Carby carb problems now!!

Discussion in '2-Stroke Engines' started by wan37, Jan 11, 2012.

  1. wan37

    wan37 Member

    Well it got cold a couple days there in December so I order a air filter and a cen clutch and changed crank thought it was going to stay cold.It got real nice yesterday so went to check it out and ride I got every thing running with the cen clutch and now no throttle,bogs down at about 5 mph and the more throttle you give it back fires and bogs down it was running alright when I started in December the only thing I did was swap air filter.any idea's
     

  2. wan37

    wan37 Member

    I thought back in December it was running rich but it Idled good a ran good,so I ask people on here the best way to lean it out,so decided to try a performance air breather first and it running bad.I'm stumped.
     
  3. Al.Fisherman

    Al.Fisherman Active Member

    If the only thing was changing the air filter...then replace it with the original and try it out. The backfiring tells me that the engine isn't in time for some reason. What engine are you working on?
     
  4. wan37

    wan37 Member

    It's a 48cc skyhawk gt2b Well in december before christmas I pull plug and it was running rich so I posted on here and came up with just changing filter thought it would lean it alittle.
     
  5. motorpsycho

    motorpsycho Active Member

    main jet partially clogged up with goo?
    backfiring out the carb usually means a timing issue, but i don't really know how these engines work in the timing dept.
    Since the timing does not advance or retard on these engines, it's safe to say that the timing is "locked down" and if it was out of time, it would not run. (just guessing).
    I'm thinking that you may have a fuel problem, and i don't think the air filter has anything to do with the problem.
    like Al said, put the stock filter back on and run it just to eliminate the filter as a potential problem.
    did you look at the choke plate? is it stuck partially closed?
    is the new filter preventing the choke plate from opening / closing all the way?
     
  6. wan37

    wan37 Member

    hey motor I thought you would know.I think you are right . I already put the old air filter back on haven't tried it yet it's cold outside and snowing.How do I clean the jets if that's the problem,I going to do the step to find the problem.thanks AL,and motor
     
  7. motorpsycho

    motorpsycho Active Member

    to check the main jet to see if it's got any goo in it you have to remove the carb, remove the float bowl and look up into the carb.
    you will see the main jet right in the center, it's brass and is screwed in. use a wide, flat head screwdriver to unscrew the jet and then look in the tiny hole in the center of the brass jet. You can run a strand of wire through the jet to clean out the hole.
    In some instances tho, the main jets have been known to fall out and be laying in the bottom of the float bowl.
    This could be another thing that MIGHT cause your problem.
     
  8. wan37

    wan37 Member

    I will check that motor thanks another good one.
     
  9. wan37

    wan37 Member

    I'm stump here switched back air filter and it runs good now.I can't believe it.The choke plate has nothing too do with it either.Wow, don't know why?It is suppose to run better with the performance air filter.I want too use it tho, anybody got any ideas how to make it work?
     
    Last edited: Jan 16, 2012
  10. motorpsycho

    motorpsycho Active Member

    I don't know, i just put my performance filter on and it works great, I didn't have to mess with anything.
    I wonder...is this filter messed up somehow?
    like, is it one of the open pleated ones (like a k&n)?
    just wondering if the filter (for some odd reason) is not breathing becvause the pleates are covered with glue?
    are you sure that the filter can breathe? is there something insode that could be blocking the air flow?
    I have no idea on this, but it sounds like the filter is not letting in enough air like it should.
     
  11. wan37

    wan37 Member

    I can breath through it pretty easy.I was thinking too much air not enough fuel,but not for sure.It's the blue low profile ufo style from sick bike parts.Tell me if You think I should try dropping the e clip down a notch on the needle and try it.At this point any ideas?
     
  12. toojung2die

    toojung2die Member

    Try running the engine without any air filter. With no air filter restriction at all it will run as lean as possible with your present main jet. Don't worry about hurting the engine by sucking in dirt because you will only run it this way long enough for a comparison between stock filter, SBP filter and no filter.
     
  13. motorpsycho

    motorpsycho Active Member

    well, if you drop the needle clip down, it will raise the needle, which will richen it up a tad.
    I honestly don't see that making a difference tho.
    if the filter was allowing too much air, your idle would jump up because it would be running leaner.
    if you run it with no filter at all (like the above posts suggests) that will give you the leanest mix possible so you can do a compairison of the 2 filters and no filter.
    if the engine runs the same way with the hi-perf filter as it does with no filter, then it's running too lean for that filter.
    This MAY require a jet change depending on how drastic it it.
    if the new filter is making a drastic difference in the mixture, your idle will be a lot higher than with the stock filter.try to take not of the idle when running it with the stock filter, and then mentally compair it to the idle with the hi-perf filter (or no filter).
    I really don't know, because like i said, i put mine on and didnlt have to change a thing.
     
  14. wan37

    wan37 Member

    Well this thing is weird, but that's what buying a gurbee skyhawk kit is, plus it's there version of a cns carb.I guess it going to be fun too find the right setting with it.I guess I like to be challenged to fix it....lol
     
    Last edited: Jan 17, 2012
  15. wan37

    wan37 Member

    Well jet change I'm still learning on this stuff which way would I go on the jet size? I'm at .68 mm stock.Sick bike parts has them just need too know where to start.Thanks
     
  16. toojung2die

    toojung2die Member

    A lot of us don't change jets, though you can buy an assortment of common sizes from SBP. I bought a pin vise with an assortment of drill bits for about $15 at an RC Hobby store. Drop a little piece of rosin core solder in the hole of the jet and melt it carefully with a butane or propane torch. Carefully, because I melted the whole jet once. Then drill out the jet using the chosen bit. I've had to go to a leaner, smaller size on both my engines, a China Girl 66cc and a Yamaha QT50. If the jet is still too rich, solder it up again and drill it out using the next smaller size bit. You can even go larger without the solder. It's a quick and easy way to re-jet for free after you have the tools.

    Changing the clip on the throttle slider needle affects mid-range throttle. Idle and wide open remain unaffected. Adjust the jet for wide open throttle first.

    Clean carbs and jets using aerosol carb cleaner. Wear safety glasses! That stuff sprays back and it'll burn your eyes really bad.
    (personal experience :ack2:)
     
  17. wan37

    wan37 Member

    I'm already set in my mind to buy new one's from sick bike parts.I just need to know what size to get ?I have .68mm stock.
     
  18. toojung2die

    toojung2die Member

    Maybe this will help: http://www.csgnetwork.com/drillsizeconvert.html

    There is no .68mm size on this chart. There is a 68 wire gauge. The mm sizes are in half increments; .60mm .65mm .70mm etc...

    I go by .000" since that's what my dial calipers measure and there's a lot more bit sizes using that scale. My experience is the jet size is not terribly critical. My bits are matched to the wire gauges and going one size smaller than stock always had the desired results.

    If I was buying jets I would get one the next larger size and two the next sizes smaller. I think stock jets tend to run rich because you can't burn up an engine by running too rich. Fouled spark-plugs and four-stroking are the result of rich jets.
     
    Last edited: Jan 20, 2012
  19. wan37

    wan37 Member

    I'm just going by the grubee size it say stock is .068mm my bad.I read some where on one of these forums.That I have to oil the filter so it restrict the air flow. I will try that and let you guys know if it help my problem.Here's a link that I found and it sums up the answers here just like motorpsycho said jet drilling.I'm on the same page on drilling toojung2die.


    http://motorbicycling.com/f13/anyone-heard-too-much-air-cns-33511.html
     
    Last edited: Jan 22, 2012
  20. HeadSmess

    HeadSmess Well-Known Member

    when drilling jets for that "perfect" size, yes, theres the wire guage/numbered/imperial (thou) sizes that can often be in between the metrics, or...

    when soldering the jet and redrilling, bear in mind the LENGTH of hole can also control fuel flow... so by filling the jet up with more solder, which increases how long the hole is, you can fine tune a certain size hole.

    ie, i go too lean on a .45, i start 4 stroking on a .5. but if i fill the jet with solder halfway then drill it at .5, its now flowing somewhere in between the two and poifect :)


    you can also tweak mixtures with the oil ratio, and fuel level.

    noone can really recomend the ideal size for you because they ARENT you! :p this is what plug chops are for! you need to tune the engine in for yourself! sorry... but altitude, oil, oil ratio, fuel... it all plays a part in jetting.
     
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