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Post by cypher1982 on Jun 17, 2020 18:20:54 GMT -5
Hello, I'm new to the forum and tried to search but havent had the best of luck. I recently bought a basically new kymco agility 50 4t. Today I checked out my stock air system and found a major restriction going into the airbox and another in the air tube between the box and carb, so I opened up the air box inlet and removed the molded ring in the air tube before the carb, now shes flat running. I ordered a jet kit to begin tuning it for this, has anyone else done this? What jet would you recommend as the starting point? I did raise my needle .5mm by a washer, and I'm going to try a second for a total of 1mm raise of the needle, but still dont know if that will be enough. Thanks!!
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Post by Mech Warrior on Jul 10, 2020 9:43:14 GMT -5
Well you can see what jet you have in it now and go up a tad let's say you have a 75 mj maybe try the 80 but its a good idea if you are doing really fine tuning to get jets in increments of 2 for what you are doing usually they come in sets of 10. You can do a plug chop to see how its running lean or rich.
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Post by cypher1982 on Jul 15, 2020 7:45:16 GMT -5
Changed the oil and gear oil today for the 1k service. Oddly it had been sitting for about 2 or 3 days prior. Since the service, it's just felt very sluggish and flatter than normal. Just like no punch. So figured I'd check over a few things and here are some findings.
Spark plug of unknown age is pretty black, so I sanded the carbon off and sprayed with carb clean then reinstalled. But I dont know how old it is.
Started looking into possible carb concerns as it's been where I've felt my issues have been. Removed the air tube and tried to get a video of it running and snapping the throttle to watch the slide move. It definitely seemed to be sluggish up and down, and I noticed it didnt fully open the century completely and left a little bit of the slide down. Now this could be due to no air tube or other problems to I dove in.
I removed the slide and started seeing how it moves without the needle in and it slid up and down very easy by hand. Next I noticed the leading edge was a hard angle so I took a little sand paper and rounded it off for better flow. Then I noticed it. With the needle installed, the air bleed port was half blocked by the neee retainer. I have some pictures I'll try to attach. Best i could gather it was half way blocked by the leg. I measured the port and it was 1.5mm. I found a 1/16 drill bit to be just barely oversized. Like 1.55mm. So I slightly opened up the hole and made sure to go through all 3 legs in case it was opened up again and then I wouldnt have to worry about which was it installed. How this works now I'll be tested probably tomorrow. I also noticed while putting it all back together the needle looked odd hanging from the slide.
I didnt get any pictures of this but it was definitely angled slightly and rubbed against the needle guide in the carb on the right side when looking down the venturi. I tried seeing if it was in the needle or in the slide itself, it seems it's a poor machining in the slide as I could spin the needle and it still seemed to slightly lean to one side. I dont know if this will have any real problems or not. I've been brain storming how to try to get it to ride truly centered in the needle tube.
Also double checked my jets for being clean and open. All look good at this point. I tested the slide operation with some compressed air and after reassembly the slide would move fully up and offer zero restriction to the carb.
Guess we see what happens tomorrow. I wish I did have a stock air box though just to check if somehow opening the flex hose caused any issues. I've also been thinking of a way to try and design a velocity stack for the carb and still use the air box.
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Post by cypher1982 on Jul 15, 2020 12:27:30 GMT -5
Got it all back together and drove up the road... right out of the gate it was ok, then fell flat and wouldnt accel past like 25ish. Came back and shimmed needle up 1.0mm and took it back the exact same trip. This time it got up to 30 and was very slowly still climbing. The return trip was better as it's very slightly downhill and managed almost 35. So shimmed needle = more top end and a little more power in the middle. Does that mean I need a different needle, a bigger MJ, or what? It definitely didnt seem to die and shudder as much. Any suggestions? It's a kymco agility 50. And needle isnt adjustable with a clip.
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Post by GrumpyUnk on Jul 15, 2020 12:29:27 GMT -5
When you put the needle back into place in the slide, make sure it has settled down to the bottom and is square to the slide. If it has an angle, it is not in properly. The needle is not supposed to bind against any side of the jet opening at the bottom of the venturi. If it binds, it will wear, and possibly get jammed instead of opening as it should do. It will affect the fuel flow if it is off center. If angled, it is more likely not sitting flat in the bottom of the slide. They can wiggle around depending on the style of the retainer. Some hold the needle tight, others depend on gravity. Was the engine completely warmed up when you noticed it 'felt sluggish and flatter than normal'? Are you sure you put the proper amount of oil into the crankcase? You should check the dipstick using the center stand on level ground. Remove the dipstick, wipe it clean, and drop it into the hole. Do not screw it down. Remove and check that oil is on the hash marks, and not above them. The level on the stick will depend on whether the front wheel is on the ground or the rear wheel. I think(no reason, it just seems right) to check with the front wheel on the ground is proper. If overfilled, you will lose power to churning the oil and having a hurricane inside. tom
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Post by cypher1982 on Jul 15, 2020 12:37:03 GMT -5
When you put the needle back into place in the slide, make sure it has settled down to the bottom and is square to the slide. If it has an angle, it is not in properly. The needle is not supposed to bind against any side of the jet opening at the bottom of the venturi. If it binds, it will wear, and possibly get jammed instead of opening as it should do. It will affect the fuel flow if it is off center. If angled, it is more likely not sitting flat in the bottom of the slide. They can wiggle around depending on the style of the retainer. Some hold the needle tight, others depend on gravity. Was the engine completely warmed up when you noticed it 'felt sluggish and flatter than normal'? Are you sure you put the proper amount of oil into the crankcase? You should check the dipstick using the center stand on level ground. Remove the dipstick, wipe it clean, and drop it into the hole. Do not screw it down. Remove and check that oil is on the hash marks, and not above them. The level on the stick will depend on whether the front wheel is on the ground or the rear wheel. I think(no reason, it just seems right) to check with the front wheel on the ground is proper. If overfilled, you will lose power to churning the oil and having a hurricane inside. tom Thank you for your input. I did not think the needle was supposed to be at an angle I'm just at a loss of how to correct it. The needle seems true and the issue appears in the machining where the head rests in the slide. I was thinking of trying to put a shallow chamfer in the bore and a slight one on the needle and hope it self centered, but this may also cause the needle to drop slightly... which then doesnt help my case. As far as my oil, I used 10w40 as recommended. I put in 700ml and checked it on center stand. It did appear to be correct, however I did thread the cap in when checking and not just resting on the top. Also, I dont believe it had a full chance to warm up, I'll give this a test tonight and report back. Thank you again. I know it wont be a rocket but it needs to be reasonable to get to speed and hopefully keep the good fuel milage
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Post by FrankenMech on Jul 15, 2020 19:07:31 GMT -5
Watch the videos on the web about re-jetting carbs, it is NOT easy to get it right. Otherwise put the airbox and carb back to stock before you blow the engine.
Those airbox restrictions have to be there to control the fuel mix. Scoots with airboxes only have half a carb, the rest of the carb is the airbox. Any modifications will mess it up.
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Post by Zino on Jul 16, 2020 23:30:32 GMT -5
Cypher go back to stock settings with the airbox restrictions .
If your Plug was Black you already were real rich and you are making your scoot richer . Your plug is black and unknown age A Sparkplug on a small scoot s a very big performance part and gives clues on how you are running. Put a new fresh plug in and see how she runs with stock settings .
After a couple tanks of gas take a look at the plug Ideal is Graham cracker brown Black is rich grey is lean .
Follow the golden rule change one thing at a time . When you raise the main jet from a 75 to a 90 . The mid range is automatically richer .
You May not even need you to richen it up it might even need to be leaner . Moving the needle 1 mm is a very large move .
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Post by Mech Warrior on Jul 17, 2020 10:56:23 GMT -5
Zino is always very helpful.He has great advice and is a true friend.
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Post by cypher1982 on Jul 17, 2020 11:26:42 GMT -5
Cypher go back to stock settings with the airbox restrictions . If your Plug was Black you already were real rich and you are making your scoot richer . Your plug is black and unknown age A Sparkplug on a small scoot s a very big performance part and gives clues on how you are running. Put a new fresh plug in and see how she runs with stock settings . After a couple tanks of gas take a look at the plug Ideal is Graham cracker brown Black is rich grey is lean . Follow the golden rule change one thing at a time . When you raise the main jet from a 75 to a 90 . The mid range is automatically richer . You May not even need you to richen it up it might even need to be leaner . Moving the needle 1 mm is a very large move . Zino, thank you for chiming in. I will consider doing just that. I think prior it makes sense to put a new plug in and do a chip. Maybe somehow it's actually close, I'm not discounting the ideas given. I just realize I havent done enough in my end to give accurate data aside from the butt dyno and actual driveability
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Post by cypher1982 on Jul 20, 2020 20:37:10 GMT -5
New updated information. This morning it's nice out, sunny, low 70s just a tiny bit of wind. So testing today. Picked a spot right in front of my house. Its 1/2 km per my app. Slightly uphill and a straight shot, perfect for testing. So it's best running was at 1.0 mm shim which may end up closer to .8 or so. Anyways, I did multiple runs back to back so conditions were the same. Run. Make a change, run again, make a change etc. Heres my numbers
Stock .35 pilot MJ filed to a .90 Slight carb smoothing to hard walls by slide inlet for airflow Initially I tried the runs for top speed to a certain marker. Testing showed as follows...all as shown on speedo not gps
First, I put a small piece of breathable cloth clamped over the air box inlet. Clamped it down and tried to go for a ride. I couldnt even get out of my driveway as it died as soon as I twisted the throttle, so I know I needed more air. So ran some tests with more air
53ish No filter 58.5 Filter 58 Filter 1 inch covered 57 Filter 2 inch covered 57ish Air box lid with modified snorkel inlet
So obviously these things like to breath, however they do not like to have open air. So some restriction actually helps
Next I fired up my tracking ap and did the same run 4 different times, 2 runs with open filter and 2 runs with box lid on. And 1 of each with 2 shims, and 1 of each with no shims
2 shim runs Lid. No lid 10. 1.1. .5 20. 2.5. 1.2 30. 5.3. 3.9 40. 11.2. 9.7 50. 27.4. 25.2 Removed shims and same runs, but limited to 40 due to traffic near top end Lid. No lid 10. .9. .7 20. 2.5. 2.3 30. 5.2. 5.5 40. 12.2. 13.2
So some wierd things... the box showed fair consistency with needle shims or without. But by far the quickest acceleration was measured without the air box lid. At least to 40kmh. I'm sure if I could have ran the no shims to 50 the data would be consistent.
I'd say this shows she needs more air. The high speed runs show the filter is better than no filter so I'd say it either starts running lean up top, or the carb just doesnt like no restrictions.
To this point I've made 2 straps to hold just the filter on and run it open with 2 shims lol. I'm thinking of modifying the lid with some extra air scoops to keep the filter somewhat covered but still be able to breath. With the airbox open as the speeds indicate I dont have my hesitation nearly as bad, if at all coming into the needle.
These were all done with a stock exhaust, head. I shaved down the rubber ring on the carb inlet tube, slightly chamfered the rim between the slide air inlet, and thats it really. I dont know of I have much more on the table currently without changing the exhaust as far as engine output. Cvt is stock.
Last fill up was ran with 2 shims, lid on and averaged over 96mpg. But if it was rich the whole time it was obviously not running effeciently.
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Post by Zino on Jul 20, 2020 21:22:01 GMT -5
Nice work Dialing it in Being Methodical about your Airbox mods . Now you have a real good idea what your scoot needs and baselines for future improvements .
Now you can see if you can adjust your jets to your best airbox setting.
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Post by Mech Warrior on Jul 20, 2020 22:00:17 GMT -5
Zino i see you changed your image lmao. I almost didn't know it was you.
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Post by Mech Warrior on Jul 20, 2020 22:27:02 GMT -5
You need to stop all the nonsense and listen to the real techs.You need to put your'e stock air box on with filter and lid THE CORRECT WAY!. Then adjust your'e jetting to suite.Like FrankenMech said it's not easy to tune but it's the right way.If you leave that air box open or make these unnecessary complicated sounding calculations that at the end of the day they amount to nothing.Zero is your'e reliability rate. The way you are trying to tune it is according to the temperature outside,wind speed,humidity,rain drops falling per second, with no filter on. You are asking for headaches.Take the advice and USE it!
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Post by cypher1982 on Jul 20, 2020 23:41:27 GMT -5
You need to stop all the nonsense and listen to the real techs.You need to put your'e stock air box on with filter and lid THE CORRECT WAY!. Then adjust your'e jetting to suite.Like FrankenMech said it's not easy to tune but it's the right way.If you leave that air box open or make these unnecessary complicated sounding calculations that at the end of the day they amount to nothing.Zero is your'e reliability rate. The way you are trying to tune it is according to the temperature outside,wind speed,humidity,rain drops falling per second, with no filter on. You are asking for headaches.Take the advice and USE it! Perhaps my description wasnt clear. I'm well aware that it needs a filter. I made a single run with no air filter, all the others were done with the stock filter in place. The only thing changing was air available to the stock filter, via essentially an unlimited plenum or through a restriction sized as the snorkel inlet, and needle position. The reason it's not "back to stock" is because of the removal of the molded o ring in the carb inlet tube and no longer having the 80 main jet it came with. I also opened up the snorkel restriction at the inlet from roughly 17mm to 22mm. Once removed it cant go back without replacing the tube or the box. Other than that, I guess I'm in a group of people who like to tinker and play and see what works. Would this be any more of an issue had it been completely stock? Or had I just purchased a high flow air filter? Or maybe an exhaust? I had the same condition while stock but limited to 30mph. Aside from buying a designed and researched mod, which I dont really feel like spending the money on, at this point, it's all the same. Even then wouldnt the advice be that there is no one size fits all, and things need adjusted to your taste and riding conditions? Such as if I asked for the ideal roller weights to swap in. There is a method to my ways and I've taken advice from what I read. Exactly why I chose not to use a pod filter and kept and will be keeping my air box and factory filter. Also the reasoning behind d the runs with the scooter warmed up, all runs on same road within 20 minutes of each other. While I dont doubt that jetting a carb and fine tuning can be hard for some, I have a good knowledge of engines, just happen to have all my knowledge in efi and modern vehicles. I mean no disrespect in this and do understand that there are probably a lot of people who have no ideas about tuning or modding and having it done well and reliably, so I'm sure some of the same stuff gets frustrating. But all our knowledge comes from trial and error, either our own or someone else's. Just hoping to have initially heard from someone who had a reasonable starting point in the main jet. In fact through this.. I actually thought of something else that may be fun to try and test out. I found this forum from watching tons of you tube videos BEFORE any changes were done on the scoot. Who knows...maybe I'll figure something out you want on your scoot... maybe you'll get a laugh if I do something stupid and embarrassing. Either way, ride safe and thanks.
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