Rebel AFR! - Page 2 - Honda Rebel Forum
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post #11 of 40 Old 09-05-2019, 10:26 AM
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Here are the measurements from an (original?) second generation needle. All measurements in mm. Total length, 42.00, not including a small raised "button" on top of the needle cap. Thickness of cap, not including "button", 1.62. Diameter of cap, 5.90. There is a short uniform diameter "shoulder" that extends 4.19 below the cap and measures 2.90 in diameter. Below that, the needle is a uniform 2.50 for the first 13.0. From that point, it tapers down to 1.30 at 39.00 below the bottom of the cap. Below that, over a distance of approximately 1.00, the taper increases down to nothing.

This is probably clear as mud unless you have a needle in hand.

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post #12 of 40 Old 09-05-2019, 10:09 PM Thread Starter
 
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flitecontrol - You've disassembled a carb. Maybe you can answer this? At WOT, does the jet needle pull all the way out of the main jet?


I'm still in Chattanooga at the hospital with my dad. He had to stay a 2nd night, but he is doing WAY better. He'll go home tomorrow. But I'm not sure if I'm going to make it back home until late Sunday. I'm his short order cook for the weekend.




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2016 Honda Rebel 250 - The "Piglet."
Totally Stock at the moment.
Bought on 6/29/19 with 44 miles.
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post #13 of 40 Old 09-05-2019, 10:37 PM
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Originally Posted by 7milesout View Post
flitecontrol - You've disassembled a carb. Maybe you can answer this? At WOT, does the jet needle pull all the way out of the main jet?
7milesout
Can't say. As much as I've tried to look, it's hard opening the carb, bending over to see, and still stay in my lane and operate the controls.

Keepin' all the left over parts. Gonna use 'em to build another bike!

'01 & '09 Rebel 250, '06 Ninja 250, '89 VN 750
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post #14 of 40 Old 09-06-2019, 08:00 AM
 
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Main Jet isn't involved other than it is the maximum fuel opening of the "High Speed System"

The "Needle Jet" diameter in conjunction with tapered needle provides transition between low speed/idle to intermediate system.. effects of needle jet taper off past 1/2 throttle and main jet comes more into play..

needle jet is held in place by the emulsion tube aka ("Needle Jet Holder" Honda nomenclature).. An important part, as it begins the processes of aerosolizing the fuel, as the needle rises greater amounts of fuel are aerosolized..
Main jet screws into bottom of emulsion tube..

The needle never pulls out of needle jet But does fully pull out of emulsion tube aka "needle jet holder"
There are performance emulsion tubes that enhance performance of some engines..

your AFR is dependent on more then static carb settings.. Altitude, Temperature, Humidity, etc. will also effect results at any given moment..
Attached Images
File Type: jpg Care & Feeding Of The Keihin Carb.jpg (16.8 KB, 2 views)
File Type: jpg Honda_Carburetion_Page_18.jpg (182.3 KB, 4 views)
File Type: jpg Honda_Carburetion_Page_19.jpg (180.4 KB, 2 views)

96 VS800 Intruder (sold 2018 ), 87 CMX250C Rebel,
79 CB400 Hawk (sold 93), 75 CB350 (sold 83), 71 CB350 (stolen 74)
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post #15 of 40 Old 09-06-2019, 12:15 PM Thread Starter
 
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Testing, Testing, 1, 2 ... 3?

Guys,


Below are sketches of the testing I'm going to do in addition to the data I'm going to check if I ever get to go home. But I made some sketches to describe the performance tests I want to do. I hope I can get these tests video recorded, both stock an with optimized main jet.







Tests:
  1. 50 - 65 mph Roll-On.
  2. Top Speed.
  3. Bunny Slope.
Attached Images
File Type: png Roll-On.png (81.9 KB, 5 views)
File Type: png Top Speed.png (73.3 KB, 4 views)
File Type: png Bunny Hill.png (73.0 KB, 3 views)

2016 Honda Rebel 250 - The "Piglet."
Totally Stock at the moment.
Bought on 6/29/19 with 44 miles.
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post #16 of 40 Old 09-06-2019, 12:17 PM Thread Starter
 
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Notice how our mighty Rebels pull the front wheel off the ground when hitting WOT in 5th.

This testing can get dangerous...

2016 Honda Rebel 250 - The "Piglet."
Totally Stock at the moment.
Bought on 6/29/19 with 44 miles.
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post #17 of 40 Old 09-10-2019, 08:28 AM Thread Starter
 
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Some data...

I did manage to get out on the bike yesterday. And got quite a bit of data. Not all. I didn't do any video recording as currently I have no way to do that. I do have a GoPro but I have not affixed it to my new helmet. I had my phone attached to the RAM mount, the AFR gauge zip tied underneath it (just cobbled it on, but it worked), and zip tied a stop watch to my left handlebar. So here's the data.


  • Choke (while cold) Idle AFR: Pig rich. 8.0:1 or less.
  • Idle (while fully warmed) AFR: 11.2 to 11.6. The warmer the engine the slightly higher.
  • Cruise AFR: I didn't get a chance to measure these. But they are lean to extremely lean.
  • WOT AFR: In 5th gear, they ranged from 9.0 (rolling on at 55 mph) to 11.5 at 70+ mph.
    • I had originally noted a highest AFR of 10.5, but it was a bit higher yesterday.
Performance Tests


  • Bunny Hill Roll-On from 55 mph: The bike gained up to 59 mph consistently. This may not mean much now, but will be relevant if my tuning improves performance.
  • Timed Roll-On (55 mph to 65 mph): I had 5 runs and this averaged 10.855 seconds.
    • I was originally going to do 50 - 65 mph, but in the course of trying to complete this testing, I didn't remember to start at 50 mph, instead started at 55 mph.
  • Top Speed 2.5 mile stretch: I hit 70 mph the first time, then 71 mph the next 3 times. Then I ran out of fuel on ON, and limped back home on Reserve.
What I did notice while pinning the throttle for ~ 2 minutes during my top speed run is that the AFR was higher than I expected. I would say it averaged about 11.5:1 (not 10.5:1). But that would quickly jump and vary from 10.5 to 12.5. So, I'm going to have to be careful tuning. That also tells me, that maybe I will make LESS improvement than I originally thought I could. All this testing was from gas pumped from an E10 tank. And other than equipping the bike with the AFR gauge, nothing has been touched.


I'm going to try to do some cruise AFR and WOT AFR, but that may require a video camera pointed at the AFR gauge and phone GPS speed to have reasonable numbers. So, I'm going to have to figure that out.




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2016 Honda Rebel 250 - The "Piglet."
Totally Stock at the moment.
Bought on 6/29/19 with 44 miles.
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post #18 of 40 Old 09-11-2019, 11:53 AM
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Gaahohaaalie! (Like Gomer Pyle). You ain't gonna believe it, you just ain't gonna believe it! I would have told you were wrong if I hadn't seen it myself.

But here's they eye opener. Bear in mind, my bike is new so everything is fresh. And with enough level ground the speedometer will get very close to 80 mph. So it is running right. But at WOT it is RICHER than optimal! Wow! I would not have believed this!

7milesout

This tracks with my experience out on the open road. I've been keeping a religious fuel/distance log for the past 5k miles, and while city/country riding returns a steady 65-70mpg (running a smaller rear sprocket) getting out WOT on the interstate returns closer to 50-55.
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post #19 of 40 Old 09-11-2019, 04:12 PM Thread Starter
 
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The Piglet is sitting on empty right now. In order for me to tune optimally, I think I better top off with 90 octane no ethanol. And just do WOT high speed pulls. In that way, I can judge that with 90 octane no ethanol fuel, does the AFR at top speed go richer? Go leaner? Or stay the same from the 87 octane E10? I'll need this info to help select the all around best main jet.


Unfortunately tonight I need to make a run up to my father's house, just to break up his week of living alone. Thursday and Friday nights, I may have football games to go to. At least Thursday.




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2016 Honda Rebel 250 - The "Piglet."
Totally Stock at the moment.
Bought on 6/29/19 with 44 miles.
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post #20 of 40 Old 09-12-2019, 02:40 PM
 
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Just as a datapoint for your top speed test runs....

I took my 2016/975 miles Rebel on the interstate today for the very first time. (Previous high speed runs have been on a divided parkway, but with 45-50 mph speed limits.)

I was just practicing, so was merging onto westbound, going up to the next exit, doing the clover leaf, and looping back on to eastbound to go back where I came from, and repeat 3 times.

Because of congestion and the short distance, I was not able to hit max speed. Each time I tried, I ran out of room and had to throttle back while the Rebel was still accelerating at a pretty good rate.

I was consistently hitting 75 mph, and there was definitely more speed left in it. I will be shocked if this bike won’t hit 80.

Flattish highway, wind not a significant factor (tested speed in both directions.) Totally stock. I do have a National Cycle windscreen, and I am running high-test gas (E10) with Seafoam added.

As a side note, I was very impressed with how nicely this Rebel cruises at 60-65 mph. After this test run, I am much more confident about doing some local cruising on the Rebel.

.

2016 Rebel 250 - - Black
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