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Tried Everything 2006 Nytro

HydrogenCyanide

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2006 Yamaha RS Nytro
2006 Yamaha Apex
I have a 2006 Nytro that my son rides. We bought this sled 3 years ago and it has always been hard to start.

1. Open choke and she fires right up.
2. She starts to spudder and stalls
3. Won't start back up unless choke is off. When she starts back up very sporadic idle and low idle and stalls out.
4. To keep her running I need to manually increase idle. She'll still stall but then fires back up.
5. Once warm I have to turn down idle or after throttle it won't return to normal idle.
6. She starts and runs great for the rest of the day.

Any idea's. I have pulled carbs and cleaned everything. Any ideas what this could be. Sled runs great when warm, but is a bear to get started when cold. Very stressful first thing in the AM trying to keep this thing running.

Thanks
 

maim

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almost sounds like it is sucking air into the fuel system when it is not running through a pin hole. have you tried clamping off the suction lines to the fuel pumps from the tank to see if it draining back? have a couple 2 strokes that do this overnight for one, the other takes a few weeks to do it.
 

74Nitro

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If you haven't sync'd the carbs, that's the first thing to do.
 

Metallicat

TY 4 Stroke God
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Northville, MI
These engines are cold blooded. I keep mine on full choke until the warm up light goes off, then instead of reducing the choke lever, I keep it on full choke and either feather the throttle or just drive it around a bit, again with the choke on full until it is warmed up quite a bit. Plus, as always, sync the carbs and clean your pilot jets.
 

Fast Lane

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2007 Yamaha Nytro
Start it with full choke.
Let it run for a minute.
Start backing the choke off.
Turn the choke completely off before the low temp light goes off.
Rev it up a couple of times.

It will idle low until its fully warmed up. Mine has been like this for a long time. A few years ago I broke down and bought new main and idle jets. It helped things a lot. Its just nature of the beast. If it stalls out. No choke and use your thumb on the throttle. Once you give it some gas you will be fine.

Set your idle when the engine is fully warmed up. If its too high TORS kicks in and thats annoying. Try to get in near 1500. If your on the lower side I find cold start can be a bit more of a pain when the choke completely goes off.

Once warmed up just turn the key. No choke needed. Ever.
 

Metallicat

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Hi Fast Lane. Your startup procedure used to be mine, exactly and 100%. I have personally found that leaving the choke full on, during warm up and even past warm up, greatly reduces the need to restart the engine and risk a fowled plug. I received this advise from this forum years ago, and it went against my own logic, but it just plain works for these engines. These carbs are obviously at least partially electronically controlled. When the cold indicator light goes off, they idle down, way down, and sometimes stall out. I've never heard a good explanation of what happens to the fuel delivery when that indicator light goes off. But something sure happens. Do you have any idea? Agree with your idle adjustment 100%.
 

74Nitro

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Hi Fast Lane. Your startup procedure used to be mine, exactly and 100%. I have personally found that leaving the choke full on, during warm up and even past warm up, greatly reduces the need to restart the engine and risk a fowled plug. I received this advise from this forum years ago, and it went against my own logic, but it just plain works for these engines. These carbs are obviously at least partially electronically controlled. When the cold indicator light goes off, they idle down, way down, and sometimes stall out. I've never heard a good explanation of what happens to the fuel delivery when that indicator light goes off. But something sure happens. Do you have any idea? Agree with your idle adjustment 100%.
The ignition timing changes, nothing in the carbs does.
 

HydrogenCyanide

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Messages
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Fort Erie
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2006 Yamaha RS Nytro
2006 Yamaha Apex
Thanks. We are going north this weekend and I will try these new procedures. It's just a bear. I tread a carb sync tool but I'm not sure I did it correctly. Going to try making the tool that was shown on the stick and see if that is an easier procedure.
 

74Nitro

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Thanks. We are going north this weekend and I will try these new procedures. It's just a bear. I tread a carb sync tool but I'm not sure I did it correctly. Going to try making the tool that was shown on the stick and see if that is an easier procedure.
Most motorcycle shops have a carb sync tool.
I will say, if one of the carbs is out of sync, it greatly affects idle quality.
Sometimes those sync screws between the carbs get turned by accident, and they can't be correctly set without a sync tool.
 

HydrogenCyanide

Veteran
Joined
Oct 21, 2020
Messages
41
Age
41
Location
Fort Erie
Country
Canada
Snowmobile
2006 Yamaha RS Nytro
2006 Yamaha Apex
almost sounds like it is sucking air into the fuel system when it is not running through a pin hole. have you tried clamping off the suction lines to the fuel pumps from the tank to see if it draining back? have a couple 2 strokes that do this overnight for one, the other takes a few weeks to do it.
I'm not sure I understand the scenario here. Could you explain a little more?
 

maim

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7,049
Location
sudbury on
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Canada
Snowmobile
2016 apex xtx
2011 apex xtx
2009 phaser rtx/x
1997 et410t/r
1988 vk 540
on the sleds that this happens to on me, i have clear fuel line from the pump to the carb on them and i see an air bubble right at the carb nipple. all clamps are tight and i did replace the fuel line. still does it. 1 takes about an hour to do it and the other takes a couple weeks. because air can get in, it pulls the fuel out of the bowl and drains it to the tank as the one needs gas in the plugs to fire up when it sits too long. the other one needs an extended crank with the e start for it to start.
 


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