Weird engine noises?

Discussion in '2-Stroke Engines' started by Oddzball, May 16, 2011.

  1. Oddzball

    Oddzball Member

    So i took my first major road trip today.

    34 miles. I know not very far compared to some of you folks. But anyway good for me since im new to motorized bikes.

    I do a lot of work on cars so when i heard this noise my mind filled with dread.. it sounded like the engine was "almost" seizing, it would screech/squeek, felt like it was stalling, then resume normal operation.

    I pulled everything off the bike that might be rubbing on say the tire, just to make sure i was actually hearing the noise from the engine, sure enough, that is definately where it was coming from.

    I am not to familiar with 2 strokes however..

    Is the engine toast or would adding more oil to my gas, stop this problem.

    I made the engine run leaner by adjusting the carb to the #3 because of my high altitude, (really improved performance so im sure THAT was a good idea) so maybe now that there is less gas, in a 2 stroke that means less lubricant also correct?

    Will adding more oil revive the motor/stop this or is it toast?

    I was running 32:1 ratio with good quality 2 stroke oil (Not outboard oil either)

    Please any advice would be greatly appreciated.

    Thanks for your time folks.

  2. DuctTapedGoat

    DuctTapedGoat Active Member

    I betcha you were 4 stroking at WOT.
  3. Oddzball

    Oddzball Member

    Eh I dont get the lingo? WOT? Are you saying i wasnt putting enough oil in? Wide open throttle?

    I was actually trying to NOT run "WOT" to be honest. i was only going about 20.

    SO is it trashed then or...?

    Ill add as much more info as i can, engine sounds fine when clutch isnt engaged, and even when it is most of the time it wounds fine, but sometimes, it makes the screech noise...
    Last edited: May 16, 2011
  4. rustycase

    rustycase New Member

    4 stroking is when the fuel/air ratio is too fat, dumping too rich a charge into the cylinder causing it to be able to fire only on every other stroke... like a four cycle engine.

    If you leaned it out and then it came alive, that would indicate the mix was too fat in the first place.

    Chances are the factory had it set up rich in an attempt to try and protect the motor during break in.

    If you are a competent mechanic, and felt the engine was screeching and squeeling internally, binding up, then breaking free and running better... all in the first 34 miles, my guess would be that you are correct and damage has been done to the engine.

    It's only a tiny little popcorn machine.... pull the head and cylinder off and have a look !
    I'll bet there is some scarring on the skirts or walls.

    IMO, short period warmup and cool downs are a good technique to break in a 2 stroke.
    First couple times, the rings are gonna take a real beating, especially on a known low-dollar motor that can not be constructed to the best of tolerances, or even use the best metallurgy for the money they get for them.

    ...The basket-case I bought from a college student was torn down for two reasons... First on the list was the busted up back wheel... took me a day of robbing parts and truing to get it functional again, but I did. and it had been taco'ed.
    Second, the carb was off the manifold and I asked why... the fellow told me he intended to make an adjustment because the engine bogged at higher rpms... My guess is that it was running too fat.

    One thing for certain, in a mini-motor basically over taxed, running at a gazillon rpm, things are gonna happen almost instantaneously, especially during break in! Most of em NOT good!

    Good luck with it,

    I just re-read your OP... It did NOT say this was a break-in run... How many miles do you have on the engine?
    How much do you weigh?
    What is your altitude?
    Do you run a fuel filter?

    Obstructions in the fuel delivery system could be causing the mix to lean out on an extended run, where it might not otherwise, during stop and go traffic...
    The plug may be a wrong heat range for an extended run.
    WOT should not necessarily be bad for a 2 stroke if the carb is set up properly.
    Actually, it should perform best at WOT.
    Yet smaller the engine, more critical the tuning.
    What is the air temp where you made this run?
    Was it different than prior short runs?

    Again, with these micro power sources, all other systems of the machine must be maintained in acceptable order.
    Poor lubrication on a chain, or in a wheel bearing could cause heat build up and increasing drag that would affect the load on the motor over a long run... Heck! a head or tailwind affects all motivators!

    Just think of all the hot-rod fun yer havin !
    AFAIK, there's no less expensive format to play with performance on.
    rc your exhaust pipe sealed tightly at the port?
    perhaps there's too much back pressure that builds on a longer run????
    maybe you could drill a hole in the exhaust to relieve some back pressure? = more noise.
    Last edited: May 16, 2011
  5. Oddzball

    Oddzball Member


    First thanks very much for the reply.

    So I should put the carb back to the stock #2 setting like it came from the factory as?

    I assumed it was running to rich due to the performance and smell so I leaned it out. I had already run a tank in it, and the guy before me surely had run at least a tank so I assumed it was broke in already, hence i figured i would be alright.

    Well live an learn if i broke it, ill just keep tinkering.

    What do you suggest I do, besides check the cylinder for scarring? Run more oil in the mix, and make it more "rich" again?
  6. Oddzball

    Oddzball Member

    I just re-read your OP... It did NOT say this was a break-in run... How many miles do you have on the engine?

    Unknown since it was used, but I have put over 100 miles on it, I started out with little 2 mile trips then just today I did a 8 mile trip, to work, and on the way back was when i noticed the noise.

    How much do you weigh?

    I weight ~170lbs

    What is your altitude?

    ~5000-6000 Feet

    Do you run a fuel filter?

    Yes, and its pretty much brand new

    Obstructions in the fuel delivery system...

    I am pretty sure there isnt an obstruction but i will check.

    What is the air temp where you made this run?

    ~85 Degrees Farenheight

    Was it different than prior short runs?

    To be honest it RAN great, except when I WASNT running full out throttle then i got the noise, almost like it was engine braking itself(If that makes any sense..)

    Again, with these micro power sources, all other systems of the machine must be maintained in acceptable order.
    Poor lubrication on a chain, or in a wheel bearing could cause heat build up and increasing drag that would affect the load on the motor over a long run... Heck! a head or tailwind affects all motivators!

    I literally tore the whole thing down and lubed all the bearing with high quality bearing grease, chain is well lubed. It was very windy however.

    Just think of all the hot-rod fun yer havin !

    I DID have a lot of fun. And tinkering with it is part of the fun, what i dont want is to have bought a "bad" motor that died in a week.

    AFAIK, there's no less expensive format to play with performance on.

    Well, happen to have a good recommendation for where i can get just an engine to replace it if i need to? Some of these dealers seemed shady which is why i bought from a guy used in person your exhaust pipe sealed tightly at the port?

    Not perfectly, I wont lie, but it is much better sealed than the original gasket, which leaked like crazy I had to make a gasket, and that seemed fine, was running beautifully for all the short trips.
    perhaps there's too much back pressure that builds on a longer run????
    maybe you could drill a hole in the exhaust to relieve some back pressure? = more noise

    AGain thank you VERY much for helping me out. Regular old V8 motors, no prob for me, but these little 2 strokes, they are SO simple its almost hard to diagnose a problem if you get what i mean.
  7. DuctTapedGoat

    DuctTapedGoat Active Member

    Stalling is a symptom of 4 stroking. Regardless of if it was WOT or not, if it was at or nearing the top of the RPM cycle, that would do it. I upjetted and tweaked on the carb needle to solve when mine did that after break in.

    Well, first - what is your high altitude?

    Next, is it making that sound at a point in the RPM range, or is it all the time? Does it make no difference if it's at WOT or at idle, the sound is still there?

    32:1 is optimal for dino oil. 40:1 synthetic is good as well.

    True that leaner on the carb needle is less gas and oil to air - but you don't want it set to where it gives you bad performance so don't worry about that.

    Worst case scenario is that you've got a blown ring. Honestly, on a used motor like what you've got where you don't know how the previous owner treated it - I'd say match the head, polish your head, jug and piston, and replace the rings. That'll bring it up to "practically/relatively new" status.
  8. adrian101

    adrian101 Member

    What about semi-synthetic, two stroke motorcycle oil example; (Havoline Super 2T)... Is semi synthetic bad to use?
  9. Oddzball

    Oddzball Member

    I was at probably 3/4 throttle. High altitude is 6k feet. Seemed odd. Didn't consistantly have the noise/problem. Was hard to reproduce.
  10. DuctTapedGoat

    DuctTapedGoat Active Member

    @adrian : Semi synthetic isn't bad at all - actually, when you buy off the shelf synthetic oil, it will always say synthetic BLEND. If it doesn't mention what percentage of it is synthetic, you can call the manufacturer and ask them what percentage synthetic their synthetic blend/semi synthetic oil is.

    @Oddzball :

    In that case, nothing is broken then! :D Or it would be consistent from idle through the RPM range to WOT.

    Sounds like it's at a certain RPM range, and that is consistent with 4 stroking on these chinese motors. Keep adjusting the carb, you shouldn't need to downjet due to elevation. Though, an aftermarket air filter and aftermarket expansion chamber exhaust will definitely make a difference. After tuning your carb to intake and exhaust, instead of 4 stroking you'll hit the power curve and really take advantage of what it's got. And if you do go that route - it wouldn't hurt to experiment with all different jets, higher and lower and find what your motor likes it's sweet spot to be at.

    Though - I would suggest still what I said earlier about matching, polishing and replacing rings, just because of the used motor aspect of things.
  11. adrian101

    adrian101 Member

    Wooo thank god for that, I've been running semi synthetic oil for months now lol
  12. rustycase

    rustycase New Member

    Sounds like the DTG is more knowledgeable on these power units than I.
    Good advice from him, IMO.

    If the engine runs better overall with the new needle adjustment, that's good.
    ... but it's more complicated than that... as DTG said, they may run fat in the mid range typically... I don't yet have direct experience with these china engines... No matter, plenty similarities in all 2 cycle motors. it's a cloned design from a russian engine cloned from a german design... Lol
    I bet Ole Evinrude is somewhere in the woodpile!

    Anyways... with the 'rising sun' bikes, jets were available, along with many different needle options, and some slide mods could be done also...

    So not only the size jet is a factor, the change in taper of the needle is an influence, along with the position it is used in.

    I just don't know enough about these, yet, so can't make specific advice.
    Jets can be drilled larger with a tiny number/letter drill set.
    Or, they can be drilled out BIG, a piece of brazing rod drove in, and you can begin again with smaller holes.

    If you are fat at midrange, but lean at top, that could mean main jet is too small and needle is too high, or skinny in size.
    Lean on bottom end is idle mix adjustment and carb slide shape... try a <1/8" square filed into the bottom of the rear of the slide to stabilize an erratic idle.

    Change, modify, or otherwise mess with the exhaust pipe... all the prior changes are OUT THE WINDOW! Lol

    A sparkplug change could bring a significant difference !

    I agree 100% with the mix oil statements. It's NOT critical on these motors until you really try for top level racing performance. Way back when, I used amsoil at 50:1 when I was trying to wring the most out of a 2 stroke... that was already broke in.

    Otherwise, they don't really care long as somethings in there for lubrication.
    With crummy oil, mixed too heavy, you'll foul plugs and build carbon in the chamber. Too much oil actually leans the mix, because it replaces that amount of fuel.

    DTG is right!!! Pop the top and have a look in there!
    Grab a couple wrenches and do it at the curb of the bike shop that has any parts you may need ! Are you in a big city where you actually HAVE a shop that sells the parts? BONUS!

    Have some extra plugs on hand, and get a small can of never-seize thread goop to use on the sparkplug thread so the head doesn't strip out. ...You can try indexing your sparkplug, for the 'racer's edge'.

    Use the W&D sandpaper method on a flat surface with a rotating motion to clean up the head/cylinder joining surface. Use a thinner/better head gasket to pump the compression a little.
    A thinner cylinder base gasket will change port timing a little... try it!

    Use a dremel tool or chainsaw file to widen the intake and tranfer ports a mm or so... DON"T raise the top of the port ! Lol

    If it's shredding rings, you can round off the very edge of the ports just a very little bit to ease the transition as the rings fly by...

    And THIS has gone on FAR too long! Lol

    Have fun!

    Somewhere in there should be to run the best gas you can get...
  13. Oddzball

    Oddzball Member

    SO i figured out what the noise was.. my drum brake was shot, kept getting stuck and making the noise..

    SO i removed my drum brake pads and made it a freewheel.. sorta...
  14. DuctTapedGoat

    DuctTapedGoat Active Member

    Wow, totally wouldn't have guessed that.
  15. Oddzball

    Oddzball Member

    Thats not sarcasm is it?
    Nah i wouldnt have noticed except when i was pushing it, clutch was ocmpletely disengaged and back wheel kept getting stuck slightly.

    Was not only making the squeeling noise but the added stress of the engine of having to fight the brake was making it bog down.

    Now if i could just get the f-ing carb to work right, i would be golden.
  16. DuctTapedGoat

    DuctTapedGoat Active Member

    Serious - no sarcasm, that wasn't even a fleeting thought! I'm glad you at least got that figured out though. Now for carb fun!
  17. Oddzball

    Oddzball Member

    Seriously, I am gonna take a dman hammer to that carb.

    You know I was running it without a air filter and it ran great though... I know i know, dont run stuff without an airfilter, but frankly i doubt that **** black songe blocks much dust anyway.
  18. DuctTapedGoat

    DuctTapedGoat Active Member

    Ya know then - you might try taking a drill to your air filter to increase flow - that's the cheap and easy way to increase air to fuel.
  19. rustycase

    rustycase New Member

    If it runs noticeably better with the air cleaner off, that's a sure sign the filter is junk!
    and that will stifle a 2 stroke and choke it back to nothing until it loads up so bad it won't run anymore...
    No point in messing with the needle or jet until you get a decent air cleaner on it.

    See if there's a K & N type filter available for starters that will adapt to it...


    Are we having fun yet?