4 stroke engine stalling out

Discussion in '4-Stroke Engines' started by Mr Hydroseed, Sep 11, 2011.

  1. Mr Hydroseed

    Mr Hydroseed New Member

    I have a 4 stroke engine kit I bought off of ebay. It worked pretty well for the first couple of rides. I loved it, I had to just modify it right away of course. So I bought a Sick Bikes shift kit for it and liked it for the most part. I did get stranded out on my first ride though because the chain wrapped around the crank sprocket. There is a lot of moving parts than can potentially malfunction here. I also ordered the high flow air filter to squeeze out a little more power. Before the bike reached a peak high speed of 38.2 MPH, but with the new set up I could only get up to 35ish. The problem was when the bike got really warmed up it would run to lean, to the point of the bike only going 32 MPH. So I read up on jetting and happened to have a .028" drill bit so I drilled out the jet. That was pretty much the last time I really rode my bike. It ran kind of rough, from idle and I couldn't tune it with the low jet screw. So I probably went a little too big with the jet? This is what happens, I can do a 200ft lap in my yard, I would make about 1 lap but then it would stall out and die. It will start right up and will do maybe a ½ lap then die. Maybe its got something blocking the jet? Maybe its not getting fuel? After it dies I close the pet cock to see if it will still run the same? It doesn't start as well and sometimes it won't go 2 ft and sometimes it will go 100ft. I open the bowl and a good amount of fuel comes out? Ok so I'm going open it up and clean it out. I did see one speck of something. I repeat this procedure several times. I happen to have another identical motor kit, so I put in the stock size jet assuming I will be running like I did before but at least running. It ran a little better but still conks out after I back off the throttle then put it back on. I'm like screw this, I'm putting on the brand new carb and the stock jet! Along with an inline filter. I'm like cool its running great, I'm on my 4th lap and then BLAH! It sputters into a stall. WHY!!! I've tried countless runs each time trying to adjust the low idle jet from 1-4turns each with ¼ turn increments.
    Whats the deal here people! I'm usually pretty good at getting small engines to run well, what am I missing? I filled the tank completely full but, but. did notice some of the black paint softening up where there was some overspray on the first ¼" of the inside of the tank. I did not see any debris inside the inline filter and fuel was getting inside the bowl everytime. PLEASE HELP! I really want to ride this bike again.
    Last edited by a moderator: Dec 18, 2015

  2. HeadSmess

    HeadSmess Well-Known Member

    what engine, what carb?

    checked your exhaust valve clearance? ;)
  3. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

    Here is a good article on re jetting the carb for a 50cc Honda or Huasheng.


    Start at 2 turns out. Range should be 1 3/4 to 2 1/4
    Last edited by a moderator: Dec 15, 2015
  4. Mr Hydroseed

    Mr Hydroseed New Member


    Like I said, I tried running it with every combination from 1-4 turns in 1/4 turn increments. My starting point was 1.75 turns. Well i don't know exactly what kind of engine it is, I'm guessing its a Huasheng? The manual says its a 142F engine. its the same engine that comes on 97% of the 4 stroke kits out there. Some one help me, I wanna ride, I wanna ride, I wanna ride!
    Last edited: Sep 13, 2011
  5. Quenton Guenther

    Quenton Guenther Motored Bikes Sponsor

    Do a serious clean on the carburetor. Check float needle to make sure it is opening & closing correctly. Check float to make sure it doesn't have a leak [replaced one about 3 years ago].

    If you opened the main jet too much, you can simply solder it closed and re-drill to a smaller size.

    I normally put Gummout carburetor cleaner in about every 4th tank of gas to keep the jets clean, as they are so small and plug up very easily.

    Have fun,
  6. Mr Hydroseed

    Mr Hydroseed New Member

    Clean a new carb?

    I tried a brand new carburetor with zero seconds of use on it, so I don't think I would have to clean that too much. The float works as it should since its brand new. The motor runs the same with the "old" carb (if you call under 10 hrs old)
    I may have drilled the jet too much but I also tried the stock jet as well.

    I used Sea Foam in my fuel, I'm barely on my second tank of gas.

    I won't have fun until this runs right :shout:

    But thanks anyways for trying to help.
  7. Quenton Guenther

    Quenton Guenther Motored Bikes Sponsor

    Hi Hydroseed,

    I know those motor inside and out, and will do my best to help you back to "having fun".

    I will share my thoughts on locating the problem, and hope it is helpful. Your problem appearers to be difficult to trouble shoot because the problem appeared after you modified the carburetor. And the mystery continues when the problem remains even after the carburetor was returned to normal and even replaced with another.

    Maybe it is related to carburetor problems, and maybe not.
    My first guideline for trouble shooting is KISS [keep it simple stupid], and always makes problem solving easier for me.

    Here are few things I would consider...................

    If both carburetor act the same it is unlikely a carburetor problem [but not impossible].

    If the problem appeared after the carburetor was removed and re-installed, might there be a bad seal between the carburetor & motor [gasket, cracked plastic manifold, bolts not torqued, etc].

    We have sold hundreds of the HS motors in our kits, and they are amazing and basically trouble free. Our warranties in 3 plus years on the carburetor are limited to one float, and one exchange [only needed cleaned].

    New gas tanks should ALWAYS be flushed out prior to use, as the most common problem is caused by the new tank. Often paint chips near the cap will enter the gas and somehow get past the filter [if used], and find its way to the tiny jets. I normally fill the fuel line with cleaner several times if I think the jets are obstructed, and often it solves the problem.

    If the motor has been operated in a no or minimum load condition, internal damage may occur. No load would be operating on a stand with wheel off the ground, and minimun load would be shift kits, and "wild" gearing. Look at valve train for bent pushrods, cracked or bent rocker arms, bent valves, and lifter clearance.

    Make sure key is intack on flywheel.

    Never trust a spark plug on a single cylinder motor. Plugs can fire outside the motor and misfire when installed, and if ever foulded should be replaced. Always suspect the plug, and replacement is the only way to be sure. I can't count the times a spark plug has let me down. I think the replacement for the HS motor is an Autolite 4194.

    A few last comments..............
    The HS and Honda motors will quickly and smoothly exceed 10,000 RPMs without a load, and is hard to tell it is running so high. Just like any motor, if run past the red line too often or too long it might decide to re-condition certain internal parts. I would strongly suggest you invest in a tachometer when using a shift kit.

    Both motors use a fiber camshaft and hasn't been a problem, but if all else fails , it should be checked to make sure it hasn't jumped time.

    Hope some of my comments leads to getting you back on the road and "having fun".

    Keep us posted, as I am sure you will find the problem.

    Have fun,

    If the plug has ever been fouled, may spark outside of motor, but not when installed. Never trust a spark plug on a single cylinder motor!!! Sub with new plug.

    Make sure plug wire is firmly screwed into the coil [can lose spark if loose].

    Almost all carburetor issues
  8. Mr Hydroseed

    Mr Hydroseed New Member

    THANK YOU! That's how you reply back!

    Now that was the great reply I was looking for!:bowdown: Much appreciated, even though it hasn't helped me yet. One important thing I noticed with the new carb or old and with the stock jet or enlarged is that it seems to stall when ever I throw down the hammer. Even if its just a little hammer. So from a stand still, 33% of the time when i give it throttle it bogs down and stalls and 33% of the time it hesitates but then gets power and 34% it will run fine but the whole process starts as soon as I back off throttle and try to go again. Wow that was confusing. AND please, of course I'm trying to dial in the low idle jet (usually between 1.5-2.5 turns) I also unplugged the kill switch harness just in case it was faulting somehow. This is driving me crazy!!!:shout:
  9. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

    Those carbs can be finicky.
    Did you take the plastic low speed jet out?
    It is under and captured by the black idle screw
    and it is removed by prying it straight up after
    the idle screw is removed.

    Be careful as it has a small O ring on it.
    Blow those passages out with compressed air.

    Just leave the mixture screw at 2 to 2 1/2 turns out.
  10. darwin

    darwin Well-Known Member

    Yea what he said...............maybe an air leak?
  11. Quenton Guenther

    Quenton Guenther Motored Bikes Sponsor

    CAREFUL! never use air, unless the float bowl is removed, as air pressure can damage the float.

    Have fun,
  12. HeadSmess

    HeadSmess Well-Known Member

    all this fiddling with carbs yet he wont tell me if hes checked the valve clearances.... :(
  13. Mr Hydroseed

    Mr Hydroseed New Member

    Sad Update.

    I did remove both plastic idle jets and sprayed them out. Sorry I haven't checked the valve clearance yet, but what I did do is install the 2nd brand new motor and a new exhaust. I used the new carb with stock jet, but keep in mind i did use it to try to remedy the first engines problem. I felt 97% confident that because everything was new and stock it would run the same as it did with my first kit... What a sad awakening of my shattered confidence. It ran so much worse! I could barely get it to start and if i did manage to do that I couldn't even ride it once because it would stall with the slightest amount of throttle. Ok so how is this possible? What have I not changed? The fuel, maybe there was water in it? maybe When I drilled the main jet awhile ago I effed up and grabbed an old fuel can and filled it up right before what i thought was going to be a long joyful ride. I drained the fuel out and refilled it with fuel that I know I just got a few days prior. Another thing is that the engine manual specifies not to use gas with a higher percentage than 5% ethenol. I'm pretty sure the pump said 10%, but I really don't think it would cause this much trouble!!! Actually before I drained the fuel from the tank, I don't even think I could get it to idle with the choke off. Now I could get it to idle but it was really finicky. The throttle had to be just right to even run. I should say that I must of removed the carb and bowl and inspected and cleaned everything at least 4 times with one carb and 4 times with the other carb and tried millions of different mixture screw adjustments. What I've concluded is that the carb is not giving the engine enough fuel. The only possible way to not have the engine stall when throttle was applied was to put the choke at 1/4 open. This is crazy! Why is this so difficult! I must own about 33 small engine powered devices and I can always get them running eventually. The only thing I can think of now is to be certain my fuel canister is clean and buy more fuel? I think I will try to take the carb off the engine with fuel line still attached and run air through the plenem to see if its atomizing any fuel. I came so close to driving over my bike with my truck repeatedly. THE END.:shout::shout::shout:
  14. bideronit13

    bideronit13 Member

    I grew up on dirt bikes and used to go out in the desert and sometimes have to do carb work out there.
    My method of finding the rite settings are simple.
    1) Turn the mixture screw in all the way till it wont even start.
    2) Make 1/4 turns till it starts
    3) Write down the starting point like 2 1/4 turns for example
    4) Turn the bike off.
    5) keep making 1/4 turns turning off the bike after each turn.
    6) find the middle point between the two and leave it there.
    7) Then fine tune the air screw

    Im not saying this is going to get your bike going but it allways worked for me.
  15. bideronit13

    bideronit13 Member

    Opps forgot to say hi so hello.
    On number one above its supposed to say turn the screw all the way in and nothing else.
    Good Luck
  16. Quenton Guenther

    Quenton Guenther Motored Bikes Sponsor

    Hi Mr Hydroseed,

    In my area we still have real gasoline, however at a recent motorbike rally I attended I had to use 90% gas 10% moonshine [corn fed fuel]. The only difference was the idle needed to be set a little higher.

    Because you didn't buy your kit from a dealer [no support], but a box seller, you will have to keep trying until you stumble across a solution.

    I find it interesting that you own 2 kits and still can't get it going.

    By changing the motors you have elimanted many possibilities, and sure makes it look like carburetor problems.

    Sounds like you have a leak somewhere in the intake system, as playing with the carburetors on both motors is the only common to both setups.

    If you can get the motor to run, simply sparay WD40 around the manifold, gaskets, spacers, etc to see if the motor changes speed or idles faster or slower. This will let you know if it is an air leak.

    If the kit was purchased from us we would have tested and replaced any items not working correctly [as would any other vendor on this site] ASAP.

    Although you didn't buy from a vendor on this site, I will offer to test, tune, and adjust the carburetor for you for a small fee if interested. You can send both carburetors and I will install on our factory prototype motorbike, and log in 50 miles to make sure it is totally correct. If all else fails, contact me and I will do my best to get you "back on the road again" We have all the necessary equipment to check CFM, flow, throttle response, and adjust under load.

    Please don't take this offer as bid to "get in your pocket" but as an offer to help, as I am sure your final cost won't be much. In fact I am guessing the shipping will be more than the labor to make the carburetors correct.

    Please make sure the issues are carburetor related, as I don't want you to spend money on a non problem.

    Have fun,
  17. Old Bob

    Old Bob Member

    The Honda uses a small carb to self limit rpm it will only over rev if a larger carb is installed.
    The Honda cam is molded nylon, not fiber,for it to jump time it will have to lose a tooth from the gear. I've never seen a Honda mini four stroke cam lose a tooth in 12 years of experience with them.
  18. Quenton Guenther

    Quenton Guenther Motored Bikes Sponsor

    I have never seen any of the motors "jump" time, but was mentioned as a possible issue to what seems to be an unusual problem.

    I have a 50 cc Honda motor with the rod blown off due to exessive RPM. It had the stock Honda carburetor. I don't know for sure if the Honda carburetor was on the motor when blown, as it was sent to me to rebuild. One of my test bikes has the Honda motor with the original carburetor [installed larger main jet], and it will easily over rev without a load. The Honda motor has the same size carburetor as the HS, except the main jet is one size smaller. The Honda motor ran too lean prior to the jet size increase, as the spark plug was completly white. After the jet change the plug is still close to too lean, as the plug still looks a light gray [not tan, brown, or black].

    I too think the Honda motor is very well made, and should out last the HS motor, and I also agree it is slower than the HS. The Honda motor has a speed regulator system, whereas the HS does not [most remove it]. I agree with Honda being a great motor, and my experience with Honda covers a 40 year history under extreme conditions [raced against them in the early 70s].

    The term "fiber" was used to describe the camshaft material, however I only used it to indicate the camshaft wasn't metal, and the HS camshaft may also be made from similar material as the Honda unit.

    Have fun,
  19. bideronit13

    bideronit13 Member

    Hey quinton in your first post you said, "it really warmed up".
    Before I came back I was just running possable things that could be going on. Well you also said that the when you first run it after sitting a while it ran then cuts out.
    I trully believe the engines oil is low, out or contaminated.
  20. bideronit13

    bideronit13 Member

    Im sorry I ment to say Mr Hydroseed