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Smoking 2's

05 Yz 25p extremely high idle at cold start up

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Did a search and it appears alot of the 05 up do this. Why? It sounds terrifying and can't be good 😲. After 5-10 + - seconds it's normal but those few seconds seem like a eternity

What's changed from let's say my 2000 which doesn't up to 05.

178 main

50 pilot

Middle clip

1/2 turn on airscrew

Tan spark plug and runs great otherwise

I just pulled carb apart looking for cracks etc and found the jet block (maybe factory IDK) has a white silicone of some sort used to seal it. It seems like real tough stuff and not moving. Either way alot of these do this so not so sure it has anything to do with it

 

IMG_20191106_105131060.jpg

IMG_20191106_105057578.jpg

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Either a too-fat needle is in it or you have a leak at the crank seals (typical for a bike over 10 years old)

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18 minutes ago, jaguar57 said:

Either a too-fat needle is in it or you have a leak at the crank seals (typical for a bike over 10 years old)

It's got 40 hrs on a complete rebuild so hopefully that's not an issue.

N3EJ is the needle, I believe to be factory.

I seen guys say even there newer bikes are doing it, there needing to either ride the kill switch or switch choke on/off to slow it down.

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1 hour ago, jaguar57 said:

According to my jetting calculator your idle jetting is too rich and so I say definitely you have a crank seal leak. fix it

Not saying your wrong but it's stock jetting/settings except the 1/2 turn on air screw.

 

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1/2 turn is a lot richer than 1.5 turns. Its set that way to compensate for the leaning effect of the leaking seals. Once the seals warm up they expand and stop leaking.

Grasshopper, trust me. Do you know how to use soapy water to test the ignition side seal?

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9 hours ago, Shawn_Mc said:

A ten year old carb could have a worn needle and needle jet too.

I put 1 step richer needle in yesterday and at 50-55° it fired up sounding what I believe to be normal compared to my 2000. No chance to ride it yet and this morning will be the true test as it's hovering around °30

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36 minutes ago, Motox367 said:

This first start you talking with choke on? 

Yep. It's like holding it half throttle or more at start up for 10 seconds. I changed needle yesterday, going to have son give her a go in abit

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so, choke out, it fires up, high idle...then you turn off the choke and the idle drops right back down?

at 50-55F, it should only need that choke for about 10-15 seconds, max.

Making the needle circuit richer should change anything at start up. At 1/8th throttle or so when kicking, you're not even close to being on the needle yet.

What you're describing sounds like a leaking crank seal, or maybe the case halves are leaking somewhere.

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It held 6 psi pressure for a long time, didn't time it but was quit awhile. I put that needle in yesterday, turned air screw back out to 1 turn and at 34° it fired up with choke on and it did a normal slightly high idle for 5 seconds + - and dropped like it should. Let it idle a few more sec. with choke on and flipped off. Sounds good and most importantly not doing a screaming start up. 

Jetting is not my strong suit

Really wish I had a rpm meter to see just how bad it was before, it was embarrassing to be around.

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2 minutes ago, Shawn_Mc said:

How long has it been since you pressure tested the cylinder/low end?

It almost sounds like the choke plunger was leaking

Yesterday

Choke was tight coming out.

I posted this same question over in Yamaha section before I remembered about this more specialized section and apparently I'm not the only one with this issue on 03 up yz's

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Yesterday
Choke was tight coming out.
I posted this same question over in Yamaha section before I remembered about this more specialized section and apparently I'm not the only one with this issue on 03 up yz's
Lots of my bikes do this even from new ,it's a sign the bike 8s lean only on start up ,if it rides nice once warm I wouldn't worry ,I used the kill switch to keep the revs down
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The plunger piston seals on the end, where the rubber part is. If it plunger was tough to pull out, it was probably hanging up in the carb body and not seating. If it doesn't seat, it will leak a touch and throw the fuel mixture out the window. If it moves easy now and stays in its detents, you probably cured the problem. Keep an eye on that plug.

 

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42 minutes ago, mog said:
55 minutes ago, Smoking 2 said:
Yesterday
Choke was tight coming out.
I posted this same question over in Yamaha section before I remembered about this more specialized section and apparently I'm not the only one with this issue on 03 up yz's

Read more  

Lots of my bikes do this even from new ,it's a sign the bike 8s lean only on start up ,if it rides nice once warm I wouldn't worry ,I used the kill switch to keep the revs down

For now it seems cured.

Cast piston then probably not a big deal but I run forged so biggest concern was a cold seize. We'll see what happens

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42 minutes ago, Shawn_Mc said:

The plunger piston seals on the end, where the rubber part is. If it plunger was tough to pull out, it was probably hanging up in the carb body and not seating. If it doesn't seat, it will leak a touch and throw the fuel mixture out the window. If it moves easy now and stays in its detents, you probably cured the problem. Keep an eye on that plug.

 

I don't think choke was the issue. It worked as it should, spring feels strong. It's something with the way there set up and I don't like it.

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1 hour ago, Shawn_Mc said:

I cant remember if the stator plate on that bike is slotted or not. You could play with the ignition timing and see what happens.

It is slotted. I'll keep that in mind come spring if I need to swap this needle back out

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