CVT emissions port

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magnetb0y
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CVT emissions port

Post by magnetb0y »

Hi,
When putting a performance exhaust on a 2 stroke scooter, and you have the
CVT port that pumps air through a filter to the exhaust, what do you do with the CVT port? I tried capping it, the bike wouldnt run, I put just a filter on it, the bike runs but is that necessary? How do 2 stroke bikes work that have no emissions? I would assume there was a way to just block off that port but the bike wont run. Putting on a new performance exhaust so curious.
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Stanza
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Post by Stanza »

All it does is push air through the hose to the stock muffler via that hose. Technically, you can take the hose, and just tuck it up on top of the engine so that it's venting to atmosphere. Or put a filter on the outlet port on the cvt, whatever you like.
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tenders
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Post by tenders »

I just routed the tubing to the left side of the engine, pointed down towards the pavement.

By the way when I took my exhaust off to replace the rear wheel, the housing of that dumb canister air filter cracked, so I removed it and kept the old exhaust in place. But what to do with the small open pipe on the exhaust now? I found a brass cap on Amazon that fits perfectly over the pipe, filled it halfway with high temperature epoxy, roughed up the end of the pipe with some sandpaper, and tapped it on with a mallet. Problem solved.

Everflow Supplies CTEC0012 1/2"... https://www.amazon.com/dp/B016Y8OI7M

Supposedly, that air is pumped into the exhaust as a US EPA directive to help combust any lingering fuel before it exits the pipe. It has zero discernible effect on a halfway-properly tuned carburetor, and is shown as “optional� on the exploded parts diagram. Color me skeptical as to its effectiveness, but maybe that kind of wizardry is how Genuine manages to keep selling 2T engines in the US market. But why is that air filtered? I probably would have left it in place if the dumb filter housing hadn’t cracked due to brittleness. It certainly wasn’t worth $40 to replace.
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Stanza
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Post by Stanza »

I can answer that one actually! I dug into this a while back while bored and curious.
The air is being pushed into the exhaust to help add 02 to the catalytic convertor, to raise the temperature and help burn off the remaining hydrocarbons. It's filtered, so that any rubber thrown off by the belt (belt dust, etc) doesn't get into the cat via that hose, and make a cloud of burning rubber smoke. As you say, it's all in the name of cleaning up that tailpipe. All of this gets thrown out the window once you start adding performance parts. But in stock form, they really are trying to keep it as clean as possible so we get to keep blasting on two strokes.

tenders wrote:I just routed the tubing to the left side of the engine, pointed down towards the pavement.

By the way when I took my exhaust off to replace the rear wheel, the housing of that dumb canister air filter cracked, so I removed it and kept the old exhaust in place. But what to do with the small open pipe on the exhaust now? I found a brass cap on Amazon that fits perfectly over the pipe, filled it halfway with high temperature epoxy, roughed up the end of the pipe with some sandpaper, and tapped it on with a mallet. Problem solved.

Everflow Supplies CTEC0012 1/2"... https://www.amazon.com/dp/B016Y8OI7M

Supposedly, that air is pumped into the exhaust as a US EPA directive to help combust any lingering fuel before it exits the pipe. It has zero discernible effect on a halfway-properly tuned carburetor, and is shown as “optional� on the exploded parts diagram. Color me skeptical as to its effectiveness, but maybe that kind of wizardry is how Genuine manages to keep selling 2T engines in the US market. But why is that air filtered? I probably would have left it in place if the dumb filter housing hadn’t cracked due to brittleness. It certainly wasn’t worth $40 to replace.
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tenders
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Post by tenders »

That’s really interesting, thank you, Stanza.

So let me get this straight:
Burning oil in the combustion cycle throughout the life of a 2T engine: OK
Potentially burning a fragment of rubber dust that might shake off the CVT belt: FORBIDDEN, FILTER THAT FILTHY BEAST’S AIR YOU SCOUNDREL

(ps, filter was in like-new condition after 10 years and 800 miles, though admittedly virtually new belts were probably not the engineering concern)
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Stanza
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Post by Stanza »

Maybe it was for emissions, maybe it was to keep burnt rubber from clogging up the cat? What'chu got against filters Mr Tenders? Did one diss you real bad back in the 80s? This sounds like a deep rooted trauma...


kidding, of course.
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tenders
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Post by tenders »

Only now can it be told: I was kidnapped by a deranged Fram filter, part number PH7328 for a VW bus, as a small child and chained in a dark room for six years while that filter abused me in every imaginable way. Now I smoke unfiltered cigarettes, drive a 2T scooter that has no oil filter, hire somebody else to clean its air filter while I avert my eyes, and run my home furnace and air conditioner with an open slot where the filter should be.

My only aversion is to spending $50 on a replacement filter and housing that is “optional� in the parts diagram, barely even sold online, and completely absent from every aftermarket exhaust.

Now that I know what it’s for, I more comfortably prefer the option of keeping my $50.
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scootiebob
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Post by scootiebob »

Mr. Tenders that was a great reason to hate filters lol. The unfiltered cigarettes got me good.

And thanks for that information Stanza it's crazy what contraptions are made for EPA standards, and even crazier with automobiles. Good or Bad? You be the judge.
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