ChrisW
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| posted on 27/5/15 at 07:20 PM |
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2-stroke experts? No power from engine
Sorry for a second "won't go" post in a week. Hoping there are some people who know a bit about 2-stroke engines.
Engine is in a goped aka scooter with an engine. It's the standard 'strimmer' type, 35cc I guess, with a centrifugal clutch and
reduction gearbox.
It starts up and runs fine, will rev up and spin the rear wheel, but as soon as any load is on it it dies. At first I thought it was a mixture issue
but try as I might I can't get it to produce any power.
Is this a sign that the engine is knackered? eg not holding compression or something like that? Or should I think about changing the carb perhaps?
My gaff my rules
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madteg
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| posted on 27/5/15 at 07:34 PM |
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Could be exhaust blocked with carbon. I used to have to clean exhaust out with caustic soda now and again, You could try it with exhaust of just to
check.
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ChrisW
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| posted on 27/5/15 at 07:42 PM |
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Worth a shot I guess! Thanks.
Any other suggestions?
Chris
My gaff my rules
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coozer
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| posted on 27/5/15 at 07:58 PM |
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Piston rings or head gasket. My 100cc was the same, start, rev but no power..
New piston and head gasket and ring ring off we go..
1972 V8 Jago
1980 Z750
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alfiebeard
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| posted on 27/5/15 at 08:23 PM |
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Stale Fuel or possibly crankcase full of fuel or crankshaft oil seals dried out (if its stood a while)
Alfie
[Edited on 27/5/15 by alfiebeard]
Old bloke on a mission with 320BHP of help
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ChrisW
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| posted on 27/5/15 at 08:41 PM |
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Thanks everyone.
Exhaust isn't the issue. It's just as gutless without the exhaust and also upsets my neighbours! 
Stale fuel is out - I replaced the fuel tank and put fresh fuel in it
Rings, gasket, oil seals etc, yeah could be. I've no idea of this thing's history.
Just been out and tried fiddling with the mixture again. It's better, turns out I had it far too lean before, but it's still hit and
miss. One minute it will go (quite well actually) but the next it just bogs and dies when you put load on it.
I take it a weak spark couldn't be the cause? I had to take the coil (with integrated magneto) and flywheel off to drill out the fuel tank
mounts that the previous owner had snapped off. I only guessed what the gap should be between the flywheel magnet and the coil.
Chris
My gaff my rules
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alfiebeard
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| posted on 27/5/15 at 09:46 PM |
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The Gap between the coil and the flywheel could cause rough running what I usually do is get the coil as close as possible without touching the
flywheel then if it runs well leave it there if not move it in 10 thou increments until it runs best. if its too far away from the flywheel it will
effectively alter the ignition timing by a small degree or two. also just another thought it has got an air filter of some description on hasn't
it? if not the mixture at high revs will be too lean.
Alfie
Old bloke on a mission with 320BHP of help
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Oddified
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| posted on 28/5/15 at 08:03 AM |
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Set the coil-flywheel gap to 0.4mm, any closer and the flywheel will rub the coil at high rpm. Check the in tank pick up, quite often they get blocked
up restricting fuel flow (not cleanable, fit a new one). Check the clutch, if the spring is very week or broken then it will bog/be flat.
Could also be a tired piston ring as mentioned above but from your description it's less likely than one of those.
Ian
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Mr Whippy
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| posted on 28/5/15 at 11:22 AM |
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If it runs well but then suddenly losses power it's most likely a blocked jet causing a weak mixture when you try to accelerate. Compression
issues don’t come and go and neither do ignition ones unless something’s falling off.
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coyoteboy
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| posted on 28/5/15 at 12:17 PM |
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Lean mixtures are hard to ignite, if the mixture is leaning out it could be showing up a weak spark.
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ChrisW
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| posted on 28/5/15 at 03:32 PM |
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Thanks guys. I'll give the carb a good clean out tonight and see if that makes any difference.
Chris
My gaff my rules
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ChrisW
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| posted on 31/5/15 at 10:15 PM |
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Ok, I think I sussed it.... I had the carb on back to front. I think that's it anyway - it seemed a lot better with it turned around the other
way but was getting a bit late to test it properly.
Will report again tomorrow.
Chris
My gaff my rules
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