2 stroke petrol breaker trouble again...

[marky2222]

Hi guys for any one that's been on here awhile you will
Probley remember me posting a question about this tool
Awhile ago any way I got it out again today to have another fiddle
But till cant get it running good

What I have is a atlas cobra 148 2 stroke petrol breaker with a tillotson carb
I never been able to get it running really

i have striped down the carb and replace parts with a carb repair kit months ago when I last attempted to fix it but still couldn't
get it running constant
any way today I have read up more about the jet screws and had a play with them and got it running after around 6/7 pulls but only on full throttle when I let the throttle off it dies I have moved the idle screw and the high speed screw but nothing it just keep dieing when you let the throttle off
Then sometimes it wont even go with full throttle any suggestions

Thanks alot

 

[the snooper]

i suppose it still could be the carb, if it were me id strip it down check the rings and pistion were good and the crank seals also the cylinder and any other obvious parts where there could be an air leak, slower speeds can be badly affected by air leaks

 

[Justme]

Sounds like the idle jet is blocked or idle mixture setting is out.

 

[the snooper]

Sounds like the idle jet is blocked or idle mixture setting is out.

the op said it will only run at full throttle

so not the idle jet

 

[shenion]

the op said it will only run at full throttle

so not the idle jet

If the idle jet is plugged, then it will only run at full throttle.

Could be idle jet passages are clogged or a vacuum leak somewhere. A vacuum leak will effect idle much more.

 

[the snooper]

what about half throttle and so on ?

 

[jonjoe]

only 3 things can go wrong with 2 strokes carb, spark plug/coil and piston/rings/cylinder. clean the carb make sure all the gaskets are put in correctly and the spark plug is clean and coil is not damaged dont thing it would be a worn cylinder.

 

[the snooper]

only 3 things can go wrong with 2 strokes .

1 carb
2 spark plug
3 coil
4 piston
5 rings
6 cylinder



dont forget crank seals / crank case air leak they cause lack of fuel

 

[octo0072000]

only 3 things can go wrong with 2 strokes carb, spark plug/coil and piston/rings/cylinder. clean the carb make sure all the gaskets are put in correctly and the spark plug is clean and coil is not damaged dont thing it would be a worn cylinder.

you forgot about crankcase seals a major problem of bad starting

 

[Lawnmowerboy]

7.Crank seals
8.Crankcase vacuum
9.Reed valves, If it has them
compression

 

[brightspark]

dont 4 get an oiled up silencer

 

[CRB]

No one has mentioned mucky fuel either.

Two strokes are really simple, until you cannot find the problem.

 

[marky2222]

Hello guys thanks for all responces

i also should of said that when i took the bottom half off i pulled the bottom piston out by mistake which came right out of the crank case there was 1 one big ring and then 3 smaller rings on the piston itself i tryed for about 1 hour to get the piston back in but because its like flanged i couldent get my fingers in to compress the rings to slide them back in the pot so i squeezed them so they wouldnt be as springy and then slid them up the pot not enough though so they were to loose to seal . but i do have abit of oily smear on the bottom half of the pot also i didnt now that each of the 3 piston rings were diffrent and had to go in the bore in the piston they came from i took all 3 off but not sure if i put them back in the same order . but even before a fiddled with all this it still wouldent start / also to answer a question it runs at full throttle and right on down but just wont idle but also sometimes wont start even on full throttle and really i havent a clue what im doing with the 2 jet screws i have read about seting them at 2 and a half turns out but nothing really seems to work.......

 

[jonjoe]

okay then maybe i forgot some things we had a saw wouldn't start damaged coil new coil and away it went.

 

[Lawnmowerboy]

With the mixture adjusting screws you really need a rough start point like say 2 turns ect. then with the engine running flat out on that setting you turn it one way if ti makes it worse turn the other untill its running at maximum revvs and then richen the mixture a little bit to compensate for load say 1/8th a turn.

what so you are saying you bent the rings a bit to get them back in the bore OH JESUS. 2 strokes rely on compression and seal to create the vacuum to suck the fuel in

If it's lacking in compression that could be a problem, if the cylinder isn't all cast into one and has a removeable head then what is the head gasket seal like. also the cylinder to crankcase seal needs to be perfect.

it could have a punctured carb diaphragm so it is running far too rich.

 

[marky2222]

cheers for responce guys when i next break it down i will take some pictures then you can have a better look at what im dealing with one thing i did find is when i fitted the bottom piston back in the bore it was very hard pull until i removed the spark plug then it went easy then then back hard with the plug back in but now that dosent happen it pulls easy runs at full throttle (sometimes) but wont idle also a question to ask out of the top of the carb what should the fuel look like at full thorttle should it be a gas mix or pure dripping fuel also with it being a vibrating breaker it makes it hard to ajust the carb when running as its shaking all over!!

 

[the snooper]

you shouldnt see fuel in liquid form

 

[the snooper]

Hello guys thanks for all responces

so i squeezed them so they wouldnt be as springy and then slid them up the pot

do you mean you took the rings off and squeezed them toghether so they would go back in the cylinder easier ? if so you have damaged them and it may not run correctly again, they will not be a perfect circle anymore

 

[pedrobedro]

What were the rings made of ? Rings are supposed to spring back out when you squeeze them into the cylinder, cast ones will break if you try to stretch them or compress them too far. The piston will hold them in shape. More modern steel wire rings are flexible almost enough to tie them in knots without breaking them and they spring back into shape. Did you line the rings up on their pins, 2 stroke have them to stop the rings turning and going into the ports.