Bike wont stay running

jerry campo

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Sep 24, 2018
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Hey everyone, I recently purchased a motorized bicycle, and about a week after riding it, most its power had gone. it went from riding at 20mph to riding at 10mph when i have the throttle fully open. then the next week it just died after a few minutes of riding. any help?

Key details: as of now, when i first start it and ride it, it speeds all the way up to 20mph strong no problem .then after about 20 seconds it goes back down to 10mph. sometimes it will randomly burst back up to 20mps after riding for a minute or two at 10mph
 

Venice Motor Bikes

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Mar 20, 2008
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(I'm assuming that you have a 2-stroke bike).... How are you mixing your gas & oil??
Do you pour oil into the tank?, or do you measure it all in a separate gas can first & then fill your tank??

What ratio are you mixing it at?
 

jerry campo

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Sep 24, 2018
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the man advertised it as a 4 stroke but i think it is 2. As of now, I did pour oil into the tank to mix it with the gas (i know thats bad). although to be fair, this all started before I even had a chance to add any oil. the man i bought it from said to use. a 4 ounces to a gallon ratio
 

Tyler6357

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Mar 15, 2012
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4 stroke engines don't require you to put oil in the gas, only 2 stroke engines require that. You should drain your tank and mix a gallon of gas with 4 oz of oil in a separate container and shake it up before you pour it into your tank.
 
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jerry campo

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Sep 24, 2018
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ill give that a shot. if that doesnt work what should i do? I know these motors are extremely tiny, in comparison to an automobile, to repair shoudnt be too much of a hassle. also, can i use seafoam in these motors?
 

Tyler6357

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Mar 15, 2012
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I would say that if that doesn't solve the problem you could try a few things.
- Remove carb and take it apart and clean it with carb cleaner
- Check for air leaks, it's possible you have an intermittent air leak. Check carb/intake connection, intake/cylinder connection, exhaust pipe connection, and around the head gasket (start the engine and feel with your hand around the head to see if you can feel any air shooting out)
- Check your exhaust pipe to make sure it's not all gunked up with oil.
- How many miles do you have on your engine? Is it 4 stroking when it loses power? It could be you need to go a little leaner on your fuel/air ratio. You could try to set the carb clip on a leaner setting or put in a smaller jet.
 

jerry campo

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Sep 24, 2018
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awesome ill start the troubleshoot. I have been 4 stroking like crazy. im going to clean everything and see if there are any leaks aswell.
 
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Tyler6357

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Mar 15, 2012
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awesome ill start the troubleshoot. I have been 4 stroking like crazy. im going to clean everything and see if there are any leaks aswell.
Oh, well if it is 4 stroking I would start with trying to lean it out, set the clip on the leanest setting and see if the problem still exists or if it has at least gotten better. I think the stock carb jet is a #70, that is often times too rich
 

Tyler6357

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Mar 15, 2012
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But I would like to know how long you have had the engine and how many tanks of gas have you run through it before this started happening? Has it always 4 stroked? hmmmm, the more I think about it, the more I think you should check for those leaks, do you see any fuel leaking at the carb connection? Even if you don't see any fuel leaking, just the smallest air leak at the carb/intake connection will cause the conditions you are experiencing. Some people in the past have used small washers to seal them but I don't really have much experience with the stock NT carb, (I'm using one like this--> https://www.ebay.com/itm/Racing-Car...-2-Stroke-Motorized-Bike-Bicycle/182713129336 I think they are easier to tune). But one way to check for air leaks is you can spray soapy water on the connections and then start the engine and look for bubbles and like I said, hold your hand close to the head and see if you can feel any air shooting out from around the head gasket when you start it and rev it. Also, check your spark plug color, is it really black or more light brown or grey? If it's really dark that indicates a rich condition. Also, usually these engines tend to run slightly leaner after they get warmed up so it's good to get it hot before making an analysis.
 

jerry campo

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Sep 24, 2018
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i see. thank you so much for your input! I only refilled the tank a single time before all this started happening. i wasnt 4 stroking before, it was running fine. I cleaned everything up and i dont see anything leaking as of yet, however , I looked closer at the fuel filter and i think it might be clogged. i looked at the bottom where the fuel s supposed to exit the filter and it black. i started to shake it around and a whole bunch of black crud started floating everywhere. i'm going to the store in the morning to buy a new one.
 

Tyler6357

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Mar 15, 2012
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Santa Barbara, CA
i see. thank you so much for your input! I only refilled the tank a single time before all this started happening. i wasnt 4 stroking before, it was running fine. I cleaned everything up and i dont see anything leaking as of yet, however , I looked closer at the fuel filter and i think it might be clogged. i looked at the bottom where the fuel s supposed to exit the filter and it black. i started to shake it around and a whole bunch of black crud started floating everywhere. i'm going to the store in the morning to buy a new one.
Ha! That sounds like that might be it. It's possible that it was restricting the flow of fuel so that when you gave it more throttle it just couldn't suck in enough gas. Replace the filter and never mix your oil and gas in your tank again. Always mix up a full gallon and then fill your tank which is only about 1/2 gal. You should drain the tank and see if you can get all the oil out of the bottom even if you have to blast it out with a high pressure hose, just make sure you let it totally dry and then completely flush the tank with straight gas before using it again. Also, you should clean the petcock valve.
 
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jerry campo

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Sep 24, 2018
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well what do ya know? the fuel filter was the culprit all the long!! no im zippin around no problem!! I have extra fuel left over though, how do i store it? i heard you can use fuel stabilizer, is this true?
 
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Tyler6357

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Mar 15, 2012
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Santa Barbara, CA
well what do ya know? the fuel filter was the culprit all the long!! no im zippin around no problem!! I have extra fuel left over though, how do i store it? i heard you can use fuel stabilizer, is this true?
Sweet! Good to hear you solved the problem. You won't need a fuel stabilizer unless the gas is very old.
 

jerry campo

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Sep 24, 2018
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alrighty then. i'm sure having the oil mixed with the gas changes its decay rate. how long does it usually take for it to go bad?
 

crassius

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Sep 30, 2012
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no way to tell as gas is not the same everywhere - high alcohol content and weather with high humidity also matter

if it sits so long it smells sour, it's bad

I don't worry about it, as I put it in a jug and use it for cleaning the bike.