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Thread: Temperamental 2 stroke engines.

  1. #1
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    Temperamental 2 stroke engines.

    I've been reading Reader Reviews about gadgets with 2-stroke engines in the 25-50 cc range. About 90% of all complaints are about starting.
    I've had a very cheap chainsaw for 10 years. No problems starting it.I had a brush cutter for 19 years, again no problems. Recently I bought a new 50cc 18"chainsaw made in Germany which is very hard to start.
    Why are 2-stoke engines so temperamental and hard to tune?
    .W.

  2. #2
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    Reading through the manuals of a couple of recent purchases (yes, I sometimes read the manuals) it mentions fuel must be less than a couple of months old.

    I've had BSA Bantams, Lambrettas, Villiers engined bikes & mowers plus all the usual chainsaws, whippersnippers etc. also my Mum had a Wartburg (2-stroke car) for a while. Most have been reliable starting except one highly tuned Lambretta but I was running a 32mm Amal carby. It couldn't suck in enough fuel to initially fire up but lay it on it's side, tip neat petrol down the inlet and away she went.
    A hedge trimmer purchased a couple of years ago stated the fuel must be less than 2/3 months old and if not being used for some time empty the tank and run it till most of the fuel in the carby has been used.



    Most 2-stroke small motors are often used infrequently so modern fuel may partly be the problem or maybe the motors have got smaller so they are highly tuned to get the power output needed ? I read somewhere that you must not use ethanol blend fuels in fire fighting pumps. Only called on to work once in a blue moon and the bloody thing won't start due to stale fuel or phase separation.

    Also the coil packs can be an issue. I have a chainsaw (Homelite) that I've used for about 15 years, starts OK from cold but hot it now will not start so I have to replace the coilpack because on checking there was no spark. Let it cool down and it starts OK.
    There was a 4-stroke Chinese mower on the market where the coil packs failed after a very short time. I was given one and its a fantastic copy of a Honda OHV motor starts, runs for a while then stops. Like my chainsaw it will only re-start when cold again.


    Colin
    '56 Series 1 with homemade welder
    '65 Series IIa Dormobile
    '70 SIIa GS
    '76 SIII 88" (Isuzu C240)
    '81 SIII FFR
    '95 Defender Tanami
    '58 Series II (sold)
    Motorcycles :-
    Vincent Rapide, Panther M100, Norton BIG4, Electra & Navigator, Matchless G80C

  3. #3
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    Most of the time the "hard to start" bit comes from 2 areas. Either the fuel isn't available or some bugger has messed with the tune. 99% of these small motors are correctly tuned out of the box.
    Regardless of whether or not there is a priming bulb on the carby (which you should always use on a first start of the day) the start procedure is the same for a cold/cool start.
    Close the choke. Keeping away from the throttle (i.e. throttle on an idle setting) pull the starter rapidly until the engine fires and then dies. It might take 10 or so pulls to get it to fire. Open the choke (on some engines this will require a half way setting). Pull the starter again until the engine fires. Use the throttle gently to warm the engine up.
    The reason they are hard to tune is that the carby is a really basic and the low & high speed circuits interact with each other slightly. The process is to tune the high speed first on wide open throttle, then tune the idle as one affects the other. Idle speed is set last.

  4. #4
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    If I want to spend an hour screaming abuse at somethign .... I'll pull out the 2 stroke brush cutter... Man that POS can be a bastard to start.

    Now my ancient super 600 Victa that has probably done a million hours work (even the tyres are worn out on it). Will always start quite easily. That thing is the most brilliant grass cutting bit of junk I've ever used. You just can't kill those victa 2strokes (and gee's they have some grunt).

    seeya,
    Shane L.
    Proper cars--
    '92 Range Rover 3.8V8 ... 5spd manual
    '85 Series II CX2500 GTi Turbo I :burnrubber:
    '63 ID19 x 2 :wheelchair:
    '72 DS21 ie 5spd pallas
    Modern Junk:
    '07 Poogoe 407 HDi 6spd manual :zzz:
    '11 Poogoe RCZ HDI 6spd manual

  5. #5
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    The best garden tool I ever purchased is the Honda 4 stroke powered brush cutter. Fill it with fuel, prime the carby, fast idle on, choke on and pull the starter cord once. It will stay running until I either run out of grass, cutting string or fuel. Bloody magic device, clean, quiet and economical. It gets the fuel tank drained at the end of the job and the carby run dry. I've never had a problem with year old fuel as it always stays in a sealed container. The fire pump is no different, Honda key start always starts on the first attempt no matter how long since the last start. The carby gets run dry by turning the fuel tap off, without fail.

  6. #6
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    I was hoping we could keep "Makes" out of this.
    .W.

  7. #7
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    My local mower/chainsaw repairer advised me that starting process was basically the same for all 2 strokes ... fresh fuel, prime if necessary, full choke, pull starter a couple of times till it fires. Push choke in, throttle lock on chainsaw, pull again and should start ... if fails try squirt of aerostart as carby probably gummed up (biggest starting issue) and needs good suction from engine to get fuel flowing, BUT do not use choke as will flood, requiring plug out, drain fuel from chamber and start process again.
    Strategy has works with every 2 stroke I've got and tried.
    Michael T
    2002 L322 Range Rover TD6, ride almost as good as a Citroen, ... luxury
    Aussie '88 RR Tdi300 (+lpg), Auto (RIP ... now body removed after A pillar, chassis extension to 130 & fire tender tray.)

  8. #8
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    The cheaper ones all have a variation/copy of a Walbro carby. How genuine the copy is determines how well they work.

  9. #9
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    Picked up an old Ryobi whippersnipper from the local tip shop for $10 complete with 1/2 a tank of fuel. Got it home and it started OK but would only run on choke.
    Quick Google and the answer was the running jet blocked. Pulled down this tiny carby, blew it out carefully with compressed air put it back together and it runs OK now.

    Had a much older McCulloch (re-badged Shindaiwa) play up. Carby off and cleaned it out and she starts & run well again.

    Recently got another old Ryobi (dark green) from the local trash & treasure market for $5. Replaced the fuel line and topped it up with fresh 2-stroke mix and after a few pulls it started and ran OK.

    So it's coming down to problems being stale fuel and carby issues, some just being from dirty fuel.

    Oh and yes, there are a few whippersnippers in my back shed......


    Colin
    '56 Series 1 with homemade welder
    '65 Series IIa Dormobile
    '70 SIIa GS
    '76 SIII 88" (Isuzu C240)
    '81 SIII FFR
    '95 Defender Tanami
    '58 Series II (sold)
    Motorcycles :-
    Vincent Rapide, Panther M100, Norton BIG4, Electra & Navigator, Matchless G80C

  10. #10
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    I'm told by the old blokes at my mower shop that modern fuel goes stale very quickly, but that fuel conditioner will alleviate the problem. As I was being lectured on this topic, the bloke from a very large tree lopping company came up behind me. He said that the use of the fuel conditioner had reduced their small engine maintenance to less than half what it had previously been. I now use it in fuel for all my small petrol engines, 2 and 4 stroke, and have no starting problems. Even my brush cutter starts usually with 1 or 2 pulls, and I bought that in 1986.
    Don.

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