|
|
Post by nikibahama on Oct 15, 2024 14:36:34 GMT -5
While I have an extensive background in Automotive maintenance/mechanics, I am new to scooters and know next to nothing about carburetors (other than them being an incredibly outdated technology and a pain in the ass).
I have a D150 (150cc) Italika 4 stroke scooter. Months ago it began sputtering and dying. I'd go 100 feet and it would die. It would take forever to start again, go 500 feet and die, etc... I drained the gas tank, drained the fuel lines, replaced the fuel lines, replaced the fuel filter, blew out the carburetor with carb cleaner, re-assembled everything, filled with fresh gas and voila... she was back up and running like new. I hypothesized there must have been water in the gas somewhere, but here we are several months later and it's back to the same sputtering and dying garbage. I drained the gas, not a drop of water in it...
I drained gas from the drain tube that comes off the carb and hangs by the rear wheel. Once drained the moped started up and ran again for a few miles. Then it started sputtering again and I repeated... ran again for a couple miles. Every time I repeated this, it ran for less distance. Some guy passing by says "put it on the stand, it will start", so I put it on the rear stand (instead of kick stand) and it starts... No idea what the stupid stand has to do with anything, but thought I'd mention it. Put it back on the ground and it just turns and turns without starting (or starts after a minute of trying). So I put it back on the stand and it starts and begins sputtering. I disconnect the fuel feed line from the carburetor. Now it runs like a beast. Revs up, redlines, holds there, keeps going... runs for a minute straight without fuel connected. Re-connect the fuel line and the thing just sputters and dies. Spark plug is black so we're obviously running rich, but this is a stupid simple system... gravity drain fuel with a vacuum-controlled valve that then passes the gas through a filter and down to the carb. There is no fuel pump here where I could possibly be "pumping" too much fuel into this thing, nor have I made any adjustments to the carburetor (it's factory). Can someone please help me understand what the hell is going on here? I can rebuild an entire 8 cylinder motor in my garage but some stupid non-pumped, gravity fed factory carburetor with less than 1500 miles on it since new, is constantly giving problems and running rich without any excessive fuel pressure or force? I'm at my wits end with this stupid piece of s___.
|
|
|
|
Post by FrankenMech on Oct 15, 2024 15:16:53 GMT -5
There is nothing wrong with carbs if one understands them but very few do. Water in the fuel will saturate the stupid paper fuel filters. Do not use the sintered metal ones either. Try a plastic mesh one that can be back-flushed and reused. A black plug can also indicate a misfire. Always use 100% gas in small engines. Never use an ethanol mix, the ethanol draws water from the environment. Also under certain conditions carbs will ice over and freeze. Aircraft were some of the first engines to find out the problems with temperature and humidity.
|
|
|
|
Post by nikibahama on Oct 15, 2024 16:45:24 GMT -5
There is nothing wrong with carbs if one understands them but very few do. Water in the fuel will saturate the stupid paper fuel filters. Do not use the sintered metal ones either. Try a plastic mesh one that can be back-flushed and reused. A black plug can also indicate a misfire. Always use 100% gas in small engines. Never use an ethanol mix, the ethanol draws water from the environment. Also under certain conditions carbs will ice over and freeze. Aircraft were some of the first engines to find out the problems with temperature and humidity. I live in Mexico and buy premium gas. Don't know if it has ethanol or not, but it's all we have available and there's more mopeds on the streets than cars here. None here in my community have this issue. The fuel filter is new from the dealer. Any idea on what is going on here based on what I wrote? |
|
|
|
Post by oldgeek on Oct 15, 2024 16:58:49 GMT -5
There is nothing wrong with carbs if one understands them but very few do. Water in the fuel will saturate the stupid paper fuel filters. Do not use the sintered metal ones either. Try a plastic mesh one that can be back-flushed and reused. A black plug can also indicate a misfire. Always use 100% gas in small engines. Never use an ethanol mix, the ethanol draws water from the environment. Also under certain conditions carbs will ice over and freeze. Aircraft were some of the first engines to find out the problems with temperature and humidity. I live in Mexico and buy premium gas. Don't know if it has ethanol or not, but it's all we have available and there's more mopeds on the streets than cars here. None here in my community have this issue. The fuel filter is new from the dealer. Any idea on what is going on here based on what I wrote? As Frankenmech mentioned the fuel filter may be clogged or something along the fuel path is stuck or clogged causing vapor lock. Gas cap vents, vacuum petcock, carb vents clogged. Also that scoot may have side stand safety interlock to keep it from starting on the side stand. |
|
|
|
Post by nikibahama on Oct 15, 2024 18:12:24 GMT -5
It has never had an issues prior with starting on the side kickstand. The fuel filter is brand new (it's not clogged). With the gas cap open it runs the same. Don't know what you're referring to as a vacuum petcock (there is a fuel regulator with a vacuum line) or carb vents. Again, I'm not familiar with carbs so just throwing out terms isn't teaching me anything. Still can't comprehend why it's so hard to put a fuel injector on a tiny motor, but the Chinese must hate technology or something.
|
|
|
|
Post by oldgeek on Oct 15, 2024 18:35:07 GMT -5
It has never had an issues prior with starting on the side kickstand. The fuel filter is brand new (it's not clogged). With the gas cap open it runs the same. Don't know what you're referring to as a vacuum petcock (there is a fuel regulator with a vacuum line) or carb vents. Again, I'm not familiar with carbs so just throwing out terms isn't teaching me anything. Still can't comprehend why it's so hard to put a fuel injector on a tiny motor, but the Chinese must hate technology or something. Is the part you are calling a "fuel regulator" round or square? If it is round and on the bottom of the tank it is a vacuum petcock. Fuel regulators are usually found on EFI systems. It's all about $$ that the Chinese use carbs. Carbs are cheaper than EFI systems. |
|
|
|
Post by nikibahama on Oct 16, 2024 16:13:41 GMT -5
It has never had an issues prior with starting on the side kickstand. The fuel filter is brand new (it's not clogged). With the gas cap open it runs the same. Don't know what you're referring to as a vacuum petcock (there is a fuel regulator with a vacuum line) or carb vents. Again, I'm not familiar with carbs so just throwing out terms isn't teaching me anything. Still can't comprehend why it's so hard to put a fuel injector on a tiny motor, but the Chinese must hate technology or something. Is the part you are calling a "fuel regulator" round or square? If it is round and on the bottom of the tank it is a vacuum petcock. Fuel regulators are usually found on EFI systems. It's all about $$ that the Chinese use carbs. Carbs are cheaper than EFI systems. Thank you for this. In the automotive/fuel injected world the part looks like a fuel pressure regulator (round with vacuum ports to the engine to control fuel flow/pressure). I now understand this is referred to as a petcock for the moped/scooter. I theorize either that is causing my issue or the float bowl drain screw. I removed the carburetor today, drained it, sprayed every opening/inlet with carb cleaner, drained it, let it dry, re-installed it and now it runs like a champ again. I'm thinking my issue has something to do with the float bowl drain screw. I just know that when I drained fuel from the float bowl drain hose, it would start up again and run for a while... Then you empty the thing completely and it runs good for a decent while. Can someone explain to me what the float bowl drain screw does and how it should be adjusted, or if it could also be causing my issue? |
|
|
|
Post by oldgeek on Oct 16, 2024 17:37:45 GMT -5
I am a 2 stroke guy, not so much a 4 stroke person. I dont see the drain screw causing your problem but it is not impossible. The float may be out of adjustment, they bend easily during disassembly and assembly.
To test the vacuum petcock pull the fuel line from the carb then pull the vacuum line from where it is connected, leaving the vacuum line connected to the petcock. Suck on the vacuum line, it will open the petcock and fuel should flow freely from the fuel line as long as vacuum is applied.
|
|
|
|
Post by nikibahama on Oct 17, 2024 10:14:19 GMT -5
I am a 2 stroke guy, not so much a 4 stroke person. I dont see the drain screw causing your problem but it is not impossible. The float may be out of adjustment, they bend easily during disassembly and assembly. To test the vacuum petcock pull the fuel line from the carb then pull the vacuum line from where it is connected, leaving the vacuum line connected to the petcock. Suck on the vacuum line, it will open the petcock and fuel should flow freely from the fuel line as long as vacuum is applied. Fuel definitely flows when vacuum is applied... I would say several times more fuel than would be necessary. |
|
|
|
Post by oldgeek on Oct 17, 2024 16:48:23 GMT -5
I am a 2 stroke guy, not so much a 4 stroke person. I dont see the drain screw causing your problem but it is not impossible. The float may be out of adjustment, they bend easily during disassembly and assembly. To test the vacuum petcock pull the fuel line from the carb then pull the vacuum line from where it is connected, leaving the vacuum line connected to the petcock. Suck on the vacuum line, it will open the petcock and fuel should flow freely from the fuel line as long as vacuum is applied. Fuel definitely flows when vacuum is applied... I would say several times more fuel than would be necessary. Likely carb related then, you have gas to the carb so maybe floats out of adjustment or float valve? |
|
|
|
Post by nikibahama on Oct 18, 2024 10:27:32 GMT -5
I am definitely thinking this is a float related problem. I haven't opened that part of the carb nor adjusted it, but I do see a float bowl drain screw on the carburetor itself. What should I be looking for? How do I test/make sure it's within spec?
|
|
|
|
Post by oldgeek on Oct 19, 2024 7:22:14 GMT -5
I am definitely thinking this is a float related problem. I haven't opened that part of the carb nor adjusted it, but I do see a float bowl drain screw on the carburetor itself. What should I be looking for? How do I test/make sure it's within spec? To adjust the float height, bend the metal tab that contacts the float valve.  |
|
|
|
Post by GrumpyUnk on Oct 19, 2024 16:20:01 GMT -5
From the above, I would suspect your machine is being flooded with fuel. The picture of the carb directly above does not reflect normal CVK with a tilted bowl. The bowl gasket surface is not parallel to the float when set properly. It IS parallel to a line going through the intake and outlet of the carb leading to the intake.
FWIW.
When you put it on the stand, you may affect the level of the fuel in the bowl, and it runs great. Put it back on two tires... and not so good.
2 cents, depreciated...
tom
|
|
|
|
Post by nikibahama on Nov 20, 2024 10:14:05 GMT -5
Well I couldn't ever find a FSM on this moped (even searching in Spanish) that contained the float height specs. When I looked up several videos on how to set the float height, I was thoroughly disgusted. How do we know how much oil to fill in an engine? Marks on a dipstick. How do we check and set our timing? Marks on the crank pulley. How do we set our cams? Marks on a timing cover. How do we set a float in a carburetor? Bend a metal tab with zero marks or indicators for where to align it... This is the most half-assed engineering and there is no excuse for it. I just went ahead and bought a new, cheap Chinese carb (all of these bikes are made in China anyhow). I had already taken the damn thing apart twice, set it per the videos, and the thing just kept sputtering. All parts inside were as clean as brand new... Nothing was wrong with it. If this new carb doesn't fix the issue, I'm saying "F it" and buying the fuel injection conversion kit for $250.
|
|
|
|
Post by GrumpyUnk on Nov 20, 2024 11:45:15 GMT -5
A month between posts... I thought this was fixed.
The exact height of the float is not required nearly as much if it is relatively
flat when the carb is mounted. With the venturi and the outlet to the intake elbow
about flat to the ground, they can be used as 'substitute' gasket surface alignment
references.
If you take the CVK, hold it upside down, and the float should be relatively parallel
to the venturi, and it will work reasonably well.
You may have had a damaged float valve, either the needle or the seat. That would
exaggerate any mal-adjustment.
Dumping the fuel from the float bowl using the external drain more or less lets the
carb start from low fuel level, or 'on target' fuel level, and it runs until the
flaky float valve lets the level get too high.
As a guess from afar, hope your replacement works. It could even be the needle is
a bit jammed and does not close off the fuel supply when the level gets high and the
float tries to push the needle against the seat. That could/would explain how it
can run for a while and then stalls..
tom
|
|
