Fuel economy and float questions

Discussion in '2-Stroke Engines' started by Jonj57, Dec 31, 2016.

  1. Jonj57

    Jonj57 Member

    Hey all, been having a strange issue and I think it has to do with either my ignition, fuel lines, or float height or even all 3. I havent been able to tell yet by pulling off the bowl but I think my engine is consuming more fuel than my lines have been able to pull from the tank and it suddenly dies and needs around 10 minutes to start again. My thoughts so far are that its a combo of too small fuel lines/and a weak spark causing poor combustion/fuel economy. The float height might be a problem but I haven't messed with that or opened the bowl in a while for it to suddenly act up like this. It's also been smoking a lot more than usual and extremely hard to start.

    Going to replace the stock ignition with a gas bike super charge, too broke for a jag but from my understanding it should still provide a much stronger spark than before an take away my possible weak spark issue. Already modified my woodruff key to put the timing more in line for higher RPM and cleaned the carb out completely. Next stop is finding out the correct float height for a dellorto 14mm sha and adjusting from there. Bought a new plug as well just in case, never hurts to start fresh!
     

  2. Steve Best

    Steve Best Active Member

    Whoa! just go simple first.
    You diagnosis sounds pretty good, so check it out.
    Pull the fuel line off the carb. Does fuel pour out or just trickle and drip?
    If it pours out the tank filter is good, try removing the float bowl (carb in place). Trickle or pour?
    If it trickles the needle valve is plugged. clean it with air, carb cleaner or a fine copper wire.

    Get it fixed before you put the new ignition on.
    Nothing like having a stack of mods on an engine and not knowing which one is screwing it up.

    Steve
     
  3. Jonj57

    Jonj57 Member

    I wanted to replace the ignition anyways, but you're right one step at a time. I'll put the new system in once I've sorted out the rest of the issue. I'll probably end up removing the tank filter as I run a paper one already mid line and don't really need it. I don't think it's the problem but it can't hurt and is one less thing to worry about, then next step is to check flow in the lines like you said, then check flow to the bowl. God I hate opening carbs up....
     
  4. Steve Best

    Steve Best Active Member

    Fear not Jon, the little Dellorto carb is a no brainer. Just don't lose any parts.
    Do it over a concrete floor or someplace you can find the needle valve if you drop it.
    Somewhere in the grass beside my garage there are many small lost parts...

    Steve
     
  5. Jonj57

    Jonj57 Member

    Haha I've take these small carbs apart far too many times is the problem... New filter? Rejet. New exhaust? Rejet. Clog? Disassemble clean rebuild. Haha I dread the day my Seca 650Rj needs another cleaning, I hate CV inline 4 carbs haha
     
    Steve Best likes this.
  6. crassius

    crassius Well-Known Member

    these things use so little fuel that almost any amount of flow that can be seen is enough to run it

    excess vibration can cause fuel to foam in the carb and cause surging, but if it goes totally dead, then I'd be looking for something heat related
     
    Steve Best likes this.
  7. Jonj57

    Jonj57 Member

    Carb cleaned and found a fuel clog in the small casting hole that flows fuel from the fuel line wheel and the float needle, just blew it out and cleaned everything else while I was in there. Runs and starts a lot smoother but still has the same problem with dying without reason. So I fixed one issue and now need to solve the other, I checked the engine while it was hot and can't find anything that seems out of norm, and on top of that it's around 10-30 degrees most of the time and has even died in freezing rain in the exact same way so I don't think it heat. Maybe the CDI is going bad and once it warms up it starts to go haywire? If that's the case I should have a new CDI/Coil in the mailbox today anyways so we'll see. Any other suggestions in case I'm wrong?
     
  8. KCvale

    KCvale Motorized Bicycle Vendor

    You running a stock spark plug?
    If so replace it with an NGK 5944 (BPR7HIX) Iridium spark plug before you start 'fixing it'.

    And while the plug is out pedal the bike up and down the street with the clutch out to blow any puddled fuel out of the crank case.

    I am still amazed what those 2 things fix ;-}
     
  9. Jonj57

    Jonj57 Member

    Oh god no! NKG plug was purchased before the kit even got to my door! And I've tried that but will do it again anyways, can't hurt to be a little extra clean
     
  10. KCvale

    KCvale Motorized Bicycle Vendor

    Hehehe, good early call ;-}
     
  11. crassius

    crassius Well-Known Member

    got one here now that does similar - while riding it sputters a bit and dies - coast 1/2 a block, let out clutch and it's good - do that 8 or 10 times to get back to shop

    in the time it takes to stop and get off bike, it has self-healed

    weather and other work prevents looking at it now, but I'm thinking heat related at solder joints on mag, internal joints in CDI or broken wire inside the insulation

    next week, I'll replace all one thing at a time and see if that fixes it
     
  12. Jonj57

    Jonj57 Member

    Well assuming we have the same issue I'll let you know tonight if it's the CDI as I'm swapping out the old one today.
     
  13. crassius

    crassius Well-Known Member

    little over a year ago, we had a rash of new CDIs failing - hoping it isn't going to happen again
     
  14. Jonj57

    Jonj57 Member

    Well my kit was bought about 6 months ago from some unknown china dealer on ebay for 94 bucks, at this point I'm surprised it runs as well as it does considering I run the thing hard and often. But then again, even cheap things last when maintained properly, usually anyways...
     
  15. Jonj57

    Jonj57 Member

    New ignition is on and man does it start easier and sound smoother! Raining hard so I can't get a real test to see if the problem is solved tho, will report back tomorrow after the ride to work.
     
  16. Jonj57

    Jonj57 Member

    Well it's done and fixed! CDI was the source of not only my large dying randomly problem, but also a few minor idle/throttle issues I thought were just jet tuning issues like a small flat spot at a certain RPM range. Much smoother and cleaner sound/rev's now.

    EDIT: Just a small recap for those who may search this thread with similar issues, Fuel flow was clogged in carburetor cast above float needle causing bowl to not replenish with fuel and engine would not start because of it.

    Once unclogged the engine dying at random times followed with poor idle persisted so I changed the spark plug *NKG B7HIX* to a fresh one and replaced the stock CDI unit to a more powerful one *Gas bike's super charge* and all issues are now gone and the bike actually idles much better and a bit lower than before and smoothed out at lower RPM and while climbing.
     
    Last edited: Jan 4, 2017
    Steve Best likes this.
  17. crassius

    crassius Well-Known Member

    I'm hoping it stays that way for you - I hate problems that come and go.
     
  18. Jonj57

    Jonj57 Member

    Well I figure if it starts happening again something about my configuration is knocking my CDI's out of whack in some way and that would be a much more annoying problem to solve... But it's fine for now and that's what counts, thanks to all for the suggestions!
     
  19. crassius

    crassius Well-Known Member

    got a break in rain today & was about to change CDI - looked just a bit funny, so I tried to see inside rubber plug and that was hard to see, but also didn't seem right - unscrewed plug wire from CDI and under good light I could see that the spring that should have gone over terminal nut was sideways up in there so that only the rubber boot was holding it in contact with plug - too cold & wet to ride today, but I'm thinking it's fixed

    checked 4 other CDIs in this set of kits and all were crooked to some degree, but not completely sideways - all straighten out easily, but I'll need to remember to check them before selling
     
  20. crassius

    crassius Well-Known Member

    POS chinese bikes - froze riding it as I couldn't wait to see if it ran OK - it don't
     
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