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ACV - Octopus - 99 - 00 - Wha/&ç!

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Before I start....I have 99 WR400. I am playing with jetting and am close, but not yet there.

My problem (one of them anyway): turning the fuel screw has no effect at all on anything !!!

It was suggested that I do the ACV air cut valve mod to regain 'control' of the pilot jet screw as the ACV is constantly adjusting the mixture.

This I did. NO EFFECT.

Hmmm.... then I realised the ACV mod is for model years 2000 and upwards....yes ?? My understanding is that the 2000 + models do not have the OCTOPUS. It is internal on these carbs and regulated by the ACV ?

The 98 99 models DO have the octopus external pipes. So if I block off the hole where the ACV 1/8 inch O ring thingy is, without doing the full Octopus there is no effect?? Anyone confirm ??

So... if I do the full de-octopus I should be in good shape ? Tell me I'm right.

Trouble is I cant make head nor tail of the deoctopussing operation described in the tech section. I am totally lost as to which pipes to block off and remove. The only thing I am certian of is how to re-attach the hot start tube.

Yamakaze, that pic of your carb would be worth its weight in gold.

NH Kevin, can you help too with a clear step by step.

Finally, is it absolutely necessary to change the start jet from a WR#60 to the YZ#65 for de-octopussing?

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Missle Man, I assume you have seen this:


The end product on the removal of the octopus will only have one hose that connects to the manifold between the [carb and the cylinder] and to the hot start switch. The hot start hose then goes to the airbox as normal. There are two brass nipples that use to have the octopus lines. These are both capped.

The YZ start jet (#65) is accessed from underneath the carb (you have to remove float bowl).

The YZ pilot air jet is accessed behind the airhorn: With the carb in your hand, look at the end of the carb that pops into the airbox. You will see two (allen?) bolts on this "end piece". Remove these two bolts and the end piece off of the carb. Underneath, you will see two brass jets. The pilot air jet is the one on the left.

As a sidenote, if you want to take a look at the installed pilot air jet, look inside the [airbox end] of your carb (carb still intact). Approximately 3 cm's in, and on the bottom of this intake portion of your carb, you should view at least one of the jets right through this cutaway portion

I hope I didn't just THOROUGHLY confuse you with this...

[ November 28, 2001: Message edited by: NH Kevin ]

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NH Kevin, anyone

As far as I can remember there are 3 hoses stuck into the ACV thing.

- one from the hot start hose which splits into a T - one to manifold one to acv. The de octopuss procedure omits the routing from the T to the ACV and plugs right into the manifold, right?

- two other smaller pipes from the ACV that route themselves around the side of the carb and link into other areas of the carb. If I remove these on the ACV I have 4 holes to plug ?

Air horn : understood what that is now, thanks.

No sweat with the jets I know how to change them/have done so already. Start Jet shouldnt be a challenge so long as I know the part numbner. I think for 99YZ it is 3TJ1494F-13-00 from this parts page. Can anyone confirm ?

Am I right on the pure ACV o ring mod only being for 2000+ models, that's why it didnt work for me on my 99?

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Yo Rocket Dude.....

I was supposed to post a photo last night of my 99 WR de-octupused....But alas the ol lady had other Ideas for me. I'll put it out here tonight. My pilot screw works as advertised after the mod...I am a little confused with Mikes post of (2) lines to the cylinder as when I removed the ACV, I plugged off the outlet that went between the Hot Start line T-fitting to the ACV and only have 1 line now running from the manifold to the Hot Start Valve.

Bonzai :)

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