RESOLVED - Small Engine (Two Stroke) Issues

Off Topic
#1

I recently purchase a used Echo Power Pruner with known starting issues. Since I’ve had it, I’ve replaced and/or checked the following:

  • Fuel filter
  • Fuel tubes
  • Air cleaner
  • Carburetor & gasket
  • Spark plug (confirmed spark)
  • Spark arrestor
  • Intake Manifold & gasket
    I also am running new premix gas through it.

I can get it to start the first time, it will run only when given 50%+ throttle and dies before that. Once started, it doesn’t want to restart unless it’s set for a while or I’ve pulled the plug or carb.

Compression seems fine and there are significant differences with the plug in/out and the choke on/off.

Running out of things to replace and open to ideas…

#2

Have you checked the needles in the carb?or the carb idle screws?

Spark arrester, did you clean it?

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#3

Spark arrester was clean when I pulled it off. No build up or clogging.

It has one of the ‘cube’ carbs which aren’t really intended to be adjusted based on what I’ve read. Since I put the new carb on, I haven’t taken it apart to ensure the diaphragm and needle are clear.

#4

Gotcha. No obstructions in the muffler?

#5

I would actually verify compression with a gauge and also monitor the spark while running and when it died (I would use scope). Do you still have spark when it dies and will it start when sprayed with fuel?

#6

Didn’t seem like it when I tried to run it without the spark arrester. Will pull the muffler, check and try running without it.

#7

Not sure I have the equipment to test these. Will have to research hacks…

#8

Make sure you don’t have an air leak going to the carb. If you have a primer bulb, it may have a slight leak, crack, or off it’s seat. Check the fuel lines as well.

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#9

I agree with the idea that it could be a compression problem. I assume that it has piston rings (unlike the old model airplane engines). Pull the head and see if you can see obvious wear of the area where the piston rings travel in the cylinder. I don’t know if those engines are designed to be repaired (e.g., are oversized rings and/or pistons available?). It’s hard to imagine that it is cost effective to repair it if it’s a compression problem, but this is coming from the guy who fabricated an itty bitty part to repair the screen latch for a Dell laptop and vacuum molded the elastomer part that connects a Casio watch band to the watch body. :grin:

#10

I doubt this is a compression issue. Firing at 50% throttle and not firing again until you disconnect something sounds like it is a fuel/air mixture problem. A jet is clogged or getting air from outside the system.

#11

That’s my thoughts as well. My brother had an Echo blower that would not run. That’s when I found an obstruction in the exhaust muffler plus the arrester was caked.

These small engines mostly are only designed for 50 hours of use.

Can’t tell you how many I have picked up for free because they wouldn’t run only for it to be a simple problem. The way I look at them is by the fire triangle. Fuel, air & spark. If the ratios are off, it wont run.

#12

I boiled down his description of the symptoms to “it only runs when cold” and that does sound like a fuel/air mixture problem – too rich to be exact. But if he already replaced the carburetor?

I am assuming that @JW_TX verified that the choke is not stuck closed.

And I wondered if having to hold the throttle open was required to get enough air in to generate some compression – that was my thinking.

Here’s another thought – a fuel delivery clog somewhere between the fuel pickup in the tank and the carburetor.

I think there’s a flexible pickup tube with a weighted end in the tank. There could be a fine screen on the weighted end or maybe an inline filter that is clogged. I guess that this would probably be ruled out if the priming bulb quickly fills up when pushed.

I have an Echo string trimmer, but I have not had any problems with it yet. Unlike the two electric trimmers that I previously purchased thinking they would be less trouble!!!

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#13

Appreciate all the suggestions. Didn’t get a chance to look at it today and will try tomorrow.

#14

PPT_Bore.jpg
PPT_Bore.jpg1011×767 137 KB

Not the best picture, but once I pulled the muffler the culprit is pretty apparent.

Looking for votes if it’s worth it to replace the piston and top-end of then engine or not…

#15

like this’n?


Do you have your eye on a kit?
Posting the model # might help folks source/price parts…

#16

Good point. It’s the Echo PPT-265. Looks like the best option is the SB1102 shortbloc kit. Cheaper than sourcing individual parts. I’m seeing them for 130-140 range.

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#17

Are there adjustment screws that allow you to change the fuel air mix ratios? Just had a problem on a leaf blower that was fixed with adjusting this. Now works like a Swiss watch.

#18

There are, but just replaced the entire carb. Seeing the scored piston leads me to believe something died in the cylinder…

#19

Based on the ~$300-400 new, already invested in the carb, I’d say go for it. That’ll put you (guesstimating on my part) at about 1/2-2/3 of the cost of a new one, and hopefully provide like-new work output… Plus, you get to tinker with a 2-stroke! That’s the real value. :+1:
(pics or it didn’t happen…)

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#20

Exactly. Sourced a new shortbloc assembly on eBay and should be delivered on Thursday.

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