Engine Trouble 7000ft+ carb jet tuning help? I've tried almost everything.

Discussion in '2-Stroke Engines' started by Lucknuts, Jun 6, 2013.

  1. Lucknuts

    Lucknuts Member

    We live at between 6500 and 10,000 ft. here and I have tried everything I can find online to fix the "way too rich" situation to no avail. Help!

    1. 3 times over every gasket is sealed every bolt is tight, including the carb to the carb pipe thing going into the head. Yes exhaust too.
    2. The chain is straight as an arrow and perfectly tight.
    3. All the electrical is functioning properly, getting great spark from this NGK plug.
    4. Air filter is sealed, working and fully open.
    5. Timing looks right doing TDC test and looking at magneto, comparing to online pics

    The bike still 4 strokes when idling and bogs down when given gas.

    So, must be too rich right?

    6. Soldered the jet closed and poked tiny hole with high E string from guitar. Opposite problem.
    7. Widened hole with pin and blow torch. Back to too rich again.
    8. Inserted high E string into carb jet (after removing all solder and using original jet size): too rich
    9. Doubled string: too rich
    10. Used B string end #24 (then doubled): too rich still
    11. B string with coiled wrapping (almost blocks jet entirely): won't start.

    Can anyone tell me where to just buy a jet that is the correct size for my altitude? Please? It's fun for me to MacGyver stuff but this is too much.


  2. jaguar

    jaguar Well-Known Member

    there is no way to know what size jet you will need. Just buy a micro drill bit set and try different sizes. Where to buy a set and what steps to take to jet it correctly is on my site. (click signature link)
    I was at 8500ft and had to solder the lower portion of the needle to get the jetting between idle and mid range correct. Getting top rpm jetting with the main jet is the easy part. I finally got a Dellorto SHA and was happy till I moved down to the coast where I could never get it jetted right. Now I use a fully adjustable Mikuni and am very happy.
  3. HeadSmess

    HeadSmess Well-Known Member

    another alternative to soldering and drilling is using strands from the finest copper wire you can find. just keep soldering one in at a time til its right. the finer the wire, the better. use a very hot iron and only "tack" the ends out away from the jet hole.

    for using a guitar string...hmmm... 020 would be around 0.5mm? high E is usually a 10, that would be 0.25mm. so id be fiddling with 18-22 guage if i was to try making holes that way... :) b or g... sometimes the inner strand of the wound strings is right...

    i do use strings to guage my holes after drilling. invariably accurate :)

    a set of microdrills from 0.3 to 1.3 in 0.05 increments should be around $20 on fleabay. you will need a pinchuck to hold them. id be trying 0.4 to 0.5 at first.

    when you look at the slide, youll notice a cut away that faces the air filter. not the narrow angled slot for the idle screw thats opposite the slot for the cable/locating pin. you wont see these when the carbs assembled. its just a shallow angle on the front face/bottom edge, visible down the throat.

    increasing this angle or its depth will lean the bottom end or idle out. avoid it, can be easy to go too far.

    main jet is wide open throttle. the needle and its height, controlled by a small e-clip, is the mid range. the angled cutaway is the idle.

    start with full throttle, get it right, move to mid, move to idle.

    plug chops and reading a plug. get a new or clean plug. run it for a good mile at the throttle setting you want (liquid paper marks on the throttle grip and housing!) and hit the kill switch keeping the throttle in position. check plug. you want light tan, a vaguely rusty colour depending on fuel and oils and plug heat range. black is rich, or too cold a plug, bone white is too lean, too hot a plug (or just right if the mix is right). if its too lean it wont run. easy.
    Last edited: Jun 7, 2013
  4. Lucknuts

    Lucknuts Member

    Awesome info, thanks guys! Can't believe I didn't think of copper wire! :banghead:

    I only had a few odd extra strings around and I didn't want to take any off my guitars. I have loads of wire around here. Also, the drill bits are inexpensive and I've already soldered it closed again.

    Unfortunately, home depot didn't have micro bits when I checked. So, the only place to get them is online? Bummer. I suppose I can wait until next weekend to finally ride it. :icon_cry: Maybe I'll try the copper wire after all. And, a blowtorch seems to work way better than a soldering iron for this stuff if you guys haven't tried it.
  5. Lucknuts

    Lucknuts Member

    Also, if I'm going to spend over 20 bucks online for a micro drill set and tiny chuck, it seems I might be better off just buying a better carburetor.

    If any of you guys want to recommend a better carb in the $20-40 range I appreciate it. Sorry, I haven't searched the forum that yet though. I'll do that as soon as I can. Thanks.
  6. jaguar

    jaguar Well-Known Member

    all the cheap carbs give cheap performance and arent made well.

    For $75 you can bolt on a Walbro carb from JNMotors but it don't allow an extended intake for low rpm power boost. A 18mm Mikjuni costs $70 but you need custom adaptors for it. A Dellorto SHA will bolt on but it is a headache because only adjustment is changing the main jet. And they eventually break where they clamp on.
  7. HeadSmess

    HeadSmess Well-Known Member

    i like having the drills cus when you get a new carb, invariably, you still gotta use them?

    new carb, old carb, it will still need jetting to suit your needs :(

    jetting is worth learning.

    imho, dont worry too much about carbs, other than some dialling in. which is what youve been doing.

    the things mainly WOT any way, anything else is just puttering around, and with under 2 hp usually, throttle control isnt really an issue... at WOT, the stocker does fine.

    all my mucking with fancy carbs has made me draw one conclusion...keep it stock.

    remember! KISS!

    hehehe, im only at 250m or summink :)
  8. jaguar

    jaguar Well-Known Member

    my experience is the opposite.
    the 12mm Dellorto gave me 8% more top speed than the stock 14mm NT carb. Both were jetted for max speed.
    A good quality carb just does a better job of atomizing the gas. The gas is entering the air stream thru 3 or 4 holes in the Dellorto, whereas the NT has only one big entrance hole. Obviously the one with the more holes is going to do a better job of atomizing. Although I dislike the Dellorto SHA for its inability to completely tune, I really like its design with multiple entrance holes for the gas. That is one advantage it has over a normal carb with two entrance points. I hope to experiment with the 16mm SHA in the near future.
  9. Lucknuts

    Lucknuts Member

    Whaaa? Cheap freaking engine, why would I pay about the same price I got the thing for, for a carb?

    See, that's the problem when people take something way too seriously; Clever marketers make y'all look like fools paying crazy money with too high a markup because it makes you feel cool.

    Anyway, I've almost got this turd tuned. It's a lot of fun when it has power.

    I started with two wires taken from a 16g strand. Then three, still too rich. Then I could barely fit the fourth and it ran just amazingly. Yet, when I checked the plug it was slightly white! Yikes, I thought the pipes were hotter than usual.

    Poked it slightly with a pin to mash the copper a bit and make a slightly bigger hole. No love. Now it's too rich again. Frak.

    I'm losing my mind over this stupid thing. It's supposed to be simple, yet it's far from that. It's supposed to be inexpensive but there's some kind of industry for this crap pushing gawd knows what for outrageous prices... have I missed any paradoxes?

    These bikes are incredibly lame and yet people race them? Wow. I don't think I could be more confused about a subject after so much research? What is this some secret mason thing? Is there a union?
  10. Lucknuts

    Lucknuts Member

    Here's the nitty gritty: I have it close to tuned for this altitude, but apparently it'll 4 stroke and bog unless the jet is just shy of too lean. Apparently that's hard to get. And if I got tiny drillbits wouldn't they just break?

    But, here's the thing. I made a stealth silencer to see if the noise I was hearing was the 4 stroking pinging or not. It's not! The freaking engine sounds like it's clattering and scraping and destroying itself and that's just idling.

    As far as I remember from mopeds this isn't right. Sure the clutch makes a lot of noise which really sucks. But, it's not that. I can hear the piston going up ancarburetord down and it sounds like it's scraping and flopping around in there, slightly.

    WTF is that? it's a metal scraping on metal sound, chug a chuga a slap slap chuga
  11. Lucknuts

    Lucknuts Member

    okay, I'm as stunned as y'all may be. but apparently I'm 1 degree from the mayor here. My buddy Benito (career elected official, last time county assessor) is friends, like since grade school with the bleeping mayor.

    It's something I take in stride these days since my wife works on movie stars regularly. The do a lot of filming in New Mexico lately and most of them apparently have rotten teeth.

    If only they knew that their "asthetic dentist" sucked and it was all schmoozing. I wish I could tell them sometimes. They could easily get better work done if they weren't so "fancy".

    They're usually as-soles though so why would you go out of you way to help a spoiled brat? Oh yeaah, those c-note tips. Doh!
  12. Lucknuts

    Lucknuts Member

    so anyway what I was saying is that y'all can go back to being bored with your boring lives. Yes, I would like NO tomatoes, please. Fruity meats are reserved for Italians.
  13. HeadSmess

    HeadSmess Well-Known Member

    youll find thats mainly clutch gear noise.

    yep. its there. unavoidable. some motors are better than others, manufacturing tolerances are dismal...

    cost issues. they are cheap. also, due to the clutch gear basically floating on a single row of bearings, its free to flop around and clatter against everything...when the clutch is disengaged! youll find a lot of the noise reduced once the clutch is engaged, simply cus the gears held fairly rigidly then.

    i agree, why pay almost as much for the engine for a carb when its only an 8% increase? doesnt sound worth it.... whilst tools are always an investment for the future! (small drills wont snap if you use a pin chuck and be gentle...)

    youre getting good results with the wires, so more kudos to you ;)

    now, over priced upgrades... if i couldnt make them, and had it conclusively proven to me that a decent exhaust system will double the power, id pay for them... two strokes depend on exhausts, and these POS china junkheaps benefit more in this area than any other mod, plain and simple. imho, it just isnt worth getting any more involved than bolting on a new exhaust. (not that that stops me!)

    trust me and anyone else that thinks tuned pipes are the ducks guts. they are. take an old yz250 or similar 2stroke for a spin...with the exhaust removed ;) compare "with" with "without"... the motor will tolerate being a bit off on the mix or compression or such, but removing the pipe makes for a noisy underpowered lawnmower. they fit that great fat shiny slug on them for a reason!

    currently, as standard, you have a basic "lawnmower" muffler :( of course youre going to be unimpressed!

    dont worry too much about the 4 stroking too much, or getting it too spot on. as long as the thing runs, doesnt produce a smokescreen, and doesnt gunk plugs or sieze, its doing fine :) if you can bear looking at it in 3 months time, contemplate a few upgrades then :jester:
  14. HeadSmess

    HeadSmess Well-Known Member

    if the plug came out white, and it was running fine...quick! go back to that one! either you had the heat range of the plug and the mix spot on, or... yep. thats it...spot on. bordering on the lean but until the electrode melts and says otherwise...perfect! if the electrode does melt but motors still running fine, use a cooler plug...go UP a number or two (ngk standards). it has to run a tad leaner so a tad hotter cus of the altitude, so id be fitting, say...an ngk b8hs instead of the normal b6?

    is only too lean if the engines spluttering and dying when you open the gas.
  15. jaguar

    jaguar Well-Known Member

    basic elementary kindergarten stuff

    I recommend a $70 carb and you complain because you say the cost is almost the same as the engine!? WTF? the engine costs $200 ! someone here is on drugs and it ain't me. The worse the product, the more money needs to be spent to make it right.

    go ahead, you and all the other cheapos, run your POS chinese carb and have it too lean at idle, too rich at mid range, and too lean at top end, so that you seize it and then cry that you have to buy a new top end.

    Why spend money for a good carb? Because it will run cleaner, sound better, give better power throughout the whole rpm range, not foul plugs, not seize the engine, not leak gas, allow it to breath better at high rpm, start easily, idle better, accelerate better, look better.

    ANYTHING WORTH DOING IS WORTH DOING RIGHT. The chinese didn't do it right. It's up to you to finish the job.
  16. Lucknuts

    Lucknuts Member

    sorry for the wacky comments I was having too much fun again last night. thanks for the input headsmess.

    unfortunately you can't polish a turd too much. I guess I'll wait and find myself a real engine somewhere. Forget this cheap chinese crap. It started out fun, but it's a piece of $%^ no matter how much love I give it.

    I call this a scam in common lingo. It's B.S. at the highest level, like our government lately. It's simply people scamming people to make money. Why are the chinese so nefarious in business. I thought the Germans sucked but this blows them out of the water.
  17. jaguar

    jaguar Well-Known Member

    OK then get a Morini (which is the same cost as a Grubee with needed modifications).

    You have to make your own way of mounting it to the frame though.
  18. crassius

    crassius Well-Known Member

    you could do that for sure - but you could also just be happy with what you have - 100s of folks buy kits, build them, and ride them without ever knowing that the factory main jet is leaving them 4-stroking

    it gets them down the street reasonably quickly, gets them up hills very well, and they're having fun

    I sometimes will jet one for better performance, but it always takes a diff sized jet from what worked on the last one, and the improvement isn't that big a deal. On days with no other stuff to do tho, I enjoy piddling with them.
  19. jaguar

    jaguar Well-Known Member

    price comparison:
    Whizzer 135cc 4 stroke kit $800
    Morini engine $660 but is engine only. You'd have to buy a $200 Grubee kit to have all the other necessary parts although you also have to weld up your own frame mount. (min total $860)
    Grubee 69cc $200 (also needed: $70 carb, $75 Jaguar CDI, $10 lighter wrist pin, $20 crank seals, $20 heavy duty chain for a total of $395)

    the choice is obvious to those on a budget. If I was rich I'd get the Morini. Otherwise the Grubee is the way to go if you are willing to do some wrenching. If you aren't rich and are a mechanical dork then there's always walking or riding a normal bicycle. Or just stay home and watch TV.
  20. PooPooPeeDoo

    PooPooPeeDoo New Member

    Ways to bore soft things.

    Ummmm OK.... This is microcleverness...

    A careful estimation etc....

    You can do this the smart way... I don;t have the tables on me...

    But there is a ratio of altitude increase to fuel decrease - as measured on a volume basis, for a given head or flow rate of the fuel.....

    You need to match fittings (hoses and pipes etc., ) with the press on fit of a fuel line, over the OD of the jet.

    You will need a small header tank filled with fuel - say about 2 meters above your bench. Sodder a bit of metal tubing into the side of the metal can or slide a weighted drilled out screw and sit that into a plastic fuel can etc.. remember this is only temporary.

    With the tank filled with fuel, at 2 meters of head, measure the flow rate through the jet in 60 seconds.

    Get a steel guitar wire that is a fairly loose fit inside the jet.

    Sodder up your main jet.

    Then cut your guitar wire and either point the tip or cut it at about 45* and use it as a drill to bore through the sodder.

    Measure the flow rate per minute again.

    Then calculate the difference on a percentage basis, and then cross reference this to the decrease in fuel, per thousand meters in altitude.

    If the second fuel flow measure it too small, hammer the cutting tip of the wire to expand it, just slightly, and rebored the sodder in the jet.

    Then retest the flow rate.

    Or if the flow rate was too much, then resodder the jet, and rebore with a smaller wire and then retest the flow rate and hammer the wire tip a little to increase the size a little and rebore it... and retest the flow rate.

    It's not hard, it's just maths.....

    Someone else can dig up the tables and ratios..

    It's better to calculate and set to those standards, than it is to play guessing games with tiny parts.

    If you want help with the maths, put it up here and I will double check the figures for you.