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Discussion Starter · #1 ·
New to the pocket bike scene. Have a mini quad I think It's called a cobra s4 or something.
Anything I should know about as I get into all of this?
 

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Welcome aboard, these bike are made in China, so the Quailty is nothing to talk about,lol. It's mainly known as a mini atv, you have a 43cc called 47cc or a 48.7cc called a 49cc. It is a reed port engine, with reeds between the int manifold and engine block with the 12mm piston carb mounted to the black manifold. The carb and reeds or intake leaks are the parts that give the most trouble.
Soon you will want to start Modding the engine for more power, there is alot you can do without spending alot of money, even with hand tools, files and sandpaper. There are alot of threads on modding these bikes. One is Cam2 Cags, Cags, and more Cags, 30 pages, you will see my name here alot.
 

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Discussion Starter · #3 ·
Hey EPR... Thank you ... I see I have a lot to learn about these things. Never knew about them Untill my father got this quad for my kids.. Now if I can just get it to run well enough to ride....lol. Are they hard to fix?
 

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That's why I love these engines, no valves, timing chain, distributor or timing light. They are really simple. First, take the plug off w/ wire on, ground the outside to metal, pull start, look for a blue spark. If you have a good spark, ( yellow is a weak spark ), put a teaspoon of gas down the plug hole, put it back, try to start. If it starts and stops, I would pull the carb and intake manifold and the reed plate behind it. Look to see if the reeds are sealing on the rubber pads. Shine a flashlight on one side and if you see light shining thru, you need to fix that leak. New reeds, or reed plate. The stock reeds are tin, but for $10 you can get carbon fiber reeds, all my eight 2 stroke bikes have them. The jets are very small in the carb under the float bowl, they clog real easy. The coils go out alot also, there about $15.
Try all these things and report back.
 

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Discussion Starter · #6 ·
I put in a new coil, spark plug and clutch. It will start now while I have the back wheels off the ground, but as soon as I put it on the ground and try to ride it.....it dies. It's starting and sounding good.....I'm getting excited... Just got to get it so someone can ride it... But so far I am really starting to like this.
 

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Sounds like the reeds are not closing, or the intake manifold. I have a 5 port 49cc B/B Cag w/ FC crank that was running great, and now its like yours, and it has a Walbro 603 carb, Its starts, but if you touch the throttle its stall like the pushing the kill button. Taking it off today, to look at the reeds.
 

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I put in a new coil, spark plug and clutch. It will start now while I have the back wheels off the ground, but as soon as I put it on the ground and try to ride it.....it dies. It's starting and sounding good.....I'm getting excited... Just got to get it so someone can ride it... But so far I am really starting to like this.
How did you gap the coil....what is the sparkplug gapped to and when you installed the clutch did you install it correctly?

Airgap is .020" and plug gap is .030"



Try bumping up the needle by lowering the c-clip on the mainjet needle in the barrelslider..If it only has 1 groove use very thin and tiny washers to raise the needle a bit...
 

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Discussion Starter · #9 ·
I did not mess with the gap... I was told it was pre-gaped . As to the clutch installation...not sure if its right but it looks like that pic.. Other than that..I have no idea what the other parts are to look at and try and do any thing to. Sorry....I don't know much about motors or what the parts are called. I am looking around where I live trying to find someone else into this that can teach me what they know. I have been looking for a long time for something that I can get into and have some fun with.. so far I think I have found it.
 

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nice atv, im not really into them since they dont have a twist throttle but welcome!
they mostly come with quarter turn twist throttles... but you can change for thumb throttle(not recomended).

I just took my thumb throttle off my 700cc polaris twin sportsman, kills my thumb during small game hunting season, especially when I'm slowly driving through a trail looking for birds.... put in a 1/4 turn billet aluminum throttle with a lockable pedal throttle, which allows me to basicly have "cruise control" since it can be set to open at different speeds.... now I can cruise in trails with my 12 gauge on my lap, and not worrying about how far out I go since my thumb doesent get cramped... I recommend to anyone who uses their quad for hunting season, or winter time.
 

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The coil is under the starter pullstart cover, screws come lose, anything is possible on these bike. Could be the reeds behind the carb and or an intake manifold leak also. Not enough gas or to much gas can kill your power too. If your clutch breaks a spring one shoe will ride on the bell and when the engine is running the bike wants to move forward, and it will make the clutch and bell get to hot.
 
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