17 agility 50cc air/fuel restriction help

[Cypher1982]

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!!

[TBR125]

The needle raise will change where the main jet takes over. It will not however change the mixture at full throttle.

[Cypher1982]

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

[TBR125]

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.

[Cypher1982]

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.

[Cypher1982]

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

[TBR125]

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.

[Cypher1982]

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?

[TBR125]

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.

[Cypher1982]

Stock airbox inlet

[Cypher1982]

Opened up a little

[Cypher1982]

Snorkel inlet compared to carb inlet

[Cypher1982]

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.

[Cypher1982]

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?

[TBR125]

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?