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Post by tocoo on Aug 1, 2017 9:20:16 GMT -5
Since I never had a chocolate spark plug, I decided to look at the jets of the carburetor. THe original carburetor from peugeot has -main jet with 78 on it -idle jet with 30 on it the new carburetor for chinese scooter has -main jet with 76 on it -idle jet with 30 on it Initially, I thought that the manufacturer used the best jets for their carburetors, but I read that it may not be the case and I read here that the number on a jet is not consistent across the manufacturers. Is it worth it to buy a set of higher jets ? There is a seller here www.aliexpress.com/item/6-main-jet-4-99-free-shipping-Keihin-carburetor-CVK-PE-PZ-main-injectors-Nozzle/32368690206.htmlwitht he sizes 75.78.80.82.85.88. I would like values such as 77,79,80,81,82,83,84 but nobody sells those this is the add for the idle jet www.aliexpress.com/item/Keihin-carburetor-motorcycle-CB400-CG125-250-vice-pilot-jet-spray-PE-CVK-FCR-available-12-injectors/32251289390.htmlwhat sizes should I try ? 30,31,33,35,38,40,42,45,48,50,52,55,58.60.62.65.68,70,72,75.
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Post by 90GTVert on Aug 1, 2017 14:50:45 GMT -5
You really don't need to have every jet number (80, 81,82,83,84,85...). Every 5 numbers is OK (80,85,90). Every 2-3 is good for fine tuning (80,82.5,85).
If the primary reason to dive into this is cold starting, I'd try making sure the valves are adjusted and setting the idle mixture and speed first.
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Post by FrankenMech on Aug 2, 2017 0:56:56 GMT -5
The manufacturers use jets for some 'theoretical' application that may not match yours. The big Chinese distributors may be selling 'overstock' carbs made for some specific application to other distributors. Tuning is almost always required for your application.
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Post by tocoo on Aug 3, 2017 2:50:28 GMT -5
I made a mistake to destroy a screw on my new carburetor, while I tried to swap the main jets from the peugeot carburetor to the new one. In the scooter, put the original carburetor in the mean time. My plan is to -create a new print for a flat head screwdriver -apply wd40 on the screw -use a impact screwdriver with flat bit -if this fails, I will use a 2mm left drill bit
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Post by tocoo on Aug 3, 2017 3:04:17 GMT -5
my next purchase -perhaps rent a tool to measure the compression -an original cdi -paper gaskets for the air manifold -some jets -if my new carburetor is stuck with this destroyed screw, perhaps a new ''unlocked'' carburetor because the carburetor from peugeot has a semi-D screw which I cannot turn which led me to purchase the new carburetor by thinking that I could increase the fuel/air ratio, but even this failed to make easier cold start on battery I ordered from amazon a ''hald-D'' but it is not the right size for this screw -some fuel hose because mine is very hard now (whereas the original one is still tender) -a new fuel filter (because the new fuel hose I put hardened and when I tried to remove the fuel hose from the fuel filter, I managed to destroy the entrance of the fuel filter) I looked at the generic manual for the qmb139 engine and I believe the red part is what I must focus on. My spark plug is never ever wet, even right after I crank.
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Post by FrankenMech on Aug 3, 2017 4:44:55 GMT -5
You are good at making things. Get a piece of steel brake line tubing that will fit the OD of that adjustment screw then collapse one side inwards to get a grip on the flat. Once you have the screw out use a dremel tool and cut a slot in it. There is nothing sacred about the casting around that screw. You may also be able to cut a slot through the screw and the casting. Just don't cut into the bowl side of the casting too far.
That ruined screw head should come out easily after you slot it for a flat screwdriver bit.
Phillips head screws are designed so that the driver cams out under load. They designed it that way to prevent twisting off fasteners in factories. I guess it was a good idea at the time. Modern assembly tools don't have that problem but we still suffer the phillips head screw BS. Impact drivers are my favorite tool to remove them. The impact action keeps the bit engaged and prevents cam-out. I try to avoid using phillips head screws as much as possible.
After a scoot has been sitting for a while the carb float bowl dries out and is empty. Getting fuel into the carb is the first step. My scoot has a fuel tank below the level of the carb so I have a vacuum operated fuel pump instead of a vacuum operated petcock. I use a small electric fuel pump in parallel to the vacuum pump to 'prime' my carb so it starts almost instantly.
If your carb throttle plates are open too far you will have a poor vacuum signal to the petcock. You can use a hand operated vacuum pump to apply vacuum to the fuel petcock.
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Post by tocoo on Aug 6, 2017 11:02:02 GMT -5
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Post by FrankenMech on Aug 7, 2017 3:27:17 GMT -5
I have a corded Dremel tool with no speed control. I made a speed control from a light dimmer. It has outlasted many battery operated tools. I try to get corded tools for infrequently operated tools or ones that get used a lot when they are used. Batteries die and have to be replaced often. Battery technologies change which obsoletes tools. Batteries are kind of a PITA. I wish they would have come up with 'universal' batteries years ago like they finally made them do for phones.
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Post by greginisn on Aug 9, 2017 2:18:20 GMT -5
You do seem to have more than one problem I think. You wrote that with your finger in the spark plug hole you only ever felt suction. You really should feel a pressure during the combustion stroke. My scoot won't run down the road for 5 minutes with valves set at .004" so had to increase gap to about .006 or .007". The valves click a bit but it starts & runs
And you wrote that the plug is never wet. Could you be having a problem with a sticky or sticking float valve?
Good luck.
Greg
One other thing, If you are using gas with ethanol in it you won't believe the crud it will create in your carb. You may have to disassemble the carb and clean ALL the passages. A thread or two of stranded copper wire does a great job and won't mess anything up.
Again, good luck.
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Post by tocoo on Aug 11, 2017 7:02:19 GMT -5
In the last few days, I installed the original carburetor. After two days of non-use, with the newest spark plug, the scooter has trouble to cold start both on the kick and the battery. Still no problem for hot start, not problem of throttle. My fuel hose dried up even more and even broke while I was using the scooter. All of a sudden, I smelled fuel and I saw a liquid dripping from the scooter. I rushed home and I saw the fuel hose cracked open just at the entrance to the carburetor, where the hose makes a 90 degree turn due to a lack of length of the fuel hose.... Then I received the left drill bit. It failed too. I drilled and drilled but at no point it turned the screwed out and all I managed was to peirced through the screw.... I do not know how to salvage this carburetor. I imagine that buying a thicker left drill bit could have better grip to the screw. Or I use a bigger normal drill bit to make a new hole. Then I would need to make new lines in the hole and purchase a bigger screw that I do not have. It seems like a lot of work and more expensive via the purchasing of new tools that I will never use again, than buying a new unbridled carburetor and use this one for spare parts or even selling it as is.
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Post by tocoo on Aug 11, 2017 7:12:30 GMT -5
You do seem to have more than one problem I think. You wrote that with your finger in the spark plug hole you only ever felt suction. You really should feel a pressure during the combustion stroke. My scoot won't run down the road for 5 minutes with valves set at .004" so had to increase gap to about .006 or .007". The valves click a bit but it starts & runs And you wrote that the plug is never wet. Could you be having a problem with a sticky or sticking float valve? Good luck. Greg One other thing, If you are using gas with ethanol in it you won't believe the crud it will create in your carb. You may have to disassemble the carb and clean ALL the passages. A thread or two of stranded copper wire does a great job and won't mess anything up. Again, good luck. Yes I use only sp95 and never ethanol+fuel. So you confirm that for the compression test, you continuously get the finger sucked in the hole for the spark plug ? Is it physically possible to remove the finger while the suction happens ?
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Post by tocoo on Aug 11, 2017 9:25:32 GMT -5
the only good news for today is that, in the original mixture screw of the original carburetor, I drilled a print for a flat head screwdriver and I removed the screw. It turns out that the o-ring was broken, so I replaced the original mixture with the mixture screw from the new carburetor. I also did set the carburetor.
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Post by benji on Aug 11, 2017 11:10:01 GMT -5
You do seem to have more than one problem I think. You wrote that with your finger in the spark plug hole you only ever felt suction. You really should feel a pressure during the combustion stroke. My scoot won't run down the road for 5 minutes with valves set at .004" so had to increase gap to about .006 or .007". The valves click a bit but it starts & runs And you wrote that the plug is never wet. Could you be having a problem with a sticky or sticking float valve? Good luck. Greg One other thing, If you are using gas with ethanol in it you won't believe the crud it will create in your carb. You may have to disassemble the carb and clean ALL the passages. A thread or two of stranded copper wire does a great job and won't mess anything up. Again, good luck. Yes I use only sp95 and never ethanol+fuel. So you confirm that for the compression test, you continuously get the finger sucked in the hole for the spark plug ? Is it physically possible to remove the finger while the suction happens ? a compression tester may be more accurate. Cheap ones are available at auto parts stores
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Post by FrankenMech on Aug 11, 2017 17:30:40 GMT -5
Yes I use only sp95 and never ethanol+fuel. So you confirm that for the compression test, you continuously get the finger sucked in the hole for the spark plug ? Is it physically possible to remove the finger while the suction happens ? With your finger in the spark plug hole you will get one 'suck' and one 'blow' every two revolutions on a 4-T engine. en.wikipedia.org/wiki/Four-stroke_engineKeep the carb for parts and buy another one if needed.
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Post by tocoo on Aug 15, 2017 7:53:46 GMT -5
I managed to remove the broken screw from the new carburetor which is installed now. I swapped the main jets, so the new carburetor has a main jet with 78 written on it. I do not see a difference, but -cold start with the kick fails after less than one day of non-use -hot start with the kick works well [only one stroke needed, after I start on battery, then turn off the scooter, then try with the kick at once]
I do have spark with the kick and compression at cold start, but somehow the scooter does not turn over.
I could not test the cold start on battery yet, because I needed the scooter and the test of starting with the battery requires several day of non use.
I will try the kick start with the main jet of 76.
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