Echo CS-310 Problems Running Under Load

[Ray K]

My Echo CS-310 (14 inch bar) is acting-up, not running right when cutting. It is stock (no mods). When I bare down on wood, it more or less bogs down and doesn't want to cut. If I get it revved-up before hitting the wood, it will sometimes cut a bit but will eventually loose power. It takes forever to cut a 6-8 diameter log.

So far I have:

1. replaced the carburetor and gaskets
2. replaced the air filter
3. replaced the magneto
4. replaced the spark plug
5. replaced the fuel tank breather
6. replaced the fuel filter
7. checked the muffler for clogs (the spark arresting screen was clean)
8. checked the break-stop and clutch

There doesn't appear to be anything out of the ordinary. It starts with a pull (or two) and sounds OK when running/revving. It just bogs down when its time to cut - the chain stops moving. The chain is not binding and rolls across the bar easily. No chain slack either.

It is as-if it is starved for fuel. When it bogs, I must ease-off the throttle or it will die. It will start right up again. The process repeats.

Looking for advice ...

 

[SEAM]

Did you adjust the carb? Echos generally want to be set a little on the rich side...

 

[Ray K]

I did not touch the carb, the original one or the replacement. The original carb was clean and appeared new. The L/H screw positions were the same (visually) from original to replacement. The replacement is a Walbro too - like for like swap.

 

[SEAM]

Carburetors need to be adjusted properly for the engine to produce full performance. Your description sound like the engine is running too lean, starving for fuel during acceleration and at full throttle. Try setting the L and H screws a little richer - like 1-1/4 turn out from seated for starters... if the carb setting screws have limiter caps on them turn the screws fully ccw.

PS: One more thing that comes to mind is the fuel line being entangled in the fuel cap string... make sure the line is free.

 

[Ray K]

The fuel line is unobstructed, I made sure of it when changing the fuel filter.

The L/H settings are stock. I never touched them before and the saw ran great. Sure, tweaking may give it more giddy-up, but it should at least run. The new carb is from Echo, stock Walbro for this saw. It has orange colored caps on the screws. Do these need to be pried off?

I am hesitant to change the L/H settings until I get it to run right, then tweak from there. One less variable to consider.

 

[SEAM]

There are no "stock" carb settings - the carburetor needs to be adjusted for performance. The stock settings (or better standard settings) only allow the engine to be started and run for adjustment... sounds like your engine runs but does not perform -- needs to be adjusted.

If adjustment does not remedy the problem the next step would be having a look at the piston...

 

[Ray K]

Seam - can you point me to the best process to tune the CS-310 for performance?

 

[SEAM]

Open up the L and H screws a little - try 1/4 turn ccw first and see what happens...

 

[SteveSr]

Seam - can you point me to the best process to tune the CS-310 for performance?

Before you attempt this you might want to test for an air leak, especially if this happened suddenly. A saw should at least run at stock settings unless there is a problem somewhere. In this case a possible air leak could make it run lean enough to cause these symptoms. It looks like you have changed about everything else!

 

[ray benson]

Seam - can you point me to the best process to tune the CS-310 for performance?

Carb adjustment in service data bulletin

 

[Ray K]

SteveSr, how do I check for an air leak?

The problem is hard to describe. The motor will rev as it should, but doesn't do so consistently. The gasket on the filter assembly to carb and carb to engine are pristine. The muffler gasket too looks perfect. Visually, nothing has been an ah-ha moment.

I'll pull the bar and re-inspect the clutch. On the saw, it looks perfect but I haven't inspected the underside. The clutch and bell (?) are clean - no oil/grease that would 'slip' under a load.

 

[SteveSr]

SteveSr, how do I check for an air leak? The problem is hard to describe. The motor will rev as it should, but doesn't do so consistently.

This could be a symptom of an intermittent air leak.

The gasket on the filter assembly to carb and carb to engine are pristine. The muffler gasket too looks perfect. Visually, nothing has been an ah-ha moment.

The usual suspects are cracked intake boot (carb to cylinder), impulse line (again carb to cylinder) , and/or deteriorated crankshaft seals. You normally won't find air leaks by visual inspection. You'll find them by pressurization and a bucket of water!

To check for crankcase leaks the best way is to block off the intake behind the carburetor and exhaust behind the muffler and use a spark plug adapter to connect a hand pump with gauge. The crankcase should hold 7-10 PSI pressure and at least 7" vacuum. Old bicycle tubes make good intake and exhaust block off seals.

Search this forum and you should find many threads pertaining to leak testing

I'll pull the bar and re-inspect the clutch. On the saw, it looks perfect but I haven't inspected the underside. The clutch and bell (?) are clean - no oil/grease that would 'slip' under a load.

This isn't your problem. The engine isn't running right. If there is an air leak that goes undetected/unrepaired you'll likely burn up your saw. This is the main reason that top ends die! When you pull the muffler to block the exhaust take (and post some good photos of the piston through the exhaust port. You should see a nice smooth surface with no vertical scoring. This forum is full of piston photos!

 

[Wow]

Ok, my guess. Just asking. Have you tried a new chain. Professionally sharpened. I once was married and owned a donkey, then I bought a cs310. Gave the Donkey to a friend, my wife married a friend and I sold the cs310 to a friend. That's how I treated my friends when I had friends.
On the 310, I did a muffler mod and re tuned the carb. Sharpened the chain and set the depth of cut deeper. That loud little saw got an attitude and really cut well enough to fool, uh impress a buyer. The buyer soon dulled the chain and (laid heavily on the saw) pushed down on the saw to make it cut as he said. When it came back for service the AV was weak and the bar floppy. I sharpened the chain back to scary sharp and it cut great again but the Springs in the AV need replacing which he doesn't want to pay for. The cs352 is a much nicer saw IMHO. BUT these saws with AV don't like to be pinched and pulled or force fed. A chain that is filed right makes the saw self feed. Now, that's a shot in the dark my thinking. Your saw may be covered by warranty too. But if not,,,your High Speed needle may be set to lean. If it's not idling your Low needle may be to lean. Not judging, just tossing out info. Did you muffler mod this saw? After I modded my cs310 it drank a lot more fuel. Getting the carb set took cutting in wood. Good luck. My stock cs352 does great like it is. I used mine today. I don't like a cs310 at all and don't want one But I don't want another Donkey or another wife either. However, I am old cranky and very picky about my equipment. . Have a great day

 

[SEAM]

Re-adjusting the carburetor is absolutely free and does not require much time... Step 1 in all of my troubleshooting procedures.
Generally, all Echos are delivered set too lean in the US (to fulfill EPA regulations) and should be re-adjusted before use to avoid problems from lean running.
If the carburetor cannot be adjusted the probability of an air leak is pretty high.
After extended operation with a lean setting or an air leak damage to the P/C is also quite common.

 

[SteveSr]

Re-adjusting the carburetor is absolutely free and does not require much time... Step 1 in all of my troubleshooting procedures.

The carburetor comes "pre-adjusted" with the limiters full CCW at or near sea level. An engine in good condition should run (maybe scream) with these settings. The OPs isn't... something is wrong.

Trying to "tune" an air leak is a fools errand. Eventually the leak will get worse and you'll burn up the saw.

Generally, all Echos are delivered set too lean in the US (to fulfill EPA regulations) and should be re-adjusted before use to avoid problems from lean running.

This is generally good advice but by being set on the lean side the engine should scream unless it has already been damaged from other abuse or has had the muffler modified without resetting the carb in which case all bets are off.

 

[SEAM]

I am out of here...

 

[Wow]

Just re-read. Wonder if there's an update.
My experience with the Echo cs310 was like Marriage. Highly over rated. Thank God I bought a cs352 and got rid of my headaches both of em. Well today I was pulling a Trailer with the little John Deer. Filling in wash outs down on the creek. Like always I had my sweet little cs352. This is the same Saw I got upset a year or so about when the flimsy chain catcher broke and the Dealer ripped me a new one. Some Righteous so called super saw operators belittled me because HEY idiot you ain't suppose to drop a chain, why don't you learn how to use a chainsaw!!! Well all that stink is located on another thread but as I cleared a path a danged saw brier caught the chain and dropped it right off. Anyone who's ever used a NARROW nosed small 14 inch bar cutting underbrush has dropped a chain unless you walk on water. Well im happy to report the DIY Repair held up great. In fact after adding more plastic to the gussets I firmly believe this thing is superior to the new OEM clutch cover I bought but never used. Back on subject. The cs352 BEATS the CRAP OUTTA the cs310 that I had. After a mm and tune the cs310 really picked up steam and the new owner loved it. BUT,,like many home owners do they ran the chain in the dirt dulled it THEN LAID DOWN on the saw. The young inexperienced guy pinched the bar tip and man handled it to loosen it. When they brought it to me for Service I installed a good used bar and chain free. Fresh mix and oil and the baby saw came alive. The AV was floppy. I cut up a downed tree near my shop and they were delighted at how well it cuts. I begged them to LET the Saw feed its self. Stop rushing it. If the saw is bogging drop the handle down a bit unload the saw. Listen to the saw. Well anyway my cs352 started so easy. Ran so sweetly and was a joy to use even after that chain was put back on. I own two other Echo saws but this cs352 is a honey. I've never done anything but maxed both needles out to the limiters, put a BETTER BAR and chain on added gas and oil and used it like a free prostitute a week before pay day. Please please guys tell your friends the cs352 is a LOT BETTER SAW than a 310 and WORTH EVERY PENNY. Unless I just got lucky one saw and unlucky on the other this is my honest belief. I could be mistaken. Your milage may vary. Good luck