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Post by Elektrey on Oct 27, 2014 21:56:33 GMT -5
Yeah I've looked into reading the plug for mixture and it seems pretty complicated for me. I think I will judge AFR by performance. What is the best way to do this? Obviously WOT but should I measure top speed, time elapsed over a set distance, RPM which the gear shifts at? what is a safe measure to test WOT performance.
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Post by niz76 on Oct 27, 2014 23:20:42 GMT -5
The other best way to tune without looking at plugs- i guess would be to install a CHT gauge- Cylinder Head Temp gauge. Scoots run great lean so it's hard to tell by seat of pants only... Plug should have a "coffee with cream" color but it takes a little while for them to get the color.
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Post by Elektrey on Oct 28, 2014 10:24:55 GMT -5
The other best way to tune without looking at plugs- i guess would be to install a CHT gauge- Cylinder Head Temp gauge. Scoots run great lean so it's hard to tell by seat of pants only... Plug should have a "coffee with cream" color but it takes a little while for them to get the color. I would probably take the point where it performs best and go rich just a bit. |
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Post by Elektrey on Oct 28, 2014 12:51:28 GMT -5
Anyone know if there is such a thing as an app for windows phone/android that will use the GPS and create data such as speed vs time so I could plot the performance differences? Like data that can be exported to a word processor/excel.
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Post by 90GTVert on Oct 28, 2014 15:22:35 GMT -5
Without CHT I will watch RPM and speed. Use a set distance. Doesn't have to be exactly a mile, but say from your driveway or some landmark to another landmark. Go both direction and note speed and RPM in each direction. Write that stuff down, with the jet size or whatever you're changing, and any observations like sputtering or how it felt. Change jets or whatever you're working with and hopefully a pattern will emerge. If two work about the same, choose the richer option. Simple idea, and can be time consuming, but it works. For best results do all tests in close proximity. Don't wanna have 2 tests when it's 70F and calm and 2 when it's 50F with 20MPH winds or it doesn't mean a lot. There are even tuning logs you can print in the Printables section if you'd like.
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Post by Elektrey on Oct 28, 2014 21:38:56 GMT -5
good idea. I just thought of something. I could take a video of a run and then do multiple runs, throw out the runs that are outliers, and compare the different runs by viewing the videos side by side so I can watch both speed and RPM changes.
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Post by 90GTVert on Oct 29, 2014 15:15:25 GMT -5
If you do it on video, then I would time the runs to X MPH if you can see your gauges. For my projects I do 4 runs back and forth and average them. Usually seems pretty accurate and helps to negate things like slight changes in wind.
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Post by Elektrey on Oct 31, 2014 19:47:55 GMT -5
So I got around to it today and got on it and wouldn't you know now it acts like a lean idle and shoots up as soon as I start it. Reduce ratio a bit and it's good. rode it around and it acted great so I didn't really test different ratios. I did notice top end was max 43mph where as before it was 45-46mph so that's kind of disappointing, probably a bit rich/lean.
One thing I notice that I'm not really sure what it is, is:
when I give it full throttle it's got this really fat wide low sound but if I let off throttle just a bit maybe 1/8 to 1/4 then it still has the same power, speed doesn't change at all, but the sound becomes more 'narrow' and quietier. Is this just the effect of pulling the valve in the carb so high that the passage for that valve becomes a small echo chamber for the reeds flapping? hope that makes sense. Or does that sound like a rich condition?
UPDATE: was just about to go tune it and it looks like today we're having 20mph winds so I headed back. Guess I will do it another day.
On the plus side, I got it to 53mph with the wind.
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Post by 90GTVert on Nov 1, 2014 19:12:20 GMT -5
Sounds like maybe you're close on the main jet or WOT circuit, but not quite perfect.
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Post by Elektrey on Nov 1, 2014 19:26:16 GMT -5
Sounds like maybe you're close on the main jet or WOT circuit, but not quite perfect. I actually looked at the forecast and it was windy for the next few weeks so I took it out tonight when the wind had died down (some) and recorded some results. Going from richest to leanest: (top speed one direction/top speed other direction) 40/41 40.5/42.5 40.5/43 40.5/43.25 40.75/43.5 41.25/44 So I think I am making progress. I cut it short due to how cold it is out now. One thing that is giving me a problem is now at the last setting I am getting a lean idle and it hangs and never drops and I am very close to all the way screwed in on the idle mix screw. |
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Post by 90GTVert on Nov 1, 2014 22:03:26 GMT -5
Check out the part throttle settings after the main is done. If you can't get a pilot jet, then raising the needle (if the engine isn't already rich part throttle) may help some.
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Post by Elektrey on Nov 1, 2014 22:11:42 GMT -5
Check out the part throttle settings after the main is done. If you can't get a pilot jet, then raising the needle (if the engine isn't already rich part throttle) may help some. if you mean moving the clip down and in turn moving the needle up: it's already in the most rich position. |
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Post by 90GTVert on Nov 1, 2014 22:17:12 GMT -5
That's what I meant. I never had much luck getting pilots for these carbs, and there are different styles for carbs that seem basically the same. To be fair, I didn't spend tons of time looking because I don't like open filters much and don't tend to need to mess with the pilot with an airbox.
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Post by Jwhood on Nov 1, 2014 23:17:30 GMT -5
That's what I meant. I never had much luck getting pilots for these carbs, and there are different styles for carbs that seem basically the same. To be fair, I didn't spend tons of time looking because I don't like open filters much and don't tend to need to mess with the pilot with an airbox. That's what I've tried explaining to him,get a stock box or an aftermarket box,and you most likely would've been tuned and running now messing with that Sanford & Son air filter its gonna give him hell,I'm not ragging know one because I tried too cut corners but 2t scoots don't like cut corners so i did it right and I run great 99.8% of the time even with weather changes!!! |
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Post by Elektrey on Nov 1, 2014 23:22:37 GMT -5
That's what I meant. I never had much luck getting pilots for these carbs, and there are different styles for carbs that seem basically the same. To be fair, I didn't spend tons of time looking because I don't like open filters much and don't tend to need to mess with the pilot with an airbox. That's what I've tried explaining to him,get a stock box or an aftermarket box,and you most likely would've been tuned and running now messing with that Sanford & Son air filter its gonna give him hell,I'm not ragging know one because I tried too cut corners but 2t scoots don't like cut corners so i did it right and I run great 99.8% of the time even with weather changes!!! Even if I managed to fit the stock box on, I don't think it would instantly be in tune because the carb is different than the stock carb, different venturi size and different jetting. and I could order jets for this one which I might do if I just can't get it right. |
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