Stihl ms 230

[mick irwin]

hi all,

i have a stihl ms 230 which will not rev high, when the throttle is touched it just cuts out, if you slightly touch the throttle sometimes it will rev as if the chainbrake is on and it cant quite turn the chain even tho the chain spins freely, it will tune and it sometimes spins the chain on tickover until you tune it to stall so i think the carb is fine? also some times it will start and rev, maybe once out of 30 - 40 starts and it only does this once but mostly it will cut out, the ignition module is fine, new sparkplug,cleaned the fuel filter and gave it fresh fuel, i did check the cylinder but i am no mechanic so im not sure, there were no scores or scratches inside the head itself so again i presume this is fine? can anybody help me identify what the problem could be or what i could try next? the saw is only a few years old and to begin with was only used for carving (i am a real novice) now tree surgery is my job i tried to use it quite a lot but again i am no mechanic so i would relly appreciate some help guys, thanks mick

[spudulike]

Typical problems are Carb internal gauze filter clogged, bad fuel line, dirty fuel filter, blocked fuel tank breather, too rich on the H screw, very low compression, carbon clogged exhaust port, air leak in the inlet manifold/crank seals/impulse line!

[JAMIE1]

Impulse hose not connected pretty mush describes these symptoms.

[morten]

Typical problems are Carb internal gauze filter clogged, bad fuel line, dirty fuel filter, blocked fuel tank breather, too rich on the H screw, very low compression, carbon clogged exhaust port, air leak in the inlet manifold/crank seals/impulse line!

 

Whatever the cause of the problem is, it sounds like it is not getting any/enough fuel. So look at the fuel supply path. Unlikely to be the breather valve, as it would run ok for a while until a vacuum is built up in the fuel tank

[mick irwin]

thanks for the replys everyone, cheers jamie1, what is an impulse line? and where do i find that? cheers spudulike ive heard your the man on here with saws, how do i check the carb filters? is it the top and bottom i unscrew? or is there more inside? and ill check the fuel lines again,

[spudulike]

I've had a couple of saws with blocked tank breathers stop the saw revving from the outset, one stopped the saw even starting!

 

Impulse line - a small rubber pipe or internal to the manifold and carb that uses the positive and negative pressure of the crankcase to power a pump within the carb body. Stihl Part 1123 141 8600

 

The gauze filter is to be found under the carb cover held on with one large screw - opposite end of the diaphragm side - it is to be found under the pumping membrane and is around 8mm in diameter.

Edited August 4, 2012 by spudulike

[mick irwin]

got it!! :thumbup1: i started it and blipped the throttle until it started to struggle, when it was about to die i turned it on its side and opened the fuel cap and hey presto away she went, bugger me i cant believe thats what it was, thanks spudulike mate, can get a new tank filler for about £6 delivered so is it worth cleaning the btreather on this one? i did have a look but not sure how do you clean the caps?

[spudulike]

got it!! :thumbup1: i started it and blipped the throttle until it started to struggle, when it was about to die i turned it on its side and opened the fuel cap and hey presto away she went, bugger me i cant believe thats what it was, thanks spudulike mate, can get a new tank filler for about £6 delivered so is it worth cleaning the btreather on this one? i did have a look but not sure how do you clean the caps?

 

First of all - sorry Morten, I just say as I find and have had similar problems to this and it was a blocked breather - don't mean to be a smart arse - I have just seen a lot - manly hug:thumbup1:

 

Glad the issue is found, the breather is a push in tube with one of those small grubscrews in it, I usually screw out the grubscrew - sometimes a couple are fitted, clean the tube and the grubscrew and then push it in to place rather than screwing it and then suck on the thing to make sure air will pass through it - if all is good then refit and try.

 

What caps are you talking about, the breather is a tube sticking out of the top of the fuel tank just above the filler cap - you will need to remove the air filter cover to see it!

 

Nice bit of fault finding and a simple way of determining tank breather issues - my nemesis was a Jonsered 630 - got it sorted in the end!

[morten]

First of all - sorry Morten, I just say as I find and have had similar problems to this and it was a blocked breather - don't mean to be a smart arse - I have just seen a lot - manly hug:thumbup1:

 

I stand corrected, and am living proof, that you learn as long as you live. I just still don't see how vacuum can build in the fuel tank immediately when starting, but I now know that it apparently does happen.

[spudulike]

I stand corrected, and am living proof, that you learn as long as you live. I just still don't see how vacuum can build in the fuel tank immediately when starting, but I now know that it apparently does happen.

 

I can only speak from my own experience where the saw would rev out for the first three or so blips and would then get progressively worse and cutting would kill it on power, so you are sort of right and never rule out the tank breather - most are well hidden and get filled with oil/fuel and dust!

 

I also had a Sachs Dolmar 100 that just wouldn't start at all until the fuel cap was loosened - that used a coarse self tapper as a breather so I ground a flat on it and that sorted it!

 

Anyway - problem well on the way to be sorted:thumbup:

 

All good:biggrin: