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“Intermittent bog” 440 fan.


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#1 Tug_Driver

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Posted 22 February 2021 - 06:44 PM

Well I figured out what the seller meant by an “intermittent bog” 😂 not him but someone previously did a carb cleaning and decided the pilot jets weren’t important. Now it does stink to be held up by two $5 parts but I did negotiate a low price because of “tinkering”. I did a baseline setup the other night and the carbs were messed up. The mag slide was 1/8” lower than the pto, both slides were hanging on the throttle cables at idle they weren’t even sitting on the idle stop screws.

Now I should have done my diligence and and pulled the carbs off but they looked pretty clean and I got them synched with a proper amount of stack in the cable. Went out to try and groom today. Run good for a while, bog bog bog, clear out run good again for a while, bog bog bog some more. Limped it back to our barn and pulled the air box off again and checked the needle height, main jets (found the mag/pto were backwards) then went oh hey, I wonder where the pilot jet it. And both of them were missing. Big difference between a #35 jet and a 1/8” open hole. Everyone was surprised it ran at all. Used 8 gallons to pull the drag 15 miles.

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#2 92plus

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Posted 22 February 2021 - 11:27 PM

If you're talking about the hole in the intake throat, that isn't where the pilot jet is. It's in front of the main jet tower.

#3 Tug_Driver

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Posted Yesterday, 07:24 AM

I know where the pilot jet goes. I had the slide out to check the needle position because it idles fine but is super rich as soon as it comes off idle. I was making sure someone didn’t pick the needles up all the way thinking they were getting more power.

Now finding pilot jets in this world of EFI is a different story.

Edited by Tug_Driver, Yesterday, 07:41 AM.


#4 92plus

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Posted Yesterday, 12:33 PM

If you need pilot jets, I have found em on ebay. Just make sure to get genuine Mikuni jets.
Price was about the same as the dealer wanted. They don't stock many jets anymore around here. When you take the float bowl off to put em in, check your float height while you're there.
If you're in need of a copy of the shop manual, I probably have one. Just PM me if you need it.

Edited by 92plus, Yesterday, 12:36 PM.


#5 Tug_Driver

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Posted Yesterday, 12:58 PM

If you need pilot jets, I have found em on ebay. Just make sure to get genuine Mikuni jets.
Price was about the same as the dealer wanted. They don't stock many jets anymore around here. When you take the float bowl off to put em in, check your float height while you're there.
If you're in need of a copy of the shop manual, I probably have one. Just PM me if you need it.

Turns out it’s not called a pilot jet. It’s the air jet. I was calling it the wrong thing. I can’t find the correct size anywhere. I found a reference to a BS30/97 0.7 as a standard size but would like to confirm that. I do know that it goes pig rich when it gets onto the main circuit so I know I need something.

Edited by Tug_Driver, Yesterday, 12:59 PM.


#6 92plus

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Posted Yesterday, 07:23 PM

Ah... The little one in the carb throat. Never had to remove one.
If it's rich coming into the main circuit, that would be either the needle, needle jet, or the main jet, unless your float level is high. That could cause a rich mixture.
I do have a manual here, as well as a VM tuning manual if you need them.




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