Fuel Mixture Not sure if running too lean, or too rich, or perfect?

Discussion in '2-Stroke Engines' started by Waxxumus, Jun 22, 2015.

  1. Waxxumus

    Waxxumus Member

    I recently switched from a stock Spark Plug to an NGK IX, and the Carb to a thatsdax.com RT carb.
    It originally ran too rich, so i went down about .05 on the jet. Runs quite well now, 2 strokes through pickup, mid, then 4 strokes out at high rpm (above about 22-24 mph). I cant honestly tell from looking at the plug after a chop if its running too lean, or too rich, ive had chops come out with a wite tinge on the plug after a long ride holding about mid throttle most way and revving full for about 10 15 seconds at a time.
    But riding normally and staying below 3/4ths throttle on level ground, it appears the plug ends up fowled.
    Its really weird.
    **** The contact in the center was wiped slightly by a rag, its not normally this white, its also a black color. As black as the Iridium Contact appears . *****
    Heres a picture of my most recent chop. This was after riding about 6 miles on it.
    IMG_4039[1].jpg

    Its got a light brown tinge on the tip, but the rest of the tip extending down to the bottom is black,

    **** the contact in the center was wiped slightly by a rag, its not normally this white, its also a black color. *****

    Also I notice, when going from my stock plug to the NGK, the threads are of a different size, but it seals on the engine head better. Im not sure if i stripped it just a tiny bit though lol. Ive been wondering how to listen for the piston hitting the spark plug, but wouldnt it be obvious on the plug itself?

    Look at the size difference here:
    IMG_4041[1].jpg
     

    Attached Files:


  2. Slogger

    Slogger Member

    The RT carb has a tendency to be too rich at full throttle. Mine did this, so I kept rejetting it leaner and leaner til it ran good up there, only to find it seemed lean and raspy (but not too bad) at smaller throttle openings.
    You might want to get a set of numbered drills and slowly lean it out (soldering the jet and redrilling it) until it pulls at full throttle. SBP sells the jets, 5mm dellorto, if you want to go that route.
    Don't go but one step at a time, or disaster may befall you. I tried to mod the spray bar with mixed results. I put the NT back on just to give it a rest for a while.
    Good luck!
    If that NGK plug is the type commonly used for the CGs, it should be ok.
     
  3. KCvale

    KCvale Motorized Bicycle Vendor

    What temp number is your plug?
    You may simply be running too cold a plug to burn off the plug buildup.

    The higher the number in the middle, like BPR7HIX, the cooler the engine runs.
    I run 7 and even 8's here in 110+F temps but you have to leave enough heat in the engine to burn everything.
    Drop a number or two lower and see, it's cheap and easy to try ;-}
     
  4. Waxxumus

    Waxxumus Member

    BPR7HIX is what i have, Running at 4 oz synthetic oil per gallon
     
  5. Waxxumus

    Waxxumus Member

    Would a better air filter help? or removing the baffle from the exhaust to allow more air?
     
  6. Slogger

    Slogger Member

    I run that much oil in ohio and have to run a #6, a little hotter, to keep the plug looking right.
    Ain't tuning fun?
    It's all part of the hobby. A well tuned engine is its own reward.
     
  7. Waxxumus

    Waxxumus Member

    Sooo many things to try with this rt carb. And just as soon as i Had the NT running perfect.. but it could never hold mids or even push as high as this RT.
     
  8. Waxxumus

    Waxxumus Member

    I wasnt into mechanics in almost any form (short of bike repair) so this was a great learning experience. Putting together the engine, replacing the mounting studs, need to do the head mount and replace the acorn nuts with some loctite, among many many other things. And get a better bike than a Huffy with bent rims.
    Mainly using the bike just for break in.
    But after the bike hit 25, the bearings in the wheels started to feel much much smoother, especially when attempting to push the bike forward with the weight of the engine up a steep hill. way easier. It appears the wheels have trued themselves. And its awesome.

    Just glad I took it slow and researched all these little nit-picky natures of these china engines before I even opened the Box with the Kit in it.
    Went for a gamble and chose Stinger SD.
    Got a winner.
    Started right up the first time. Well the second time. Dumb NT carb had a vacuum leak.
    Aah. That was a happy day.
     
  9. Waxxumus

    Waxxumus Member

    Over the years, i am likely going to take this engine body, and go through replacing almost everything in it over like 30000 miles.
    Ported and Polished and Lightened Pistons, Better bigger intakes, high compression head with double spark, hi performance cdi, timing fix for high compression, new wheels with crazy good bearings/axle and super strong spokes, CNC milled back sprocket, etc etc.
     
  10. Slogger

    Slogger Member

    I tried it without an air cleaner, then I put a very restrictive Dellorto SHA filter on, even though the jetting requirements changed, the basic trouble remained.
    When its nice and fat on the bottom, and still too rich on top.
    Leaned out on top, a tad too lean on the bottom.
    The muffler has less effect on the air flow than the air filter does. I put on a poopoo pipe with no baffle, jetting was the same as the stock (slightly modded) muffler.
     
  11. Waxxumus

    Waxxumus Member

    What height are you above ocean level. And hows the weather there.
    One day its 70 and cool here, next day its 90 with 90% humidity and the air is crazy thick.
    So its reall hard to tell with all this climate change.
    Texas man.
     
  12. Slogger

    Slogger Member

    I'm at about 800' ASL, the temps here have been from the 70s to the high 80s. It wasn't as humid as it has been here the last couple weeks.
     
  13. Waxxumus

    Waxxumus Member

    Soooo, can any of you tell me if the picture of the 1st Spark plug is too rich or too fowled? Is some black ok as long as the tip is that brownish sheen? or am i aiming for a brownish tint on the ceramic surrounding the contact?
     
  14. Waxxumus

    Waxxumus Member

    Id imagine thats not too much different from us. We are At about 500 - 800 above as well. Lots of Hills. Big hills.
     
  15. Waxxumus

    Waxxumus Member

    I can ride a giant hill from the top left corner of san antonio, all the way to the bottom left. Its about an hour ride @ 15 mph. But its just a big long hilly ride downhill 95% of the way. Fun stuff.
     
  16. Slogger

    Slogger Member

    Mine looked pretty much the same til I went from a #7 to a #6. Even with the plug looking better, it has no effect on the mixture of course.
    It looks a little rich, and with our 32/1 mix, black goo will build up on a too cold plug. The piston crown will show the same deposits.
    Leaned out some, little hotter plug and the black goo recedes.
     
  17. Slogger

    Slogger Member

    I went through basic training there, man that place gets hot.
    The hill sounds fun, til you have to go the other way. ;)
     
  18. Waxxumus

    Waxxumus Member

    Yep, you get used to it though. 90% of the year for 4-5 years in a row its 90+ degrees all day every day. Plus humidity. And no rain for ever. Then one year out of like 10, like this one, we will get rain for 7 months out of the year almost every week, and it will feel great, and I would ride, but rather not, on slick roads.
     
  19. Waxxumus

    Waxxumus Member

    Here it rains a little, gets slick, stops, drys out, gets oily, rains a little, gets slick ect ect in a vicious cycle
     
  20. Waxxumus

    Waxxumus Member

    We have had flash flood warnings so many times this year.
     
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