High RPM, few seconds and start to fail

DanielMaia

DanielMaia

New Member
Hi guys!

I have a problema with my motorized bike. Since a few days, when i push up the throtle, she goes fine..at 38..40kph, and then, 10 or 12 seconds later, she starts to fail, and become very unstable :(

Sometimes, i have to stop the bike, wait 20 or 30 seconds, and start again. 1 or 2 min after that is happening again.

I dont know if i explain the problem correctly, but my english is quiet bad :(

ps: i change the spark plug and the wire from de bobine, and the problem persists.

Thanks for any tip
 
Check the easy things first. I was having a very similar issue where my choke was vibrating and closing a little bit. Which restricted airflow at high RPM and made my engine loose power.
My engine was also running a bit lean at WOT, but right at all other RPMs, and raising the float helped.
 
your problem sound like it might be fuel related. Might be too rich at wide open throttle.
You can check the color of the spark plug if its wet and oily/ full of black deposits then it's way to rich.
normal spark plug will look tan around the center insulator/ porcelain. if its too lean it will be white and can have a blued tint on the electrodes.
Stock main jet size is 0.70mm
I run a 0.65mm main jet but I'm at 3200' above sea level. The more in elevation you go the more you will need to lean out the main jet.
You might also have a problem with fuel flow and the main jet is ok so if you do not have a fuel filter do get one. I've heard of the gas tank cap not venting but I've not ran across this my self as all my caps will slop out fuel if I fill the tank up.
I have had problems with fuel flow and its trash in the tank or a stuck float needle.
this isn't real good advice but if I'm motoring along and she just quits and I know the tank has fuel and I can't see any fuel in the fuel line I'll take off the gas cap and pressure up the tank with lung pressure this will get the fuel going again, just do not inhale the fumes. See I told you it was not real good advice but it works. I can take off the cap and wait for a while and it still won't run until I give it a little pressure, I do not know if its the float needle sticking or the tanks filter plugging off. I haven't tried the fuel tickler or tapping the float bowl to see if it will go ahead and let in fuel.
Norman
 
Thanks guys!

I'm at under 100m above sea level, and i put the main jet totally in the top. From top is the 4th trace. I tested all, and i think this is the best, but according with the sea level, which trace should i put from de top?

I thought about de fuel filter, i dont have one..it can be that..i will purchase one tomorrow ;)

Thanks again guys ;)
 
Daniel
I'm referring to the main jet on the carb it is at the bottom of the brass tube in the carb's center most are drilled at 0.70mm if the hole is not drilled correctly/or a wobbled out hole it will affect the mixture mostly at wide open throttle being too rich or lacking any power for wide open throttle/bogging or even stopping.
You are talking about the needle e-clip on the throttle slide stock setting is #2 notch from the top or the fat end of the needle.
Most carbs will work fine up through the low to mid range and experience running way to rich at wide open throttle if that is the case then it needs to have a smaller hole in the main jet.
You do need to get a fuel filter to help catch the fine trash that can get into the needle and seat on the float making the needle stick shut starving the carb or stick open causing it to flood and fuel will pour out of the carb , trash or dirt can plug off the main jet starving engine for fuel.
If you have a Wall Mart close by they sell a paper element filter in the lawn and garden area about $5.00 they will fit the fuel line on these engine kits nicely. Plus you can see the fuel in the filter and see the dirt that they will catch.
 
I changed the e-clip to the second trace, and the problem persists :(

I'll get the fuel filter, and clean de carb. with a compressor of air at 10 bars :D

For me, is cheapiest buy a fuel filter :)

Thanks norman ;)
 
e-clip on #2 trace from the top and clean all the carb with an air compressor, and seems that the problem is solved, but the bike is running quite bad..i only can reach 25mph, and before i could reach 28mph and uphills very well..

I really dont understand :(
 
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