Echo 2 Stroke Compression

homegrown55(9)October 1, 2011

Hi sports fans: I have a 21cc Echo chrome-plated cylinder off an older SRM-1501 Trimmer. I installed a new ring. Old ring end-gap was .030. New factory ring end-gap is .007. Compression has been tested to be 95psi. This has been the reading on 2 different cylinders (both "used") that I have. The engine will NOT start. It pops on occasion with an old plug (new coil installed). With a new plug and the new coil, it doesn't even "pop". Flywheel key has been checked and is OK. Do I need to hone the cylinder? If so using what EXACT tool, a brake cyliner hone, a flex ball hone or what type: aluminum oxide etc. Will honing (deglazing) the cylinder increase the compression and the ability for the engine to start and run? Can a chrome -plated aluminum cylinder even be honed to produce a "cross-hatch"? It has a Rebuilt carb, decarbed engine, new plug, new coil, new ring. I haven't been able to do a crankcase vacuum test. A Spark tester verified spark. So, 2 stroke experts....can you help me out here?

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roadbike

Are the crankcase seals good? Is it pulling fuel mixture into the cylinder? Is the carb any good?

    Bookmark   October 2, 2011 at 9:28PM
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walt2002

Comprssion is OK, I would not hone the chrome-plated cylinder.

Is spark plug wet? Have you tried priming it directly thru the spark plug hole? Probably some small thing you are overlooking.

Walt Conner

    Bookmark   October 3, 2011 at 8:19AM
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homegrown55(9)

After disassembly a time or two, it did run for a few seconds after priming with carb cleaner thru the plug hole with the new ring and new coil. ( I know, use proper fuel mix). I haven't tested the crankcase. The plug did get wet the only time I tried to start it with fuel in the fuel tank. Carb has G & D kit (new). There is NO primer bulb, just a choke and the tank is below the carb. I usually prime um and if they run, then I fuel them. I feel the engine has no choice but to run.Crankcase seals appear OK (I did not split the case) as Echo has a full crank. Crankshaft seals could be suspect maybe. Case and shaft seals appear to be original, but I don't know the history of this machine. I have tried fuel mix, carb/choke cleaner and starting fluid. Thanks for the replies, and Walt; I can only hope that is some small thing......but what? I have been working on this one a while and my patience is wearing thin.

    Bookmark   October 3, 2011 at 3:38PM
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ewalk

HG: Honing at home is pretty well out , Diamond Honing is required for Chromium and Nickel Plated surfaces. As for compression 125-130 would be optimium for the Echo . I would suspect inadequate base compression , do the vacuum leak down test , I think the crankcase seals may be the culprit although internal fuel circuit restriction still can't still be ruled out as a contributing cause :)

    Bookmark   October 3, 2011 at 5:07PM
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homegrown55(9)

Update. With only premix in tank, I choked it. It popped, and....after a couple pulls, it began running. I don't know exactly WHAT the problem was or still is. Ewalk could be on track but it is NOT the carb. After running about 4-5 minutes, I shut it off and it would NOT restart after about 20 minutes, but when it ran, it ran strong, it would also idle. I tweaked the adjustment (from 1 1/2 turns out) on the L and H screws and turned down the idle speed screw. Upon attempting the restart, the plug was wet, but it did not "pop", nor seem flooded. I think repeated atttempts at starting prior may have flooded it and it finally dried out some. That is ALL I can think of. It has a ZAMA WT-598 carb with NO primer as I earlier stated. The book I have said 90psi minimum for the engine and .012" minimum ring end-gap (with new ring is .006-,007). So there you are sports fans...it runs, but is HARD to start. (I knew the darn thing should run!). I am using older fuel though treated with Stabil and synthetic oil.

    Bookmark   October 3, 2011 at 6:05PM
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walt2002

" As for compression 125-130 would be optimium for the Echo . I would suspect inadequate base compression ,"

I respectfully disagree. While those figures may be optimum, I believe it will run down to about 60 psi. Fuel mixture really doesn't care what brand of engine it is in.

Walt Conner

    Bookmark   October 3, 2011 at 9:56PM
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1saxman

I know it ran on the old gas, but I would recommend replacing it with fresh mix anyway. Your basic problem seems to have every indication of an ignition problem.

    Bookmark   October 4, 2011 at 11:08AM
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homegrown55(9)

Saxman: I made up a batch of fresh today. The unit's original coil failed while I was working on it recently. It now has an OEM ignition coil. I pulled the flywheel and the integral key on it was NOT sheared. Air gap has been set at about .010". Plug gap is set at .025. I have an older Champion and a brand new NGK for it. So, what ignition problem could it be having?

    Bookmark   October 4, 2011 at 1:48PM
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ewalk

HG: Most of the Echo units I have had in for repair were Walbro Carburator's with Primer /Purge bulbs' The Zama without a Primer is relying on good base compression and top end compression for quick starting . You have not stated the vintage of the unit and dryed out or worn crank seals and marginal rings you will experience less than stellar starting. Compound this with sour gas and no pop or poor starting is to be expected. Since you have stated that a spark tester has been used your coil would appear fine .

Walt: I agree that 60-90 psi compression along with good base compression and elect. components should be ok , but with anything lacking weak coil , plug , condensor or points etc. will give suspect results. So many varibles on older units . Having a dry plug then wet indicates no fire scenerio or less than adequate compression .

    Bookmark   October 4, 2011 at 3:45PM
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homegrown55(9)

I mistakenly gave a Walbro model number for the carb as I am working on 2 machines. I apologize. I follow the theories you have stated ewalk and appreciate it. The carb is no-prime Zama C1U-K9A. I think that it may have a fuel induction problem as after repeated start attemps the plug isn't real wet, just real damp. So base compression may be weak and top compression is marginal/acceptable at 95psi. This is with new ring in a used cylinder.

    Bookmark   October 4, 2011 at 5:47PM
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ewalk

HG: Try adding a few squirts of sae 30 oil or WD-40 down the cylinder and pull over the unit . This may bump up the compression for a quick test . Spray some carb cleaner within the spark plug hole and reattempt to start the unit . If unit starts immediately then compression is questionable. If unit starts then falters you will have to check all carb hoses and flange connections along with cyl base and head bolts for proper tightness. Only a leak down test will verify base compression (good seals) . This with a proper carb including fuel filter cleaning may resurrect this old unit . As I said previously fuel restriction cannot be ruled entirely out . Remember Fuel , Air , Compression , Spark lol :) All the Best keep us posted.

    Bookmark   October 5, 2011 at 1:23PM
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1saxman

I think ewalk is on the right track, but what I meant was, just because a coil is new does not make it good. And there is undoubtedly a switch in the circuit....

    Bookmark   October 7, 2011 at 10:20PM
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homegrown55(9)

Another update. The vintage Echo saga continues! After restoring a 31cc Troy Bilt to run again, I'm back on this Echo. I put the starter off of an SRM-210 on it as the nylon pawl was worn. It pops, then it runs a few seconds, then it floods badly. But yes, it will run. I had put a gasket and diaprhragm kit in the carb earlier and adjusted the L and H mixture screws 1.5 turns out. I have taken the carb apart to see if there was any foreign dirt or debris in needle seat area. Needle tip still coated grey, not orange. DID not mess with the metering lever height. No need to. I Checked it with Zama gauge...it is fine. Needle opens and closes like it should.. Last time it ran, it accelerated then dropped down to a slow steady RPM and then flooded. I am currently letting the crankcase dry out. This has been one of the more challenging projects I have done, bad carb, bad starter, bad coil, bad cylinder, bad ring, broken starter spring...one thing after another. They don't make this model anymore (GOOD!)...the SRM210 is it's latest relative. I will keep you guys posted. Any ideas??

    Bookmark   October 9, 2011 at 1:51PM
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1saxman

In the spirit of not throwing any more good money/time after bad, I believe I would shoot it. I threw away a 14 yr old Ryobi trimmer power head that was mechanically perfect except it started flooding. I've tried to mess with the 'box' carbs a few times with no sucess so I cut my losses and got a new one.

    Bookmark   October 9, 2011 at 5:35PM
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homegrown55(9)

I play with these carbs and machines as a hobby (for now). Flooding of them is a tough nut to crack and Zama (The carb manufacturer) has a tech guide that lists all the causes for flooding (mechanical and carb related). I rarely ever give up and last time I had a cube carb doing this, I had the L and H mixtures screws set way out of spec.

    Bookmark   October 9, 2011 at 6:40PM
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ewalk

HG: Since the concern now appears flooding why not tweak the metering lever gap a little for a little less flow . Since you have the guage you can aways readjust if this does not help the excessive fuel issue once started . I would assume you have tweaked the low speed and high speed already from 1-1/2 out to perhaps 1-1/4 ? You seem to have done everything else mechanically , the Zama's can be a little tempermental . Once you get it up and running you will have to do a plug check occassionally to verifiy engine tuning is proper (long term).

    Bookmark   October 12, 2011 at 4:53PM
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homegrown55(9)

Hi ewalk, I DID tweak it as you mentioned. Took carb apart 2-3X. Changed out the needle valve. Carb still floods badly, this mind you, after running very well a few days ago. Gas/oil comes out the muffler. New diaphragm pushing on LOWERED metering lever. If anyone, can tell me, what the heck caused this bad flooding, I would be grateful. I can't take it anymore and found a NEW carb on Ebay. I wanted so much to make the old one right, maybe it was just worn out as I guess it is 10-12 years old or so.

    Bookmark   October 12, 2011 at 6:45PM
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homegrown55(9)

Since this Zama carb has NO primer bulb, I feel that old, swollen check valves in the MAIN NOZZLE and the IDLE circuit, may have been the contributing factor to the flooding; but Zama states it's flooding causes in regards to carbs with primer base assemblies on them. Even with lowered metering lever and new diaphragm and the mylar fuel pump (butyl rubber one pumps more)...flooding did occur. A test on the needle valve showed for the most part it was closing and opening properly (even though it was a USED needle valve). I probably should have got the RB kit, not the G & D kit. I will post one final time on this machine once the NEW carb is installed.

    Bookmark   October 13, 2011 at 6:05PM
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homegrown55(9)

New carb is OK. No fuel is being drawn UP into the combustion area. It is drawn in by the engine pulse and then pushed right out the exhaust port. Ported engine, no reed valve, just an intake manifold block. Interestingly, sprayed engine with WD-40 yesterday and today, it popped, then started and ran for about 5-7 seconds (no fuel in tank) and then would NOT restart with fuel mix in the tank. Base Compression issue?

    Bookmark   October 19, 2011 at 5:14PM
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ewalk

Since the WD-40 is sealing the rings intially I would say it is a combination possibly of less than optimium Top End Compression and potentially weak Base Compression. Unless you do a leakdown test to verify the seals . You have some crankcase pressure and vacuum otherwise you would not be recieving fuel to the carb. Is the manifold gasket new and torgued properly ?

    Bookmark   October 20, 2011 at 10:09AM
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homegrown55(9)

A friend recently sanded the glaze off of the used Echo 21.2cc cylinder on this engine. I have switched it to a rotary type Zama carb with the primer bulb. The machine NOW starts and it NOW runs. The mirror slick walls of the used cylinder ( the original had light score by exhaust port), in conjuntion with a new piston ring may have led to less than stellar base compression. I am surprised and relieved it runs now, though at 90-95 psi compression, I always felt it should.

    Bookmark   November 4, 2011 at 4:01PM
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ewalk

HG: Thanks for the follow up ! Great to hear that you have the Ole Echo up and running anything close to 100 Psi is good to go for a engine of your vintage . Ensure you use a premium grade oil at 50:1 and enjoy your resurrection Bro :)

    Bookmark   November 5, 2011 at 3:19PM
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homegrown55(9)

If you have one of those older Zama rotary type carbs (like RB-K70 or RB-K75), it is advisable to remove the plastic plug and the brass liner to access the main jet. It is located right below the fuel outlets on the primer base. Newer carbs may not have this. These carbs are set very lean at the factory and after accessing the main jet and opening it up some, the engine will run better. Just some advice as I tried this after installing a G & D kit on the carb and the Echo trimmer then started right up and idled and ran great. My setting was about 1 to 1 1/4 turns out from seated position.

    Bookmark   January 14, 2012 at 2:55PM
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homegrown55(9)

The actual culprit on this 21.2cc Echo was the flywheel in the end. The cast-in key was worn and there was "slop" in it on the shaft. Also, one of the 3 magnets was very weak and one was marginal. That flywheel has been retired. When it situated in the right spot on the crank, it would run normally. When the flywheel moved and "deviated" a couple degrees from where it should have been, it wouldn't start and repeated attempts caused the flooding.

    Bookmark   January 17, 2012 at 4:58PM
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ewalk

Never a dull moment with old 2-strokes !

    Bookmark   January 18, 2012 at 5:52PM
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