Stihl 024 air leak

[ihatesaws]

Hi. I'm back.  Brace yourselves!  I'm giving this a go again after leaving the saws sit in boxes for a decade.  I'll give a quick summary of the issues with the saws as you probably don't want to read back over five pages and given the length of time parts that were working may no longer be.

 

First saw is a 024 with a replacement cylinder and piston kit.  Its compression is around 110psi.  The last thing done to it  ten years ago was to replace the crank seals which didn't help to make it idle properly.  Saw had been pressure/vacuum tested, all rubber components, tank vent etc tested for leaks, blockages.

 

Second saw is a 024s with original cylinder and compression of 170psi.  This was not idling properly either.  Passed pressure/vacuum test.All hoses etc fine.

 

Carbs available for testing:

a chinese noname thing I bought cheaply in 2017 and had never tried out

a wt194 that was new a decade ago

a wt22b that has corroded a bit.

 

I thought if I could just get the 024s going I'd be happy as that is quite powerful.  I pressure tested it again  and put the chinese carb on it.  I got it to run at 1.5-2 on the L and around 2 on the H screw.  I cut with it for about 15-20 minutes and it was idling okay but I think the next time I went to use it I had to adjust the carb again.  I tried the wt194 on it as well and generally with both carbs it's a case of having to richen up the mixture slightly after a while to keep the revs down at idle. Tilting the saw downwards can cause the revs to drop as well.  

 

I was wondering what to try next or was there anything left to try.   I was looking at the crankcase gasket on both saws and underneath the muffler there was not alot to be seen.  There is no aluminium heat shield so I wondered whether the heat might have damaged it.   I thought it would be better to split the 024 first as I would prefer to damage that and I could learn from any mistake if I had to do it again with the 024s.  So I split the 024.  There seemed to be only the colour of the gasket left around the front of the oil tank but I think there was some of it still left to seal the crank.  I had to cut off what was left.  The saw now has new bearings, new crank seals, a new crankcase gasket and a new cylinder gasket.  It has some aluminium underneath the muffler that came in a kit.  The saw would fire and wouldn't then start or if it did start it would die quickly.  I pressure/vacuum tested it but it passed.  The bloody spark plug would spark fine if you tested it by pressing it against the cylinder and pulling but when you tried to start it if was only firing once and then no more.  I only found this out when I tested both the coils and plugs from the two saws in an ms290.  It ran normally except with the plug from the 024.  So new plug in 024 now and I can be sure that that and the coil are working properly.  With the chinese carb it runs at around 1 3/4 turns on the L but I had to keep adjusting the L richer to keep the idle down.  I put the wt194 on it and I turned in the idle screw so the saw would idle.  Turning the L screw in I got max revs of around 3700 at 1 turn out.  I turned the screw back  to 1 1/8 turns out and turned the idle screw out to get the revs down to 2500.  I set the H to max out at around 12k.  The max allowed is 13k.  The saw will start and idle on this setting.  I can cut and the saw comes back to idle so everything seems fine but after a while the idle will begin to stay higher so it can occur that the L screw goes out to 1 1/4 or even to 1 3/8 turns out. The saw won't start on that setting though and I have to turn it back in to 1 1/8 and then it starts and idles.

 

I don't have any carb that I know for sure is working properly.  There is a guy tinman on youtube and he describes chinese carbs as being able to imitate an air leak.  They won't hold the adjustment.  Some carbs are fine and some are not.  This wouldn't explain the wt194 acting up though.  The wt194 and wt22b have spent 5 minutes in a jar of petrol in an ultrasonic cleaner at 50 degrees C.  For how long would you normally  clean a carb?  The metering diaphragm on the wt194 didn't look the best so I put one from a cheap chinese carb kit into it.  I see online I can get a new genuine tillotson carb for €60 and a new better quality carb kit for the wt194.  I am tempted.  On carb kits there seems to be a k10wat recommended for the 22b and a k20wat recommended for the 194.  Is there any difference in thickness between the metering gasket supplied in these two kits?  Is a tillotson carb hu-136a more/less reliable, more/less easy to adjust than a walbro?

 

So I seem to have similar issues with multiple saws and multiple carbs.  The only conclusion I can draw from this is that the problem is with the fellow adjusting them.

Edited April 9, 2023 by ihatesaws

[pleasant]

I wouldn't clean a carb in petrol. Use a proprietory cleaner specifically made for the purpose. Did you take the carb off and just put it in the cleaner 'as is' or did you strip it down to component form so it was just the alloy block plus separate parts in the cleaner? Generally (depending on the ultrasonic cleaner, the temperature and the cleaning liquid) I usually 'cook' mine for 30-40 minutes.

[ihatesaws]

I stripped down the carbs.  I see people online using petrol to clean. It got quite dirty after 5 minutes.  Maybe I should have left them in there longer though.

[adw]

You can leave them in as long as you like, it will make no difference, that is not the way to clean the carb, other than the outside.

[spudulike]

Firstly...110psi is shyte ...if correct...170psi is nice so the 110psi cylinder is particularly poor and is unlikely to ever give good performance.

On the carb issues, I have had similar with old 026s and after a similar frustrating time, swapped out the carb with the much more reliable WTE-1 carb from the later MS260. Sometimes carbs do get to a point where they just get very unstable on the idle and nothing you do works so getting a used MS260 WTE carb, servicing it and trying it is worth a go.

The aftermarket carbs can be anything from a damn good option to something you would throw at someone you don't like.

[Stere]

Quote

more reliable WTE-1 carb

 

Thoose carbs seem rare as hens teeth  hence the £170?!

 

Stihl Carburettor - 1121 120 0602

WWW.DIYSPAREPARTS.COM

 

 

 

 

 

[spudulike]

I got mine off ebay etc but that was a fair time ago! 

[ihatesaws]

15 hours ago, Stere said:

 

Thoose carbs seem rare as hens teeth  hence the £170?!

 

Stihl Carburettor - 1121 120 0602

WWW.DIYSPAREPARTS.COM

 

 

 

 

 

I might as well just buy a new ms170 for that money.  It would be alright for light jobs.🤔

 

15 hours ago, spudulike said:

Firstly...110psi is shyte ...if correct...170psi is nice so the 110psi cylinder is particularly poor and is unlikely to ever give good performance.

 

 

I have the original cylinder and it doesn't look too bad.  I'd have to clean it up and get a meteor piston but I want stability first and then I'll worry about performance.

[spudulike]

Good call on cleaning up the cylinder and then fitting a Meteor piston. Also worth looking out for the WTE carb, I used to pay £15-30 for a good secondhand one and was generally well worth the spend.

[ihatesaws]

Would the compensator lid fit inside the 024 tank housing though?  Would a flat plate from a WT carb fit the WTE-1?