Discussion in 'General Questions' started by HeadSmess, Sep 6, 2014.

  1. HeadSmess

    HeadSmess Well-Known Member

    :hurray: it finally happened, a year of abuse, and the last week has been a rather strange rattling noise. she finally seized on me! :willy_nilly:

    was it my 50:1 oil ratio? :detective:


    was it revving the poor lil thing to 8000+? :detective:

    mmm, possibly. though no sign of ring flutter or any other type of damage everyone will tell you will happen if you do such things. :shock:

    just the same old same old for me :rolleyes: ...the stupid ring locating pin let go! i seriously hate it when they do that! i dare say it happened a week ago, due to the sudden loss of power and subsequent rattling noises, but the final straw must have been the circlip for the gudgeon pin snapping off today. bores a mess! pistons even worse! and i didnt even port this one this time! never even opened it! phooey!

    everything else? perfect :) no shattered big end bearings, no play in anything other than whats normally there.
    i blame it on my exhaust pipe :smug2:

    was my bore, other than the dirty big gouges in it, worn at all?

    no. surprising. someone on this site is adamant that running anything less than 25:1 causes excessive bore wear. ill stick with my preferred ratio, thankyou very much :)

    i can now say a stock standard 48cc will take over a year of (almost) daily abuse at 50:1, revving its head off, only failing due to an inherent weakness... offset ring locating pins.

    from jennings two stroke tuning guide...

    Screenshot from 2014-09-06 20:49:45.png

    "the “offset” ring-locating pin may prove prone to precisely the sort of loosening
    and subsequent failure described in the preceding paragraph, which will lead you into a
    piston modification that can be very tricky: installing a new locating pin in the back of
    the ring groove. This gets tricky because in many cases the pin will be half-in, half
    above, the ring groove and it is impossible to drill the hole for a new location after the
    groove is machined. Impossible, unless you cut a small piece of aluminum to exactly fit
    the ring groove, filling it flush, in which case you drill your hole half in the piston and
    half in the filler piece. Then you remove the filler and your hole is ready for the pin -
    which introduces yet another problem: what to use for a pin? Steel wire is a good choice
    on grounds of strength, but is likely to work loose simply because the aluminum in which
    it is pressed grows and contracts so much with changes in temperature. A small-diameter
    “split pin” (which is like a rolled tube) is a better choice, but if suitable sizes are not
    available, then a pin made of hard brass is at least as good."

    i think im going to have to have a go at this, not relocate the pin itself, but simply replace the pin with something else... i call them "roll pins", also known as "spring pins"...a split pin, as ive always been aware, is the lil doodad you poke through a castellated nut, such as on the wheel bearings of cars. "roll pin" is far more apt, as the things are rolled! at least, its what i was told they were called back in the day.

    while i like the idea of "A" in the diagram... it holds the pin in the hole... it would also require new rings of a type that dont actually exist.

    sorry about the lousy pics. just threw my digi at the ground because it refused to take a pic at all when it did finally decide to turn on! not that it was much better than the phone cam anyways! why do i have such issues with cameras? gimme a good old SLR any day... grrrrr. at least they worked!


    time to go clean the ports up in my new replacement cylinder :) finally use my dentist drills!

  2. Fabian

    Fabian Well-Known Member

    Now finally, you are talking sensibly; contemplating the notion that if an engine is deliberately operated outside of parameters that the engine manufacturer designed it for, then it will fail.
    In this case, you have failed the engine, because it's been operated outside of what could be considered sensible use.

    Why don't these things happen to my engine?
  3. HeadSmess

    HeadSmess Well-Known Member

    isnt it you that requires a customised head and demands that everyone else follow suit because you have issues with the standard equipment?
    isnt it you that demands that everyone replace standard big-end bearings with crowded needles because you have trouble with the stock bearings?
    isnt it you that has issues with worn out bores after only 4000 miles though i cant detect any sign of wear after 15000+km, twice the amount, despite running half the oil?
    isnt it you that has issues with detonation thats easily fixed by dropping a gear and letting the engine rev a little bit faster?
    isnt it you that has decided any oil ratio weaker than 25:1 spells certain doom?
    wasnt it you that mentioned the necessity of having to replace your bottom end on a (fairly) regular basis due to bearing failures while im quite happy slapping on another cylinder and piston without even bothering to look in the crankcase, and will also be using the same wristpin/little end bearing? (though i will drop a magnet in there to catch any stray steel debris)

    oh! sorry! i must have you confused with the other fabian that seems to find that two stroke engines are a nightmare, fraught with frustration, taking years to sort out all the bugs! my sincere apologies :eek:

    only weak spots ive found in a stock 48cc engine is the locating pin and the crank seal, despite my love of running them at what, in my experience of small two strokes, is a relatively low speed, (not that i really expect much more out of them as they will only hit such speeds down hill, 7500 is more in line with normal cruising) but in your view of the beasts, is bordering on ludicrous.

    the crank seal issue is fixed by using 15x27x7mm R23/TC Double Lip oil seals. yes, a 7mm deep seal fits perfectly well behind the magneto. theyre also a much tighter fit than the stock seals in the bore and on the shaft.

    i shall also take this chance to use proper circlips, the ones with little holes that require them special pliers, rather than the soft pieces of wire currently supplied, as thats exactly what they were designed for.

    the pin issue should hopefully be fixed with a simple roll pin, if i can find one that small, or else, as suggested by a world famous will be brass, having a much closer coefficient of expansion to piston alloy than the current steel pins.

    guess it will take another YEAR or more to find out for sure...

    and sorry, the pins come loose from 1; being smacked sideways by the ring as it is forced back into the ring groove as it clears the exhaust port, and 2; aforementioned thermal expansion.

    nothing to do with how fast an engine is revved, other than the number of cycles point (1) is repeated. all to do with the shape and width of the ports.

    each to their own.

    next argument, please :jester:
    Greg58 likes this.
  4. crassius

    crassius Well-Known Member

    sounds like you plan to put a top end on it

    I will put a top end on a customer's bike if he wants it, but Usually with a warning that it may fail quickly if the motor didn't 'fail clean' the first time (usually broken muffler studs or some such)

    in the case where there has been obvious debris flying about, I have never been comfortable in thinking that none of it is hiding in a bottom end bearing somewhere just waiting to lunch the whole motor
  5. butre

    butre Well-Known Member

    I killed mine just the other day and am just replacing the whole motor. I'm pretty confident I had some debris fall into the bottom end as well so I figure I may as well replace the whole thing and avoid any later headache
  6. jaguar

    jaguar Well-Known Member

    Fabian that pin problem can happen even when you do keep standard parameters because it happened in my Suzuki 100 recently. Lucky for me the ring ends didn't snag a port though. That problem is due to bad piston manufacturing tolerances, in this case the pin hole needed to be slightly smaller before they pressed the pin into it.
    It happened on my Suzuki, not with the Suzuki piston, but with a cheap chinese replacement piston.

    HS, what oil do you run at 50:1?
  7. HeadSmess

    HeadSmess Well-Known Member

    jaguar...penrite hi-per semi synth. aussie made, only stuff i'll use. (not that im patriotic, ive just found it to be the best) ive tried getting hold of their "green slime" (TS40-C)for aircraft, but apparently they no longer make it, and claim the hi-per is the new equivalent. but also have a disclaimer saying "not for aircraft use", mostly for legal reasons? they also have the same disclaimer on standard NGK plugs...

    crassius... yep. while it wasnt exactly "clean", the amount of stuff that could be in the bottom end amounts to a segment of circlip. magnet, and a triple rinse with fresh petrol, i feel happy :) i do so at my own risk ;)

    i might split it anyway, im inclined to try and match the transfers up while i got the grinders out. just seriously hate making new gaskets and all that sort of stuff, leading me to...

    butre... i need it, and cant wait that long ;) gunna have to order a couple soon anyway. one for the dyno, one for the bike.
  8. crassius

    crassius Well-Known Member

    I did magnets, gas, & hot water & soap - won't get a sliver of aluminum scraped off the cylinder wall out of a bearing if it has already been mashed down a bit by the rollers. Big-end rollers are the worst, but have found crap tucked into the cage of the mains.

    Kinda luck of the draw here, hope you have luck with it.
  9. HeadSmess

    HeadSmess Well-Known Member

    this is true :thinking: can usually tell by the way they feel, if theres any notchiness... i woulda been splitting. magnet came out clean though. sometimes i can be really rough... :rolleyes: if it bites me on the bum, tis my own fault :wacko:

    as it is, running again without even getting it out the frame :) initial run in up the closest steep hill feels good. i do my homework (fixing a dustcatcher on a concrete grinder that i will need tomorrow) or see if i can get to my mates place and back? 100km (60M) round trip :whistling:

    ah, tis only 2:15pm still... plus its on/off raining. im staying in!

    btw...first real test of my dentist drills....bewdiful :) not a shred of casting flash left ;) couldnt be bothered doing the transfer match between cylinder and case, wait for a new engine for that. (lot of metal to remove...) do a complete "blueprint" then. reminding me i forgot to do the piston cut. oh well. :shrug:

    all i really need now is some ball hones, straight cylinder hones are good for plain honing, but the balls automatically chamfer the ports...

    always spending, always spending...grrr!
  10. Fabian

    Fabian Well-Known Member

    On close examination, you most definitely have the 'right' Fabian.
    Oh yes, for the uninitiated, these Chinese 2-stroke engines can be a complete nightmare, however, for the seasoned professional (like myself) they are a pillar of reliability; with billet (high surface area) cylinder head, Jaguar CDI, optimally jetted NT carburettor set up to perfection (or a much better Walbro style diaphragm carburettor), a crowded needle roller big end connecting rod bearing crankshaft and 25:1 oil/fuel ratio.

    Without these things, and when revving the engine to 8,000 rpm, it's not only a ludicrous concept; inviting mechanical catastrophe, but it invites nothing less than total unmitigated disaster from one end of the engine to the other, as you have so found out, against all sensible advise to stop being completely silly.

    I have never had any issues with the standard crankshaft seals, but then again i don't rev the living bejesus out of the engine.
    I also have never had any issues with the piston circlips, but then again i don't rev the living bejesus out of the engine.

    Again i say: stop being silly and operate the engine sensibly. This will give you more time to get your dyno up and running and producing interesting data.
  11. Fabian

    Fabian Well-Known Member

    60 mile round trip :ee2k:
    By your own admission, you can't even get 2 miles down the road; with parts falling off your bike; leaving a steady stream of items that (if collected) could be forgiven for being a Meccano set that's fallen off the back of a truck.

    If you want to successfully complete a 60 mile round trip, the only way it's going to happen is if you were riding "my" bike - - - in a sensible (mechanically respectful) manner.
  12. HeadSmess

    HeadSmess Well-Known Member


    you never fail to make me lose control of my bladder :jester:

    meccano? who, me?! meccano mechanics are very thorough when it comes to tightening their little nuts with their little tools in their little hands.

    not I!

    i do 60 miles+ every two days :rolleyes: its not that far really. i think everything that can fall off has fallen off now...why put it back on? :wacko:
    Fabian likes this.
  13. Fabian

    Fabian Well-Known Member

    Some of us are born with the gift :devilish: and you provide me plenty of material to use it !!!
  14. jaguar

    jaguar Well-Known Member

    I see you two have got over your temporary buddy phase and are back to fighting like cats and dogs.
    The more things change, the more things remain the same.
  15. Fabian

    Fabian Well-Known Member

    Someone has to provide the comedic entertainment on here and myself and HeadSmess are somewhat skilled at providing it; especially when his logic proves to be a little silly :evilgrin:
  16. UP Rider

    UP Rider New Member

    too bad these two can't give us some rookies some usable info

    Just kidding Fabian and HS

    I have read many of your posts along with many others and have found some very useful info. But I do however enjoy the banter between you two. Just hope I don't read about you two meeting on the road and playing a game of chicken.
  17. Fabian

    Fabian Well-Known Member

    You don't have to worry about us meeting on the road and playing a game of chicken, because i can always rely on HeadSmess to rev his engine to 8,000 rpm; and with predictable reliability, he can demonstrate disassembly of his piston without the use of hand tools; conveniently storing piston components in the bottom of his engine.
  18. HeadSmess

    HeadSmess Well-Known Member

    no, no, no, i store them in the exhaust and in the furnace, or when theyre really spectacular, on a shelf :)

    call it aussie compatrism or rivalry or something :wacko:

    we agree to disagree on certain points.

    8000 is nothing, while one ring was broken i got it up to 9250 :evilgrin:

    what i really want, really really want, is a, is a, is a conrod to let go! then i know im getting somewhere! or going nowhere?

    i doubt fabians game to ride approx 1000km to come play chicken, so maybe if we meet halfway, somewhere around gundagai (on the road to ;)). been a long time since i was down that way. wait for summer though, i dont have much tolerance for the cold :( gotta give him a weeks head start too, he only does 20 an hour :p but he has the trailer for the jerry can of fuel already. :9898:
    Last edited by a moderator: Dec 15, 2015
  19. Fabian

    Fabian Well-Known Member

    It seems that you are once again, massively overstating the reliability of your bike.

    We both know that you'd be lucky to make it to the end of the street before the bike starts to self-disassemble vital components.
  20. Fabian

    Fabian Well-Known Member

    We only agree when you are talking sensibly, and i only disagree when you are talking complete claptrap, like 50:1 oil/fuel ratio and using "8,000 rpm and reliability" in the same sentence.
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