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Post by Deleted on Jul 25, 2014 20:02:41 GMT -6
Hi, i receive my new 20mm carburetor to replace my origianl 18mm carb. I have a 80cc with original air box and exhaust.  Inside de new one they put Pilot Jet #32 and Main Jet #91. On my 18mm carb, i have Pilot jet #35, Main jet #85. I try the new carb with the jets #32 and #91, run not bas but have some ("cough" jolt) and i try to adjust the air screw, nothing... So i install my old Pilot jet #35 i have in my 18mm carb, noe i can adjust the idle correctly. I make a ride 5 miles, i always have (Jolt), but my new sparkplug was WHITE when i check it!!!! I install a main jet #95, after a ride, the color of the sparkplug start come tan, but a have a lot of ("cough" jolt) at low and medium speed!  The needle clip in the carb is at middle! What i need to do to solve the problem at low and middle speed??? Put a bigger Pilot jet??? |
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Post by alleyoop on Jul 25, 2014 20:36:46 GMT -6
Move the clip UP 1 notch on the needle
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Post by Deleted on Jul 25, 2014 20:41:59 GMT -6
Ok i do tomorrow!
2 Questions!
When we need to change the Pilot Jet?
When we need to change the needle clip?
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Post by alleyoop on Jul 25, 2014 21:48:22 GMT -6
Ok i do tomorrow! 2 Questions! When we need to change the Pilot Jet? When we need to change the needle clip? Q1. When do we need to change the Pilot Jet? 1. If you turn the Fuel Ratio Screw CLOCKWISE all the way until it stops AND it does NOT kill the motor Then the PILOT JET IS TO BIG and you put in the NEXT smaller Pilot Jet. 2. If you have to turn the Fuel Ratio Screw OUT more than 3 turns for it start and idle Then ythe PILOT JET IS TO SMALL and you put in the NEXT bigger Pilot Jet. 3. A Good Size Pilot Jet is when you adjust it to get the HIGHEST IDLE the pilot jet is anywhere from 2-3 turns out from the closed position. HERE IS HOW TO ADJUST THE CARBS FUEL MIXTURE: thescooterprofessor.proboards.com/thread/3001/4-stroke-carb-tuningQ2. When do we need to change the Needle Clip? 1. When the PILOT JET is adjusted right and MAINJET IS CORRECT and it BOGS, STUMBLES or HESITATES in the Mid-Range and then runs good after the BOG, STUMBLE or HESITATION all the way to the top end that is the only time the Needle should be adjusted. Reasons Why the needle would need to be adjusted ONLY IF IT HAS A HESITATION OR BOG OR STUMBLE IN THE MID-RANGE otherwise leave it alone. 1. If you put in a BIGGER MAIN JET now it may have TO MUCH FUEL in the Mid-Range and you need to DROP the Needle a little to take some fuel away from the mid-range. 2. If you put in a SMALLER MAIN JET now it may NOT have enough fuel in the Mid-Range and you need to RAISE the Needle a little to give it more fuel in the mid-range. |
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Post by Deleted on Jul 26, 2014 8:04:02 GMT -6
Thank's a lot Alleyoop you realy help me!!!  But if i obtain the highest rpm speed with the mixture screw after 3½~4 turns, did i need to reduce the Pilot jet or bigger? |
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Post by alleyoop on Jul 26, 2014 11:47:08 GMT -6
One size bigger if you get the highest rpms 3 1/2- 4 turns out, but you already have a #35 right? so something is not right a #35 is what all your 150cc motor take and yours is just a 50cc motor which should not need a bigger pilot jet. Don't think that MORE GAS will give you more speed that is a NOOBS thinking. You do NOT pour a gallon of gas and think it will give you more speed. But if it is running good with it 3 1/2 -4 just leave it with the #35, it just needs a little more fuel because the carb is bigger and more air is coming in so you have to match the fuel mixture with the amount of air coming in.
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Post by Deleted on Jul 26, 2014 14:20:15 GMT -6
I have 2 18mm carburetors and both have Pilot jet #35, but the 20mm carb come with Pilot jet #32. Today i try all the Combination i can do with jet #91 and #95 Pilot jet #32 and #35 and needle clip! Worst acceleration was with Pilot jet #35 and hard to adjust, sometime the mixture screw was complet close and i always have a idle speed... With Pilot jet #32, it was better, quick acceleration but some hesitation and bug, if i put main jet #91 and needle clip raise at Max, the spark plug look lean again, but good top speed.(see pic) If i didn't have any hesitation at low and Mid-Range i leave it like this.  If i put main jet #95, poor acceleration, less top speed and black spark plug and i play with the needle, acceleration was worst... I think i buy a main jet #92! The Difference between #91 and #95 is too big. |
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Post by alleyoop on Jul 26, 2014 15:13:32 GMT -6
Yep, LEAN try a 92 and move the CLIP 1 or 2 DOWN on the needle right now you have it at the top to lean in the mid-range
to get the bog out.
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Post by Deleted on Jul 30, 2014 15:05:33 GMT -6
I re-install my 49cc today, when i make a ride, at around 40Mph, the motor start to slow down! Same thing if it was too lean...!? I check the spark plug and it look Yellow! (See pictures) I don't understand, i put back the original main jet #75 inside the original carburetor 18mm!? I check the intake to see if no leak... Is it possible because i use the same head gasket? If iT leak I would see Oil leak!!   I start to hate this motor...  |
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Post by alleyoop on Jul 30, 2014 15:21:40 GMT -6
That is to LEAN, you are trying to get to much speed out of your motor. A motor will make more power running LEAN BUT you will destroy the motor pretty quick. That shows it is running really HOT, So you better richen it up and loose a little speed otherwise you will not have a motor.
Alleyoop
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Post by Deleted on Jul 30, 2014 19:03:05 GMT -6
No, i don't want go faster, i just put the 49cc with all the original setup.
The original jet was #75 and i put the #78 to be sure and i give this result!
I think i have some air leak somewhere, i check the intake, see nothing...
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Post by alleyoop on Jul 30, 2014 20:00:19 GMT -6
If that is the stock 49 motor the 75 should be more than enough, so you must have a very bad air leak someplace that motor is running REALLY HOT.
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Post by Deleted on Jul 30, 2014 21:28:47 GMT -6
What can make bad air leak on a 4 stroke!?
All i can see, it's AIR INTAKE, CARBURETOR or the TUBE between air box and carburetor?
Valve adjustement? i don't think so!
Beyond that?
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Post by alleyoop on Jul 30, 2014 22:35:46 GMT -6
Bad Intake manifold crack in it or broken gasket underneath it were it connects to the motor or a bad vacuum lines. Take a couple pictures of the top of the motor with the carb on and everything, maybe someone can spot something.
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Post by gatekeeper on Jul 31, 2014 2:16:43 GMT -6
To find an air leak, while the scooter is idling spray some carb cleaner along the air filter housing, air tube and intake manifold. If the idle speed increases, that is wear the air leak is.
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..BAD TO THE BONE..
