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Andy no gooder

Original Poster:

367 posts

51 months

[news] 
Monday 14th June 2010 quote quote all
Hi,

I am having some really frustrating problems with a spear and jackson sjbc 30 petrol strimmer and brush cutter.

I shall jump to the knit and grit. Last year i started the strimmer with old/stale petrol and oil mix. After i learned of my mistake i drained the tank and stored it away untill now. The strimmer starts then slowly dies i can prolong it by revving but it will eventually die out. I have fresh petrol/oil mix cleaned spark plug. Helppppp.

Thank you.

ndtman

371 posts

66 months

[news] 
Monday 14th June 2010 quote quote all
I have a strimmer and a brushcutter, both two stroke. The moment it starts I open the choke or it just dies. Check your choke if off/open once started.

Flintstone

8,644 posts

132 months

[news] 
Monday 14th June 2010 quote quote all
Idle screw?

That's not an offer by the way.

Simpo Two

59,618 posts

150 months

[news] 
Monday 14th June 2010 quote quote all
All the people advocating petrol strimmers on another thread seem to be keeping their heads down hehe

julian64

10,425 posts

139 months

[news] 
Monday 14th June 2010 quote quote all
Difficult one because very small two stroke engine manufacturers tend to cut various corners in, let say, the quality of design.

Old gammy petrol tends to form a resin which blocks jets, interfers with the needle valve operation in the float chamber etc.

Unfortunately the whole lot needs to come apart.
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Busamav

2,954 posts

93 months

[news] 
Monday 14th June 2010 quote quote all
Simpo Two said:
All the people advocating petrol strimmers on another thread seem to be keeping their heads down hehe
biggrin

Have you checked the air filter ?

Most problems with these little motors will be down to old fuel or crud in the fuel.

I put all fuel through a filtered funnel for my garden machinery

netherfield

1,300 posts

69 months

[news] 
Monday 14th June 2010 quote quote all
Throw it away and buy a 'Stihl'

Matt Harper

3,553 posts

86 months

[news] 
Monday 14th June 2010 quote quote all
julian64 said:
Difficult one because very small two stroke engine manufacturers tend to cut various corners in, let say, the quality of design.

Old gammy petrol tends to form a resin which blocks jets, interfers with the needle valve operation in the float chamber etc.

Unfortunately the whole lot needs to come apart.
This is correct - but cleaning some of the minute carb parts and getting all of the hard deposits off the jet/needle assy is pretty much impossible. You need a whole new carb assembly, which should cost no more than 30 quid.
Even with fuel stanbaliser added, the fuel/oil composition is highly susceptible to 'gumming', so if you use the machine infrequently and although it's a pain, you really should drain the fuel out of it.

dilbert

7,738 posts

116 months

[news] 
Monday 14th June 2010 quote quote all
Matt Harper said:
julian64 said:
Difficult one because very small two stroke engine manufacturers tend to cut various corners in, let say, the quality of design.

Old gammy petrol tends to form a resin which blocks jets, interfers with the needle valve operation in the float chamber etc.

Unfortunately the whole lot needs to come apart.
This is correct - but cleaning some of the minute carb parts and getting all of the hard deposits off the jet/needle assy is pretty much impossible. You need a whole new carb assembly, which should cost no more than 30 quid.
Even with fuel stanbaliser added, the fuel/oil composition is highly susceptible to 'gumming', so if you use the machine infrequently and although it's a pain, you really should drain the fuel out of it.
More than that. If you can you should never cut the engine when you've finished. Turn the fuel off at the tank, and let the engine empty the carb out.

If the float bowl has a drain on it, use that after the engine has stopped, just to be sure.

Edited by dilbert on Monday 14th June 16:34

Andy no gooder

Original Poster:

367 posts

51 months

[news] 
Monday 14th June 2010 quote quote all
I have checked the idle screw, air filter, choke. Im begining to think its more of a internal engine problem. I have took the carb off and gave it a once over did not go into it to much tho.

I will just have to keep fiddling with it i dont really want to just bin it because its only 2 year old with about 15-20 hours running time if that.

The other half is not to impressed as we seem to have our very own beanstalk growing and the garden needs a good goin over. I should just pave the whole lot and be done with grass cutting tools. lol

Thank you for your replies.

Silent1

18,962 posts

120 months

[news] 
Monday 14th June 2010 quote quote all
Can you tickle the throttle to get the revs up? It could well be oil in the carb and once it's warm it'll pull it through and sort itself out.

julian64

10,425 posts

139 months

[news] 
Monday 14th June 2010 quote quote all
on the subject of the gum, these small cheap bubble tanks people buy for cleaning rings etc are very good on removing the gummed up bits.

Matt Harper

3,553 posts

86 months

[news] 
Monday 14th June 2010 quote quote all
dilbert said:
More than that. If you can you should never cut the engine when you've finished. Turn the fuel off at the tank, and let the engine empty the carb out.

If the float bowl has a drain on it, use that after the engine has stopped, just to be sure.

Edited by dilbert on Monday 14th June 16:34
I don't think it will have a float bowl. All the 'carb' consists of is a venturi shaped metal tube with a jet and needle built into it.
Weed-whackers are designed to be inverted/operate at different angles, so a conventional carb (which needs to remain moderately upright) wouldn't work on these machines.


Wings

4,466 posts

100 months

[news] 
Monday 14th June 2010 quote quote all
The first thing I would try on any non starting petrol garden machinery, would be to drain off the fuel from the tank, and replace with fresh, new fuel.

Then to help the machinery to start, remove spark plug and pour a drop of petrol down spark plug hole, replace plug and try starting the strimmer.

If that fails then take the spark plug out, and just give the same a clean, checking the gap, which should be 25 thou., then repeat the above.

For future reference you might like to download the following link;

http://finance.groups.yahoo.com/group/milling/mess...

koolchris99

7,351 posts

64 months

[news] 
Monday 14th June 2010 quote quote all
my 2 strokes on the blower, strimmer, chainsaw and all the other gubbings always stall the first few times you start them, just give it some serious revs and it blows out all the crap and works fine after that..

although this afternoon i snapped the chain on the chainsaw so will have a fun evening repairing st.

Silver993tt

8,534 posts

124 months

[news] 
Monday 14th June 2010 quote quote all
It's a classic sign of 'varnish' in the carb. It needs to be stripped down and then all the jets/bowl etc left to soak in carb cleaner overnight.

Wacky Racer

22,138 posts

132 months

[news] 
Monday 14th June 2010 quote quote all
Almost certainly blocked neoprene fuel pipe or carb jets, two stroke fuel is notorious for "gumming up" after a few months.

Change the fuel, fit a brand new spark plug, and if it still won't start therin lies your problem.....biggrin

Always always drain all the old fuel out in autumn, (before winter storage), and empty the float chamber..(if possible)

Andy no gooder

Original Poster:

367 posts

51 months

[news] 
Wednesday 16th June 2010 quote quote all
Ok people i have been messing around with this today i cleaned the spark plug put it back in started it up kept it alive for around 45-60 seconds. I pulled the spark plug back out and it was black again.

The piston seems to be like a black sooty type colour could this be the problem?

convert

3,134 posts

103 months

[news] 
Wednesday 16th June 2010 quote quote all
Sounds like it's running too rich. Check the operation of the choke.

Edited by convert on Wednesday 16th June 12:49

Silver993tt

8,534 posts

124 months

[news] 
Wednesday 16th June 2010 quote quote all
Andy no gooder said:
Ok people i have been messing around with this today i cleaned the spark plug put it back in started it up kept it alive for around 45-60 seconds. I pulled the spark plug back out and it was black again.

The piston seems to be like a black sooty type colour could this be the problem?
could also be too much oil in the mixture.
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