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PostPosted: Thu Nov 09, 2017 10:02 am 
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Joined: Wed Jun 13, 2012 9:00 pm
Posts: 971
Location: Eagle Wisconsin
From what I read reversion if thats the correct term does happen with reeds because of the reed opening and closing it creates some sort of flow problem I cannot grasp completely but when the reed closes it causes the flow from the carb to suddenly stop and reverse which can be a problem and by adding or subtracting length between the carb and the reed it can change that particular problem.

Now understand I wasn't going for that I was going for a "look" but didn't want to do something that would be stupid and cause a problem.
But it has me thinking

I also watched a couple old videos don't know how it relates, but it did help me to realize that its way more complex than I am able to process and that with the speeds of the flow in intake its not straight forward.
https://www.youtube.com/watch?v=DOUfyDHxkYQ
https://www.youtube.com/watch?v=7SkWxEUXIoM


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PostPosted: Thu Nov 09, 2017 10:16 am 
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Joined: Wed Jun 08, 2011 11:34 pm
Posts: 9826
Location: North Central NC
OK, that can be considered reversion, but it's way less than when a piston port engine is running below its tuned RPM, and has a piston coming down, but the intake port is not yet covered, and air-fuel mixture that just got into the engine gets pumped back out the intake tract.

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PostPosted: Thu Nov 09, 2017 11:55 am 
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Joined: Tue Jun 07, 2011 6:37 am
Posts: 10460
Location: Rio Rancho, New Mexico
Yes, complexity in simplicity. ;) :wtf: Reversion is just from the very basic design of a 2 stroke. Just like when a piston rises in a cylinder, when the transfers and exhaust ports are covered by the piston, compression is created, when the piston starts down it is also trying to create compression in the crankcase. This pressure gets bled off through the intake port until the piston skirt covers it. This is reversion, as the flow through the intake system is reversed. What this does, and why it's bad, is, the less pressure/mixture in the crankcase, the less mixture pushed/pulled through the motor, IE less power. Add in, that a carb doesn't care which way the airflow is, when the air flow goes back through the carb, fuel is picked up. Which is called doubled Carburation, which makes jetting difficult, and also the turbulence of the flow having to reverse again to fill the crankcase on the piston up stroke. A piston port is just a very simple design, and reversion is a big drawback on that design. Yes, there are ways of reducing the effects of reversion as was posted, with intake length and area. And also by limiting intake port duration timing.

As far as your manifold mod, I doubt you will be able to tell much, if any difference. The added area between the carb and reed, in theory, would decrease the pressure on the reed when closed as there is more area for mixture to compress into. But it is so minute, it should not be a big deal.

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Twist the throttle, tilt the horizon, and have a great time. What triples are all about...........


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PostPosted: Thu Nov 09, 2017 6:36 pm 
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Joined: Wed Jun 08, 2011 9:56 pm
Posts: 449
Location: New Hampshire
I just get on my bike and ride! :thumbup:


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PostPosted: Thu Nov 09, 2017 9:06 pm 
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Joined: Thu Jun 09, 2011 3:35 pm
Posts: 562
Location: Cedar Rapids, Iowa
In my testing I have found, as the video says, it's hard to predict what will happen to your air flow and subsequently power and powerband as you try different intake configurations. Adding intake length between the carbs and air cleaners has boosted the bottom to mid-range power of each of my three triples, all of them being piston port. The biggest boost was on the 500, they are notoriously soft at lower RPMs, besides that, my H1 likes a 90 degree bend in the tube. The H2 and S3 like a 45 degree bend in the tube.

Between added intake length and squish heads, the difference is very noticeable, the mods make the pipey 500 into a very easy bike to ride, with enough low RPM power to ride it all day, 2-up, and not have to exceed 5000 RPM. Of course this is from experience. Why would I keep the revs down that low? 2-up rule #1..."Don't scare the passenger!"

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PostPosted: Thu Nov 09, 2017 10:15 pm 
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Joined: Wed Jun 13, 2012 9:00 pm
Posts: 971
Location: Eagle Wisconsin
JayDav wrote:
I just get on my bike and ride! :thumbup:

Solid Advice!!
But seeing its down and needs pistons this intake change seems like small potatoes, and there will be a couple other changes, I got some new reed petals, looking at a new exhaust, and I may try my Zeel iggy again.

Battleax your testing really does shed light on intake air flow, it amazes me that every one of your bikes is different, each one has its own needs.


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PostPosted: Fri Nov 10, 2017 10:25 am 
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Joined: Thu Sep 29, 2016 4:32 am
Posts: 615
Location: Indianapolis, IN
I had an H1A as a teenager (I think it was actually an H1 but didn't realize it at the time) and a brother had an H1B. I know the exhaust baffles are different on those two, but think the powerband difference seemed like the short intake rubber carb boot, the three piece type, compared to the longer tubes of the H1B changed it some, and gave it a little more midrange.
As a side note, I watched a Youtube video last night of a guy who took the rotary valve disc out of a small 2 stroke and it still ran, but had a lot of fuel standoff out of the carb!

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PostPosted: Fri Nov 10, 2017 11:10 am 
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Joined: Tue Jun 07, 2011 6:37 am
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Location: Rio Rancho, New Mexico
Once you get to an rpm where the cycling time is very short, they really is no time for the reversion wave to kick back the flow. Reed motors will do that too.

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Twist the throttle, tilt the horizon, and have a great time. What triples are all about...........


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PostPosted: Fri Mar 30, 2018 3:28 pm 
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Joined: Wed Jun 13, 2012 9:00 pm
Posts: 971
Location: Eagle Wisconsin
Thought I would post some pics of some of the stuff I have been doing the last couple days, I posted a few in the new purchase section, still a ways to go but its coming along.
Joe Herriges, on Flickr
ImageUntitled by Joe Herriges, on Flickr
ImageUntitled by Joe Herriges, on Flickr
ImageUntitled by Joe Herriges, on Flickr


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PostPosted: Fri Mar 30, 2018 4:36 pm 
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Joined: Tue Jun 07, 2011 6:37 am
Posts: 10460
Location: Rio Rancho, New Mexico
Looking good Joe, going to be awesome! :thumbup:

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Twist the throttle, tilt the horizon, and have a great time. What triples are all about...........


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