KymcoForum.com
Scooters - 125 to 300 => Super 8 150 => Topic started by: Rdeangelis on April 15, 2012, 08:08:09 PM
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Hey all. What would cause my bike to backfire when decelerating when the engine is cold?
Ok, originally the bike didn't backfire at all. Winter hit and when it was really cold the engine would backfire just a couple times after startup when decelerating within the first minute of riding, but not after that. When it got warmer it wouldn't do it. I figured the cold was making the oils thick and making it happen, didnt worry about it too much.
Now though it's starting to do it even warm. It never lasts beyond the first couple minutes of being turned on, and they're not huge backfires, just baby farts, but it doesn't seem like a good thing that it happens every time I first start the bike up again till the engine warms up. Only when taking the throttle off.
So can anyone tell me what the likely cause of that is and what I can do to remedy it? Also, are these little backfires going to hurt the engine or parts in any way, or is it just annoying to me?
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It is unburnt fuel inside the pipe. The auto choke may be on it's way out. When cold the auto choke allows extra fuel in the air mix to give easier starting. If it fails you will be flooding when warm. If yours is taking longer, and longer to return to Norm. I would replace the choke. It wont hurt anything by back firing a little, but if it gets too bad it can blow a hole in the baffles or pipe.
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My Super 8 125 back fires. A tiny "tick" sound when decelerating. Does not do that when it was new. Is replacement of the choke the only answer? can't this be serviced or anything?
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Some times the idle mix screw is far enough out of wack to make it happen. But if it only happens when cold it is the choke. You can actually buy a whole carb on ebay for parts cheaper than buying an OEM choke. Any gy6 type carb will work for parts
http://www.ebay.com/itm/NEW-50CC-SCOOTER-MOPED-GY6-CARBURETOR-CARB-SUNL-ROKETA-/330476352602?pt=Other_Vehicle_Parts&hash=item4cf1ecf45a&vxp=mtr (http://www.ebay.com/itm/NEW-50CC-SCOOTER-MOPED-GY6-CARBURETOR-CARB-SUNL-ROKETA-/330476352602?pt=Other_Vehicle_Parts&hash=item4cf1ecf45a&vxp=mtr)
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Buy a whole carb assemby? wow! my scoot is only 7 months old!
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I'm suggesting buy the carb. just for the auto choke. You'll want the slide/diaphragm too. You can toss the rest in the bin. The choke alone is 40 bucks shipped from any OEM source. The math says... whole carb. = $avings
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Thanks Zombie! :)
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;)
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Thanks for the info! I'm planning on checking valve clearances sometime soon too, so that'll be a good chance to look around inside the scoot a little more and get a little familiar.
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You can take whole scoot apart with just the tools that fit in your pockets. It is really fun once you've opened it up a few times.
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You can take whole scoot apart with just the tools that fit in your pockets. It is really fun once you've opened it up a few times.
It's not fun in the Super 8. You need to wrestle a lot with the panels before you can take them out. The hardest part is the assembling back. It's just a good thing the plastics are tougher than some scoots.
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Well it seems I have that issue, the super 8 started to backfire a little yesterday and today when cold, and I don't think the carb is going out, the super 8 is 1 and a half Month old. Wonder if it needs some adjustment.
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Well it seems I have that issue, the super 8 started to backfire a little yesterday and today when cold, and I don't think the carb is going out, the super 8 is 1 and a half old. Wonder if it needs some adjustment.
That makes three of us already on this thread. Three Super 8s. Hmmm...think, think...
I found this in another site. http://www.ch250.net/techtips/21.htm (http://www.ch250.net/techtips/21.htm) Although its for a different scoot, the principle behind may help.
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Yeah I would have said all that but the "Q" button fell off my keyboard.
Excellent score Vivo!!!
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Hahaha!!! Good morning sir!!!
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Morning? Hell I'm late for yesterday... Or is it tomorrow? It can't be today already can it?
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Ooops! I forgot you're on the other part of the globe. Well, it's 11:00 a.m., April 18, 2012 here!
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APRIL? Wow...
I gotta get out more.
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Hey I am thinking about going with an Iridium spark plug, can anyone recommend one for my Kymco super 8 150?
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Cool, thanks for that find Vino, lots of places to look to fix the problem and may not have to buy new parts for it. Also, I just changed the oil yesterday to a 10w-40 full synthetic, and interestingly the backfires seem to have gone 90% away... All I got leaving work was one barely audible "puh."
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Hey I am thinking about going with an Iridium spark plug, can anyone recommend one for my Kymco super 8 150?
What is the OEM plug?
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the spark plug is an CR7HSA
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Denso IUF22 iridium spark plug - NGK equivalent CR7HSA
NGK CR7HSA Spark Plug ... NGK CR7HIX Iridium Spark Plug
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You might want to try an 8 or 9. 7 is pretty hot.
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sorry for my ignorance, what you mean by hot and what the numbers mean?
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sorry for my ignorance, what you mean by hot and what the numbers mean?
The operating temperature of a spark plug is the actual physical temperature at the tip of the spark plug within the running engine. This is important because it determines the efficiency of plug self-cleaning and is determined by a number of factors, but primarily the actual temperature within the combustion chamber. There is no direct relationship between the actual operating temperature of the spark plug and spark voltage. However, the level of torque currently being produced by the engine will strongly influence spark plug operating temperature because the maximum temperature and pressure occurs when the engine is operating near peak torque output (torque and RPM directly determine the power output). The temperature of the insulator responds to the thermal conditions it is exposed to in the combustion chamber but not vice versa. If the tip of the spark plug is too hot it can cause pre-ignition or sometimes detonation/knocking and damage may occur. If it is too cold, electrically conductive deposits may form on the insulator causing a loss of spark energy or the actual shorting-out of the spark current.
A spark plug is said to be "hot" if it is a better heat insulator, keeping more heat in the tip of the spark plug. A spark plug is said to be "cold" if it can conduct more heat out of the spark plug tip and lower the tip's temperature. Whether a spark plug is "hot" or "cold" is known as the heat range of the spark plug. The heat range of a spark plug is typically specified as a number, with some manufacturers using ascending numbers for hotter plugs and others doing the opposite, using ascending numbers for colder plugs.
The heat range of a spark plug is affected by the construction of the spark plug: the types of materials used, the length of insulator and the surface area of the plug exposed within the combustion chamber. For normal use, the selection of a spark plug heat range is a balance between keeping the tip hot enough at idle to prevent fouling and cold enough at maximum power to prevent pre-ignition or engine knocking. By examining "hotter" and "cooler" spark plugs of the same manufacturer side by side, the principle involved can be very clearly seen; the cooler plugs have a more substantial ceramic insulator filling the gap between the center electrode and the shell, effectively allowing more heat to be carried off by the shell, while the hotter plugs have less ceramic material, so that the tip is more isolated from the body of the plug and retains heat better.
Heat from the combustion chamber escapes through the exhaust gases, the side walls of the cylinder and the spark plug itself. The heat range of a spark plug has only a minute effect on combustion chamber and overall engine temperature. A cold plug will not materially cool down an engine's running temperature. (Too hot of a plug may, however, indirectly lead to a runaway pre-ignition condition that can increase engine temperature.) Rather, the main effect of a "hot" or "cold" plug is to affect the temperature of the tip of the spark plug.
It was common before the modern era of computerized fuel injection to specify at least a couple of different heat ranges for plugs for an automobile engine; a hotter plug for cars which were mostly driven slowly around the city, and a colder plug for sustained high speed highway use. This practice has, however, largely become obsolete now that cars' fuel/air mixtures and cylinder temperatures are maintained within a narrow range, for purposes of limiting emissions. Racing engines, however, still benefit from picking a proper plug heat range. Very old racing engines will sometimes have two sets of plugs, one just for starting and another to be installed for driving once the engine is warmed up.
Spark plug manufacturers use different numbers to denote heat range of their spark plugs.
Thanks Wikipedia!!!
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Before I got to Thank's Wiki... I thought you were f***ing with us. I couldn't figure if you were a rocket surgeon or a brain scientist for a second.
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On the top of the vavle cover there is a steel pipe that wraps around to the exhaust port, that's a scooter version of an egr valve it dumps air from the Carb into the exhaust pipe to burn off smog, but it also klls proformance and causes back fires! It can be plugged with a 1/4 inch threaded bung screw from Lowes. Highly recommended if you have a straight or glass pack pipe.
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Before I got to Thank's Wiki... I thought you were f***ing with us. I couldn't figure if you were a rocket surgeon or a brain scientist for a second.
Gotcha!!! ;D
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On the top of the vavle cover there is a steel pipe that wraps around to the exhaust port, that's a scooter version of an egr valve it dumps air from the Carb into the exhaust pipe to burn off smog, but it also klls proformance and causes back fires! It can be plugged with a 1/4 inch threaded bung screw from Lowes. Highly recommended if you have a straight or glass pack pipe.
Is this on the Super 8 or every other scooter?
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Is this on the Super 8 or every other scooter?
Yes, there is on the Super 8. It's part of the scoot's emission system which includes the catalytic converter inside the muffler. . Causes backfire when there's a leak. Burns not smog but unburned fuel which makes the scoot Euro III (I think) compliant. Some owners I know just plug this or put a rubber hose and plug with a small marble.
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Hi all, I'm new here and I've got a Super 8 125 that backfires in the exhaust during deceleration especially from higher speeds (say,70-90kmh). They are really loud POPS, like gunshots and its scaring the hell out of my wife(and me too!!!),who rides piliion with me in the mornings to work. I've notice that it happens during sudden roll-off deceleration from speed. If I roll-off the throttle gently,it does not happen, so I've had to change the way I throttle off (gently) to avoid the "gunshots" but not when I need to panic brake.... My scoot is almost 3 yrs old now and has only done about 19900km (mostly to and from work, about 28km per day). I live in a tropical & humid country with lotsa traffic. I have recently checked & adjusted the valve clearances to 0.004 for both valves and removed the carb.to clean it with carb. spray (removed both the jets but did not remove the fuel mixture screw...). It hasn't been performing like it used to since a couple of months back(poor pick-up and hesitation while reapplying throttle at speed...),which prompted me to check the valves & clean the carb.in the first place, but now its the backfiring tat's giving me a headache. I've been tinkering with the fuel mixture screw (screwing it in and out,.BTW,which way enriches the mixture? In or out?)without much help.Went back to the scooter shop & the mech.told me its the secondary air injection unit that's causing the backfiring & tat I should remove it. Is he right? Should I let him do it or can I do it myself or is it something else instead?
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Went back to the scooter shop & the mech.told me its the secondary air injection unit that's causing the backfiring & tat I should remove it. Is he right? Should I let him do it or can I do it myself or is it something else instead?
Just have it plugged, then see if the backfire disappears.
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To enrichen the idle turn the screw counter clockwise. Try what Vivo suggests, and pull the carb cap to check the Diaphragm for swelling/holes.
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Thanks guys, will try plugging the unit myself and also check if the diaphragm's OK. Will keep U all posted. Cheers!!
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Hi guys, I have removed the metal cap above the carb. and a spring popped out. Beneath it is a thin round rubbery shroud attached to a short plastic cylinder. Under this cylinder is a needle which fits into a small recessed hole (think it leads to the float bowl or somewhere...in the carb.body). The rubber shroud still looked OK. There were no holes in it. Sprayed silicon all over it and reinstalled it. Guess tat would keep it soft and tender I hope... The additional air injection pump (a small black tennis ball-sized thing...) has 3 rubber hoses sprouting out of it. Two of the hoses are fat ones while one is skinny. One of the fat hoses is connected to the cam-cover, the other fat hose is open-ended (for fresh air intake?) and the skinny one...well I can't quite see where that one leads to but it appears to go in the direction of the carb,or block..... Ehh, which hose should I be plugging? ??? The fresh air intake hose? Thank U
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1. Plug the one on the block (cam cover).
2. Plug the hose going to the manifold. Use a metal ball or marble.
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Thanks Vivo and the rest of U guys for the advice. I have blocked the fat hose going into the top of the cam-cover and the thin one going into the intake manifold and the backfiring from the exhaust stopped. No more 'gunshots' heard,not even small farts. One question, will the sys. (exhaust muffler,etc) clog up over time with the air pump dismantle or will it possibly cause the engine to fail?
Thanks again!
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No. But unplug the fat hose on top of the cam cover. The scoot needs that on to vent the crank case. Just run a new hose from that nipple to the bottom of the engine near the center stand.
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No. But unplug the fat hose on top of the cam cover. The scoot needs that on to vent the crank case. Just run a new hose from that nipple to the bottom of the engine near the center stand.
;)
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Okie Dokie,thank U very much guys!! Cheerio!