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Post by litninrod on Feb 28, 2011 16:47:41 GMT -5
OK I got my air filter box today and installed it. Then I followed the carb adjustment procedures I've read here.
I don't have a tach, so I set the idle up until the wheel turned freely then a bit more for good measure.
Slowly turned the a/f adjustment in waiting for it to almost die out. It never does. Instead, it actually hits it's highest RPM when the screw is all the way in.
Backed it out slowly listening for changes. It gradually slows down the further out I come. So I ran it all the way in and backed out 2 full turns.
Dropped the idle down to where the wheel stops turning.
Top speed is now 26 MPH. I don't have a washer restricting the variator, and I went with the 'performance' CDI which is not supposed to have any rev limiter.
So is 26 MPH the best I should expect without doing roller weights and carb jets?
And why didn't my carb attempt to die out during adjustment? Perhaps a needle setting?
Guess I should specify - it's a QMB139 50cc. The coil and CDI are new 'performance'. Carb, NGK plug, battery, regulator/rectifier and stator are all new.
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Post by scootercapecod on Feb 28, 2011 18:38:00 GMT -5
First of all, if your scoot didn't die or just about do so with the A/F screw all the way in, you're running WAY too rich which means you'll need to do a needle adjustment. Second, The A/F screw shouldn't need to come out more than 2-3 turns at most. It almost sounds like the little O ring is missing. The idle adjust screw above the throttle assembly should be set for the LOWEST RPM needed to keep the motor running or just below the point at which the wheel starts turn, then adjust the A/F screw for HIGHEST RPM when the motor is warmed up. Then set the idle lower again as needed. As for Rejetting, I'd wait to do the carb right first but mostly you're going to want to go up a size or so.
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Post by buiditright on Feb 28, 2011 20:41:10 GMT -5
You have something wrong if it does that. You should not have to touch your needle. If you turn your A/F screw all the way in your scoot should shut off. You should let your scoot warm up and set the idle up until the back wheel stops. The A/F screw should be backed out 2 or 2 1/2 turns. The go either way to get your highest rpm then back it off till it just starts to drop that is where your adjustmwnt should be. But you should not have to change your needle setting.
Bill
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Post by edfr on Feb 28, 2011 21:04:33 GMT -5
Question, why did you have to get a new Air Filter Box? It appears the Air FIlter box is very restrictive and is causing it to run RICH if you had to turn the Air/Fuel mixture almost to the closed position. The reason I think your mph are low is because you then turned the Air/Fuel mixture out 2 turns and now you are running rich as heck.
If you did not get a new carb or put on a bigger carb and it is the orginial we have to find what is restricting the air into the carb. That would point to the Air Box you just put on, and it may not be allowing enough air causing the carb to suck in more fuel. It is acting like a choke.
Or if its a New Carb is it the same size that was on there?
Can you take pictures of the air box and around the carb area that would help.
Lefty
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Post by litninrod on Feb 28, 2011 21:34:18 GMT -5
Lefty, I got this scoot out of a barn. The carb and air filter box were missing, so I had to replace both. Both are stock replacements for this engine. Before I got the new filter, I tried to adjust the carb, and had the same result when the a/f screw was all the way in. In addition, I could only get about 10 mph on a test run and it bogged down. After reading posts here, I deduced that no air filter box at all was causing a lean condition. I taped off half the air intake hose to restrict flow, and got 22 mph on a test run. I don't have a pic of the air box but here is the engine area with the carb  Add a standard box to the back of that intake hose and you have it. |
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Post by litninrod on Mar 1, 2011 0:11:42 GMT -5
OK I took current pics. Carb ( I realized from this pic I put good fuel line above the filter but left the stock line below. Oh well...was gonna change to a better filter anyway )  Carb looking back to air filter box  Air filter box  Air box open to show foam filter  Foam filter, about 1/2 inch thick  Looking through the intake toward the carb  I did smell gas when I opened it up, and it's only run maybe 30 minutes since I installed it. Does that indicate rich mixture? No obstruction in the intake from the frame to box, or from the box to carb. Both hoses are clear. |
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Post by edfr on Mar 1, 2011 0:26:23 GMT -5
Yes ,just like I thought you are running rich and not making power. That is a CLOSED system where is the HOSE that feeds air into the box. I see the bigger hose to the right which looks like the one that feeds air into the box. Make sure the opening on that hose is placed where it can freely suck in air into the box. Also the Hose coming from your Carb into the box I would have the hose not come to far into the box. Try to position just inside the Air Box.
Lefty
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Post by litninrod on Mar 1, 2011 0:50:09 GMT -5
That fitting is glued into the box that way...no adjustment in or out. You asked "where is the HOSE that feeds air into the box?" This pic shows the hose from the body panel leading back to the air box.  Here is without the hose. It mounts on the far side. Circle on the near side shows what the outside of the body panel looks like where the hose meets it.  So it's too rich. Do I just need to adjust the a/f screw in or are we talking a needle adjustment? (I'm a newbie at this so raise or lower to get leaner?) |
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Post by edfr on Mar 1, 2011 1:02:23 GMT -5
You know what, try it the way it is WITHOUT that long extra hose connected to the Air Box, see if it runs better.
But to Lean it Out Turn the Air/Fuel Mixture Clockwise, your RPMS should go up Try it at 1 turn out since you have it out at 2 turns. BUT WITHOUT the Hose connected to the Air Box. And see if it improves for you. If it improves then try it with the hose if it is the same then you can maybe help it by Lowering the Needle One Notch to Lean it Out some.
Lefty
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Post by litninrod on Mar 1, 2011 1:08:35 GMT -5
Thanks a bunch! I'll give it a go.
~Rod
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Post by edfr on Mar 1, 2011 1:11:44 GMT -5
Nice looking scoot, you will have a nice scoot once its running right. And think all the stuff you learned so far. You have learned a lot and will know your scoot backward and forwards. They are simple machines but when problems crop up sometimes it can be several things that cause the same symptom. So once you learn how it works it makes it easier to go to the possible culprits. Your doing a terrific job.
Lefty
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Post by apittington on Mar 1, 2011 1:45:04 GMT -5
I for one am impressed with the progress you are making! I remember how it was to figure out what was wrong with my scoot right after I got it. Lefty was a HUGE help. Don't give up, and when your lost ask for help, and you will end up with a nice running scoot, and enough knowledge to fix almost anything that could happen to it later, all without having to find out just how bad your local scooter "mechanics" are, or how huge the bills are for work you can do yourself in under an hour! Haha!
Adrian
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Post by buiditright on Mar 1, 2011 9:00:22 GMT -5
Rod ,
I am not sure and if I am wrong I am sorry. You said you pulled it out of the barn. If your scoot has been sitting for any longer then 3 or 4 weeks you really do need to clean your carb. NOt sure how long it has been sitting but if it has your going to need to take it out and take it apart. Once you get it apart you will need to take your jets out and clean your passages. The cheap ass gas that we have will break down and cause you problems. It also will eat away your hoses if you have not changed them you should. The chinese hoses are really crap.
Bill
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Post by edfr on Mar 1, 2011 12:18:30 GMT -5
Builditright,
Its a QMB139 50cc, and all the following are new, Performance Coil, Performance CDI, Carb, NGK Plug, Battery, Regulator/Rectifier and Stator, Air Box. So all the major parts are working and the scooter is running but not at its best.
Now we are working on getting it to run better and faster.
It appears that the Air Box is very restrictive and not allowing much air in and is causing it to run rich which robs you of power. Once that is fixed then we can move on to the CVT.
Lefty
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Post by litninrod on Mar 1, 2011 12:26:29 GMT -5
I tried Lefty's suggestion about removing the hose to the air box with no difference in the way it runs. So I went for a needle adjustment. But the needle seems to have no adjustment. And the carb appears slightly different than the pics I've seen here on needle adjustment. I was just about to say "F*** it, in my ignorance I bought the wrong carb for this thing" and get a different one. But I figured I'd show it to you guys first before throwing more money at it. So top of the carb. Mine is plastic and I see some are metal:  Top off shows spring and diaphragm as expected  Pull diaphragm and look inside...no screw holding the needle  Because the needle is in a plastic assembly attached to the diaphragm  Looking in the diaphragm at the top of the needle  Needle raised to show the top and a little plastic tripod clip that covers it  Needle and tripod clip  Needle top. No clip or adjustment...just a disc permanently attached to the needle  So is this the wrong carb? Or is it missing something that adjusts the needle? Anyone seen one like this before? |
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Post by edfr on Mar 1, 2011 12:53:31 GMT -5
Litninrod,
BUMMER!! But I notice that the cylinder itself has stepped curves. Maybe that is how you can raise or lower the needle by just rotating the entire cylinder on that carb.
So first put the cylinder in and LOOK at it from the AIR INTLET SIDE and rotate it one slot at a time and rotate it till you see it at the lowest part. Then Rotate it one slot again and you should see it go up. Count the number of slots and set it down one lower.
Did you Lean out the Air/Fuel Mixture at least 1/2 turn in? You mentioned that as you turned it in the RPMS increased which is what we are trying to do.
Lefty
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Post by oscar on Mar 1, 2011 13:45:59 GMT -5
Same carb I have. Stepped curves on the cylinder???
Hard to find nylon spacers at the hardware store to shim needle. Maybe the motorcycle shop has something. I'm going to purchase a number of larger main jets instead of messing w/ the needle depth.
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Post by edfr on Mar 1, 2011 14:20:21 GMT -5
Yes, stepped curves on the cylinder look at it in the picture. I do not know for sure but it may be how you are able to raise or lower the needle.
There is no place to shim the needle it is held in place by that Plastic Tower piece that the head of the needle clips into the top of the tower.
Lefty
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Post by dr1445 on Mar 1, 2011 16:44:38 GMT -5
it looks like there are 2 slots cast into the carb body that the '"throttle drum" rides in [for lack of a better word] that prevent it from rotating. if so its position is fixed and the only way to raise the needle is via a washer. in motorcycles there are after market sources to replace the fixed needle, but the use of a washer is common. something like a 3mm washer, steel or nylon, should do it.. slicing a piece off a plastic tube works to.
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Post by edfr on Mar 1, 2011 17:00:00 GMT -5
And where may i ask are you going to put the washer? The tower has a plastic insert to put the head of the needle in it to hold it. Any type of washer would have to ALSO be able to fit inside the Needle Holder on the Plastic tower.
Lefty
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Post by litninrod on Mar 1, 2011 17:57:58 GMT -5
Yeah the stepped look is an optical illusion from the camera angle, and the slots do prevent any turning, so it only goes in one way. The coil spring when you first remove the cap sits on top of that clip above the needle, so presumably a washer would just raise the clip and the spring would be a hair more compressed. So that could work. Problem though is it's too rich. Adding a washer would raise the needle making it even richer wouldn't it? I've been tinkering for a couple hours. If I run the a/f screw all the way in then back it out half a turn, I can get a couple more mph, so 28-29. In first warming up I noticed that the choke kicks in after a second or two and picks up the RPM. About every minute, it gets a bit faster. After 5 minutes the valve cover was warm but not hot to the touch, so I let it warm up more. After a couple more minutes the valve cover was getting hot, so it should have been warmed up enough. (note: 60 degrees in the garage where the scoot is parked and 61 outside). The RPM still hadn't dropped, so I'm wondering if the choke is always on causing the over rich problem. It also lopes a bit while idling - plus or minus 100 RPM, but that may be common for an older scoot? Newbie don't know. I tried unplugging the choke and saw no difference. Took it out and covered the hole and ran it to see if I could see the choke needle move. I couldn't but if it's a small movement I could have missed it. To check air flow issues, I took the input hose off the air filter box. Then took the cover off, then took the foam filter out, then took the box off leaving just a hose into the carb. Adjusting the a/f screw at each step, at no time does running the screw all the way in cause the scoot to stall. So it's still too rich at idle even with no filter box, although too lean under load when I only get about 10 mph as it bogs down. Lefty you know way more about these than I do, but I have to say that in this case it's a problem within the carb rather than the air filter assembly. So this carb doesn't seem to adjust properly, has no needle adjustment and a suspect choke. I'm going to have doubts about it all the time now. It has lost my trust. A new one off Ebay is $23.90 shipped. That's not a lot and I'm thinking that's an investment that might solve my problems and ease my mind. If a site sponsor has a comparable price or someone has a suggestion about a premium carb I should look at first, let me know. Otherwise I'm going with this Ebay carb. cgi.ebay.com/ebaymotors/50CC-SCOOTER-MOPED-GY6-CARBURETOR-CARB-SUNL-ROKETA-JCL-_W0QQcmdZViewItemQQhashZitem25618a728aQQitemZ160550253194QQptZOtherQ5fVehicleQ5fPartsThanks for all the help and suggestions as I worked through this issue. ~Rod |
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Post by dr1445 on Mar 1, 2011 18:06:56 GMT -5
the photo of the needle is out of focus but there has to be a fixed head at the top, otherwise the needle would fall through. the washer fits under the head to raise the needle and yes the washer od sometimes can not be larger than the fixed head on the needle. many times a washer is used as a 1/2 step on needles with an e-clip.
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Post by litninrod on Mar 1, 2011 18:29:19 GMT -5
Sorry about the fuzzy photos. My camera has 'auto focus' which can't seem to figure out what I want focused on in close up.
So yes it's a fixed head on that needle. But again, wouldn't a washer under that head raise the needle and just make a rich problem even richer?
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Post by edfr on Mar 1, 2011 18:45:53 GMT -5
Ok, the choke you can see if it is shutting off. After it is nice and hot like you did and the RPMS did not drop, take the ENRICHER(CHOKE) off and pull it out and see if the PLUNGER is EXTENDED or still RETRACTED. If it extended you should see a SPRING between the Plunger and the Rubber holder. Here are pics so you know what I mean. Lefty This is what it SHOULD look like if it is EXTENDED WHEN HOT and that would SHUT OFF the extra fuel which means it is working:  This is what it will look like if it is RETRACTED WHEN HOT and that means IT IS NOT WORKING it is staying RETRACTED and MUCH FUEL when HOT.  |
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Post by dr1445 on Mar 1, 2011 18:59:17 GMT -5
yes, raising the needle will make the mid range richer. highly unusual to see a fixed carb needle setup rich, most are set up on the lean side due to environmental concerns. it might well be the choke causing a rich condition as suggested.
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Post by edfr on Mar 1, 2011 20:08:05 GMT -5
Yes, if its not the Choke, then the next thing to do would be to put in 1 size smaller Pilot and Main jet or get a different Carb.
Lefty
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Post by litninrod on Mar 1, 2011 20:14:18 GMT -5
Thanks for the choke pics. It's definitely not working. I was just looking for the center needle to go in or out a little. I didn't know it should be so obviously extended, and it definitely wasn't.
So the choke appears to be the problem.
I need to check the harness to see if the choke is getting juice. Anyone know how many watts/amps/ACvolts/DCvolts/Ohms it should be getting?
(I have a multimeter but am not knowledgeable about it don't know which I should be checking for)
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Post by edfr on Mar 1, 2011 20:19:46 GMT -5
Litninrod,
GREAT!! Now one question before you go and order a CHOKE. As it it warming up check if the CHOKE is getting WARM it will not be HOT but it will get warm. If Not follow the wires and check if it is PLUGGED in and the wires are ok. If it is plugged in and the wires and connectors are ok then you need a new one. NOW here is the thing You can get them for around 10-15 dollars or you can order the Carb for another 10 bucks.
Lefty
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Post by smokiestover on Mar 1, 2011 21:03:03 GMT -5
So the choke appears to be the problem. I need to check the harness to see if the choke is getting juice. Anyone know how many watts/amps/ACvolts/DCvolts/Ohms it should be getting? (I have a multimeter but am not knowledgeable about it don't know which I should be checking for) The choke is 12 volt...most likely AC and only powered when the engine is running. It probably has a resistor located in the ground circuit. Trace the two wires from the choke to the wiring harness. Unplug them and check the wiring harness side for ground. Do this with your multimeter set on 20 volts DC....hold the + probe on battery + while checking the harness connections with the - probe. When you read 12.5 volts or so, you found the ground...the wire might be green and the power side might be yellow. If you have ground, re-connect the ground wires and run a jumper from Battery + to the + wire running to the choke (the one you did not re-connect). If the choke is not fully extended in 10 minutes it's bad. If it does extend, you are not getting power on the + side when the motor is running. |
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Post by Beachy on Mar 1, 2011 21:53:51 GMT -5
I went through something similar last year, and it drove me nuts. The scoot had been sitting for a year or two and I cleaned out the entire fuel system, I must have cleaned the carb 10 times and finally bought a carb from Scrappy. I think it was about $40 and after some adjustments it runs like a charm.
It saved me hours of grief and now I have a back up carb for parts if I need it in a pinch.
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