Thanks.
Not changed the plug. Checked and monitored the spark, it's good, tank filter s clean and blows through lovely, the breather I Think was too restricted, but 30 seconds running, on a half tank? Sounds too short to be tank vacuum?
- Thread starter minimutly
- Start date
Not changed the plug. Checked and monitored the spark, it's good, tank filter s clean and blows through lovely, the breather I Think was too restricted, but 30 seconds running, on a half tank? Sounds too short to be tank vacuum?
I think I will rebuild it, try it and if it isn't good those are my next steps. Also temp remove the breather tube.
What sort of vacuum, for how long? And how do you seal the bore?
Sorry for the dopey questions, 2 strokes are a black art to me.
I mucked around with an old b&s engine the other day. It wouldn't start. I checked for a spark looking at the plug that was in it. None. I thought 'oh, dirty points or stuck crank plunger'. I pulled the flywheel, got to the points. Clean as a whistle and plunger was fine. Bemused I put the flywheel back on, tried another spark plug from something else and it sparked. Cleaned the old plug and it fired straight up. Must has spent 2 hours fart8ng about and a quick wire brush on the plug would have done.
Smallfry
HE's Spartacus.
- Messages
- 2,791
- Location
- Kent UK
I have a Honda lawnmower that would start first time, as Hondas generally do. Run for about a minute, then stop. New plug cured it. Tried old plug in another machine, and it stopped.
The pickup filter is always a favourite for this too. Once it has started, try loosening the fuel cap, with the cap pointing upwards, this will confirm tank vacuum, athough as you say 30 seconds is not very long. On the other hand, with a full tank and high revs, it wouldn't take much.
Well I rebuilt it, nice and clean and shiny. Squirted some carb cleaner into it and away it went. So I had the air cleaner off and wanted to see if the fuel stopped coming out of the jets - well it did, and the thing stopped just like before. I wanted to check again, this time it kept running - so I did some jet tweeking, and boogad me, it cleared up nicely.
So what was wrong with it? I'm not sure...
So what was wrong with it? I'm not sure...
pedrobedro
Man at Matalan
- Messages
- 13,108
- Location
- CX near Chesterfield
My MS460 had this, it would tick over for a while them cut out and the fuel line looked good but I swapped it anyway and it cured it.
It is old. But in very good mechanical condition. What you've pointed out fits the symptoms exactly, and although I checked both lines out, maybe not a bad idea to order one of each...
Spent an hour with the bar clamp chain sharpener last night, and whilst one or two teeth didn't quite clean up, it's mostly as sharp as a sharp thing, so will do some test cutting later.
The minute main and pilot jets block so easily, often just due to stale fuel.
Ultrasonic cleaners are not always a reliable solution as you can’t guarantee that the cleaning solution is in contact with the blockage.
Strip the carb down and clean the float valve, main jet, emulsion tube etc with carb cleaner to confirm that they are all clear of varnish.
Also squirt carb cleaner through the pilot airways to ensure they are clear.
Glad to see you’ve got the saw running.
Ultrasonic cleaners are not always a reliable solution as you can’t guarantee that the cleaning solution is in contact with the blockage.
Strip the carb down and clean the float valve, main jet, emulsion tube etc with carb cleaner to confirm that they are all clear of varnish.
Also squirt carb cleaner through the pilot airways to ensure they are clear.
Glad to see you’ve got the saw running.
Norsk
Member
- Messages
- 878
- Location
- Norway
The mechanics are one thing,rubber full of fuel for 30 years quite another.
I would change out the fuel lines flush the tank and put a new carb on it. Fiddling around with carb kits on most saws just isn't worth it. Sometimes the ht lead can also go bad,bit since it starts your likely ok. The magnetic pickup can also just expire in some old saws,once it warms up it won't generate lekky any longer
DAPPH
as dyslexik as I'm daft
- Messages
- 7,329
- Location
- Near to Cross Hands Llanelli SouthWales GB
IIRC ... ( I'm getting old and absent minded )No bulb, not sure how you are meant to prime it
I checked the spark before stripping it, it's good.
I wondered about crank seals from the beginning - no idea how to check them though?
It runs for 30 seconds or so, then just dies
With the air filter removed .......... as soon as it runs , rev it high if possible then as it peaks immediately pop a piece of pre-shaped to size hardboard.... smooth face to the carb ,,,,over the air intake till the machine dies .
Repeat this several times, each time remove the spark plug , it to heat dry it off . This should drag any crap / slime etc. through the jets , drillings , reed valves or the needle valve seat areas in the carb.
Do check the integrity of the fuel lift line and the viability of the fuel filter on the end inside the fuel tank often a micro crack in the fuel lift tube where it goes into the tank or casings or connects to the carb will show up as a similar no run problem as the amount of air drawn in increases . I have found slime in the fuel line several times ( dirty fuel cans and no fine water catching filter funnel being used when refilling the fuel tanks as well as no end of dirty needing replacement fuel filter ends and one way end /valve filters on the fuel lift line when too much oil or the incorrect one has been used in the 2 stroke mix and the petrol, The petrol has evaporated out the mix over the time of the machine not being in use for months thus leaving a thick syrupy sludge in the fine passages & drillings of the chainsaw & fuel filter .
Plant matter such as tree sap or resins in sawdust in the fuel container or fuel tank can also lead to a snotty blocking sludge so a good inspection and a clean out is always sensible during repairs & properly clean the fuel filler cap and if there is one the air vent in the cap or an air vent elsewhere /
Crank case compression usually shows as a micro mist blow back at the carb or as a dam darkened soiled with more dust than usual place on the air filter and a warbling engine noise when on full bore some times leading to over wetting the spark plug and killing the engine .
Have you checked the free flow of exhaust gasses from the silencer .. if it looks black & oily on the inside of the outlet hole ( too much oil in the fuel mix or the incorrect grade oil ) carefully and gently remove the silencer don't shear the bolts or studs securing it . Now use a blow lamp to get it red hot to burn out the accumulated carbon & oil inside ( lots of heating's an d gentle tapping on a wooden block as it cools will see the heating and tapping remove a lot of crud .
I often washed the treated carbs out with plain hot water afterwards then compressed air dried them out internally .
Wrecked or well worn crank seals should show up on a wet & dry compression test . If you don't have a suitable tester use an old spark plug carefully remove the guts and earth electrode & braze in a brass tyre neck off a lorry tyre innertube braze a threaded collar on the place where the Schrader valve used to be and use a screw in compression tester on a flexible hose .to connect up and leave your hands free to do other things .
Write down the reading figures for wet and dry , pulling over several times and watch how quick the crank pressure flickers when the piston is ported to the crank.
You can also pressurise the crankcase from this spark plug adaptor and watch how quick it discharges .
DAPPH
as dyslexik as I'm daft
- Messages
- 7,329
- Location
- Near to Cross Hands Llanelli SouthWales GB
Had a FFR Landrover on critical work that had run out of fuel at 16.30 hrs. Radio operator teams problem , before mine ... Finding it would not restart on refilling both petrol tanks they sent for me the flying fitter .
I got there at around 22 .00 hrs had to steal a battery off a truck , as they'd flattened all of them .
Drained the fuel lines , tank change over tap , carb filter bowl & fuel pump . Two tank FFR Landrovers are prone to getting a few inches of water in the bottom of the fuel tanks on such duties .
Would it start ..... .would it *%$K.
The CO. is going spare & hairless as the FFR radio had to close down the radio station due to not having a radio battery charging facility , so putting people at risk .
Tried the spark plugs , they sparked , put them back in nothing . Checked the points gap incase the back fires had caused them to close up a bit & checked the capacitor .." Yep all OK " . Put in a new set of plugs. nothing . removed them all put both sets in my pocket combat jacket pocket inside my overalls to keep them safe & dry where I could easily find them in the dark .
On turning the now plug-less engine over . I saw a fine misting of water caught in the beam of my torch being sprayed out the plug holes as the engine was turning over .
Waaagh or
something like that , it's now almost 01.00 hrs turned the engine over for 20 or so seconds on yet another charged battery and water was still coming out the spark plug holes . OMG , check the radiator ..it's OKOAF-HOOK I have to remove the inlet manifold , sure enough water cascaded out the dam thing . I got it reasonably dry and reassembled , took the old spark plugs to the cook house where I got a bacon & egg banjo & a mug of tea as they toasted the spark plugs on a No 2 petrol burner for me , carrying them in a cardboard box as I dashed to the Landy & then fitted them still &&%&$ hot as hell in the engine .
Four turns of the engine and the dam thing fired up .
So a daunting very tired trip back to base 14 miles or so away was the new order for me , to be greeted with on arriving dead dog tired " Hello Dave , glad to see you're back , you're on sentry duty in 14 minutes " .
The tragic thing is the corporal on the radio watch when it ran out of in both fuel tanks got promoted to sergeant a few weeks later .The commissioned officer also doing the radio operators previous 6 hrs. watch earlier escaped without recourse to his stupidity for not filling the Landy up in both tanks at the end of his radio watch .
