# Need Help with my 2stroke hedge trimmer that won't start



## kaplang (Aug 19, 2015)

The 2 stroke 26cc engine # UT40502 on my HT26 hedge trimmer will not start.

What I have done.
checked for spark to plug and it is OK
Installed new carburetor, gaskets and fuel lines. Carb was installed correctly
Used fresh fuel with oil.

trying to start it and not even a pop.

I removed the plug and It is completely dry telling me that fuel is not getting to the cylinder even though the primer bulb does get fuel to it. I am at a completely loss as to why fuel is not getting to the cylinder with a new carburetor.
Any help anyone can offer would be appreciated.

Thanks,

George


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## geogrubb (Jul 28, 2006)

kaplang said:


> The 2 stroke 26cc engine # UT40502 on my HT26 hedge trimmer will not start.
> 
> What I have done.
> checked for spark to plug and it is OK
> ...


Some things to check. Try putting a teaspoon of fuel in the spark plug hole to see if it will start. If it starts check that you did not block the pulse port when you replaces the carb, some gaskets only have a hole on one side for the port. Remove the muffler and check the cylinder walls and piston for scoring and deep scratched. Check the compression. Have a good one. Geo


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## kaplang (Aug 19, 2015)

geogrubb said:


> Some things to check. Try putting a teaspoon of fuel in the spark plug hole to see if it will start. If it starts check that you did not block the pulse port when you replaces the carb, some gaskets only have a hole on one side for the port. Remove the muffler and check the cylinder walls and piston for scoring and deep scratched. Check the compression. Have a good one. Geo


Thanks for jumping in

I did try putting some fuel in the Spark plug hole but still no luck. The carb gaskets are on correctly and I could see the piston though the intake port when the carb was off. Piston looks good, no scaring. When I pull the start cord it does have compression but I don't know how much. I could check it with my compression gauge but I don't know what it should be. Do you?

Thanks


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## 30yearTech (Sep 14, 2006)

kaplang said:


> I removed the plug and It is completely dry telling me that fuel is not getting to the cylinder even though the primer bulb does get fuel to it. I am at a completely loss as to why fuel is not getting to the cylinder with a new carburetor.
> Any help anyone can offer would be appreciated.
> 
> Thanks,
> ...


An air leak into the crankcase such as a crankshaft seal, crankcase cover gasket or loose cylinder could cause a similar issue. 

Compression needs to be a minimum of 90 + lbs/psi for engine to start and run. 

Even though you have spark, timing can be off, if the key in the flywheel somehow got sheared. If the timing is off, the unit may not start, but it *would not* affect fuel getting to the cylinder or getting the spark plug wet.


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## kaplang (Aug 19, 2015)

30yearTech said:


> An air leak into the crankcase such as a crankshaft seal, crankcase cover gasket or loose cylinder could cause a similar issue.
> 
> Compression needs to be a minimum of 90 + lbs/psi for engine to start and run.
> 
> Even though you have spark, timing can be off, if the key in the flywheel somehow got sheared. If the timing is off, the unit may not start, but it *would not* affect fuel getting to the cylinder or getting the spark plug wet.


Timing being off may be the problem since I am getting nothing even if I put a little fuel in the cylinder via the spark plug hole.
Is the key made from soft metal to save the crank if something jams the blade? I know that Briggs and Straton 4 stoke engines have that feature.

Thanks


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## 30yearTech (Sep 14, 2006)

If you have a large air leak they may not fire off with a prime either, most of these units have the key cast in as part of the flywheel, it's very soft as it's only there as an alignment aid. 

If the flywheel is not properly torqued, or if you hold the flywheel while attempting to loosen the retaining bolt/nut the key can get sheared.

If the timing if off, you may never get even a "pop" out of the engine at all.


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## finaprint (Jan 29, 2006)

You can spray a very small shot of ether (starting fluid) in if you have already some fuel/oil in crankcase. The ether vapors up much better than fuel/oil and it can start even if the plug has been wetfouled. The ether can scar up cylinder though since it carries no oil so don't try it a lot. One second of running won't hurt though and tells you the timing at least is on. 

With starting issues your fuel needs to be five minutes old, older fuel quickly loses it's aromatic qualities these days and often that may be all that's wrong. If your local fuel has ethanol in it the supply needs to be well sealed, I've seen fuel that could breathe in the supply container be phase separated in 24-48 hours if you are unlucky. Phase separated fuel is crap and will not start for spit. So fresh may not be as fresh as some think. I clean parts in fuel, it will separate in five minutes with agitation and a humid day, there will then be water in it. 

If plug gap too wide as compared to spec you can get spark with plug out of engine but none when under pressure, the pressure blows out the spark. Rare but possible. Close your gap up a bit for a test. A partially shorted mag coil can do the same, less intense spark. 

While new carbs are great they are untested until you have run them for a while and therefore highly suspect. I myself generally never buy a new one, rather clean the old one to then go back to working fine but then I do all my work and it works out fine. Most though are better off simply buying the carb. To me the old one was proven to run, the metering valve was set for sure right, if anything wrong I can find the issue in a minute or so. Really few reasons to change them other than it is cheaper when somebody else is doing the work. 

You never really set up any preconditions at the start, like how long the unit sat, did it quit starting way back then, anything else oddball. Very hard to check a small 2 stroke like these with compression gauge, the displacement is too small to really move the gauge, the longer the hose the worse it is being most are using a car gauge. If flywheel key sheared you should be able to know what did it, they generally don't just do it out of the blue, something has to happen to produce it. There's probably a coil airgap in there somewhere that can affect starting too, I often close them up a little bit past spec to increase the signal strength there, it starts easier. With ether in it if you pull the rope at 1/2 the normal speed you can often feel a kickback if the flywheel has moved, the engine will try to start but can't and just rars back against the rope because the timing is whacky. Compression test can be simply holding the device by the rope and let its' weight bump the motor over to unwind the rope, if it only unwinds in slow short jerks and not all at once the compression is probably OK.


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## 30yearTech (Sep 14, 2006)

finaprint said:


> You can spray a very small shot of ether (starting fluid) in if you have already some fuel/oil in crankcase. The ether vapors up much better than fuel/oil and it can start even if the plug has been wetfouled. The ether can scar up cylinder though since it carries no oil so don't try it a lot. One second of running won't hurt though and tells you the timing at least is on.


Ether is NEVER a good idea for 2 cycle engines! It's very explosive and the combustion can cause excess pressure in the crankcase and blow out seals and cause air leaks that did not exist prior to priming with ether. Good fuel mix is the best for priming to test.



finaprint said:


> While new carbs are great they are untested until you have run them for a while and therefore highly suspect. I myself generally never buy a new one, rather clean the old one to then go back to working fine but then I do all my work and it works out fine. Most though are better off simply buying the carb. To me the old one was proven to run, the metering valve was set for sure right, if anything wrong I can find the issue in a minute or so. Really few reasons to change them other than it is cheaper when somebody else is doing the work.


Newer Carburetors have check valves that are not serviceable as per EPA guidelines. A carburetor with a leaking check valve will not operate correctly and cannot be repaired by cleaning or installing a kit. A replacement carburetor (tested or not) is a factory set component that will operate correctly (unless defective) and will correct issues associated with leaking check valves that cause lean run and top end stall. 



finaprint said:


> Very hard to check a small 2 stroke like these with compression gauge, the displacement is too small to really move the gauge


Compression is compression, regardless of displacement! If you are using a good compression gauge you will get a reading no matter what the size of the engine. If the gauge doesn't move, then you don't have any compression!



finaprint said:


> If flywheel key sheared you should be able to know what did it, they generally don't just do it out of the blue, something has to happen to produce it. There's probably a coil airgap in there somewhere that can affect starting too, I often close them up a little bit past spec to increase the signal strength there, it starts easier.


I agree you should be able to figure out why the key sheared, but it can be for many different reasons, such as a loose flywheel retaining nut/bolt, or priming with ether and having the unit backfire. Incorrect removal of flywheel retaining nut or bolt can also result in key shear on some units.

While the air gap on the coil can somewhat affect the ignition timing, closing it up will not make the spark any stronger. Keep it at spec and you won't have to worry about damage to the flywheel or coil lamination while running.


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