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Old 3rd June 2018, 15:10   #11
RPWC
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Originally Posted by mss View Post
A new spark plug, or at least a clean one that fires, is a good idea Rich. However, I would say it is 90% likely to be the carb.

Modern petrol turns into a gel and then crystalises, blocking the fine orifices in the Walbro/Zama type carbs. Also, Chinese diaphragms harden relatively quickly unlike the original Japanese ones - they use poor quality rubber. I would strip it down completely, remove all the gaskets, diaphragm, mesh filter screen etc. and blast all the orifices with carb cleaner.

Then rebuild with a new diaphragm kit.

It's a simple job provided one marks all the components to indicate positioning/orientation and preferably takes photographs during disassembly.

There are lots of good "how to" guides on Youtube.

https://www.youtube.com/watch?v=cDaOcNrS6BM

https://www.youtube.com/watch?v=EKXwoP9Pa1U
Thanks for the links Maninder, but I’m not going to try it myself, cleaned the fuel,pipes from tank to primer button, and from primer to carb. The bloke who services and repairs the barden machinery stuff, will replace the plug anyway, so no point in me doing it.

PS the air filter is just a bit of sponge. The maxhine itself only cost me £90 brand new,its a Titan, and I have had it about 3/4 years, so if a service and repair costs me £50/60 quid, its not alot , and cheaper than renewing it.
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Old 11th June 2018, 16:07   #12
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Default 2 stroke engines

My 2 stroke Mc'culloch strimmer has a muffler in the exhaust that gets blocked with oil from time to time. This manifests itself as a reluctance to rev first of all and then finally a reluctance to start. The muffler is a very small sheet of wire gauze and I clean it by soaking it in petrol overnight and then scrubbing it with a toothbrush and prodding the tiny holes with a cocktail stick.
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Old 12th June 2018, 07:15   #13
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My 2 stroke Mc'culloch strimmer has a muffler in the exhaust that gets blocked with oil from time to time. This manifests itself as a reluctance to rev first of all and then finally a reluctance to start. The muffler is a very small sheet of wire gauze and I clean it by soaking it in petrol overnight and then scrubbing it with a toothbrush and prodding the tiny holes with a cocktail stick.

That has never happened to me in 20+ years of using such machines. I would ensure that semi-synthetic 2-stroke oil is being used at the correct ratio - say around 40:1.
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Old 12th June 2018, 20:50   #14
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Hi try running on aspen 4 it lasts for up to 5 years and wont gum up your carb, about £32 for 5 litres though, get it on internet dont forget to mix your oil with it though . regards john
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Old 14th June 2018, 06:11   #15
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The biggest problem is that today's fuel, I will call it fuel, as it's no longer petrol, is designed for fuel injection systems. It wrecks havoc on carbs, piping, metal petrol tanks. Because the fuel is designed for injection in a sealed system you will find that in an un-sealed carburettor system it will evaporate at an alarming rate. It will turn your brass jets black or sometimes green. And it will leave tons of residue in your carburettor when it evaporates, which causes even more problems with blocked jets and passageways cast into your carburettor.

Rant over!

My guess is your carb needs a good clean out because it's full of NAUGHTY WORD-NAUGHTY WORD-NAUGHTY WORD-NAUGHTY WORD- from evaporated ethanol.
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Old 16th June 2018, 10:08   #16
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Ahh two strokes. Best engine in the world so long as you don’t want to many revs.First I would check the air filter. Second the spark plug. Third if the others are ok and you have nice blue spark across the plug points,check the carb by taking it to bits, there is not much to take to bits. My son went on holiday and I thought I would give his lawn a cut. Grass cutter would not start. Plug was ok,good spark, plenty of fuel. Looked at the filter and could see it was a bit? Dirty. Changed it, and away it went. I always start at the cheap end first because I am a tight wad. On the other hand,my m/cycle would not start, BSA Bantam 150, tuned. Tried everything but could only get a very weak spark. Puddled it down-to electrics. Decided it must be the coil. When checking the coil, it was apparent that the insulation was discoloured, burnt. On stripping the insulation of, you could see where the wire had broken, and the spark had been happening there rather than the plug. Got new coil, and everything was back to normal. . .
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Old 16th June 2018, 13:32   #17
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I think the ethanol added to petrol is what causes the problems. Usually buried in the depths of the manual, is a line about not using ethanol-blended fuels.


The ethanol is hygroscopic, and the absorbed water wreaks havoc in the tiny drillings in a small engine carb.


Having replaced the carb on our old strimmer twice, I bit the bullet and bought a 4-stroke machine...
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Old 16th June 2018, 15:43   #18
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.................


Having replaced the carb on our old strimmer twice, I bit the bullet and bought a 4-stroke machine...

Why do you believe that will help?

Carbs on 4-stroke small engines (strimmers, blowers etc.) are the same as those on 2 stokes except for the little spring behind the diaphragm to compensate for the lack of a strong pressure pulse.
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