Discussion in '2-Stroke Engines' started by Lorin, Aug 25, 2008.

  1. Lorin

    Lorin New Member

    (RE: "80cc" Chinese engine)

    I'm a bit concerned that after running through barely a tank of fuel on my new engine, I'm seeing lots of leaking. The biggest leak seems to be coming from around the bottom of the fuel line (yes, when tank is switched of). It's hard to tell for sure though. The fuel line seems to be pushed in tight, so maybe it's something else.

    The leak that concerns me the most though is the head gasket. It's not pouring out, but it seems to me that if it's leaking at all, I'm screwed - right?

    The engine does seem to be running a little rougher than when I first got it. And I was dismayed to discover that my initial fuel mix was probably wrong. I didn't have time to install this kit myself, so I had a motorcycle gearhead do it for me. The guy has his own shop, so perhaps I took for granted that he knew what he was doing. When we fueled it up for the first time after installation, the mix was 4oz oil per gallon. I didn't question it, and I should have. After running through most of the tank, I realized that the break-in mix should be closer to 8oz per gallon! Can I blame this head gasket leak on his bad initial mix? Is there any solution to the leak besides replacing the gasket?
    Last edited: Aug 25, 2008

  2. BoltsMissing

    BoltsMissing Active Member

    Try some fuel resistant thread tape on the threads of fuel tap, but don't over tighten,
    or, replace with brass, similar type as on pic, expensive.
    use a inline fuel filter
    Retension head bolts, use a tension wrench, 12ft lbs.
    Use fuel ratio calculator,scroll down to see the chart in gallons.

    Fuel ratio for new motor is 16:1 while running in with high quality 2 stroke oil, then 20:1, others say 25:1 or 30:1
    My personal choice is now 25:1 and 95 octane fuel and about to change to Amsoil brand, but have used valvoline, castrol, some others, synthetics lawnmower oil, still working.
    Don't mix oil brands too often though when re-fueling .
    http://www.beta.id.au/2 Stroke Fuel-Oil Ratios.htm

    Attached Files:

  3. Lorin

    Lorin New Member

    Thanks for the reply. Just to be clear, you're saying to try tightening the head bolts correct? (Not "try retension head bolts" as-in specific kind replacement bolt to swap out with the originals).

    Most importantly - What are the chances that the improper break-in mixture caused this specific problem? I'd like to know if I have any recourse with this guy who installed it and mixed the fuel wrong. I know these aren't the best engines, but I didn't expect to see this kind of problem this soon.
  4. BoltsMissing

    BoltsMissing Active Member

    Well, I have never had any of my HT head gaskets leak, yet.

    Re-tensioning a new engine is normal procedure, the way I was shown, ya have a tension wrench set, in this case 12ft lbs and ya have another socket and bar on the ready to.
    One by one in criss-cross, back off each head bolt with the bar and socket so you hear the crack sound,( it may not crack if it came lose, or it may not crack at all, point is, back off 1/8-1/4 or a turn, one at a time,)
    then tension.
    You don't back off the nut or the bolt using the tension wrench.
    You only have to do the back-off bit once initially, but keep checking the tension periodically on the HT.
    If it leaks still, then you have done in the head gasket so it may need replacemet.

    Sorry dude, that is for you to decide, you know what he mixed it with, I posted a fuel ratio link, so ya gonna have to do ya numbers and sort it out...I won't "go there" on that one.

    Forgot to add, that is why the oil/fuel ratio is in the 20's,25's and 30's using high quality oil.

    FYI, the cylinder "lining" is a form of chrome plating, not sure of the exact terminology, when it stuffs up it's cheap and simple to replace. A quality issue though can be obtained by one's own progress on these engines, in fact the manufactures are doing us a favour, many skills are re-learnt by doing our own progressive "quality upgrades"...for what it's worth.
    Last edited: Aug 25, 2008
  5. Lorin

    Lorin New Member

    This was MOST helpful. Thanks! I re-torqued the bolts just as you said and this morning there was not even a drop around the cylinder head! It's fixed!

    However, the other less serious, yet more voluminous leak(s) remains:

    You can see the paper towel under the carb assembly SOAKED with fuel.

    It now looks like this is NOT a leak out of the fuel line to carb attachment. Last night it appeared to be pooling under the clamp that attaches the carb assembly to the engine block. I tightened this down, but leaking continues. From this picture, it also looks like it's leaking out of the tickler or maybe it's just pooling there. Other posts talk about debris in the line causing this problem. I'm going to try to get an in-line filter for this thing today (hoping autozone has these). But is there an easy way to deal with the debris already in there?

    On your suggestion, I'm definitely going to switch to a higher grade oil and higher octane gas. I'm not happy with how it's running now at all.
    Last edited: Aug 26, 2008
  6. BoltsMissing

    BoltsMissing Active Member

    They sometimes leak no matter how tight the screws are tightened.
    It's the rough finish of the castings where the gaskets go.
    So, ONE of the ways is to get some hard setting-fuel resistant gasket paste.
    I use Stag, so I don't know of any other brands names. Stag is a bit tricky to use with fuel. So go down to the motor parts place and tell the bloke ya want gasket stuff for carburetors, explain what ya doing cos there are many types out there.
    Try Stag jointing past if you want, but it may not work the first time, takes a little getting used to. IF you do however, let the Stag paste set for 24 hours before any feul gets through, don't use too much on carburetors, it goes brittle and may clog up fine points.
    Remember to tighten the part where the fuel line goes into, that tiny washer leaks to.
    Don't over-tighten or you will squash it and make matters worse.

    I never suggested hi octane gas, the "book" says 92, but I cheat and go to 95.
    Have tried 98, it ran worse than 95.
    If you are new to this game, play it safe during runin and stay on 92 as reccommended then gradually move up the scale AFTER everything else on the bike is ironed out, including the brakes.
  7. tibim

    tibim New Member

    That is quite a leak.

    Take your carb apart(two phillips screws) and check the float to make sure it's not full of fuel. It's the plastic donut looking thing inside the carb. It should be full of air, not fuel. If it's got a hole in it it's not going to float properly and shut off the fuel to the carb, causing fuel to overflow.


  8. BoltsMissing

    BoltsMissing Active Member

    missed that bit, that don't seem like a gasket leak.
    Thanks for pointing that out tibim
  9. wayde

    wayde Guest

  10. Lorin

    Lorin New Member

    I'm think it probably wasn't leaking underneath the clamp. I took the carb apart. Didn't really seem to be dirty at all. The float WAS full of fuel. However, I'm starting to get suspicious that the petcock is not really closing all the way and is allowing gas to seep into the carb. This would fill up the float, right? Or would this still be a gasket issue?

    I've the ordered the brass petcock that Boltsmissing recommended. In the meantime, I've disconnected the fuel line and will just hook it up every time I want to go for a ride. If my pipe and muffler are full of unburned fuel, will that eventually "work its way out", or do I need to take it apart, etc, etc. (Please answer "no" to the take-apart question, if possible :grin:)

    I installed my inline fuel filter and the ngk plug. I'm Amazed at how much better this plug does vs. the old plug. Thanks again for all the advice everyone.
    Last edited: Aug 26, 2008
  11. BoltsMissing

    BoltsMissing Active Member

    You mean the white plastic donut, was full of fuel ?
    Without pics, need to be very specific, can you look to see if it's cracked or got a hole in it somewhere ?
    It is not suppose to be full of anything except air, so it floats. If it don't float, that explains the excess fuel cos have a look at the way the carby functions, it shuts off a valve.
    Can you see that ?
    Last edited: Aug 27, 2008
  12. Skyliner70cc

    Skyliner70cc Active Member

    Maybe he mean float bowl was full of fuel.

    Maybe float needs adjustment so that fuel is shutoff when float bowl level is high.
  13. jmccrury

    jmccrury Member

    I had fuel leaks with mine too. The major one was were the hose attaches to the carb. I just used a small hose clamp around it. I didn't think that fixed it at first because there was still fuel dripping off the carb every morning. It turned out to be leaking from where the petcock screws into the tank. I finally read on here that the red o-ring that comes with it is supposed to go there. oops. It was running down the hose and onto the carb that's why I thought it was leaking there or that the carb was leaking. I just rubbed some caulk around it even though I didn't think it would hold up for very long with fuel and oil, but so far I haven't had a leak since. I just thought you might want to make sure it's not leaking from the petcock.
  14. Lorin

    Lorin New Member

    Yes, that's what I meant. Sorry. The float bowl, not the float was full to the top. I'm still trying to understand exactly how this works. I know it's supposed to have some fuel in the bowl (hence the float), just not overflowing out of every hole on the carb.

    Yes, I think the petcock is the problem with mine, but in a different way. I have the red ring installed, but I think the pedcock is still defective and not really closing all the way. So the carb is pulling fuel out of the line. I ordered a brass pedcock yesterday to replace the current one. In the meantime my fuel line is disconnected and my carb is bone dry.

    It was kind of fun taking the carb apart though. I'm just glad that there doesn't seems to be any major problems with it that I have to fix.
  15. tibim

    tibim New Member

    The donut floats up as the carborator fills with gas, eventually pushing up on a "fork" looking lever which shuts off the fuel to keep the carb from overflowing.

    You should be able to move this lever up and down with your finger and see how it works. Try it with the gas on and it the gas should stop flowing as you push up on this lever.

    Your carb may be overflowing because it's getting too full. Try to bend the forks down so the donut doesnt have to float up as high to shut off the fuel, thus preventing it from overflowing. It's kind of like a toilet :D

    Also check to make sure there is no debris or anything in the carb internals keeping the fuel from shutting off. Check the valves, levers, etc.


  16. BoltsMissing

    BoltsMissing Active Member

    lorin, when you get the brass petcock, check out the thread, it might be tapered so when it screws into the tank, it seals within the threads. If you tighten too much, the taper will split the tank's threaded outlet. So you might need to get fuel resistant thread tape and some sealant, combine the 2 and it ought to fix that section of the fuel leaks and it will be postioned right to be able to operate the tap-lever.