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I have acquired an old two stroke mower built in 1959. It was being chucked out as the owner said it wouldn't start. Anyway I hate to see old things chucked away so I took it away and stripped it down. The carb was full of oil and the jet completely blocked but after cleaning all that out and putting fresh fuel in it, it started after about 20 pulls. I have used it a few times since, it will start from cold first time but when hot it is a pain to start. Does anyone know why this might be? I have cleaned the airfilter and put a new plug in.
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Try stopping the engine by turning the fuel off and let it run out. This stops excess vapour filling the sump. Regards Peter
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I wonder what effect unleaded fuel has on this old 2 stroke however I can not see a connection between heat and unleaded although it is less stable. I assume compression is OK hot and you have a spark from the magneto. Now there is a word I did not think I would be using too often. Regards Peter
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Do you still get a healthy ignition spark when the engine is hot?
There may be insulation somewhere in the ignition electrics that?s breaking down when it gets hot. Or a capacitor, perhaps.
Zebra
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Do you still get a healthy ignition spark when the engine is hot? There may be insulation somewhere in the ignition electrics that?s breaking down when it gets hot. Or a capacitor perhaps.
I think this is the most likely area to look at myself. In my experience of chainsaws, strimmers and outboards, the most common cause of erratic or starting difficulties is a breaking down magneto coil. The infuriating thing is that they do give you a weak spark which fails under compression and allows the thing to start occasionally.
The only other thing could be the crankshaft seals. If these are old and hardened they may be allowing vacuum to leak from the crankcase. But my money would be on the magneto coil.
Edited by Roly93 on 27/05/2009 at 10:15
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Roly, check the date of the post. Hopefully by now the problem has been resolved, or it's in lawnmower heaven ;o)
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Is it an old ATCO with the Villiers engine? If so I have the same problem and would love to know what the cause is and what the cure could be.
Sometimes when it runs very hot the engine on my mower just stops. Will only restart when it is cold. I have checked the plug, (looks OK) points are OK, (very difficult to adjust). Magneto seems OK so my suspicion is on the capacitor breaking down when it is very hot?
Q.
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iirc my 1929 Riley 9 magneto used to fail when hot due to the shellac insulation on the windings failing with the heat.
Or: have you checked for fuel vapouristion? If the float chamber is empty when hot or pressurised due to petrol vapour, it could prevent frsh fuel flowing (I assume it's gravity feed). Had that problem on an old mower (and a Rover 16).
or:
Just try swapping the condenser (had that problem on a Mini 1962).
or
The plug lead insulation is cracked and you lose HT ignition when it's hot becasue there is voltage leakage to earth
(try changing it: not expensive).
Or the points gap closes up with temperature (there may be pips on the faces.. (had that as well).
Run out of ideas:-)
madf
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At least we know what is not and that's the ECU. Regards Peter
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If it's an old Briggs & Stratton engine, the throttle needs to be closed right down. Made that mistake with an old rotavator once.
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I was unaware that Briggs & Stratton made two strokes and thought they were all side valve four strokes.!!!!
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I was unaware that Briggs & Stratton made two strokes and thought they were all side valve four strokes.!!!!
D'oh. Pass me the dunces hat.
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It could just be worn out. Two-stroke engines don't just need good cylinder compression, but are dependent on gastight crankshaft seals too. They probably leak more when hot.
Of course knowing the fault, you could just keep it running and avoid having to restart when hot.
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It's an old JAP two stroke engine and yes it's gravity feed. The magneto is producing a healthy spark. Don't know about the points, I would have to strip the engine down to get access to them. I will post a picture in the next few days. It's an amazing little thing really with wooden rollers front and rear. I suspect it will be impossible to get any parts for it now.
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Cliff Pope's idea could be right-my first transport was a Bantam,it rattled like mad but the seller(or con artist)assured me it was only the tappets needed adjusting.I soon learnt there weren't any and it needed a rebore.Point is it only started cold,so does it rattle?Should be simple enough to whip the head off and check piston/bore interface. As said spares may be a prob.,when I took my sixties B.S.powered Hayterette to the local mower shop it was looked on with contempt and I was told it was obsolete.I told them my grass did not think so.
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I found I could still buy spares over the internet for my 1973 Hayter.
I stripped down my 1980s Atco and found the bore was worn out. I found it was more economic to buy a 1 year old secondhand mower than rebuild the engine:-(
madf
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Have you seen how much petrol mowers are selling for in places like Focus?
They're getting so cheap now they'll soon be cheaper than electric ones!
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Yes I know they're cheap. I only took this mower on because I thought it was a shame for it to be dumped. It's a hobby project thing, that's all - a bit of fun to get me out of the house :-0
While the mower starts from cold, I am reluctant to strip it right down in case I damage something else. Anyway thanks for all the replies.
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You can not beat a petrol cylinder mower for quality and presentation of cut. No cables, no faffing around, cutting the lead, RCD's or burnt out brushes. Jusr years or service and the odd drive belt. Regards Peter
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Two-strokes in my memory (esp Villiers) tend to 'nip up' when very hot but increasing the ratio of oil to petrol sometimes helps, if you can put up with the smokescreen. My Stihl 2-stroke brushcutter seems to run happily on 50-1 but old strokers often need 16-1 IIRC.
PS: I have a Briggs and Stratton mower engine with OVERHEAD valves - ta-da! You can't stop the relentless progress of American engineering - they'll be experimenting with overhead cams next...
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Steady On there. !! Regards Peter
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You can not beat a petrol cylinder mower for quality and presentation of cut
Exactly! Although modern cylinder mowers are large, bulky, over-safe and overpriced compared to the rotary types or earlier Suffolks, Punches etc.
Our Punch was having hot running difficulties (stalling shortly after cold starts) until dad eventually stripped out the old points which were badly worn with a 'step' and full of oil. New ones in to the tune of £7 which will hopefully be good for another 35 years.
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Mike Farrow
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You can not beat a petrol cylinder mower for quality and presentation of cut>>>
I have used cylinder mowers for years, but approx 5 years ago switched over to a Honda rotary with rear roller and would rate it against any cylinder mower for superb striped cut and when it comes to reliability, the Honda engine is in a league of its own. Not cheap at £625 new but you can keep your cylinder mowers as far as I am concerned.
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If it won't start when hot maybe the mixture is set too rich, usually there is an idle and high speed mixture adjustment by means of an adjustable jet.
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Drip-feed was mentioned. Is that an oil- feed feature, so making petroil unnecessary?IIRC two strokes of that era ran on 20-1 petroil, if they used petroil. Surprisingly for those flat out on the tank, increasing the oil proportion weakens the mixture (oil don't burn too well) and then the engine seizes. Ashless two-stroke oils are also required otherwise the plug whiskers.
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From my experience with outboards, two things to look for are does it smoke excessively even when you are absolutely sure the petroil mix is perfect, if so it needs a rebore. Secondly, a lot of 2 stroke starting problems in outboards are due to the top crankcase oil seal leaking air and hence vacuum in the crank case, the only way around this is to replace the seal. Finally, a fault I have come across several times with strimmers, chainsaws and outboards is a 'weak' magneto coil. This is an infuriating fault because it does allow you to sporadically start the motor ok, and at other times the thing dies when it is hot and wo'nt go again. If you take the plug out you will have a spark at all times, but it seems that it fails under compression.
It is my bet that the latter problem has a high probability of being your problem.
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>>If you take the plug out you will have a spark at all times, but it seems that it fails under compression.
For this reason, one of my most useful tools is a modified plug with no thread, but a croc clip to earth the body, and a modified electrode pair with a very large gap to simulate the extra load of compression on the spark.
I got mine under a Vauxhall part number, which was called up in an ancient service manual for the Senator A - I don't know if these tools are available anywhere else.
Number_Cruncher
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Try Bradex "Easy Start", available from Halfords and other motor factors.
--
L\'escargot.
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Thanks for all these replies. Looks like I shall be busy over the next few weekends. In the meantime here is a picture of it cleaned ready to be used...
tinyurl.com/s26hc
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The Nash Boadicea in all its glory:) They must have used the same recycled WW2 aluminium for the casting as my in-laws heavy-duty saucepans. They don't make them like that any more.......
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Magnificant! thank you, almost as much fun as putting 'kharman ghia' into a search on ebay! I had an old 2 stroke mower that responded to being started by pressing the rubber disc part of a black & decker sander attachment onto the top of the flywheel, winding it up to goodness how many revs with the drill and then opening the throttle (on the mower) Brutal, but it worked.
Papho
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I Know this thread's old now, but do you still have the boadicea?
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