4 stroking causes

Khalil Brooks

Member
May 10, 2020
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Once I read a thread that explained the factors involved in what causes 4 stroking in a 2 stroke engine, and now it seems I’ve been stricken with 4 stroking. Would someone be able to point me to that thread or potentially explain what are the reasons behind 4 stroking? At 3/4 to WOT I lose rpm for a second or two then it comes back, then cycles like that, I’m guessing that when I lose power it’s 4 stroking

Any and all info appreciated
 

FOG

Well-Known Member
Mar 3, 2019
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In general I think the words 4-stroking are used to describe what happens when you have an overly rich mixture. Blubbering. Popping. Farting. Take your pick! But it's definitely bad behavior.

What you're describing, and this is just guess work over the internet, sounds like a fuel starvation issue. I say that because you need more fuel to support the motor at big throttle settings. When the fuel level gets too low in the bowl it'll crap out. When the level has a chance to catch back up it''ll go. Because this just came up I'd be looking at your fuel filter. Or maybe the tank cap.

If you leave the fuel line off the carb and the cap off of the tank you need a full flow of fuel to know you're good. Hope that helps.
 

Khalil Brooks

Member
May 10, 2020
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That would make sense given my carb setting is at its leanest. This wasn’t a problem for a while but I moved and i live about 500ft higher in elevation. Hopefully thas all that I need. We’ve got to wait till my sprocket adapter comes in to test.

still open for more info and opinions on the matter
 

Greg58

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May 1, 2011
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Newnan,Georgia U.S.A.
Sound like it's too rich, higher elevation mean thinner air so less fuel is required. From 3/4 to full throttle only the jet controls fuel flow, when you snap the throttle open there's a increase in fuel because the needle is completely out of the jet.
 

Khalil Brooks

Member
May 10, 2020
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Is there a way other than trial and error to know what size jet goes with what elevation? What size jet does the NT carb come with
 

Greg58

Well-Known Member
May 1, 2011
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That’s the only way, what works for one doesn’t always work on the next. I have 3 bikes at the moment and one needed a smaller jet than the others.
 

stevennf94

New Member
Sep 3, 2020
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Newfoundland, Canada
In general I think the words 4-stroking are used to describe what happens when you have an overly rich mixture. Blubbering. Popping. Farting. Take your pick! But it's definitely bad behavior.

What you're describing, and this is just guess work over the internet, sounds like a fuel starvation issue. I say that because you need more fuel to support the motor at big throttle settings. When the fuel level gets too low in the bowl it'll crap out. When the level has a chance to catch back up it''ll go. Because this just came up I'd be looking at your fuel filter. Or maybe the tank cap.

If you leave the fuel line off the carb and the cap off of the tank you need a full flow of fuel to know you're good. Hope that helps.
I prefer to say that the China girl is "quifing"