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Post by twitchytoes on Oct 17, 2017 22:50:22 GMT -5
I acquired my second 49cc, the first one had a bit of a mishap with the body kit (My own fault) and I sold it to someone who isn't nearly as OCD as I am. I've begun tuning this one and need guidance on the next steps, as well as my current situation. The carb is the one I replaced my previous scooter's carb with, the original in it developed a leak. It had a 78 main and 34 pilot stock. I have sizes, mostly in steps of 5, from 75 to 98. I will be ordering a pilot jet kit as well, the idle mixture screw has to be fully screwed in or the engine dies at idle, so I think I need a smaller pilot. A larger pilot caused it to run SUPER rich and have black smoke, as well as very ragged idle. I ordered a tach today so I can more accurately deal with tuning. I'm not positive I'm using the right jet with where I'm at, I started with an 85 as I suspected lean running, as well as replaced the spark plug then. I dropped down to an 80 now and I'm not positive if it's right there, either. The 85 was very obviously too rich by how it ran, so I pulled the diameter restrictors in my airbox to see if I could lean it out enough doing that but it didn't seem to matter. I haven't put them back yet with the 80 but will be soon to see how it reacts. I'm not sure if I'm still too rich or not, it tends to bog, and occasionally die coming from idle, as well as runs very poorly when cold (though it's a bit chilly here now, too, which effects that running normally or not.) My next steps, ideally, would be clutch springs and swapping to sliders with a more optimized weight. I'm looking to obtain better take off/accel from that, while balancing top speed. My end goal is to learn enough to do more or less any repairs/maintenance, as well as drop in a 72cc big bore and achieve around 50-55 top speed out of it(Optimistic goal, more realistic is 40-45, I know). Any advice for anything I may require would be greatly appreciated. I have also changed engine and gear oil in it since buying it, and the miles (or is it kilometers?) read on the odometer is 960. I used 10w40 standard oil in the engine and 80w90 synthetic in the gearbox.
Edit 1: How does one tell if they have a heavily restricted exhaust?
Edit 2: Decided to try something a bit unscientific but may help. I first used a piece of paper, then a broken, white colored piece of plastic/metal, and I held it behind the exhaust while revving 1/2 and full throttle. With the airbox restricted, as well as unrestricted, there was blackening from the exhaust, as well as visible smoke (but not black to the naked eye). With the airbox side off, but filter still in place, making an effective free flow filter, there was no blackening and little to no visible smoke. Would this be enough of a sure sign of rich running?
Edit 3: I will continue updates on this project in the form of edits to the OP. Just changed needle, 1 step down (richer if I'm recalling right) and accel and top speed are better, top speed by 1mph, accel just feels better. Dying/bogging on take off is notably worse. I feel like my idle jet is very much large for the way this is set up. My idle jets won't be here til monday, though.
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Post by pinkscoot on Oct 18, 2017 10:04:47 GMT -5
 A little information will help. What model scoot? 2stroke or 4stroke? What kind of carb? Which side of the carb is the mixture screw on? If you look here in the directory you will find everything you need to know.
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Post by tortoise2 on Oct 18, 2017 10:51:15 GMT -5
acquired my second 49cc . . end goal . . around 50-55 top speed Save yourself a LOT of aggravation and replace with at least a 125cc scooter . . unless this is a liquor-cycle situation. |
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Post by twitchytoes on Oct 18, 2017 11:13:32 GMT -5
 A little information will help. What model scoot? 2stroke or 4stroke? What kind of carb? Which side of the carb is the mixture screw on? If you look here in the directory you will find everything you need to know. Not so good at finding models, it's a 4 stroke 139QMB, carb is a stock style carb but it was purchased off ebay if I recall right. The mixture screw seems to be on the fuel side, so fully tightened being the least fuel if I'm thinking right. It's a sunny body style Peace scooter, I bought it used though. |
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Post by twitchytoes on Oct 18, 2017 11:14:02 GMT -5
acquired my second 49cc . . end goal . . around 50-55 top speed Save yourself a LOT of aggravation and replace with at least a 125cc scooter . . unless this is a liquor-cycle situation. It's more of an optimistic goal, I'm mostly doing it to learn about it as I go up and to have something to do, really. |
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Post by edwardtennant on Oct 18, 2017 16:18:02 GMT -5
try this, buy two new spark plugs. Cr7hsa. Take one new plug, screw it in and run it with the air filter cover on for around 20 mins, then pull the plug. The colour should look like a cup of tea, if its black its rich, if its white its lean. Then do the same with the other new plug wihout the airbox cover on
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Post by twitchytoes on Oct 18, 2017 16:28:46 GMT -5
try this, buy two new spark plugs. Cr7hsa. Take one new plug, screw it in and run it with the air filter cover on for around 20 mins, then pull the plug. The colour should look like a cup of tea, if its black its rich, if its white its lean. Then do the same with the other new plug wihout the airbox cover on That's a good idea, not sure why I didn't think of it. I have two here, one the previous owner said was new and one that was actively in it. How can I get them clean enough? Do I need to hit my rear brake to stop the rotation as quickly as safely possible? Edit: Pics of the current spark plug after a few high revs, kinda held the brake a bit for load but was a bit shy to ruin my brakes riding the brake like that. With and without flash. I'm not really sure how to interpret this. These were done with stock air box, snorkel, restriction and diameter restriction removed. Filter in place. Jet: 80, Pilot 34.     |
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Post by edwardtennant on Oct 19, 2017 14:00:45 GMT -5
Those photos, really help, thanks for them twitchy. As you can see, the plug is white on the bottom one (I assume without airbox cover) and a little bit white on the top one (Assuming with airbox cover). What this means is that you're running the engine with too much air and not enough fuel to compensate for it. What you will need to do is adjust the carbrettuor in order to get the air/fuel mixture correct. I would try going for an 83 main jet, or adjust the air/fuel screw to change the mixture.
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Post by twitchytoes on Oct 19, 2017 14:33:10 GMT -5
Those photos, really help, thanks for them twitchy. As you can see, the plug is white on the bottom one (I assume without airbox cover) and a little bit white on the top one (Assuming with airbox cover). What this means is that you're running the engine with too much air and not enough fuel to compensate for it. What you will need to do is adjust the carbrettuor in order to get the air/fuel mixture correct. I would try going for an 83 main jet, or adjust the air/fuel screw to change the mixture. Those are actually all the same plug, just wanted to cover more lighting scenarios to be sure. They were with the airbox on, but restrictors removed. Current jet is at 80, pilot jet is at 34. It tends to die on take off, or minimally bog if it has been idle more than about 30 seconds, I.E waiting for an opportunity to come out into a primary lane. I previously used an 85 jet but it seemed to be too rich. I was suspecting the idle jet being rich cleaning it at the end, as the threads are pretty blackened. |
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Post by edwardtennant on Oct 19, 2017 14:44:23 GMT -5
the part you really want to look at is te tip and the ceramic around the electrode. It does seem to be lean, if you dont want to tear the carb apart to change the jets, try blocking off half of the air intake and see if it runs better. if it does then you need to upjet the carb
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Post by twitchytoes on Oct 19, 2017 14:52:49 GMT -5
the part you really want to look at is te tip and the ceramic around the electrode. It does seem to be lean, if you dont want to tear the carb apart to change the jets, try blocking off half of the air intake and see if it runs better. if it does then you need to upjet the carb I'll be tearing it apart on saturday hopefully to install my tach, but my steps up from 80 are pretty large, being 85 88 and 90+. I'm still not positive if the idle is high, because I have to have the air/fuel mix for idle cranked all the way in or it'll die on idle without any gas fed. Edit: Swapped jet to 85 and put my needle at 1 step above where it originally was to bandaid the idle bog/death for now. Pilots will be here tomorrow and I can do it more appropriately. Gotta head to work today or I'd have left it alone. |
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