17 agility 50cc air/fuel restriction help

[Cypher1982]

Here us a picture of the front hinge you asked for

[TBR125]

Thanks! That is identical to the 125cc. Same seat box and hinge probably.

[Cypher1982]

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.

[Cypher1982]

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

[Cypher1982]

Stock carb mouth

[Cypher1982]

Smoothed transitions into carb and slide inlet. As well as slightly chamfered at the bottom around the air inlet port