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Scooters - 50cc => Agility 50 => Topic started by: Cypher1982 on June 17, 2020, 09:53:07 PM
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Hello, I'm new to the forum and tried to search but havent had the best of luck. 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 ring in the air tube by the carb, now shes flat. 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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The needle raise will change where the main jet takes over. It will not however change the mixture at full throttle.
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Yes, my issue is I cant get it to even begin to take over.... about 1/8 throttle it's ok, but if I open it at all it just wants to die. But it feels nice up till it attempts to transition, but it doesnt seem lean enough to stall on me while moving.
Update, I added my second shim, if it improved at all it's barely. I'm thinking it just needs a bigger main to fuel the new air movement. If I can figure out how to upload the pictures I will
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You have begun on the jet tweak journey. I would buy an assortment pack of jets, a bag of screw drivers, and go drive. I have swapped jets in gas stations, church parking lots on week days, and at Walmart.
Good luck, would be glad to hear what size you decide to stick with when complete.
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Well my phones pictures are too big to upload. Tonight I went for a better ride with the 2 washers. Its definitely in the main jet. With the 1.0mm spacer on the needle it slowly built back up to speed. So I had already ordered a jet kit which is supposed to come friday, so I'll be able to see how it affects her. Also gonna either machine the vari boss or replace it.
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So I opened up my airbox Inlet and removed the restriction. It's now 25mm, didnt get a before but I'd bet 20mm or less. Took it for a drive and it was bad...barely moved over 15mph. I shimmed up my needle .5mm and not any better to speak of. Shimmed to 1.0mm and it would get to 30 but a lot slower. I drilled out my main to .84mm and no shims and drove again, better than a shimmed needle and stock MJ. I reinstalled the snorkel in this config and it drove well again, just a small hesitation at transition to needle jet. So i still need fuel. It has nice pickup after that jet opens up more. So any one else ever mess with these things that we can talk about it? On a side note..I really with I could post pictures...my phone takes pics that are too big
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There are many free pic resize apps for android and I think a few for Apple phones. I went through that with the agility but it was simply a matter of changing jets until the transitions were smooth. I simply removed the entire air intake system and installed an 8 inch clamp on Uni filter. Insanely oversized but I will use a big block kit in the future.
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Ok, sorry this update gets technical but bear with me.
I calculated the area of my MJ and intake snorkel and air box
Air box inlet 500.5mm2 25% larger
Snorkel inlet 398.4mm2
MJ .80 stock .5mm2
MJ .84mm bored .554mm2 11% larger
Did 2 back to back runs with snorkel installed and not installed and took averages of time to get to speed. Only carb mods are a single .5mm shim under the needle.
With snorkel, these were averaged of 2 runs
10kmh 1.05s
20kmh 2.3s
30kmh 4.75s
40kmh 9.6s
Then removed the snorkel and ran same.route a few moments later
10kmh .6s
20kmh 2.2s
30kmh 5.5a
40kmh 11.4s.
Based on these findings I'm looking at the slow jet being near perfect, although when first start up, I noticed some light white puffs out of the exhaust until its thoroughly warmed up.
That being said, it's faster down low without the snorkel but up top with, leading me to think I need to upjet some more to get more needle fuel and MJ fuel. My next size up is a .90mm but if I open it up, making it smaller is a lot harder lol.
Any thoughts on my findings?
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Congrats on gathering factual numeric data. I agree it is running very lean. Unless you have access to O2 meters and exhaust analyzers it is probably best to enrich until it is non-disputably rich on both jets. At that point you can back of until you find peak power and pull. The exact perfect point is often between jet increments, and you may need to get several different jet kits that have staggered sizes. If, when at peak performance on both jets there is a stumbling lag at the jet transfer point you typically want to enrich the main until it meshes as one throttle response. To seamlessly transfer the engine needs to have a little extra fuel to boost it through the fuel change.
In general it takes a much larger main jet increase than one would think. One my agility 125 The main went from a 102 to a 115 by just changing the airbox with not even a hi flowing foam uni filter.
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Stock airbox inlet
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Opened up a little
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Snorkel inlet compared to carb inlet
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This morning I decided to open up the main jet again, took it to .90mm. Start up and idle obviously not affected. I took it for a drive. Same way I did with my other tests but my data ap was being a bit screwy so it's all butt dyno results based on feel.
What I noticed, with snorkel the transition from pilot jet slow and felt unresponsive. Overall felt rather wimpy and I noticed after a longer WOT ride it smelled overly hot and heard what i can vaguely describe as a sizzling sound from the exhaust, which maybe an issue with overheating the cat if its overly rich or lean.
Took the snorkel off and drove again. At this point it felt still very sluggish at transition to needle for some reason. Off the line felt good till 15ish kmh. However, one it seemed to wind up it felt ok. Strangely the last day or 2 it seems like my top end struggles to get back to where it began. It feels like I get there a bit faster but the last 5kmh just dont seem to come. While riding without the snorkel I can reach down and cover some of the inlet, when I do this the power seems to die fast. When letting off the throttle it immediately starts slowing down and dropping power so I dont think it's too rich, but it does concern me with how big is too big with how it's set up? I did NOT notice the sizzling sound nearly as much if at all with no snorkel and running WOT. So..... keep going? Lol on a side note...my first tank I hand calculated 105mpg, but I am not sure just how full it was, second tank dropped to 70mpg, this last tank was 75, which I dont think is too bad since I took 2 long really slow rides with the kids.
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Update here. In the last few days I was able to install a new variator boss. I used the same ap for logging as I did prior but changed it to measure in mph instead of kph. I am not sure if my hesitation is in fact a hesitation or the cvt starting to shift. You can see from the shot that the first 10-15-20 all appear to pick up reasonably well. This is without the air snorkel by the way. The acceleration then appears to shift its curve and begins leveling off in what appears to be a pretty linear curve. I guess I'm just confused now. I could probably do some plug reads to see condition that way, but as of now I have no odd sounds or bogging from being too rich and once it winds up it seems to be ok. The other thought I had was is this an operating normalcy from the cv carb transitioning?
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I thought my 125 was restrictive but that intake looks about half the carb opening diameter which is almost 1/3 flow. I tried spark checking for tuning but couldn't check it for the main when the pilot+idle were rich as the plug sooted before I could get the engine shut off.
I don't know about body parts compatibility between the 50cc and the 125 and am looking at potentially swapping for a 50cc single place seat for larger rack space. Could you post a pic of the front seat hinge and seat underside?
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Here us a picture of the front hinge you asked for
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Thanks! That is identical to the 125cc. Same seat box and hinge probably.
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Quick update for anyone following along. 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 odd 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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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 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 covers
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 59 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 it 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 thatd 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 well.
Figured someone might find this data interesting
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Stock carb mouth
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Smoothed transitions into carb and slide inlet. As well as slightly chamfered at the bottom around the air inlet port