Homemade ram air intake=WOWPOWER!

Darkwolf

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#1
So after dealing with the annoying higher rpm four stroking capping my 80cc China girl rpm range I got creative. I know it's caused by rich conditions of the stock main carb jet, i had already done some backyard tweaks by shaving the head, swapping a bosch platinum 2 plug from my old impreza which intrudes into the combustion chamber upping compression and allowing for better spark, and deleted the baffle in the muffler, and being a mechanic I know there's 2 ways to fix a rich burn... decrease fuel or increase air! Well after about 20 minutes I made this abomination... and holy hell what a difference! I gained way more rpm and eliminated the four stroking problem! I kid you not I was passing cars in a 35mph zone where people drive 40 or higher regularly!

Feeling creative and experimental? Try it!
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#6
How well does it work? I did something similar to mine and made a huge difference. I would recommend using a CNS carb so you can adjust the air mix from your handle bar as you ride.
 

Street Ryderz

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#7
How well does it work? I did something similar to mine and made a huge difference. I would recommend using a CNS carb so you can adjust the air mix from your handle bar as you ride.
There is no ram air for a 2 stroke,it's an open venturi that allows better flow from not having the restricted filter housing.The CNS carb's second cable and thumb lever on the bars is an enrichment valve used as a choke but instead of restricting air to increase the amount of fuel entering it pulls fuel directly from the bowl and put's it in the air stream after the metered flow through main body.There is no change in air delivery as you add fuel with this valve.
 

Darkwolf

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#8
How well does it work? I did something similar to mine and made a huge difference. I would recommend using a CNS carb so you can adjust the air mix from your handle bar as you ride.
It works amazingly well! Took it for a 40 mile ride today and rode past one of those radar signs that says "your speed is ____" on a slight incline and was clocked at 36mph which is way better than before... if hit 35 on a decent downhill descent.
 
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#9
Almost everything I've read says that ram-air doesn't have much affect, if any. Guys that know their engines inside and out explain why it doesn't work. But can anyone tell me why it could theoretically work? There has to be something to it because multiple people (myself included) trying it say they have had a noticeable difference. I'm genuinely asking for an explanation other than "it forces air into the carb". Anyone?
 

Street Ryderz

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#10
Almost everything I've read says that ram-air doesn't have much affect, if any. Guys that know their engines inside and out explain why it doesn't work. But can anyone tell me why it could theoretically work? There has to be something to it because multiple people (myself included) trying it say they have had a noticeable difference. I'm genuinely asking for an explanation other than "it forces air into the carb". Anyone?
Ram air doesn't work for a 2 stroke because the intake pulse is actually a vacuum and it's timmed duration is a function of the piston and the port.The improvement noticed is due to the now open venturi witch helps with velocity due to no restriction that the air filter housing creates.No ram air is affective until a certain velocity is meet,that velocity is attained at speeds from 60+ so in reality ram air doesn't work at slow speeds anyway,And because a 4 stroke use's a full down stroke with the intake valve open for intake it allows the ram air to increase that velocity being drawn in.The 2 strokes intake pulse is short and fast,as the vacuum created by the up stroke(below the piston) meets atmospheric pressure it creates velocity through the carb body and the open venturi just allows the max available air to be used in that short burst.
 

Arty

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#11
Street Ryderz:
Thanks for your description of how a 2- stroke's intake works. It was really helpful for me. - I hadn't really spent much time thinking about it before. Now what I'm thinking is that lengthening the distance between the carb intake and the air filter should help - is that correct? - - Nola's picture indicates no air cleaner was used, so naturally some benefit would be realized.
 

Street Ryderz

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#12
Street Ryderz:
Thanks for your description of how a 2- stroke's intake works. It was really helpful for me. - I hadn't really spent much time thinking about it before. Now what I'm thinking is that lengthening the distance between the carb intake and the air filter should help - is that correct? - - Nola's picture indicates no air cleaner was used, so naturally some benefit would be realized.
That's true to a point and takes some trial and error testing to find what length matches the flow rate best,added length in the intake up to 7.5 " from piston face to the carb's slide also aids in bottom end throttle responce but takes away from the top,so again trial and error to find the best suited length is required.
 
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#13
I use an off-set carb intake and a flex-hose with the filter on the end. But my carb is nothing too special. Would you suggest loosing the ram air and buying a high end carb? I'm only doing this set-up bc it's free. If so, what carb would you suggest?
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Street Ryderz

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#14
I use an off-set carb intake and a flex-hose with the filter on the end. But my carb is nothing too special. Would you suggest loosing the ram air and buying a high end carb? I'm only doing this set-up bc it's free. If so, what carb would you suggest? View attachment 84130
Unless your going to port it to flow more that cns carb is fine,and if it's working well for you then just use it until you need more volume.
 

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