Stihl 024 air leak

[ihatesaws]

The company seems to be reputable. I got the cylinder kit off them as well. On the main body of the carb it says WT-194A so I assume it is a walbro carb. The only other carbs I have are the two 22B's. I already saw one of them leaking loads of air out of the throttle shaft and I wasn't able to pressurize the crankcase any easier with it than with the 194A.I'm sure that if I put on the two steel plates and dip it in the bucket it will be a similar story. The other one I think I damaged by firing compressed air into the holes on the metering side of the carb. I don't have an ultrasonic cleaner. Am I right in thinking they are expensive? Anyway I suppose I could put that one back together if it still has all the pieces so I could test how its throttle valve shaft behaves.

 

When I first got the WT-194A I tried it on the 024S as well and although the idle rpm increased a bit as well it didn't seem to be as bad but it was a while back and I don't remember too well. Maybe these saws in general just don't have a very stable idle. You must have alot more experience of them than me though.

 

I doubt I can get a replacement from Sägenspezi for the carb given the amount of steel I've ground off the back and front of the carb at the collar screw holes due to my overtightening. All that messing around with the M5 nuts and the carb boot - a big waste of time I've no confidence anymore that a new 194A would be any better anyway

[spudulike]

I have to say, the 024 can be a little sod, sold one to a local guy, seemed OK but it came back with an unstable idle. Rebuilt the carb with a new kit, cleaned it in the US cleaner and it seemed OK but it came back again so I put another secondhand carb on it and it was fine:confused1:

 

Rebuilt another 024, tried the same troublesome carb and it was perfect on the saw, got it hot, tached it, all good - hope it stays that way as the guy next door but one has it but it seemed very stable and dialed in to good idle and revving straight away????

 

Your saw is a bit weird, perhaps there is some other factor and we are missing it - I said before that one of my troubles was the carb impulse connector not making good contact with the impulse hose but we have rulled that out.

 

It may be worth rebuilding the carb - set the metering arm so it is level with the carb body or it may have a raised lip around the metering arm - use this if it does!

Set the saw to 3/4 turn out on each screw - I have had frouble with blowback of fuel on to the air filter if set richer - we will set it up later!

 

Start the saw up and turn the L screw out until the saw revs drop, turn back in until they peak and start to drop, undo until the saw drops in idle speed again and the engine note sounds sort of poppy, then set the H screw so the saw revs out and try it again.

 

It is possible you set the carb a little lean, this can cause issues and some 024s are little buggers to set up right. If the saw was a little richer, a bit of extra air through the throttle shaft would make less difference!

[ihatesaws]

I sealed up the two WT-22B carburetors and stuck them in the bucket of water. They showed exactly the same behaviour as the 194A. If I constantly pump I can the pressure up to around 5psi and there is a big stream of bubbles out of both ends of the throttle valve shaft.

 

I was rather hoping to find some way to stop the air leak rather than managing it. I mean you wrote earlier about expecting leakage in the pressure test of the whole saw from 10psi down to zero over 20-30 seconds and not well under. This must classify the air leak I have as major. Maybe there is a reason the stihl manual only does the pressure and vacuum testing without the carb. Maybe they don't care about leaks in the carb.

 

The reason my name is ihatesaws is that adjusting the carburetor screws is the thing I hate the most and has me pulling my hair out. This is probably because with an air leak the saw does not behave in a predictable manner. You can find a carb setting that seems to work and you cut. Next time you try to start the saw it may not start or it might be racing at idle with the same setting.

 

The metering arm seems to be level with the carb body. I see the raised lip you're talking about. The arm seems to be maybe 1mm below it. I can bend it up slightly. You want to make things richer in general so.

 

>>Start the saw up and turn the L screw out until the saw revs drop

Won't they start to drop immediately as the mixture is getting richer? Do you mean turn out until the saw revs drop down to like 2000 rpm and it sounds like it is about to die?

 

>>turn back in until they peak and start to drop, undo until the saw drops in >>idle speed again and the engine note sounds sort of poppy

Okay but why don't I just set the L screw straight away so that the saw revs at 2500rpm on the tachometer?

 

>>then set the H screw so the saw revs out and try it again.

What does revs out mean? I'll be adjusting the H screw to see how the idle is affected or you want me to adjust H at WOT to get near the max recommended rpm of 13000 and then adjust L again to poppy at idle?

 

What would you recommend me to start off with for the idle screw? Two turns out?

[spudulike]

I sealed up the two WT-22B carburetors and stuck them in the bucket of water. They showed exactly the same behaviour as the 194A. If I constantly pump I can the pressure up to around 5psi and there is a big stream of bubbles out of both ends of the throttle valve shaft.

 

I was rather hoping to find some way to stop the air leak rather than managing it. I mean you wrote earlier about expecting leakage in the pressure test of the whole saw from 10psi down to zero over 20-30 seconds and not well under. This must classify the air leak I have as major. Maybe there is a reason the stihl manual only does the pressure and vacuum testing without the carb. Maybe they don't care about leaks in the carb.

 

The reason my name is ihatesaws is that adjusting the carburetor screws is the thing I hate the most and has me pulling my hair out. This is probably because with an air leak the saw does not behave in a predictable manner. You can find a carb setting that seems to work and you cut. Next time you try to start the saw it may not start or it might be racing at idle with the same setting.

 

The metering arm seems to be level with the carb body. I see the raised lip you're talking about. The arm seems to be maybe 1mm below it. I can bend it up slightly. You want to make things richer in general so.

 

>>Start the saw up and turn the L screw out until the saw revs drop

Won't they start to drop immediately as the mixture is getting richer? Do you mean turn out until the saw revs drop down to like 2000 rpm and it sounds like it is about to die?

 

>>turn back in until they peak and start to drop, undo until the saw drops in >>idle speed again and the engine note sounds sort of poppy

Okay but why don't I just set the L screw straight away so that the saw revs at 2500rpm on the tachometer?

 

>>then set the H screw so the saw revs out and try it again.

What does revs out mean? I'll be adjusting the H screw to see how the idle is affected or you want me to adjust H at WOT to get near the max recommended rpm of 13000 and then adjust L again to poppy at idle?

 

What would you recommend me to start off with for the idle screw? Two turns out?

 

Pressure checks are always done with the inlet port blanked off between the carb and the cylinder and the carb is only deemed suspect if the idle is found to be up and down and is traced back to leaks in the carb, the only thing we don't know is if your carb is OK or not.

 

The spraying of the fluid over the throttle shaft showed a dramatic change which I would think is suspect but TBH, have not tried this as it has never been an issue!

 

The tuning of a carb is a bit of a personal skill. Your comment about setting the idle with a tach is misleading as you could set the revs at 2,500 rpm with the L screw on mixture only and any idle screw setting but it doesn't mean it is correct!!

 

I usually set the idle screw so the pointed part of the idle screw contacts the throttle lever around the middle - this is just the start.

 

I usually fire the saw up, screw the L screw in until the saw races due to the idle being lean and on the point of it dying, take the screw back out past the highest revs point and around 1/4 turn more until I hit my popping sweet spot and THEN use the idle to adjust the revs to around 2,800rpm. If the saw idle is too low through this, I screw the idle in and if it is too high and I am not achieving the tune I have just described, I turn the idle screw out.

 

I have a feel for making this sort of adjustment based on doing it hundeds of times - not showing off or being big headed - it is just what I can do and have some sort of affinity with machines in this way:thumbup:

 

If you follow the above, the idle MIX, and SPEED are correct, you can just set the carb to factory 1 turn out L&H screw and then just adjust the idle screw, you end up with the saw running OK 4 out of 5 times!

[ihatesaws]

I bent the metering lever in the WT-194A carburetor up to be level with the lip, set the H and L adjustment screws to 3/4 turn out and the idle screw to 2 turns out which is halfway on the tip of screw.

 

After 10 or 11 pulls the saw started with the choke. It then wouldn't start normally as I think 3/4 is too lean and when the choke was open there was then too much air to start. I turned the L screw to 1 turn out and the saw started. I could rotate between 3/4 and 5/4 turns out before it either got too lean or too rich and died. I could get it sound kind of poppy at around 9/8 turns out and then adjust the idle screw to get the rpm 2500-2800 but any settings I would use wouldn't really have any lasting effect.The rpm would vary more widely and upwards especially by having the saw on one side or after returning from WOT.It would inevitably die but I could restart it immediately.

 

I put the 024S back together with a new impulse hose. I see what you meant earlier about the hose sticking out from the back of the tank housing.It has a different design to the one I put in before.It is hard to push it in fully. I took the WT-194A off the 024 and put it on the 024S. It started straight away. It is louder. You can tell from the sound of it that it is a more powerful saw, although that probably has more to do with the cylinder being original than the longer stroke. I turned the L screw out slightly to 5/4 to idle okay but it started to behave erratically as well.If the rpms started to drop I would turn the screw in. It would then slowly go up and at times continue over 3000, so I would turn the screw back and it would go down again.So I could influence the direction the revs would go in by turning the L screw back and forth slightly but there wasn't any real fixed link for any prolonged durateion of time between a certain L position and a certain rpm. Turning the saw on its side was one sure way of getting the rpm to climb.

 

Then I gave up because I was sick of it.

[spudulike]

I bent the metering lever in the WT-194A carburetor up to be level with the lip, set the H and L adjustment screws to 3/4 turn out and the idle screw to 2 turns out which is halfway on the tip of screw.

 

After 10 or 11 pulls the saw started with the choke. It then wouldn't start normally as I think 3/4 is too lean and when the choke was open there was then too much air to start. I turned the L screw to 1 turn out and the saw started. I could rotate between 3/4 and 5/4 turns out before it either got too lean or too rich and died. I could get it sound kind of poppy at around 9/8 turns out and then adjust the idle screw to get the rpm 2500-2800 but any settings I would use wouldn't really have any lasting effect.The rpm would vary more widely and upwards especially by having the saw on one side or after returning from WOT.It would inevitably die but I could restart it immediately.

 

I put the 024S back together with a new impulse hose. I see what you meant earlier about the hose sticking out from the back of the tank housing.It has a different design to the one I put in before.It is hard to push it in fully. I took the WT-194A off the 024 and put it on the 024S. It started straight away. It is louder. You can tell from the sound of it that it is a more powerful saw, although that probably has more to do with the cylinder being original than the longer stroke. I turned the L screw out slightly to 5/4 to idle okay but it started to behave erratically as well.If the rpms started to drop I would turn the screw in. It would then slowly go up and at times continue over 3000, so I would turn the screw back and it would go down again.So I could influence the direction the revs would go in by turning the L screw back and forth slightly but there wasn't any real fixed link for any prolonged durateion of time between a certain L position and a certain rpm. Turning the saw on its side was one sure way of getting the rpm to climb.

 

Then I gave up because I was sick of it.

 

Beginning to feel the same way about your saws...just to recap, do either of your 024 Stihls work fine with any of the carbs you have? If the new carb is having the same effect on both the saws you have, it looks like the carb is at fault unless both machines have exactly the same issue - this is not inconceivable!

 

The saw turned on its side playing up is probably either puddled fuel in the crank case causing issues or a sign of the crankcase seals not being good. If you leave the saw idleing for a few minutes and then give it a yank on the throttle, do you get a cloud of smoke or is it relatively clean, a cloud of smoke indicates the idle is a little rich and fuel is gathering in the crankcase and the carb needs leaning up.

 

Is the fuel line and filter in good nick, is the fuel line long enough and is the breather clear? Probably said all this before!

 

Have you also done a thorough vac test on the saw - it is possible that a saw may leak under vcuum and not under pressure or vice versa.

 

The new carb not working is baffling - a new carb would generally dial in pretty quickly and only older carbs with wear on them generally exhibit tuning issues!

 

I think I am nearing the end of my road where I can't do much else without inspecting the saw and that is in no way an invitation, think you can keep those saws to yourself:lol:

[ihatesaws]

I took the HD-19B carburetor off the ms290 (one of your favourite saws) and sealed up both ends and stuck it in a bucket of water. It leakes like a sieve out of the throttle and choke shafts so I believe you now that it is not an issue. I guess constant air leaks are not a problem. You just tune the carburetor to compensate for them.

 

>>do either of your 024 Stihls work fine with any of the carbs you have?

I suppose it depends on how you define fine. They do afterall cut pretty well and idle to a certain extent at times. If by fine you mean consistent behaviour at idle then I would have to say no.

 

I took the clutch and the oil pump off and poured water on the seal while the 024 was running. No sign of any bubbles. I sprayed carburetor cleaner down on where the cylinder meets the crankcase but couldn't see any change in rpm. I was thinking that maybe there were airleaks only when the saw was running and got hot but I couldn't test anymore areas with it running. I took off the flywheel for the first time (hurray!) and pressure tested the saw. I pulled and pushed on the crankshaft on both sides of the saw but no drop in pressure. I rotated the crankshaft constantly but no drop in pressure and no bubbles. It definitely isn't loose. I then did the vacuum test. If you wait a few minutes you can see a tiny drop but it is only when you rotate the crankshaft constantly that the vacuum goes from 0.5bar to 0.4bar in 10 or 15 seconds. If I could rotate it quicker it might go even quicker. You can then rotate all day but the gauge shows no further change. I read in the manual that only if the vacuum increases to 0.3bar within 20 seconds are the oil seals bad.

 

I started the 024S with one of the WT-22B carburetors. The idle did seem a bit more stable than when I tested it with the WT-194A but I wouldn't put money on it. At one stage I got it idling between 2400 and 2800 rpm for a few minutes. If I tilted the right hand side of the saw up in the air the rpms would rise to the upper value and if I let it back flat on the ground it would sink to lower values. I did a small bit of cutting and when I let it idle it would be around 3000-3200 rpm. I could adjust that down but the saw wouldn't start then with the new settings. I guess the saw is pretty usable as it is. It is just not likely to idle for any great length of time especially if you're moving it but I suppose I can either leave it flat on the ground or if I'm moving press the throttle now and again if I hear it beginning to die. I think I damaged the other WT-22B so testing it might be just adding more confusion (if that were possible).

 

I never get any cloud of black smoke after idling for a while and then going full throttle. It is kind of bluish or transparent. The fuel line and filter on the 024 is new and long. If by breather you mean the tank vent then that ought to cause problems at WOT as well and the problem should appear with time as fuel is used rather than a constantly inconsistent idle. I can test without the vent though. I am afterall desperate at this stage.

 

What's your postal address, Spud?

[spudulike]

GO back to the vacuum check, having removed the flywheel and clutch/oil pump and oiler worm drive pinion, do the vac test again and see the vacuum drop from 0.5 - 0.4 bar and then turn the saw on its side.

 

Put oil around the seal or grease and repeat the test - if you get no shift in the vacuum then that seal needs replacing - if you still get the drop, try it on the other side of the saw and see if it halts the loss of vacuum.

 

I reckon you have a slight air leak that doesn't show much under testing but is worse on running. Just done a MS460 and it was exactly like this - gotta get clever to fix stuff like this - you get out what you put in:thumbup:

 

Cost of shipping to and from Ireland will be bloody expensive - choice is yours - all I will be doing is what I have described here in this thread!

[ihatesaws]

Great stuff, Spud. You keep giving me hope. We'll win in the end!

 

>>all I will be doing is what I have described here in this thread!

Yeah but you'd be doing it right.

 

I'll give that vac test a go again. I just remembered that when I replaced the cylinder and gasket I had no hylomar at the time (nor did I know I needed it) so there is none between the gasket and the metal. I will lift the cylinder up as high as I can without the rings springing out and spread some on.

[spudulike]

Great stuff, Spud. You keep giving me hope. We'll win in the end!

 

>>all I will be doing is what I have described here in this thread!

Yeah but you'd be doing it right.

 

I'll give that vac test a go again. I just remembered that when I replaced the cylinder and gasket I had no hylomar at the time (nor did I know I needed it) so there is none between the gasket and the metal. I will lift the cylinder up as high as I can without the rings springing out and spread some on.

 

TBH, on a typical 0.5mm paper gasket, a smear of grease is all I use with exception of those rubber covered steel ones fited on large Stihls that get a light smear of liquid gasket!

 

The vac test will hopefully show a seal that is on the way out - tha vacuum will draw the oil or grease in and seal the leak if there is one:thumbup: