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Post by userix on Apr 30, 2014 2:49:18 GMT -5
This has happened to me on two separate occasions probably a month apart. I was wotting it down a flat street when all of a sudden I start losing power and when I came to a complete stop the engine just dies. Any attempts of trying to start it back up doesn't work. The starter does turn the engine freely, just no combustion I checked he fuel pump and can see file flowing to the carb freely. Gas tank is still half full. Carb was cleaned only a few days ago. No debris in float boat or clogging the jets. Vacuum lines are fine and not clogged or loose. No leaks either, as evident in me being able to ride after letting the bike rest a few minutes. After chilling for about 5 min, I can start the bike up again with no problems and I can still ride as if everything is fine. Nothing else changed. I have no idea what the problem is. There are other days where I am wotting all over my city for around 1 hr and have no problems whatsoever. This is a rare occurence but it has happened twice so far. Is it a faulty CDI? Am I overheating? Though I rode it much harder the day beofre without problems. I have no clue. Thanks for any help!
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Post by ramblinman on Apr 30, 2014 16:41:34 GMT -5
hard to say without more info. my only thought is the carb floats are not adjusted to the right height. but if that was the case then you would expect the bowl to empty everytime you rode WOT for extended period of time so idk. i think it is going to be hard to diagnose if it randomly happens. maybe someone with more experience can help.
welcome to the forum btw.
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Post by alleyoop on Apr 30, 2014 19:21:15 GMT -5
When was the last time you adjusted the valves they are probably tight espeically the Exhaust Valve and depending on the temps and how hot the motor is getting the valves will not close all the way and you loose compression. Then you have to wait for it to cool off before they will start again. So I think your on the edge and it happens now and then depending on the temp outside and how hot the motor gets.
So I suggest adjusting your valves both to .004 inchs.
Alleyoop
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Post by userix on May 1, 2014 11:42:53 GMT -5
Thanks guys for the replies. What alleyoop said does make sense. Since I don't always get this problem consistently. It is really random and only once in a while. My gy6 engine is brand new. Had it for about a month now. I been following the break in procedure for the first 50-100 mi of alternating the throttle and not wotting it all the time. What's the stock valve setting for both intake and exhaust? So a really tight valve that sticks can cause the backfire problem with immediate engine dying upon start? Because it is stuck in an open position, causing a loss in compression. Then once it cools down for a bit the valve will unstick? And by loosening the valve a little bit, I won't have this problem anymore. Is my logic and understand correct? Thanks again!
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Post by shalomdawg on May 1, 2014 22:24:38 GMT -5
howdy, since no one else has answered, i'll give you an opinion concerning what you said in your last post. the problem that allyooop referred to wouldn't be the valve sticking but when all the metal parts have expanded from the heat, the valves will not completely close which results in reduced compression and eventually will cause damage to the valves, stems, and seats. ---and cause the engine to be hard to start and run poorly when hot.
lotsa miles and smiles to ya
ken
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Post by nulldevice on May 1, 2014 22:54:18 GMT -5
If valve adjustment doesn't help, is the fuel pump a vacuum operated one? They can fail to work well at low vacuum conditions, like during WOT operation, especially when the gas tank isn't nearly full.
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Post by userix on May 2, 2014 11:11:05 GMT -5
howdy, since no one else has answered, i'll give you an opinion concerning what you said in your last post. the problem that allyooop referred to wouldn't be the valve sticking but when all the metal parts have expanded from the heat, the valves will not completely close which results in reduced compression and eventually will cause damage to the valves, stems, and seats. ---and cause the engine to be hard to start and run poorly when hot. lotsa miles and smiles to ya ken That makes sense. Will adjusting the valve gap fix this problem? It's starting to happen more often now during my rides. |
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Post by userix on May 2, 2014 11:17:34 GMT -5
If valve adjustment doesn't help, is the fuel pump a vacuum operated one? They can fail to work well at low vacuum conditions, like during WOT operation, especially when the gas tank isn't nearly full. Yeah. I have a mikuni fuel pump. But I always had this pump before and it didn't have any problems like this occur. This doesn't happen every time I wot either. Shouldn't I be having this problem every time I wot if it is the fuel pump having issues? Why does it not work too well when the tank isn't nearly full? I mean the fuel is still getting pumped to the carb consistently since the inlet valve in the gas tank is still completely submerged in gas. I do notice sometimes that there are bubbles coming from the pump in the fuel line to the carb. But I don't see any leaks of gas around the pump either. This is such a annoying problem. Since it usually happens at stop lights, after hearing some backfire from deceleration followed by the engine dying at stop, I wind up having to hold up traffic behind me to push the bike to the side of the road. It's embarrassing lol |
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Post by userix on May 2, 2014 12:03:22 GMT -5
Recent Update: I just rode my scooter to work and after only 2 min of riding from a cold start, I started getting lots of backfiring upon deceleration to a red light. During this time, if I apply throttle, it only bogs the engine down to stalling out. I barely wotted for only maybe 20 sec. I know the engine is probably not up to normal operating temperature and it's still having this problem. It sucks because now my ride is so unreliable. It's a new GY6 engine that I recently broke in following the proper procedure. Could it still be the fuel pump or maybe the valve is being too tight? I need to purchase a feeler gauge later today and check it out when the engine cools down. This is so annoying.
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Post by nulldevice on May 2, 2014 16:50:25 GMT -5
I suggested a low fuel level as a possible source of difficulty because the higher the pump has to lift the fuel the less volume of fuel it can pump.
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Post by userix on May 2, 2014 19:55:39 GMT -5
I suggested a low fuel level as a possible source of difficulty because the higher the pump has to lift the fuel the less volume of fuel it can pump. I just filled up today and it still has the same problem. It died again after a short wotting session. I'm suspecting valve too tight, running lean due to air leak. The air fuel ratio screw on the carb won't fix my problem? I heard it's only for idling and low speed? If it's running lean does switching the main jet to a larger size make it run richer? |
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Post by alleyoop on May 2, 2014 20:36:02 GMT -5
If it is backfiring on Deceleration, you have a bad air leak. The most common problem with backfiring on Decel is the Flange where the your pipe connects to the motor. With vibration and maybe the muffler not secured it loosen the nuts on the Flange and some times the nut actuallu comes completely off.
So I would Check if it is leaking there, no you can usually tell because you can hear the exhaust escaping from there your sound is much louder and different than when only the muffler is making the sound.
IT IS NOT that you need a bigger main jet it was running fine before with the jets you had in there. OF COURSE if you changed to a free flow muffler and or a free flow Air Filter that would most likely require at least a main jet 2 sizes larger.
Alleyoop
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Post by alleyoop on May 2, 2014 20:39:29 GMT -5
If it is backfiring on Deceleration, you have a bad air leak. The most common problem with backfiring on Decel is the Flange where the your pipe connects to the motor. With vibration and maybe the muffler not secured it loosen the nuts on the Flange and some times the nut actuallu comes completely off. So I would Check if it is leaking there, no you can usually tell because you can hear the exhaust escaping from there your sound is much louder and different than when only the muffler is making the sound. IT IS NOT that you need a bigger main jet it was running fine before with the jets you had in there. OF COURSE if you changed to a free flow muffler and or a free flow Air Filter that would most likely require at least a main jet 2 sizes larger. Alleyoop  |
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Post by userix on May 4, 2014 16:11:25 GMT -5
If it is backfiring on Deceleration, you have a bad air leak. The most common problem with backfiring on Decel is the Flange where the your pipe connects to the motor. With vibration and maybe the muffler not secured it loosen the nuts on the Flange and some times the nut actuallu comes completely off. So I would Check if it is leaking there, no you can usually tell because you can hear the exhaust escaping from there your sound is much louder and different than when only the muffler is making the sound. IT IS NOT that you need a bigger main jet it was running fine before with the jets you had in there. OF COURSE if you changed to a free flow muffler and or a free flow Air Filter that would most likely require at least a main jet 2 sizes larger. Alleyoop Yeah. The exhaust gasket and flange was the first thing I checked. The gasket is in excellent condition and no leaks there. |
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Post by alleyoop on May 4, 2014 16:33:31 GMT -5
Then check your air intake side of the carb or your intake manifold you have a bad air leak someplace.
Alleyoop
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..BAD TO THE BONE..
