What seems to be the problem here?

Discussion in '2-Stroke Engines' started by Nickledyme, Apr 19, 2014.

  1. Nickledyme

    Nickledyme Member

    Here we go, I have 3 carbs here n have been trying bout all I can think of. Here's the first one
    This one purrs like a kitten n looks pretty nice. It's very smooth but I can't get no power out of it. There's no way to adjust it as it has no needle that I can find and the floater isn't adjustable from what I can see. I tried swapping the jetting from a stock carb and seems to run a bit better but still not great.

    Here's carb #2
    This one ran awesome! I had tons of power and could fly up almost any hill. Now it starts off nicely but then it accelerates rapidly and springs/pulls back. I thought it was the chain or the tensioner at first and those were fine. I checked the clutch,spark,cdi and nadda.
    I went back to the stock carb and everything is running smooth. Anybody got some pointers? I'm still learning my way so plz explain in easy terms lol

  2. jaguar

    jaguar Well-Known Member

    by "springs/pulls back" do you mean you get surges of power followed by power loss, back and forth?
  3. Nickledyme

    Nickledyme Member

    I wouldn't think a power surge but it does speed up very rapidly. After that I feels like something snags or catches on something but doesn't. The chain does appear to jump a bit but it feels to me fuel related. I called up the guy who works on my bike alot about it and he agreed. I decided to try the stock carb and no issue but I use carb #2 and all hell breaks loose. I'm thinkin about trying the jet from the stock carb in the speed carb n see what happens as I really did like that carb as I did carb #1. It's just one of those things that will drive a man crazy trying to figure it out lol
  4. jaguar

    jaguar Well-Known Member

    instability can be caused by an air leak.
    the seal where the carb attaches to the manifold has to be 100% free of any leaks
  5. Nickledyme

    Nickledyme Member

    It could be but for now I guess I'm using the stock carb until I can get what I need to check for a leak. What would you suggest I do to check that? That will be my project on payday as I'm not working and will have the time to really check things out.
  6. jaguar

    jaguar Well-Known Member

    those NT carbs are metal on metal there and you are just lucky with your other NT carb. It should be leaking too just by its poor design.
    Good carbs have a gas resistant o-ring there for sealing.
  7. HeadSmess

    HeadSmess Well-Known Member

    dont be a a :dupe:

    no mention of jetting, so, you havent progressed that far, thats ok.

    the stock carb works, and does the job. stick with it, learn what jetting is, then contemplate fiddling further on down the track.

    they invariably need smaller jets, being set rich from the word go.

    the jet size is the only adjustment on air/fuel ratios.

    the new carb, whatever it is, is too lean. whether this is due to an air leak or the jet being too SMALL, is pretty simple to figure out.

    the air leak will be fine at WOT, but will be erratic on the IDLE.
    you have the exact opposite, or at least, you didnt mention anything about idle speeds being out of the roof and nothing you do seems to lower them, so, from that alone, i will say, you require a slightly LARGER jet, and the mention of an air leak is the usual situation of people talking nonsense and scaring poor initiates that dont know any better. mountains from molehills. false accusations, even! possibly, just possibly, by stretching definitions...slander!

    dont fall for it ;)

    silicone works for most people when a small air leak is experienced, and rather than try and find the air leak, be pre-emptive! apply silicone to the carb spigot when installing it. dont need much! just a smear! spigot, gaskets, you name it, you wanna silicone it, go for it :) just dont use too much! it blocks things off...
  8. HeadSmess

    HeadSmess Well-Known Member

    do it. it should behave like the stock carb does, if the jet(hole)s are different sizes.

    thus proving that its better to learn how to tweak the carb you have rather than buy something "better" that is actually worse until, well...tweaked too. which still doesnt make it any better?

    not really, its dead simple with a bit of practise, though, i admit, removing, dismantling,and reassembling four linked carbs of a 4cylinder motorbike can get reallllllly annoying... and dont talk to me of the carbs that place low speed screws in the throat! they SUCK! have to take the things off, just to give em an 1/8th of a turn! then theres airfilters and wiring and all that other silly stuff that has to be replaced before the testride, only to be pulled off again in a few minutes. grrrr.
  9. 074KU

    074KU Member

    I would suggest sticking with the NT carb until you have everything dialed in, Then really thinking about it.
    The first carb I don't know much about other than it is a Dellorto clone.
    The second is just a slightly reworked version of the NT, and if there is any actual "speed" increase it will just be jet, needle or combo which you can do in the NT for a lot less $$.

    It really isn't that hard to get the NTs running reasonably well for only a few dollars and a little bit of your time. When they do, unless you are heavily modding your engine you wont know really see a difference worth the dollars.
  10. jaguar

    jaguar Well-Known Member

    HS you say my air leak suggestion is "nonsense" and then go on to tell the guy how to prevent one! As always your logic is astoundingly screwed up.

    And the people saying to stick with an NT carb either haven't made the switch yet or they wouldn't know a 10% power increase if it bit them in the azz.

    NT problems:
    poor sealing from air leaks
    no idle circuit at all
    no different size main jets or needle available for purchase
  11. butre

    butre Well-Known Member

    Carburetors are so simple that there's no such thing as a bad carb, but a better one is never hard to find. The NT carbs work just fine if you can get them jetted right and seal up all the holes. Much cheaper than buying a $100 mikuni or walbro or whatever carb it is that you're advocating. It's always nice to have a better carb but air is air and gas is gas and any carb that can deliver those two things is going to work just as good given enough tweaking.
  12. butre

    butre Well-Known Member

    And don't think I'm saying you shouldn't upgrade the carb, I've got a shiny new VM18 on mine and am perfectly happy with it.. I'm just saying sometimes a little ingenuity goes miles further than money. If it's a tuning problem then spending a load of money on a new carb will still leave you with a carb that needs some tuning.
  13. 074KU

    074KU Member

    I tend to agree with Brute here,

    Jets are out there, took me 5 minutes to find that one supplier. http://www.pistonbikes.com/product-p/mp775mm.htm
    Needles not so easy to find.
    The main air leak where the carb mounts to the intake manifold can be solved with (I think) a P17 O-ring from a generic kit.
  14. Nickledyme

    Nickledyme Member

    I have my doubts on having an air leak but anything is possible. I have swapped the jet screw from the stock carb n put it in the Dellorto clone it did work better but not as good as it could. I'm gonna try it with the speed carb and see what that does and maybe take the one from the speed carb and see what that does on the other 2. I don't know anything about sizes of jets or how to tell but I do think I'm on to something here. I do have high temp silicone to seal a leak if need be. What size jets should I be looking into with a 66/80cc chinese motor?
  15. 074KU

    074KU Member

    That can really depend on your altitude and degree of modification. I would suggest trying your needle in the middle position on the jet you have and checking for rich/lean condition (4-stroking, plug colour, power.) as you work your way to either end of the needle.


    Aim to get a nice chocolate colour with 4-stroking not being evident under load. If to rich, go for a smaller jet (or 2) to lean, larger but most likely will me to rich.

    I hope this doesn't confuse you more, I have only just woke up and haven't even had my Coffee and Ciggy yet, feel special! :grin5:
  16. Nickledyme

    Nickledyme Member

    I think I found an air/fuel leak earlier. Got high temp silicone on it and will hopefully stop what looks like gas leaking from where the gas goes into the motor. Hopefully this makes a difference.