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Post by eman on May 22, 2016 16:52:04 GMT -5
Used 50cc scooter that is hard starting. Battery is new and fully charged. Cranks over great and valves are adjusted properly. Runs good once started. Start problem appears to be fuel problem. Carb has just been removed and cleaned, new air filter and fuel filter. When carb was disassembled electric cold start unit was bench ck'd and is working and voltage and ground to electric cold has been verified. I have no idea if this is the priginal carb as scooter was well used before I bought it. If you turn the throttle a few times before cranking, actuating the acc pump it will start and stall, if repeated it will stay running. Once running and hot it will still give trouble restarting. Adjusting the idle mixture as per instructions on this site has made hot start better. I did see on the Scrappy Dog site they list larger idle jets for hard to start scooters.
Should I be looking at jet replacement or carb replacement? If carb replacement which one and where is a good place to purchase?
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Post by lain on May 22, 2016 17:58:32 GMT -5
Clean the carb again, clean it more. Check for vacuum leaks and intake leaks. Make sure the intake spacer isn't cracked, and if it has been removed or moved you need a new intake gasket.
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Post by JerryScript on May 22, 2016 18:11:53 GMT -5
You mention new air filter, is the new on the same as the stock one?
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Post by larrball on May 22, 2016 18:29:00 GMT -5
You mention new air filter, is the new on the same as the stock one? I want to add to what jerry said. Did you adjust the A/F mix screw? Close it (turn it all the way in clockwise) Turn it out 2-3 turns (counter-clockwise) It's getting close to summertime, so you want to run just a bit on the rich side. Brent, at www.49ccscoot.com has a great guide you might want to take a look at. www.49ccscoot.com/faq/carbtune.htmlThank you Brent. ----------------------------------------------------------------- tortoise (the post below mine) has nailed it. Do that frist then go for the carb. (I got'a stop riding my 2 stroke..... well no, i kinda like to go fast.) |
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Post by tortoise on May 22, 2016 18:42:00 GMT -5
Test cylinder compression. If reading does NOT rise after squirting a little oil in the spark plug hole . . valve seats may have carbon deposits causing marginal compression. May be able to rent a compression tester from an auto parts store . . 10mm spark plug adapter is required for GY6 50/125/150cc engines.
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Post by eman on May 22, 2016 20:42:52 GMT -5
Stock air filter and box. Mixture adjustment is at 2 1/2, been to 3. I don't have a 0mm adapter for my compression tester so I ordered one. I have sprayed carb cleaner around manifold and adapter with no change. Once I verify compression I'll go from there.
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Post by lain on May 23, 2016 8:23:13 GMT -5
You mention new air filter, is the new on the same as the stock one? I want to add to what jerry said. Did you adjust the A/F mix screw? Close it (turn it all the way in clockwise) Turn it out 2-3 turns (counter-clockwise) It's getting close to summertime, so you want to run just a bit on the rich side. Brent, at www.49ccscoot.com has a great guide you might want to take a look at. www.49ccscoot.com/faq/carbtune.htmlThank you Brent. ----------------------------------------------------------------- tortoise (the post below mine) has nailed it. Do that frist then go for the carb. (I got'a stop riding my 2 stroke..... well no, i kinda like to go fast.) You gave him wrong information. You do NOT want to run rich during the hot weathersummer! Disregaurd his message please that's false, unless you wan to foul plug after plug and build up tons of carbon deposit on the top of your piston... Summer tuning = LEAN Winter tuning = RICH Never tune too far, just tune until the RPMs start to drop THEN turn back about 1/8-1/4 of a turn. The reason we tune rich in the winter and NOT in the summer is because the density of the air, and the amount of oxygen and other stuff in the air is higher, so obviously you have to tune to have more gas int he winter to counter having more air. Density of air in the summer is less because heat expands the atoms in the air which make each atom drift away from each other slightly and in total has less air because of the fact the density makes air take up more space. |
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Post by eman on May 23, 2016 9:15:18 GMT -5
Again I appreciate the help. I've got a handle on the A/F ratio deal. I use this scooter as a pit bike for my drag racing.
Are these scooters very prone to carbon buildup from heat? Any recommended ways to prevent carbon? On generators I've used Seafoam mixed with the gas.
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Post by tortoise on May 23, 2016 9:58:53 GMT -5
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Post by eman on May 30, 2016 21:39:07 GMT -5
OK, adapter came so I ck'd compression 120psi cold. Squirted a little oil in the cyl and it rose a pound or 2. Valves are sealing fine, reck'd valve adjustment cold .004in.
I ran scooter this weekend and it didn't want to run. Would stall, wouldn't start hot or cold at times. When it did run it would run like it was starving for fuel. I disassembled carb. I found the o-ring at the top of the needle looked bad and it has a washer under the clip that sits on the o-ring. I removed the washer and installed a new o-ring. Clip is in the middle groove. Disassembled everything and cleaned all passages and blew out with air. There was no dirt at all, all passages were clear. Intake manifold is perfect and so is the insulator under the manifold. Put it back together and it started but did stall while idling for a short time. Adjusted idle mixture and speed. It will hunt a little at idle. On cold start it doesn't have any fast idle, idle speed doesn't change as it warms.
Problem is definitely fuel. If I want to buy a carb which is best and where to purchase?
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Post by scootdoggydog on May 30, 2016 22:02:47 GMT -5
I would keep it simple and just get a stock replacement.
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Post by JerryScript on May 30, 2016 22:36:23 GMT -5
Sounds lean to me. If you have already turned a/f out 3 or more turns, then it's either got a plugged spot (I know, cleaned and cleaned, but sitting allows our ethanol gas to gel in spots you sometime swear are clear), or you need to upjet the idle jet.
A plugged or restricted spot could be anywhere along the fuel system, the hoses, the filter, the petcock, the float bowl, and all of the jets and ports.
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Post by eman on May 31, 2016 8:31:54 GMT -5
Is there a jet/drill size chart? Jets have no numbers on them, I've looked with a magnifying glass. To jet up I need to know where I'm at.
Stock replacement carb is all I would buy, just what is a stock replacement. I don't know if this is the original carb.
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Post by pistonguy on May 31, 2016 22:16:57 GMT -5
I would keep it simple and just get a stock replacement. Yes there dirt cheap. Very Good Idea. I like simple. And Above all the Ethanol is Very Corrosive to Aluminum, you can clean your brains out with cleaning cocktail's and you will Never Get the Corrosion out, its done and junk. My Methanol Motors had to be Flushed with gas after every use or my nice Alky carb was junk in one week. |
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Post by pistonguy on May 31, 2016 22:48:43 GMT -5
I want to add to what jerry said. Did you adjust the A/F mix screw? Close it (turn it all the way in clockwise) Turn it out 2-3 turns (counter-clockwise) It's getting close to summertime, so you want to run just a bit on the rich side. Brent, at www.49ccscoot.com has a great guide you might want to take a look at. www.49ccscoot.com/faq/carbtune.htmlThank you Brent. ----------------------------------------------------------------- tortoise (the post below mine) has nailed it. Do that frist then go for the carb. (I got'a stop riding my 2 stroke..... well no, i kinda like to go fast.) You gave him wrong information. You do NOT want to run rich during the hot weathersummer! Disregaurd his message please that's false, unless you wan to foul plug after plug and build up tons of carbon deposit on the top of your piston... Summer tuning = LEAN Winter tuning = RICH Never tune too far, just tune until the RPMs start to drop THEN turn back about 1/8-1/4 of a turn. The reason we tune rich in the winter and NOT in the summer is because the density of the air, and the amount of oxygen and other stuff in the air is higher, so obviously you have to tune to have more gas int he winter to counter having more air. Density of air in the summer is less because heat expands the atoms in the air which make each atom drift away from each other slightly and in total has less air because of the fact the density makes air take up more space. Ok lets Throttle this Way back. This is just plane silly. This is a CV carb, the Most Forgiving Carb on the Planet, a cave man can work this. Thats a reason there on a Ped. Set it and Forget it. Ya gotta be way out to lunch fouling plugs on a 4-smoker and the whole Carbon build up things is much over rated problem on tv created by marketing slime bags like Me to sell you all kinds of Cleaner Chemicals that you don't need and do nothing. Advising to run Lean Or Fat anytime of year? or anywhere anytime is just silly again. Gunna try to keep the air density thing simple, keeping in mind were working with the set it and forget it CV carb, Theres no darn reason on a Ped we need to go out and re-jet for Cold Winter or Hot summer. On the Oxygen thing, as a certified Rescue Diver also Certified in Nitrox Mixed gas to 42%, Nitrogen is my enemy, other than the Navy dive tables I were two computers, I DIE if I don't pay attention.On Nitrox (Oxygen Enriched Air), I have a Depth limit, If I exceed this limit I go oxygen Toxic and I go into Oxygen Toxic convulsions and DIE. I'm intimate with AIR Air is Air, Up there, Down There, Over There. Round Numbers for example is Air is 79% Nitrogen and 20% Oxygen with trace gases making up the difference. That remains the same in cold or hot high or low, thick (dense) or thin. Air Density is also greatly affected by temperature and Humidity, Yes a Cold Charge may be a Denser Charge and May take more Fuel but also keep in mind that Fuel is also Cold and is Also Already a Denser Charge, so you really need to set it and forget it keep it simple. Hot Rod tip, make one at home, did this back in the day, We call it a "Cool Can" Run a bunch of Fuel line in Coils inside a can and fill it with ice or Dry Ice, hence a denser fuel charge.  |
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