Engines idles DOWN as it warms? Then dies when warm. Edit 2: May have found a culprit! See post #32

[ANewSawyer]

Still fighting that Shindaiwa trimmer engine. I am going to take it to a local two cycle shop but I won't get it there for at least a week. I ain't gonna give up yet.

It will idle when cold but as the engine warms the idle goes down until it dies. An air leak would cause a high idle right? Well, if I hit the throttle as the engine is idling down, it runs like it is super rich for couple of seconds. Lots of smoke too. Then it evens out and runs high. But by this time the engine is warm and she won't idle at all. Strange. A lot of people here thought this was an air leak and I agreed at first. Now I am not so sure. Shouldn't the engine idle up as it warms when there is an air leek?

 

[banditt007]

Sounds like your low speed needle is too rich. Try warming up the trimmer (rev it or do whatever you need to do to keep it going) then SLOWLY start leaning out the low speed needle. You can rev the engine a few times after each adjustment to see where you stand. But the engine is somewhat slow to react to the low speed needle adjustment (unlike the high speed), so you must do it slowly. You want to find the highest idle speed you can attain with the low speed needle. Now after you get there, open up the low speed needle about 1/4 turn rich (CCW). Check for crisp acceleration from idle when you punch it. If it sounds like BOAH BOAH BOAH very boggy sounding when you throttle quickly from idle, richen it CCW more. If it stumbles, smokes and kind of clears out after a little bit of time its too rich. Now readjust your idle screw (the one that physically holds open the throttle body) to a speed that just barely starts turning your trimmer line. Now back it out CCW 1/4 turn and make sure the clutch isn't "ringing" and that the trimmer line isn't still trying to turn. If either of those is the case slowly back out the screw a little more. Now for the high speed. Load up your usual trimmer line at the longest length you will ever use (to the cut off blade). Now go wide open throttle. You want to achieve the highest RPM you can get. Once you are there, open the high speed screw 1/4 turn or so. Now recheck your throttle up from idle and make sure its crisp. make sure your idle screw is still good also. you should be good to go now. A lot of trimmers have a hidden low and high speed screw on them. If you don't see traditional high and low speed needles this may be the case and you will need to access them. Now if you don't have access to a tach for setting the high speed. Go WOT and richen the mixture until its blubbering/4 stroking, now slowly lean out the high speed needle until it just stops or breaks over back and fourth between 2 and 4 stroking. And you will be all set.

To me it sounds like your low speed is too rich. From what i've seen with 2 strokes is the first few seconds on cold start the engine may idle a bit high. I think this is b/c the fuel isn't atomizing and kind of sticking to all the cold metal in the engine instead of flowing efficiently. (not sure exactly what is happening but thats what i think) so it acts a little lean and you get a higher initial idle. then once it warms some it goes to its usual idle. If its too rich on the low speed it can idle normal ice cold, but as it warms the too rich mixture starts accumulating in the crank case and eventually causes the engine to be so rich at idle the idle goes lower and lower until it eventually stalls, or stalls once you tilt the trimmer to the side. This is what i think you are experiencing. especially since you say when you punch it it smokes super rich and then clears out. thats clearing out the crank case but then it slowly gets richer and richer again and does the same thing. Hope this helps i don't know how much experience you have with this stuff so if it sounds a little bit beginner oriented don't take it to heart

 

[ANewSawyer]

Very informative post! Thanks! I am somewhere between novice and medium skill. I understand most of your post. It sounds very much like my problem. I wonder? I have been setting the screw to the factory setting of 1/4th turn. Maybe I could just crack the needle. Just far enough to allow fuel and try again. Maybe the L needle or seat are damaged? Thus allowing way to much fuel.

I have a stupid question, too. In general, should an engine start with the L needle fully seated?

 

[huskihl]

I have a stupid question, too. In general, should an engine start with the L needle fully seated?

It might start with the choke, but should stall after a few seconds. My 034s would run with the L needle all the way in. Rebuilt the carb and got my adjustment back. I agree 100% with what bandit said. Your L is rich

 

[ANewSawyer]

No, it seems to run fine at WOT with the L needle firmly seated. I just did a carb soak and blast out with carb cleaner. Won't idle with the L needle seated, of course. But this is an ancient Japanese TK carb. Really weird to me. I will go out tomorrow, when it is light, and see if I can get it to idle when warm by just barely opening the needle about 1/16th of a turn. I will report what happens.

Is there anything else that would affect how much fuel passes through the L circuit? All I can think of is the L screw and its internal seat in the carb. Metering needle maybe? I doubt that though. If it were a metering needle problem, it should flood the H circuit too. Thanks for the help.

 

[redtractor]

BOAH BOAH BOAH

All I can picture is Gilda Radner in a big blonde wig saying "This is Boah Boah Wa Wa"

 

[ANewSawyer]

OK, I had the engine running and idling, with the L screw all the way in!!! I am going to replace the L screw and see what happens. I looked at the screw with my jeweler's loupe. I can just tell that there is some kind of damage to the tip. But I couldn't tell if the tip had snapped off or what.

 

[Full Chisel]

I've had the same problem with the L needle set too rich. It will load up at idle, slow down and die and get flooded and hard to restart. But if it's idling with it turned all the way in there is something wrong for sure.

 

[ANewSawyer]

Ya, Maybe the new L needle will fix it. If not I will have to look for a problem in the carb. Not much I could do about that, though. Let us hope the new needle solves my problem.

 

[ANewSawyer]

Went to my dad's house for easter dinner and I happened to remember that he has a Shindaiwa T-27. IPL says that my 25 and his 27 have the same L speed screw. I switched them out with his blessing but no dice. My 25 still won't idle when warm. It worked longer and didn't act like it was flooding. But the thing still won't idle. Nrrg...

BTW, his 27 doesn't idle either but I bet that is because his gas is 5 to 10 years old! I ain't touching that.

 

[Full Chisel]

Once you get that thing working right you will be very happy with it. I ran that series of trimmer all last summer and it was flawless. The only issue it had was the throttle cable wearing thin and breaking. Easy fix...15 mins at most.

 

[ANewSawyer]

I have done everything I know to do without buying a compression tester and a vac/pressure tester. I really didn't want to buy both for such a cheap engine. And since I don't really plan on doing a bunch of work after this, I might not use them again for a long time.

Got a spare throttle cable here. Will need it soon cause the current cable is heavily worn.

Thanks for the help guys!

 

[huskihl]

Did you rebuild the carb yet? It's only $10-15 and will probably fix your problem

 

[ANewSawyer]

I have already rebuilt the carb but one gasket (metering gasket) wasn't available so I had to cut my own. I did not look perfect but is should work. It might be a tiny bit thicker. Also,the metering lever might be off but it would be tiny, even by the standards of meter lever settings. This unit wouldn't even run without the carb rebuild. I can often get it to fire on the first or second pull after the rebuild. The only other weird I have noticed after rebuilding the carb, is it that fuel was running out of the return pipe all the time when the unit was running. I drilled a hole in the fuel tank and put the return line in. I was careful to flush the tank out afterwards to keep debris off the filter.

By all rights, it should run but...it doesn't. I don't get it.

 

[huskihl]

I have already rebuilt the carb but one gasket (metering gasket) wasn't available so I had to cut my own. I did not look perfect but is should work. It might be a tiny bit thicker. Also,the metering lever might be off but it would be tiny, even by the standards of meter lever settings. This unit wouldn't even run without the carb rebuild. I can often get it to fire on the first or second pull after the rebuild. The only other weird I have noticed after rebuilding the carb, is it that fuel was running out of the return pipe all the time when the unit was running. I drilled a hole in the fuel tank and put the return line in. I was careful to flush the tank out afterwards to keep debris off the filter.

By all rights, it should run but...it doesn't. I don't get it.

Make sure the metering gasket goes on the carb first, then the metering diaphragm, then the cover. On the other side, the reed diaphragm goes on first, then the gasket, then cover

 

[alderman]

Fuel shouldn't be running out of the return line. Something is messed up.

 

[LegDeLimber]

Here's a general manual for the Shindaiwas.
http://golftechs.us/Manuals/shin trimmers.pdf
I haven't read all of it yet and I haven't touched one of those old slide types
since the early 80's,
so my recall of the metering circuitry is non-existant now.

For what it's worth, I'd be curious what the compression is on that unit.
I belive it mentioned that it might have a few hours on it.

 

[Rx7man]

It could be that the metering lever is set a smidge too high, and that the fuel you're getting at idle is coming entirely through the H circuit.. at WOT this would easily be compensated for, and the engine uses a whole lot more air, thus not affecting it as much...
I don't think you should need to check deeper in the engine,.. take the metering cover off the carb, hold the metering needle in place, and press the lever down gently to bend it a little... Measure (or at least eyeball) before and after... I think if you bent it just 1 - 1.5 mm it might fix all your problems.... it's a cheap and easy thing to try

 

[mountainlake]

It could be that the metering lever is set a smidge too high, and that the fuel you're getting at idle is coming entirely through the H circuit.. at WOT this would easily be compensated for, and the engine uses a whole lot more air, thus not affecting it as much...
I don't think you should need to check deeper in the engine,.. take the metering cover off the carb, hold the metering needle in place, and press the lever down gently to bend it a little... Measure (or at least eyeball) before and after... I think if you bent it just 1 - 1.5 mm it might fix all your problems.... it's a cheap and easy thing to try

Finally some one is on the right track, also get the right gasket and make sure the diaphragm is in right. Your needle is letting too much fuel in. Steve

 

[timbrjackrussel]

Here's a general manual for the Shindaiwas.
http://golftechs.us/Manuals/shin trimmers.pdf
I haven't read all of it yet and I haven't touched one of those old slide types
since the early 80's,
so my recall of the metering circuitry is non-existant now.

For what it's worth, I'd be curious what the compression is on that unit.
I belive it mentioned that it might have a few hours on it.

Thanks for the link.