49cc 142F HS Air Breather Blow Back Issue

Discussion in '4-Stroke Engines' started by Milkedglass, Jun 7, 2016.

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  1. Milkedglass

    Milkedglass Guest

    Greetings All--

    I have a new HS engine with under 200 miles on it and I have had considerable "blow back" from the air breather hole since Day 1.

    Blow back is a gas/oil mix and I typically collect about 3-4 oz from a 20mile ride. I was told it is normal by the guy who sold it to me but I'm just not buyin that anymore. I have a hose running into a container to collect it all so it's more of an annoyance than anything. The engine runs great with no power issues. I'm relucant to open it up and make any valve, etc adjustments but any thoughts/ideas are appreciated...

  2. Frankfort MB's

    Frankfort MB's Well-Known Member

    My HT 2 stroke does this but I don't have any air filter. I also don't have a reed valve so this is my problem.
    I don't know much about 4 stroke kits but I would think that the valves would be off. You would think there would be a power loss or be rough running
  3. HeadSmess

    HeadSmess Well-Known Member

    how much freakin oil is in it? thats the first thing to suspect... over filled. they will spray it everywhere if they have too much oil!

    if its dipstick fitted, it should touch the end of the stick, but shouldnt spill out the hole, when the engines level. pretty well much flush with the bottom of the filler is the standard amount.

    could be the little separator valvey thing in the carb is defective, blocked, etc. the hose from the crankcase should be entering the rear of the airfilter. if its not hooked up, it will spray oil everywhere. just try taking the dipstick off of any motorbike when its running!

    it sounds like it doesnt even HAVE a hose? 3-4 inch tube from breather to airfilter...

    straight fuel, not premixed :p.

    its always a good idea to check the valve clearance occasionally, its only a five minute job...
  4. Milkedglass

    Milkedglass Guest

    I had a breather hose connected to the air filter but of course it dumped fuel/oil back in it. Gunked all up.

    I don't have it over filled with oil, just the recommended height.

    Maybe I'll just go ahead and figure out a valve check.
  5. Milkedglass

    Milkedglass Guest

    Adjusted the valves to .004 ex and .003 in as both nuts were loose.

    Corrected the problem it seems...but I somehow cross threaded the spark plug. Ahhh!!! Ordered a thread chaser and hoping for the best :confused:
  6. HeadSmess

    HeadSmess Well-Known Member

    oh dear...

    still got some options. helicoil. take it to a shop and if your lucky they wont charge you a fortune. buying a whole kit is a bit silly. ring around, find a good price.

    could order the next size tap and use a different thread/shank plug thats still a match. i think the "D" is a 12mm, where the "C" it normally has, is a 10mm. just change the first letter when you order replacement plug. cant remember how much clearance is between the valves and plug hole, might not work... a "B" is definitely too fat!

    do all the drilling while its at TDC while both valves are just cracked open and you could possibly just blow/flush it out, rather than have to tear it down to get the filings out... give it a thorough wash out so its clean with no sticky stuff before doing anything...then again, four strokes dont mind a little bit of stuff going through the cylinder... its mainly just getting fine bits in the ring grooves that cause problems.

    or you can just crack it open, they arent that hard to do.
  7. Milkedglass

    Milkedglass Guest

    Fixed the threads pretty easily and all is well in that sense. That was a relief...until...I realized the blow back issue is still ongoing!

    It is definitely something with the valves not seating right or timing because there was gas all throughout the head area and the rocker nuts had loosened again from all that, even with loctite.

    I have to open this thing up and fix?? Ahh!!! Thanks for any help
  8. HeadSmess

    HeadSmess Well-Known Member

    gas shouldnt be able to GET IN to the rocker area...hows your oil look? is it getting diluted with petrol?

    thats the thing with fourstrokes...the gas/air mix goes in the port and only into the cylinder...meaning theres an issue in there somewhere...

    my suspicion is the valve stem seal is leaking. its the only real way you can get that sort of blowback... that or theres a hole/crack/flaw in the casting in the general area... bent valve? how are the valve shafts regards fit in their little holes? some wriggle is normal, like half a mm at most...1/64" if you must use imperial...

    you got one weird issue, that at least is a definite.

    shouldnt need to locktite the adjustors, so for them to be loosening off is peculiar... normal adjustment is to allow for wear in the valve seat... otherwise theyre basically set and forget.

    ps, its nearly impossible to grind the valves on these things...
  9. Thanks for the advice.

    The thread chaser worked.. until I did another plug chop and it didn't anymore. Last few threads are the culprit so it wont tighten. Damn! Blew it.

    I'll give your suggestion a try here and open it up while I'm at it to look at the valves. Or hopefully give to my buddy to do. My spirits are low and I'm frustrated with how much time I've had to spend on this bike. Cheers
  10. Milkedglass

    Milkedglass Guest


    Man, why do I have the sick feeling that this isn't gonna be an easy/or even possible fix after opening it up? Ha! Fml

    Yes indeed, my oil has been getting diluted with gas/petrol to varying extents and I change it constantly from the blow back loss anyway. It seemed to be getting better lately but I kinda doubt it now. Yikes. Would that mean an engine flaw or typical for this kinda thing or ? Guess there's only one way to find out but I'm bout ready to start over with this 142f
  11. Old Bob

    Old Bob Member

    If you are getting 3-4 oz in a 20 mile ride your engine is shot.
  12. Frankfort MB's

    Frankfort MB's Well-Known Member

    Might be head gasket?
  13. HeadSmess

    HeadSmess Well-Known Member

    they dont HAVE a head gasket... unified cylinder, head, and 1/2 the crankcase...

    possible ring issue. missing/broken rings can cause blow by into the sump, then the extra pressure during combustion just helps spray everything out the breather... would be running pretty poorly though, if its so bad its diluting the oil. really poorly...

    not having it here in front of me, and you not having another 142f with no issues to compare it to... im stumped :)

    this definitely isnt normal. never had a 142f blow much but oil mist. few drops of oil when overfilled... never enough to make a mess though...

    cmon, tear it apart! they arent that hard to do! bit fiddly getting that crankcase to pop apart the first time, few gentle taps with the hammer does the job... theres only about 20 parts, all up :)

    if the guy that sold it to you says it is normal and is running a business...name and shame! he either has a bad batch of engines, doesnt know what he is talking about, or a combination of the two...

    maybe best just to get another one...from someone else this time ;) usually the 142f or any other huasheng is pretty well much fine, outta the box. have had several die from misadventures (people dropping them, hitting them, breaking bits off) but only 1 has died from mechanical issues and that wasnt even mechanical but more a strange deposit of carbon that ended up interfering with the exhaust valve (why i know the valves are hard to grind:p). the engine was otherwise faultless... and there was one with a carb issue... but that was nothing major, either.
    Last edited: Jun 27, 2016
  14. Frankfort MB's

    Frankfort MB's Well-Known Member

    I just said a head gasket because anytime something like that happens on any other engine, that's what it is.
    Just trying to help
  15. Frankfort MB's

    Frankfort MB's Well-Known Member

    Any way it goes, something is getting where it's not supposed to be:)
  16. HeadSmess

    HeadSmess Well-Known Member

    is ok... no criticism intended. its definitely got an issue though :)
  17. Milkedglass

    Milkedglass Guest

    :eek:Let's see what's happenin in there!

    But how do I get the flywheel and nut off? This is gonna be a parts engine soon. Broke one of the flywheel blades(?) trying to loosen the nut. I need it off to access the last two bolts holding the engine together...

    Then how best to pry this apart? Rookie adventures in motorized bikes
  18. HeadSmess

    HeadSmess Well-Known Member

    jam something between the coil and the fattest part of the flywheel for removing the nut. timber, whatever... dont expect the fins to take any force!

    never bothered with a puller, just two screwdrivers/tyre levers under the edges of the wheel, (lightly) and then a few taps with a hammer around the hub, usually pop straight of. key is part of the flywheel from memory, so you cant lose it ;)

    failing that, repeat the whole process but blast the hub with a blowtorch to about 120c (i guess thats about 250 f?)

    remove rocker cover, back off valve adjustors.

    remove cam cover, revealing cam, two cam followers, two pushrods, pull em all out... seem to be identical so no point marking them.

    there will be a dot on the cam gear and crank gear that line up at tdc (or bdc?) thats about all thats important. and noting which side any washers/shims are on.

    case is split diagonal but comes apart in line with the shaft. hold the bottom half, tap the end of the shaft on that side with a lump of timber (or wind the nut back on and hit THAT with a hammer...not the shaft itself cus that stuffs the thread. if thats the side with the thread...)

    it will be tight, theres locating dowels, gasket goop, and one of the bearings all holding it back. i think there are two prying lugs cast near the join somewhere? screwdrivers. dont slip and scratch the sealing surface. dont hammer them in. easy does it. dont overwack it and drop the top half, including crankshaft, on the floor... and it will just suddenly let go, usually as you let your guard down :D
  19. CrazyDan

    CrazyDan Active Member

    stick enough rope down the spark plug hole to jam between the head and piston to seize everything up to loosen the nut