Need help with a Shindaiwa weedeater. Runs and I see what was wrong! Heh...

[ANewSawyer]

See post #25 and all will be explained!

Been working on the carb for this new to me Shindaiwa S-25 (AKA T-25) weedeater down in handheld equipment. I finished a soak and rebuild on the carb. I have put the carb back together and bolted it back in place. I can prime the carb and the weedeather will cough when the choke is fully on. It only takes one or two pulls. I back the choke off a little and will start, run for about 2 seconds. Then it dies. I can pull starter rope again right away and it will repeat. Choke settings doesn't seem to make a difference except that it hasn't started at all with the choke open. The gas came with the weedeater but it is stabilized, good gas. The guy who had this Shindaiwa before me rebuild two cycle engines for a living.

You should know that this is a TK carb. The choke and the throttle are completely separate. As per the starting instructions, I have the throttle locked open. When I had the carb on the bench, I tried to seat both jets. I turned them in until they wouldn't turn any more without a lot of force. Then I backed them out to the factory settings. I tried to reset the meter lever height but I found I didn't have an accurate way to measure it. It may or may not be off. I got it as close as I could. I shows wear and will be replaced later.
There are a couple of things I can think of:
1: Operator error when starting. I doubt this because I am following what is written in the owners manual. But there might be something I don't know about starting.

2: The hi/low jet screws are at the wrong setting. I realize that the factory setting are a guide line but I would think a newly rebuilt carb should at least start and run a little at factory settings.

3: I installed the pump diaphram and gasket in reverse order. Not likely but worth checking.

4: The in tank fuel line has a hair line crack that is sucking air. Quickest way I know of to test this is to fill the tank. I will have to mix some new fuel and check this. Or I could use the 32:1 fuel I already have.

5: Tank breather is clogged. If the weedeater started, died and then wouldn't start until the gas cap was opened, I would look at this in depth. I will probably replace the breather but I don't think it is causing my current problem.

6: Would be a pressure test but I don't have a pressure tester. I have read on here that I can test this by removing the spark plug and putting my thumb over hole. If it has good compression, it should pop my thumb off the hole.

 

[Roll Tide]

Its running lean. I'd turn the H screw counter clockwise 1/4 turn then try again. I'd also check your fuel lines.

 

[o8f150]

diaphrams in wrong???? or wrong kit????

 

[lone wolf]

Carbs are cheap for those online look it up it ain't worth messing with some times.

 

[Rx7man]

does it stall when you rev up? does it bog when you rev it? does it idle? does putting some choke on it help? Really hard to diagnose it with the info you've given

 

[HarleyT]

try fresh fuel first.

 

[HarleyT]

You will have a hard time finding a new carb for this one.

 

[lone wolf]

You will have a hard time finding a new carb for this one.

That stinks. OEM avail?

 

[HarleyT]

If you can find them anywhere, you could sell the hell out of them. TK is still a company in Japan, would be great to find a way to get parts or even new carbs.

 

[Rx7man]

I can nearly guarantee the carb is fine and doesn't need to be replaced.. though perhaps there's still a clogged passageway somewhere. Without knowing more of what it's doing it's impossible to tell if it's too rich or lean, or even just the throttle stop/air screw is too low

 

[HarleyT]

Yeah, and they run like **** on bad gas too.

 

[RedFir Down]

What spark plug is in it?
My dad has the same unit with almost the same symptoms. I went through the entire fuel system, still had the same issues. I put a new recommended spark plug and it runs like new. (Im not sure it was the heat rating on the plug but the old plug had the next hotter heat rating).

 

[ANewSawyer]

diaphrams in wrong???? or wrong kit????

It is the right gasket kit. I am just going to check that I didn't installed the gasket and diaphram in the wrong order. That was all I was trying to say.

EDIT: I didn't take the carb apart but I can see the layering of the gasket and diaphram. According to this IPL( http://www.partstree.com/parts/shin...ters/t25-shindaiwa-string-trimmer/carburetor/ ) I have them in the correct order.

I can nearly guarantee the carb is fine and doesn't need to be replaced.. though perhaps there's still a clogged passageway somewhere. Without knowing more of what it's doing it's impossible to tell if it's too rich or lean, or even just the throttle stop/air screw is too low

What other info do you want? There isn't much more to tell, besides what is in the description in the starting post. I start the unit it runs about 2 seconds and then fall flat on its face.

What spark plug is in it?
My dad has the same unit with almost the same symptoms. I went through the entire fuel system, still had the same issues. I put a new recommended spark plug and it runs like new. (Im not sure it was the heat rating on the plug but the old plug had the next hotter heat rating).

I had that thought while driving home today. I might get out a wire wheel for my bench grinder and clean it.

 

[Adirondackstihl]

Low speed jet is too lean

 

[Rx7man]

It is the right gasket kit. I am just going to check that I didn't installed the gasket and diaphram in the wrong order. That was all I was trying to say.

What other info do you want? There isn't much more to tell, besides what is in the description in the starting post. I start the unit it runs about 2 seconds and then fall flat on its face.

Most likely it's set too lean on the low speed, but will it rev up? what about with the choke on half? Might have to increase the throttle stop a little as well

 

[ANewSawyer]

Low speed jet is too lean

I have been thinking along those lines so I turned the low jet out a bit. It is starting easier but still not running. And it showed a new symptom. I got it to start with the choke off and throttle closed. I know the throttle was closed because the air filter cover was off and I was looking right at it. And it didn't idle, it ran fast enough to engage the clutch and spin the string head. It wasn't quite full throttle but it was still pretty fast. How on earth could it run that fast with the throttle closed??? Massive air leak???

Most likely it's set too lean on the low speed, but will it rev up? what about with the choke on half? Might have to increase the throttle stop a little as well

It won't rev because it won't run for more than two seconds and when it starts, it is running at max throttle until it dies! Choke(!) or throttle setting has made no, repeat, no difference. Except maybe to make its starting RPM just a littler lower. If it starts at all, it runs high speed for two seconds and flop. Dead. I don't know what to make of this.

 

[ANewSawyer]

Ok, I have noticed a pattern of it not wanting to start unless it is reprimed after it runs. I turned the high speed jet out another 1/8th turn and she started with the choke off. It ran high then dropped way down in rpm went back up then dropped again and died.

 

[Rx7man]

I'd look at the intake boots, etc to make sure they're sealed well, including the impulse port.
If you're sure the intake is on right and sealed well, then keep richening the idle and high circuit until it stays running, then back down the throttle stop and fine tune the idle and high side.. first you gotta get it to stay running though.

How is the fuel filter?

It is sounding pretty weird, and if nothing else will make it behave, there must be a massive air leak elsewhere.. crank seals, crankcase gaskets, or something. Before you tear into it, make sure that the impulse system is working, which may explain why you need to reprime it every time..

When I start tuning a saw from scratch, I usually start with 2 turns on each.. a rich engine will usually still idle to some extent, giving me time to fiddle with it.

 

[ANewSawyer]

Thanks for the help!!! What would a partially blocked impulse port do?

I read in the service maual that you could check the impulse port in the crank case by putting a drop of oil on it. I tried twice but I think I used too light of an oil. The two drops ran into the case and I didn't want to fill the crank case with anymore oil, so I quit.
It was mineral oil, btw. That was all I had handy.

 

[RedFir Down]

Try using a little grease.