/XC-W/XCR-W (4-Strokes)
  • Hot  28 replies
Forums
Photo

YZ450F 03 Sparks driving me crazy by SirAttard


Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 5 replies
Forums
Photo

Is it worth it? (Cam and High compression piston) by macgi77


Dirt Bike   Make / Model Specific   Honda   CRF 150/230 F/L
  • Hot  36 replies
Forums
Photo

Snake pit oct 30th by The Anvil


Dirt Bike   Dirt Bike Regional Discussion   California
  • Hot  293 replies
Forums
Photo

2016 YZ450 by CaptainKnobby


Dirt Bike   Dirt Bike Technical Forums   Suspension
  • Hot  59 replies
 
x

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.