husqvarna k750 2-stroke - lent to a friend and now it wont run : (

[the snooper]

try it again with the choke on or part on if it runs better that tells you straight away a blockage in the carb

 

[DAPPH]

Just a thought but are you sure the person you lent it to was using two stroke and if so at the right mix?

Seconded and some .

The compression should be about 18 pounds a square inch on a good pot and piston .
If you manage to get it running does it kind of hum up & down off load , does the air filter get moist with fuel ,if so and you get a low cylinder pressure of 15 psi or less it's an indication of a back pressure in the crankcase due to lots of wear in the barrel & around the piston ring or a carbon-ed up /part blocked silencer . A reading of 12 PSI or less dry usually means it is knackered due to extravagant wear .

Doing a " wet oil" compression test will see the top pressure leap up to 25 or more PSI on a good cylinder and to 18 or more on a workable worn one , if it cannot reach 15 PSu it's time for a new one

Sometimes when you take the silencer off as suggested & take the spark plug out then shine a torch in the plug hole & look though the exhaust port into the cylinder there will not be noticeable scoring of the piston or the walls of the cylinder , but the will be a noticeable area of dull coloured heavy wear instead.

If all is nice and bright do take care putting the exhaust box back for not only may you introduce rust particles into the cylinder , you may also find that the silencer is clogged up with a thick oily soot because too much oil has been used in the mix and this carbons up the silencer & also give rise to a back pressure in the carb...... Burn it out in a small hot fire fed with clean fire wood / a blow lamp or a big flame wedding torch held at a distance so you don't melt the canister, occasionally gently tapping (Not braying the bloody lights out of it ) the body of the now almost dark cherry red silencer to loosen the adhering soot deposits .. they do burn , usually with quite a bit of white smoke.

 

[julianf]

I sent them away with a can of fuel also, so it will be the same mix as ive been using - i assume!


Ive been looking, with no success, for a service document. The owners manual says things like "check the fuel filter" or "check the muffler" in its routine maintenance schedule, but gives no further information.

For example, i know the fuel filter is within the tank, but not how to get it out. Its certainly not on a tie to the filler cap or anything.

The muffler seems to have two visible bolts approaching the head, but i suspect i need to take the arm off before getting to them.

Rather than ask a load of questions here, can anyone point me to anything that i can read to see how to do all this? Or, f its a one line answer... (?)

Thank you : )

 

[jordan1]

What colour/condition is the plug?, could be an ignition problem.

 

[Wendelspanswick]

Change the plug, it only takes a couple of minutes.
See post #10

 

[julianf]

I think the manual says to check the plug first, but, of course, i have not done so yet! : )

 

[julianf]

right - a rubbish phone shot, but does this tell you anything?

(apart from the fact that i have a velcro dog)

 

[julianf]

The colour is a kind of redish brown. The plug is dry.

 

[Paul99]

Light brown / tan means the mixture is spot on - it doesn't mean that the plug isn't knackered though so might be worth replacing. Have you tried started it with the air filter off? - load it by cutting wood (to void kicking up dust) obviously don't run it without a filter for long but will be fine to rule this out completely. The fuel filter is inside the fuel tank and can be fished out with a long nose plies / forceps etc. If you're lucky there will be a long enough piece of flexible pipe inside the tank to simply tip the filter out of the filling plug.

 

[the snooper]

Another way to tell if it's ignition or fuel, with ignition problems the cut out / loss of power is instant, with fuel the power fades away which can be quick but not instant like the loss of electricity

 

[julianf]

I forgot to try with the choke.

The engine fades. If i take it off load (ie lift of the job) it would rev up again (somtime, not always), and then, when back cuting, would fade / stall again.

Would restart on the very first pull, and i could continue. But close to the end, it was getting worst and worse (as in the time it would run on load) so i gave up.

 

[julianf]

Have not tried without the air filter.

 

[dobbslc]

With the old RC car glow plug engines I used to race symptoms like that usually meant low compression!
Get a new plug first then if it still won't work try some new fuel, then I would have the carb off for a good clean with carb cleaner NOT brake fluid as its not good for some of the rubber seals. Blow it through with an air line as well?

 

[norlander]

(apart from the fact that i have a velcro dog)

can't see the piug too well, but your dog is running rich and fouling.

I just had same thing with me chainsaw,muppet had been pulling it over with the kill switch on.Tried all the usual stuff- I had to sort it by taking the plug out, gentle compressed air thu plughole, left overnight with plug out. Runs fine now.

 

[jordan1]

I had an Homelite chainsaw with started ok the misfired badly before cutting out, turned out to be the ignition pick up coil.

 

[normspanners]

rough check of Compression on chain saws etc if you can pick the saw up,by the cord without the starter cord pulling out, comp should be good enough to start it.
sounds to me like it needs carb kit they work by pumping the fuel into the carb with diaphragm worked by crankcase pressure. if that is holed they can have those syptoms

 

[jordan1]

Could also be a worn crankcase seal, losing the pressure.

 

[ronan]

I hope you learned your lesson, lending tools or whatever always ends badly.

 

[julianf]

Its the same chap i lent my compressor to...

Thing is, i dont actually think he is killing them. But its not great all the same.

 

[the snooper]

Its the same chap i lent my compressor to...

Thing is, i dont actually think he is killing them. But its not great all the same.

was the compressor dead aswell