Viewing 33 posts - 1 through 33 (of 33 total)
  • 2 stroke engine help please.
  • Premier Icon twinw4ll
    Free Member

    My wife’s 50cc 2 stroke Yamaha scooter has been laid up a while it starts straight away but won’t accelerate under load, I’ve checked the carb jets and they are clean, if I had to guess float bowl not filling quick enough!?
    It’s NOT drive belt related.
    Any ideas gratefully received.

    Premier Icon thols2
    Free Member

    Pour petrol on it and throw a match at it. Two strokes are the spawn of Satan, you’ll be doing everyone a big favour.

    Premier Icon tjagain
    Full Member

    is it smokey? could be crankcase seals but more likely something fuel related. Check the filter in the fuel line? check the fuel tap is not blocked?

    Premier Icon airvent
    Free Member

    How long has the fuel/oil been sat in the tank

    Premier Icon ofked
    Free Member

    Spark plug?

    Premier Icon sobriety
    Free Member

    I’d drain the tank and give it a tank of fresh petrol – modern fuels with ethanol in do not keep well.

    What do you mean by “won’t accellerate under load” does it rev up cleanly with nothing happening, or does it splutter and mis and try to die?

    If it’s been sat, you have check that the rear wheel turns freely – it’s not something silly like a siezed on rear brake is it?

    Premier Icon julians
    Full Member

    If it worked before it was laid up, but doesnt now, then I would suspect one or more of the following:-

    – Stale fuel – change the fuel
    – Carb gummed up/varnished – take carb apart and clean each bit individually with carb cleaner

    Premier Icon sobriety
    Free Member

    To add to that – and I don’t really want to say these options as they’re ones that begin to fall into “pain in the arse” territory.

    As TJ said – Failing crank seals – this will cause lots of smoke

    And my addtion

    Gummed up piston rings – this would show itself as not pulling under load, but I’d also expect it to be hard to start as well.

    Premier Icon fasthaggis
    Full Member

    All the above,I am sorting out a Scooter that has been left for a while,had to drain the tank and take the carb to bits for a good clean.Does it have an inline fuel filter?
    Also check rubber intakes for cracks.

    Premier Icon Rubber_Buccaneer
    Full Member

    Check nothing has made a nest in the air box

    Premier Icon pondo
    Full Member

    I’d check the tank vent tube as well, although if that was blocked, it’d stop completely. But clean carb, clean air filter, new spark plug and fresh fuel FTW.

    Check nothing has made a nest in the air box

    I once had a squirrel fill the expansion chamber of my dismantled KX100 with acorns. 🙂

    Premier Icon Murray
    Full Member

    Check nothing has made a nest in the air box

    Happens to the best cars too

    Premier Icon bedmaker
    Full Member

    It’s either been sworn at too much, or not enough.
    I could never find the right balance.

    Premier Icon sobriety
    Free Member

    I once had a squirrel fill the expansion chamber of my dismantled KX100 with acorns.

    The neverending RD200 restoration that I’m stalled on had mice in the airbox, fortunately they didn’t get to the carbs as their piss utterly destroys them.

    Premier Icon RustyNissanPrairie
    Full Member

    Strip the carb and bung it all in an ultrasonic cleaner if it’s been left with fuel in the float bowl

    Premier Icon mc
    Free Member

    What RustyNissan said, or in the case of having no ultrasonic cleaner, bung it in an old pot, cover in water, add some laundry detergent, and give it a boil up for 15 minutes or so.

    Oh, don’t put the float itself in. The heat may cause it to split or collapse once cooled again.

    Premier Icon dyna-ti
    Free Member

    Pour petrol on it and throw a match at it. Two strokes are the spawn of Satan, you’ll be doing everyone a big favour.

    Seagull 2 stroke outboards. Probably the best little outboard engine there is. Cute. Much better than these modern things. And you’ll get about 40 years use out of it.

    Premier Icon posiwev
    Free Member

    Probably a blocked jet, carb may need ultrasonic clean, could be silencer coked up also ?

    Premier Icon db
    Full Member

    40 years out of a Seagull! We have a late 1950s 40 that still starts every year. The 10:1 petrol oil mix is not great and starter is not a recoil so you end up flicking the started cord into the face of who ever is rowing but it’s a family heirloom now and brings back memories of fishing with my grandpa.

    Premier Icon brads
    Free Member

    **** 2 stroke evil spawn of satan should be burned then skinned alive then burned again, then fed to dogs.

    Unless it’s a Lambretta obv.

    Strip the carb, dump the lot in a bucket of hot detergent filled water overnight or longer then clean it and rebuild. Fresh petrol then start from there.

    Also ,and this is important, set the gap on your plugs. Like really.

    Premier Icon neilnevill
    Free Member

    Strip carb and replace diaphragm. If it has a rubber intake hose between carb and case, replace that. Also replace the fuel line.

    My limited 2 stroke knowledge made me think air leak, but as it’s developed while sat I’d check fuel problems first…e5 evil… Rubbers will have dried and split. E10 coming soon. Tuk.

    Premier Icon martymac
    Full Member

    My money is on the fuel.
    I wouldn’t leave fuel in a carb for any longer than a week or so, it dries out and goes like varnish.
    Had it on my gt380, what a pain in the arse it was to get it going properly after that . .

    Premier Icon oldmanmtb2
    Free Member

    Change fuel, plug…

    Does it rev freely in neutral? If its failing to accelerate under load it could be plug lead or electrical.

    The 2 stroke is by some distance more robust and reliable than any 4 stroke shite.

    Please note i have riden/raced motorcycle enduro for over 30 years and modern 4 strokes are designed to eat engine spares….

    Premier Icon pandhandj
    Free Member

    Oh my word!

    I have nothing useful to add but just wanted to say out loud, that I haven’t had any two stroke fun since 1996, when I sold my RGV! Happy days!

    Premier Icon Sandwich
    Full Member

    Two stroke exhaust when run on Silkolene synthetic oil is fabulous stuff. Straight back to a mis-spent youth and mid-twenties. (NS 400 was a revvy, riot of fun).

    Premier Icon Murray
    Full Member

    Silkolene? Castrol R please!

    Premier Icon twinw4ll
    Free Member

    Stripped the carb completely and lathered in carb cleaner, said a short prayer to the 2stroke God’s and Bobs yer uncle, that’s when I noticed the oil running down the left forkin hell!!!
    Thanks to all who contributed, a couple of new Honda 125 4 strokes look a tempting proposition ATM. 😁

    Premier Icon sobriety
    Free Member

    A four stroke carb/injector will gum up with bad fuel just as well as a two stroke one 😉

    What’s leaking oil?

    Premier Icon sharkattack
    Full Member

    This thread has got me thinking. I’ve got a YZ125 that hasn’t been ridden in about 7 years and I’ve never ridden one in my life.

    I drained black petrol out of it last year but didn’t think about the carb. I should probably learn how to remove it and clean it before the maiden voyage.

    Premier Icon bob_summers
    Full Member

    Worth stripping the carb and cleaning – if you’ve never ridden one then it might run like crap and you’d be none the wiser!

    My last stinkwheel was an race bike that ran Avgas premix – carbs & tank drained after each meet if I remebered, saved hassle later on. Also had a tuned 500 Gamma (4 carbs!) which didn’t get a lot of use and was fussy about fresh petrol.

    Premier Icon sobriety
    Free Member

    I should probably learn how to remove it and clean it before the maiden voyage.

    It’s fairly easy – undo the jubilee clips that hold it to the manifold and airbox, unscrew the top so the cable and slide can slide out of the body, pull off the fuel feed and oil feed (if it has one).

    Wiggle carb out of the bike.

    Some of the screws on it will control airflow/slide position, screw those fully in and count the turns before you unscrew them, so you can set them back to where they were on reassembly (do them up, then back them off the number of turns it took to tighten them from their original postion as noted in your note book – you did note it down, didn’t you)

    The others things to watch for are the needle postion in the slide (they tend to have a series of grooves in them with a circlip in one of them to set the position) and the float level – usually set by bending some tabs to give a pre set distance between the float and some part of the carb body (you shouldn’t need to do this if it hasn’t been messed with and you don’t bend anything taking it apart)

    Everything else should be a case of unscrewing things and giving them a really thorough clean. Look for pitting/corrosion on the brass bits and renew the jets/valves/tubes/needle that are damaged. Job jobbed.

    Premier Icon Russell96
    Full Member

    I’d second/third the Fuel filter, old Yammy peds would have a little plastic nut under the fuel tap that was hollow for all the crud from the tank to settle in. I’d look at all of the fuel line from tank to carb. Then if that’s clean, flush the tank and refill, then after that look at the carb.

    Spark plug (checked before fuel system) then a look at the ignition system. Clean plug in lead touched somewhere to earth on the ped and start it and see if you get a nice big clean spark.

    Premier Icon lesgrandepotato
    Full Member

    If it revs off load and stutters under load it’ll be spark. Fresh fuel and assuming it has points fresh clean points and it’ll be golden.

    I reckon the points gap has closed and the fuels off so it won’t go with a weak spark.

Viewing 33 posts - 1 through 33 (of 33 total)

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