2 stroke motor four stroking? HOME REMEDY!

Darkwolf

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I'm sure everyone has experienced the higher rpm issue on the generic and stock 2 stroke engine kits when you're riding at full throttle, the engine goes from a whine to a power losing putter and acceleration pretty much halts, capping your top end speed at what feels like a lower rpm than what it's truly capable of.

Well that's because it IS capping off your top end at a lower rpm than what it's truly capable of! Why? Well come to find out these carburetors have a main jet that is a bit too big for these stock motors and dumps more fuel into the motor than the motor can ignite at higher rpm every combustion cycle so instead of firing every time it starts to fire every other, essentially killing power and your rpm range.

Now normally the solution is to buy a new smaller jet, adjust the clip height for the needle and so on, reducing the fuel amount that is sprayed into the motor at wide open throttle and thus helping eliminate the higherrpm four stroke issue... but if you're like me you don't want to buy or replace anything that isn't broken and have a bit of ingenuity and fabrication skills. If you do, then I propose the alternative way to eliminate four stroking all together and unlock your stock motors true potential!

Instead of reducing the amount of fuel your motor gets, allowing for a more ideal air fuel ratio but limiting performance in the process you can keep the oversized stock jet, not have to rip your carburetor apart and fix the rich air fuel ratio by feeding more air into your system with a RAM AIR set up! These motors have the carburetor behind the motor so air first passes over the hot motor before it can be scavenged up by the vacuum of your carburetor. As a mechanic for 15 years now I can assure you that not only is that a recipe for poor performance, but that also means the engine is working harder to suck air in than it really has to.

I decided to get creative, using two pieces from an old vacuum I had lying around (you can use pvc pipe elbows or whatever floats your boat) and made my own intake tube, shaped in a way where it scoops the colder air passing above the motor and funnels it down to the carburetor, and just like that my four stroking problem vanished! The engine pulls harder and hits a much higher rpm than it was ever able to before... so much higher my 80cc generic China girl which I've only backyard tweaked 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 deleting the baffle in the stock exhaust, to propel my 170lb body over 40mph! Seriously! I couldn't believe it! I was skeptical at first figuring it might help a little, but the difference is astonishing! So if you wanna have a little fun I implore you to try and make a ram air system for your motorized bicycle, i guarantee you won't be disappointed!
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I'd much prefer to have some sort of air filtration. The stock air-cleaner is a little restrictive, but the filter element it comes with is way too porous.

I made a flat plate style from an old, quart yogurt container lid with a donut of 300 pore per square inch open cell polyurethane. It now breathes much better and there's no dirt and dusty trash on the carb throat. If you want to custom build a decent carb filter intake take a look at old school two stroke motorcycle and old 2 stroke cars. Most had a straight intake hose into the filter casing, added some intake tuning and delivered a smooth flow of non-turbulent air to the filter and carb.

Old SAAB 850 car engine...
3723840959_cf67cd836f.jpg
 
I'd much prefer to have some sort of air filtration. The stock air-cleaner is a little restrictive, but the filter element it comes with is way too porous.

I made a flat plate style from an old, quart yogurt container lid with a donut of 300 pore per square inch open cell polyurethane. It now breathes much better and there's no dirt and dusty trash on the carb throat. If you want to custom build a decent carb filter intake take a look at old school two stroke motorcycle and old 2 stroke cars. Most had a straight intake hose into the filter casing, added some intake tuning and delivered a smooth flow of non-turbulent air to the filter and carb.

Old SAAB 850 car engine...
3723840959_cf67cd836f.jpg
Very cool! Most of my mechanic skills have been obtained from 4 stroke designs but a lot of knowledge is transferable to the 2 stroke engine. I was dumbfounded by the performance increase of my ghetto ram air intake to be honest... it's a whole new beast!
 
Very cool! Most of my mechanic skills have been obtained from 4 stroke designs but a lot of knowledge is transferable to the 2 stroke engine. I was dumbfounded by the performance increase of my ghetto ram air intake to be honest... it's a whole new beast!
The stock airfilter housing is very restrictive as is the filter it's self when it starts to get wetted with fuel/oil mix.The change you notice is due to the now open venturi effect not from ram air,There is no open valve to push air into,the two strokes intake pulse is a timmed vacuum and it creates the velocity when met with the atmospheric pressure,ram air need's a higher velocity to be affective.
 
The stock airfilter housing is very restrictive as is the filter it's self when it starts to get wetted with fuel/oil mix.The change you notice is due to the now open venturi effect not from ram air,There is no open valve to push air into,the two strokes intake pulse is a timmed vacuum and it creates the velocity when met with the atmospheric pressure,ram air need's a higher velocity to be affective.
Either way, even if it's not a "true" ram air... it works incredibly well and solves the four stroking problem with much higher rpm range
 
Thank you I shall!
I am really confused. Your thing gets cold air instead of warm air, how is that important. I assume that your thing catches more cfm so it runs leaner, which is bad? Did you adjust the carb needle so it runs richer with your mod? THX
 
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