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I'm not sure if it's a technical term, but I hope you know what I'm talking about. One you hit the top of the revs, the engine emits that trademark 2-stroke "burbly" sound. Almost like a rev limiter kicking in.

What goes on in the engine at that point? Fuel starvation? Vapor lock?

What can be done to bring the revs higher before burbling? I hit it sooner than I like, at least in first and second gear. Especially before the engine has warmed up. In third and fourth my (essentially stock) engine doesn't quite get there.
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VNB VSC VMA VSX - o9c vmb vse
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Burbling (what is it?)
Burbling - the sound of molten medal as your piston begins to fuse/melt to the cylinder wall. Also, the sound made by the manifestation of fear and shock that usually emanates from your ass concurrent with the realization that you are about to seize. Burbling. Clown emoticon
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Seriously... I hope some experienced folk chime in on this. *Curious.*
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07 GTS250(RIP), 07 LX150, Several Lambrettas
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I think you are just experiencing a temporary rich condition before completely warmed up when all the fuel is not ignited or burned off in the exhaust. I've heard the term "four stroking". Wait longer, until fully warmed up before you ride it like you stole it.
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1958 Allstate 125
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UTC quote
How early does this "burbling" sound start? If it doesn't go away when you're warm, you might be jetted too high. What is your setup?
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@mathias avatar
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UTC quote
wheelhorse2347 wrote:
How early does this "burbling" sound start? If it doesn't go away when you're warm, you might be jetted too high. What is your setup?
It's hard to describe at what rpm without a tach. When cold it appears much lower. Not so low that I can't comfortably move on to the next gear - which I should do anyway, so I don't rev it out too much when cold.
When it's warmed up for 10-20 minutes, in first and second gear I'd say it burbles at about 80% of what it "feels" like the engine can do. It sounds a bit as if it's clearing its throat.

So your machines don't do this? If you stay in first at full throttle, what happens? Does it just smoothly and happily sit at a really high rpm (until it explodes)?

It's a P200E, stock, except for a Sito+. 120 jet.
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07 GTS250(RIP), 07 LX150, Several Lambrettas
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Only the first few blocks I drive in the morning and after work. Once completely warmed up (3-4 blocks) it's gone. If you push it too far, too soon, too cold, your piston and barrel may expand at different rates, and no longer be at the optimum tolerance. Possible seize conditions.

Just take it easy before it's completely warmed up, and if it continues you likely are jetted too rich. Look at your plug, and don't try to adjust anything til you are warmed up. Otherwise you are chasing your tail.
mathias wrote:
So your machines don't do this? If you stay in first at full throttle, what happens? Does it just smoothly and happily sit at a really high rpm (until it explodes)?
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starreem wrote:
Only the first few blocks I drive in the morning and after work. Once completely warmed up (3-4 blocks) it's gone. If you push it too far, too soon, too cold, your piston and barrel may expand at different rates, and no longer be at the optimum tolerance. Possible seize conditions.

Just take it easy before it's completely warmed up, and if it continues you likely are jetted too rich. Look at your plug, and don't try to adjust anything til you are warmed up. Otherwise you are chasing your tail.
The cold condition only lasts for a minute for me as well. I'll check the plug (it's been a while), and go from there.

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