2 stroke scooter smokes like crazy on startup after few days layup ..advice pls

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  • 2 stroke scooter smokes like crazy on startup after few days layup ..advice pls
  • they all do that – its oil / carbon deposits building up in the exhaust. needs a real good thrash or decoking

    Premier Icon tomaso
    Subscriber

    Fuel and oil leaking into engine builds up when standing unless fuel tap is off?

    Premier Icon JAG
    Subscriber

    I’m guessing it’s got a separate tank for the oil and mixes it’s own as you ride?

    …and you say it clears once warm and run for a while?

    If so then I’m afraid it’s a case of ‘they all do that sir’

    kaiser
    Member

    apart from ditch the little bugger!
    anyhow..got a 1998 honda 50 for the missus . 6000 miles twist and go. Run well but produces an embarrassing amount of smoke on startup if not used for a few days . After a mile or so it all clears out and is not a problem . also fine if used daily. Apart from changing to an expensive synthetic low smoke oil is there anything I should be looking at ? I’m not experienced with 2 strokes but presume it’s a result of oil somehow very gradually leaking into the carb over a period of time when not in use and so on starting it all has to be burnt away. Any ideas what to check / how … ,,,is there normally a valve that is supposed to shut when the motor stops to stop any oil creeping in ? don’t have a manual unfortunately.
    many thanks for your help and advice
    regards
    Bill

    Premier Icon totalshell
    Subscriber

    simples to fix. ride for 15 minutes with no oil to burn the excess away then just use a quality synthetic smokeless product ( we use pj1) dont use the oil tank if it has one but pre mix it so get a plastic 5lt fuel tank and put 70ml of oil in there before putting your 5 litres of unleaded in. guarenteed smoke free
    we have two scooters and 7 other two stroke bikes ( trial mx enduro) and use this method every day..

    kaiser
    Member

    hey all do that – its oil / carbon deposits building up in the exhaust. needs a real good thrash or decoking

    TJ ..unlikely to be that as 1/ recently cleaned out and repacked exhaust 2/ it’s only on startup and as far as I’m aware oily exhausts really get smoky once the temperature has risen quite high.

    good idea totalshell but

    70ml of oil in there before putting your 5 litres of unleaded in

    are you 100% that’s enough oil as that works out at 70 to 1 fuel to oil ratio ….I always thought 30 to 1 was roughly what many recommend? please educate me further !

    Premier Icon totalshell
    Subscriber

    ask any of my nine bikes if thats enough.. none smoke i win events on 3 of them.. too much oil is a killer.. thick heavy oily deposits in cylinder loss of power pinking and .. smoke on start up. use a quality smoke free synthetic oil ( PJ1) and you ll be home and dry..
    the smoke your having at the mo are the unburnt oil from the last time you ran the thing ie you had too much oil in the fuel as the bike is mostly on half revs or less the oil isnt all burnt off and deposits accumalate in the top of the cylineder and are burnt on start up the bike will also be running hot as it is running too lean if there is too much oil in the fuel. you ll probably find that the exhaust and top of the piston are heavily carboned. so rid ewith no oil then follow the 70.1 guide.

    Do not use premix – use the injection. If you premix in the tank you are effectively replacing petrol with oil – so it will run lean and ruin the engine unless you adjust the jetting.

    Injection is far better anyway as it adjusts the amount of oil for the amount of throttle and revs.

    70-1 is far too low a ratio as well.

    check the oil pump adjustment but I am almost certain its simply deposits in the pipe.

    Junkyard
    Member

    they both have a point which does not help you.
    Either way the cause is as totalshell says and personally I would just live with it – design flaw but unlikely to break it.

    kaiser
    Member

    hope you( TJ and TS )will continue to discuss further as now 2 people who seem confident in what they are saying are offering opposite advice . 🙁

    Mr Woppit
    Member

    I used to own a Puch 125 many years ago which did exactly the same thing if I forgot to turn off the (fuel? oil?) flow switch between rides…

    Kaiser – stock is best. what total shell says about premix is simply wrong.

    the bike will also be running hot as it is running too lean if there is too much oil in the fuel.

    for example – if teh oil is using an injector pump the amount of oil has no effect on fuel air ratios.

    Oil pumps use less oil that premix as they adjust to throttle position and revs so only put oil in when needed.

    uplink
    Member

    I wouldn’t rule out a weeping seal or gasket allowing a bit of gearbox oil into the crankcase
    It doesn’t take much oil to create a load of smoke so you wouldn’t necessarily notice the loss from the gearbox but check it anyway

    kaiser
    Member

    Ok TJ ..appreciate the advice but can you quickly address why you still think that it’s probably being caused by an oily exhaust as doesn’t that tend to show up only when the pipe is pretty hot and not on startup?
    also ..any advice on cleaning her out without taking off the head ?
    redex or similar any good or best steer clear?

    Premier Icon totalshell
    Subscriber

    i can only offer 20 years experience with competing on two stroke motorcycles as my experience and the nine that are sat in my garage which i compete on and maintain myself if you check out my blog you ll see i do everything myself

    seperate oil tanks are popular in consumer bikes as they are simple and require less rider input ie oil in one hole fuel in another however specialist bikes MX trials enduro racing do not use seperate tanks thus ensureing an even mix at all times wheras a bike relying on an injector could get flooded or blocked and be starved or flooded with oil

    the issue of the bike running lean if it is over oil is simple if you for any given ratio of fuel to air add oil to the mixture less fuel will be drawn in making the mixture leaner in petrol.

    if you removed the cylinder head you would likely find the head and the top of the piston carboned up you may also find that the bike has a clear knock as you close the throttle especially as it returns to idle this is as a result of the carbon on the upper surface of the piston and / or the fuel been poor quality (super unleaded is a quick cure)

    ”Oil pumps use less oil that premix as they adjust to throttle position and revs so only put oil in when needed” exactly the principle that premix works on.

    one of the first bikes i had a yamahe dt125 had the same symptoms as you describe i removed the oil pump and used premix only at 70.1 and the problem was solved. 40.1 50.1 had thier day when fuel and oil were less sophisticated than today so didnt lubricate as well.

    http://pre65trials.blogspot.com/

    ps dont use redex to clear it out the solvents will also clear out the oil from the bearings which is whyit is there in the first place.

    sobriety
    Member

    i can only offer 20 years experience with competing on two stroke motorcycles

    I’d imagine you rebuild the engines regularly as part of your maintenance routine then, which is something that the OP probably won’t want to do.

    For a 50cc twist n’go I’d just live with it being smokey, it’s a two stroke, that’s all part of the fun.

    totalshell – you are still wrong about the oil leaning out the air fuel mix – premix does this but pump delivery does not and pump delivery does use less oil. The pump is separate from the carb. It does not alter the air fuel ratio as it adds oil. Premixing does lean out the oil fuel ratio – you have to jet up to compensate

    Do you actually have any experience of modern two stokes?

    _ 35 years experience of running two-strokes 🙂 – from old stuff to modern stuff.

    uplink
    Member

    The pump is separate from the carb. It does not alter the air fuel ration as it adds oil

    Don’t know the engine in question but a lot of oil pumps inject into the carb, which’ll lean it just the same as if it was premix

    The OPs issue only happens after a long stop, so I’d still suspect a crank seal of some description, I wouldn’t bother doing anything about it though

    yes uplink – but its does not go thru the main jet so does not alter fuel metering. thats my experience anyway

    Premier Icon totalshell
    Subscriber

    well i have a 2011 beta, 2007 ktm 2004 gas gas,1982 fantic 1974 montesa 1963 Francis barnett 1957 bsa plus an ’84 c90 and a ’96 peugeot but ffs dont tel mrs tts..

    uplink
    Member

    TJ – indeed but the mixture in the engine is leaned up regardless

    You would need to rejet if you took the pump out and used premix though

    For arguments sake and to make the sums easy, if you switched to a 20:1 premix, you’d need to increase the jetting by 5%
    In a perfect world, of course 🙂

    kaiser
    Member

    You would need to rejet if you took the pump out and used premix though

    not according to TS ! ( not stirring just commenting!)

    btw Totalshell …lovely looking bike on your blog but I can’t read anything from that link ..just get a big photo surrounded by smaller component pics …why’s that?

    uplink
    Member

    not according to TS ! ( not stirring just commenting!)

    Well he’s talking about using 70:1 which will only mean a change of around 1.5% in the mixture
    I suspect most 2 stroke engines could easily handle that without a noticeable difference, doesn’t make it optimal though

    There’s too many other things – environmentals, fuel quality etc. that affect mixture a lot more than 1.5%
    So if you’re happy with 70:1 go for it

    Are you sure the pump is correctly synchronised to provide the correct amount of oil? It’s usually a case of adjusting a cable to line up two marks – dead easy.

    As it’s a 50 we can take it for granted that it’s at full chat most of the time so should keep itself clear.

    Premier Icon porter_jamie
    Subscriber

    just use a proper oil. expensive is just a matter of perspective really. i woundn’t run anything other than silkolene comp2 in an injector bike and pro2 in a premix one. fancy stuff smells nice too.

    Premier Icon totalshell
    Subscriber

    kaiser .. scroll down..

    kaiser
    Member

    kaiser .. scroll down..

    DOH !!! brain now engaged!
    thanks bud ..looks good stuff . from the little I read I must admit it does look as though you should know what you’re talking about ! 😀

Viewing 27 posts - 1 through 27 (of 27 total)

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