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Post by userix on May 10, 2014 10:04:16 GMT -5
Have you tracked down the source of the bubbles in your fuel line yet? Bubbles mean extra air, which could make it lean when they are present. It weird, I actually don't see anymore bubbles in the fuel lines right now. Not sure what happened but so far they are gone. But the problems still are present. So mind boggling... |
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Post by userix on May 10, 2014 3:31:42 GMT -5
Your main jet has nothing to do with the De-Cel popping when you let go of the throttle the needle drops down into the main jet and shuts off all gas coming out of it because the BUTTERFLY is closed and closing the air from creating pressure in the venturi. This popping stuff is all due to the fuel from the pilot jet. Did you change the pilot jet and to what size? Alleyoop I use a CVK Keihin carb and the pilot jet size is 36. And I haven't changed this jet since I got the bike. But because I still run into the occassional stalling out problem during WOT, that still means my main jet is too small? And once I come to a complete stop, the engine just dies. But it usually can be started again right away. As for the pilot jet, I am really confused now. Because I had the issue where a quick twist of the throttle causes my idle to drop way below normal idling RPM, it means my pilot jet is too rich, or too big. But at the same time, I still have the decel popping noise problem, which I just checked today during a ride, it could occur at any range of the RPM, from near WOT and also down closer to the idling RPM. And decel popping is indicative of a lean condition, which mean my pilot jet is too small. I'm not sure with the two opposite problems I am having, if the pilot jet is too small or too big. |
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Post by userix on May 9, 2014 20:24:10 GMT -5
No actually If the IDLE drops down below your set Idle and it kills the motor that is a sign of it being to RICH. No your pilot jet is not to small maybe TO BIG. POPPING during decel is LEAN it could be caused by your IDLE set to low the idle should be 1500-1800 where ever it idles the smoothest. If the Carb has a ACV valve that is what feeds it extra fuel on DECEL for the sudden closing of the throttle so it does not run lean. Now from WOT and you let go of the throttle and it starts to pop, when does it start to pop almost down at idle or as soon as you let go of the throttle when the rpms have yet not dropped. That could be caused by your AIR BUBBLES which would make it run lean not getting gas. So Like Jerry said I would FIRST find what is causing the AIR BUBBLES because that is what is throwing everything else off. Alleyoop Ok. So it makes sense now, my pilot jet is probably too big because that is a problem I have been having for a while now. Now as for the popping, it occurs as soon as I let go of the throttle. Sometimes it happens maybe a little higher than halfway down from idle. But it mainly immediately after I release the throttle and the RPMs are still fairly high. It's nowhere near idle rpm speeds when the popping does occur. So as of now, it looks like the pilot jet might be too big and my main jet might be too small? |
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Post by userix on May 9, 2014 15:03:05 GMT -5
Dipping in RPMs during idle is usually and indication of an air leak, or fuel flow problem. Since you have those air bubbles at times in your fuel line, I would say you need to find the source there before attempting to find air leaks. But the dipping in idle only happens if I quickly twist the throttle to wot and let go. If I let it idle by itself, then then idle is consistent and can idle all day long. According to the af mixture screw tuning guide linked by alleyoop, if the idle dips below normal idle after a quick throttle twist, then it means it's too rich. But that goes against the fact that I am too lean, as indicated by popping on deceleration. I'm confused as to what is really wrong lol |
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Post by userix on May 9, 2014 3:33:56 GMT -5
Thanks for the reply. Now what about the weird dipping in idle RPM after a quick flip of the throttle? Is that caused by a pilot jet that is too small? Sometimes the RPM dips so low that it kills the engine.
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Post by userix on May 8, 2014 21:33:51 GMT -5
Another thing I notice, and this has been like this from before I started having the popping/stalling issue on WOT, when I blip the throttle (WOT it for maybe half a second) from a standstill, the RPM dips really low (~700rpm) and almost completely stalls out, and in some cases, the engine does stall. But if it doesn't stall, the RPM will return to normal idling of ~2000rpm within a couple seconds. What causes this to happen? Is it related to the slow/pilot jet or A/F mixture screw? How do I fix this problem?
I also notice when I start popping on decel, I notice lots of bubbles in my fuel line going to the carb from my Mikuni pump. I just rebuilt the pump using genuine mikuni parts and I made sure all vacuum lines and gas lines are tight. As soon as the engine returns to normal, the fuel lines are free of bubbles. I'm not sure why there are bubbles only during the time I get popping on decel and loss of power during WOT.
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Post by userix on May 7, 2014 1:30:13 GMT -5
Ok, popping on decel you need MORE FUEL, POPPING on EXCEL or at HIGH SPEED to MUCH FUEL. So richen up the fuel ratio mixture give it 1/4 to 1/2 turn COUNTER CLOCKWISE to richen feed it more fuel(this is the FUEL RATIO MIXTURE on the LEFT SIDE of the CARB(not the IDLE SPEED SCREW on the Throttle cable side with the spring under it). Richen it up might also help your loss of power sometimes. Alleyoop Thanks. I understand the idle screw and air mixture screws are different. But I thought the air mixture screw only affects idle and low speed. I thought wot was completely dependent on the main jets And before the popping happens, I start to lose power and stall during wot. I checked the main jet. It is a 102 |
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Post by userix on May 6, 2014 21:15:18 GMT -5
RIGHT ON JERRY  Ok lets clear this up, NOW your saying it is popping during EXCELERATING that is a completely different fix. POPPING at WOT is caused by your MAIN JET being to big. What size main jet have you got in it? Alleyoop Sorry for not being clear in my description. Ok. When I wot, sometimes I lose power randomly, as if I ran out of fuel. As soon as I let go of the throttle, then the popping happens, hence during deceleration. It doesn't pop during the wot, but it does stall out during the wot. The popping sounds only happen once I let go of the throttle. I just don't get why it doesn't happen all the time. It's just once in a while randomly. Is the jet size printed on the jet itself? I'm not sure what size is currently in there. Should be the stock carb |
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Post by userix on May 6, 2014 15:38:05 GMT -5
In your previous Post you said in order to richen up the mixture, I should turn it counter clockwise. Isn't it suppose to be clockwise to richen, according to what you said earlier in your post?
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Post by userix on May 6, 2014 15:27:03 GMT -5
ok, lets be clear about the sound you are hearing when you decelerate. Is it really a BACKFIRE or is it a POPPING sound big difference. Backfiring is LIKE A GUN GOING off "POW" "POW", POPPING IS just that a POP POP sound. Backfiring is a VERY LEAN CONDITION and usually occurs with a bad AIR leak but it can be caused by not enough fuel when the Butterfly is all of a sudden closed. A POP POP is also a lean condition but will not cause damage like a BACKFIRE will. So first when it is nice and hot at what RPMs does the motor IDLE at? A. The pilot jet fuel outlets are right by the BUTTERFLY, There are usually 4 of them. The Idle speed screw turning it clockwise moves the butterfly back EXPOSING more of the fuel outlets. That is why the IDLE GOES UP more fuel and little more air is being sucked in. Turning it Counter Clockwise lets the Butterfly move forward COVERING more of the fuel outlets and air and your IDLE GOES DOWN. So when you let go of the throttle it may be covering to many of the little fuel outlets due to the idle being to low. 1. If the IDLE is to low it can cause it to run lean from a WOT run from a sudden cut off of fuel down to idle and not enough fuel is sucked up to keep it from running lean. 2. If it is idling at 1500-1800 rpms then rich-en up the Fuel Mixture 1/4-1/2 turn counter clockwise and give that a shot. Alleyoop Here I labeled where the fuel outlets are so you get how the butterfly covers the tiny pilot jet fuel outlets or expose them.  Ok. It's more of popping noises. Not bang bang loud. But this problem happens only during wot. It actually starts dying during wot. Like I lose power while wotting, then as soon as I let go of the throttle it throws a few pops and the. The engine dies. But most of the time, I can start the bike right back up almost immediately. I'm just so confused what is wrong. I mean if it was fuel ratio mixtures and all that I should be consistently running into problems. But this issues only appears once is a while. Seeing how I replaced gasket for exhaust and intake manifold and I made sure no leaks are coming from head gasket base gasket and valve cover, I'm not sure what else it could be. The only thing I can think of is maybe fuel starvation? Could it be my pump having issues? But again if it was the pump going out I should be having problems very often. It just doesn't make sense how after this problem occurs, I can continue riding at wot for a good 30 minutes without any problems for the rest of the ride, which is usually an hour or so more. It probably can't be the electrical system either like CDI? And I'm guessing because this is only happening on wot, the air fuel screw has no effect on it My idling right now is roughly 1800-2200 rpm at running temp. Idle is pretty steady too. Thanks so much for taking time to help me out. This problem is driving me nuts. I keep having to push my bike to the side of the road at traffic lights. Lol |
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Post by userix on May 5, 2014 11:55:14 GMT -5
Then check your air intake side of the carb or your intake manifold you have a bad air leak someplace. Alleyoop I checked the carb and intake as well the intake manifold is brand new and there are no leaks there as well. The carb works fine too. If it was a bad air leak, wouldn't I be having problems all the time? My problem happens like once randomly during a ride and continues to run perfectly fine afterwards. Could it still be the valve gap problem? What about a head gasket leak? Could that cause the problem? |
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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 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 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 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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