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Boot
05-29-2012, 06:32 PM
My weed wacker will idle ,but not run when the gas trigger is advanced it dies. I can't see buying a new carb for it . Price is $60 . I'll buy a whole new machine if I can't figure it out. I had carb off and looked inside. It looks ok. Had muffler off and it is clean. Also cleaned the foam air cleaner and it's good. New sparkplug in it. What else could be wrong with a 2 cycle engine? Thanks for any input , Boot.

sasquatch
05-29-2012, 06:48 PM
Is this a "Weed eater" ?

Just bought a carb kit for mine today, it owes me nothing, paid $89.00 for it 11 years ago, never touched it till just now, not getting any fuel.
Full carb kit was like 16 bucks, and new fuel line $1.30

Interesting little carbs, picky to work on, but enjoyable to get them to run right again.

Boot
05-29-2012, 06:57 PM
I checked. It's a Sears and I guess they want you to buy a new carb or a new machine. I checked a couple of carb kit suppliers and they don't have kits for it. as far as I could tell. It is made by MTD.

Fasttrack
05-29-2012, 07:13 PM
Hard to justify working on most of those when the cost of a new one is so low. I picked up a "Remington" trimmer on sale for $69 and it has been very reliable so far. At that price, I figured even if it only lasted me the summer it was worth it, given what it costs to hire someone to do lawn care.

Sure sounds like you've got a carb problem. I say take the carb off and remove all the gaskets/plastic parts you can without damaging anything and soak in carb cleaner. Put it back together and try it out. If it still doesn't work, got get a new one and sell the old one to the scrap man.

SteveF
05-29-2012, 07:34 PM
The ones I've fixed generally got that way from having fuel mix sit in them for months. Pull the fuel hose off the carb, spray it full of carb cleaner, drain the fuel tank and put in fresh mix. That fixed most of the them, if not, the carb will need to be disassembled and cleaned.

Steve

GadgetBuilder
05-29-2012, 07:37 PM
If you opened the carb up and cleaned the little screen, that's one of the more common problems. If the gas line is pinched that could be an issue too.

When it idles and won't accelerate, it often helps to open the Hi speed jet 1/8 turn or so - don't make big changes lest it gets way out of whack. If you move it more than 1/2 turn, something else is likely the problem.

The last one I worked on the H/L screws were surrounded by metal and didn't have a slot in them to allow adjustment - probably an EPA thing.

Here's the machining content. ;) I chucked up a small round piece of plastic, turned it down so it fit into the screw housing, and end drilled it so it was a push fit over the Hi speed jet screw. It doesn't take a lot of torque so this little tool works fine. I scratched a witness mark on the screw head so I could keep track of the rotation, opened it 1/8 turn and now it works normally.

John

armedandsafe
05-29-2012, 07:44 PM
We had a similar problem which turned out to be fuel gum in the outlet inside the fuel tank. Drove the shop nutzo for a little while. They finally cleaned the tank with acetone until they got a good stream out of the fitting.

Pops

Bob Fisher
05-29-2012, 08:24 PM
I had the same problem, and fixed it the same way as Gadget did. I made a plastiic "screwdriver", heated the end gently and pressed it onto the head of the adjusting screw. The jet adjustments nowadays have serrated heads to prevent "tampering", Not that any of us would stoop so low as to doubt the EPA's good intentions! I took some flak at the time for not fixing the "real" problem, but my 2cycle edger is running just great without having to be at half choke. 2 years now and runs great. As was mentioned, it should not need a major change. Bob F.

lakeside53
05-29-2012, 08:30 PM
When it idles and won't accelerate, it often helps to open the Hi speed jet 1/8 turn or so - don't make big changes lest it gets way out of whack. If you move it more than 1/2 turn, something else is likely the problem.


John


Not sure what opening the H screw does to transition. To accelerate from idle to high, you need to adjust the L screw slightly richer. You might need to advance the idle screw setting slightly to compensate.

A typical carb kit is less then $10. The carb manf and model number will be on the carb body (very few equipemnt manfs make carbs). Inlet screen (in the pump side of the carb), stiff metering diaphram and blocked jets are typcial of this problem. Swollen and kinked fuel line if you are using ethanlol gas.


Check the exhaust screen (if it has one) and make sure mud dauber wasps haven't blocked the exhaust outlet.

And.... failed electronic ignition can also act like a bad carb.

sasquatch
05-29-2012, 08:37 PM
Good points Lakeside!!

J. Randall
05-29-2012, 08:39 PM
Agree with the previous post, most likely a Walbro carb, could be a Zama, not to many makers. Get the name and number off the carb, a kit should be available. One thing not mentioned is the fuel filter on the end of the hose inside the fuel tank, make you a wire hook and fish it out the fill hole, either clean it or replace it if plugged.
James

lakeside53
05-29-2012, 08:43 PM
Good points Lakeside!!


Easy stuff.... In a past life I did this for a living;) You get about 5 minutes to diagnose, and 20-30 to fix. If not you loose money.

h12721
05-29-2012, 08:47 PM
I have a Stiel Chainsaw, one Day I could not start the thing. I brought it in for repair to the Stiel place. After $80.00 got it back. Carb needs to be replaced.
Was told by the Stiel guy don't use the low test gas, use high test only. Some thing in the low test eats some diaphragm in the cab or so. Now it is high test only and no problem in Years. I read the book after I paid the $80.00 and it says so right in there. 1:50 mix. with high test only.
Hilmar

lakeside53
05-29-2012, 08:57 PM
Stihl has required 89 or better for about the past 20 years, primarily becaue of the high compression (150-175psi) and resultant detonation issues.

The reason for the high-test recommendation is that gas loses about 1% of it's octane per week of storage (in typical consumer containers AND in the engine gas tank). Doesn't take long to get below 89. It has nothing to do with what's different between 87 and 93. Of course, ethanol blows fuel components any octance...

The best recommendation I have is NOT to store gas in your saws/trimmer/blowers. Run them out unless you use them reqularly. Don't use the current ethanol pump gas more then 3 month old unless you add stabil. If you want gas to last for years and never damage fuel components, use 100LL - available for boats and all small plane airports, and a quality synthetic mix oil. Never use TCW-3 rated oils - those are for water cooled boat motors.

boaterri
05-29-2012, 10:09 PM
Here is a trick I have used on small outboard motors and a couple of chainsaws. Take the carb off, disassemble removing all of the jets, needle valves etc. Soak overnight in mineral spirits.

Buy (or borrow your wife's jewelery cleaning) ultrasonic cleaner. Take it OUTSIDE and fill with the parts and fresh mineral spirits, run it for several cycles but not beyond the mineral spirits getting slightly warm.

Reassemble, and all should be well, if not, wash, rinse, repeat.

Good luck,

Rick

Carld
05-29-2012, 10:19 PM
Boot, the low screw is the one to adjust. If you set the idle to where the clutch just wants to start the string head turning then open the low screw 1/4 turn and open the throttle and it stalls then open it another 1/4 turn until it doesn't stall. Then open the throttle and start turning the high speed screw out until the engine starts slowing and then turn it back in until it peaks out then open it 1/8 turn.

You should be good from there. Been there, done that, owned a small engine shop in the past. That works for almost any 2 cyl engine. I set the high end on a chain saw while cutting a log. It's tricky but gives the best results.

lakeside53
05-29-2012, 11:41 PM
Adding to what Carl said - make sure your trimmer line is at the correct length (and size and number) before making your high end adjustment. The line is the load.

You may need to remove the EPA required limiter caps. If the overall adjustments are not close to factory (say 1 turn out - but this varies from carb to carb), look for the reason. Incorrect needle valve lever height is often the reason for high end run adjustments not being correct.

Robdiesel.707
05-29-2012, 11:57 PM
I've had issiues with my power equipment, the fuel, I found that the fuel lines get crackes in them where it goes onto the fitting's. I bought new fuel lines and purge bulb if equiped and that solved the problem. I have a Mantis and it wouln't run, changed the fuel lines ect., took the carb off and disassembeled it and found green chalky looking deposits in the passages. There is a small screen in it and I removed it and un-stuck the check valve ball. Put it back together and it ran great. The fuel we have in California has 15% ethenol in it, so I try to buy ethenol free gas at the fuel distributer, 91 octane is what you need in small power equipment, and I use 50:1 mix. I have had better luck with the ethenol free gas, it is $5.25 per gallon in Eureka,Ca.

KIMFAB
05-30-2012, 12:44 AM
I know this will not help on the carb problem but several years ago after having the same problem I gave up and bought a propane unit.

I no longer worry about octane, dried carbs or mixing oil.

oldtiffie
05-30-2012, 06:44 AM
I was warned by my mower supplier to not leave gasoline with methanol in it in the tank over winter and if the tank is not drained to use an additive to help prevent "gunk" in the tank and carby. Best bet is no methanol.

I don't use the additive and I don't use gasoline with methanol in it anywhere - car, mowers, gen-set, chain saws and "whipper snippers" etc either. I have no trouble starting the machines after several weeks or months.

My mower fuel gets turned over every few weeks in the cutting season so the fuel is relatively "fresh".

I hadn't used my chain saws for about two years - started second or third pull and never missed a beat.

The "Honda" gen-set is a dream to start and use.

GKman
05-30-2012, 07:59 AM
BMW m/c's have compression over 11:1 (I just bought a '02) and need high octane. Guess what? So little high octane sold riders complain about getting expensive, STALE fuel.

Don't know what's up with Stihl's recommendation (89 octane in my MS 260 Manual) compression ratios in 2 strokes can't be very high given the height of the transfer ports in the cylinder and the flame travel distance from the plug to the outer edge is minuscule. Octane rating is about detonation not a Good, Better, BEST! rating.

Glad to add to the confusion.

ecortech
05-30-2012, 09:48 AM
Most small engines do not need the octane, the high octane recommendation is because most high octane premium pump gas, does not contain alcohol. Using fuel with no alcohol eliminates many problems with small engines.

Ed

Machtool
05-30-2012, 10:56 AM
Remarkable. A Thread about Weed Wackers, and “down under Inc” still manages to slip in a plug.

I was warned by my mower supplier to not leave gasoline with methanol in it in the tank over winter Are you sure your not just parroting something you have read here, Googled or Plagiarised?

Given there’s a very good reason the pumps at a cheap fuel Stations say E85.That’s because we do Ethanol mix not Methanol.

But you would have read a thread about “Sta-bil’ and worked your way into that. A product that’s hardly known down here.

I hadn't used my chain saws for about two years.
Why would the chain saw be any different from your other machines?


The "Honda" gen-set is a dream to start and use. Interestingly enough, each and every time you trot the boys out for a photo shoot, there’s no Gen-Set, Honda or otherwise.Nor a photo of it ever: Just saying.

http://i200.photobucket.com/albums/aa294/oldtiffie/Shop_and_tools/Shed-ext3.jpg (http://i200.photobucket.com/albums/aa294/oldtiffie/Shop_and_tools/Shed-ext3.jpg)

Are your sure that really exists? Or are you just embellishing the **** out of this story, like normal?

Wouldn’t this be closer to the truth, from just 12 days ago. Hint "This will be my next one"

http://bbs.homeshopmachinist.net/showpost.php?p=770193 (http://bbs.homeshopmachinist.net/showpost.php?p=770193)

You have some crap compressor, but would like to invest in a Honda, That’s normal, but why B.S and play it up, pretending you have one all ready? Is that a Navy thing?

SteveF
05-30-2012, 11:58 AM
You may need to remove the EPA required limiter caps. If the overall adjustments are not close to factory (say 1 turn out - but this varies from carb to carb), look for the reason. Incorrect needle valve lever height is often the reason for high end run adjustments not being correct.

When the engine was shipped from the manufacturer, the adjustments were set to give the correct A/F mixture, then sealed. If the engine isn't getting the correct mixture now, the problem is caused because of contamination in the carb. Thoroughly clean out all the contamination and the carb will work fine.

Steve

lakeside53
05-30-2012, 12:35 PM
They are not "sealed - just set to within a limited range. And... they don't stay in adjustment. Some engines are rated for 50 hrs, some for 300 (total engine emissions, not just because of the carb). The needle wears and the lever needs adjusting, and the diaphragm gets distorted or stiff. Also, butterfly shafts wear and leak air. Any time you disassemble a carb, you need to remove the limiter caps if for no other reason than to clean out the relevant port.

Limiter caps are there to stop the end-user from enrichening beyond EPA limits. It's pretty much impossible to tune a carb with them on as the adjustment is deliberately limited. The high end from the factory is often set way too lean giving little room for error with fuel and mix. Over the past few years I have a few hundred burnt pistons... add a tiny amount of water to the ethanol fuel/oil mix, shake up and and watch how it forces separation of the oil. Not good. Use a quality synthetic mix oil - MUCH better in the presence of ethanol.

An overlooked area in such carbs (the primary reason why they get tossed) is the fuel nozzle in the venturi - typically this has an integral non-return valve (just a flap of material). It's non-repairable and is not supplied in carb kit. Take great care with compressed air... I've seem these valves destroyed by good intentions. On the same topic, modern epa carbs often have these valves in the L and if equiped, mid-range jets. If they get messed up by old gas, ethanol or compressed air, it's new carb time. As suggested in prior post, and ultrasonic learner can recover stuck valves and remove varnish. I use Coleman lantern fluid (naptha "white gas") for this. Be very careful using flamables in an ultrasonic cleaner.


For the carb fuel pump to function correctly, the crankcase vacuum cycle has to get to it. There is either a separate line (impulse hose) or a a direct connection though the carb body mount. Either way, this must not leak. Check the carb screws for tightness, and if a direct connection the gasket. Poor idle or starting is often leaking crank seals creating a low vac condition for the carb.

lakeside53
05-30-2012, 12:41 PM
Most small engines do not need the octane, the high octane recommendation is because most high octane premium pump gas, does not contain alcohol. Using fuel with no alcohol eliminates many problems with small engines.

Ed

Not in most (all?) of the USA.... all grades have up 10%-15% ethanol. The recommendatrion was from way before the ethanol was added. Adding ethanol raises the octane of gas.

lakeside53
05-30-2012, 12:51 PM
Don't know what's up with Stihl's recommendation (89 octane in my MS 260 Manual) compression ratios in 2 strokes can't be very high given the height of the transfer ports in the cylinder and the flame travel distance from the plug to the outer edge is minuscule. Octane rating is about detonation not a Good, Better, BEST! rating.

Glad to add to the confusion.

It's definitely about detonation. It doesn't take much octane loss or carbon buildup on the piston top or cylinder changer to start this - you see this on the eroded exhaust side of the piston crown.

An MS260 (there are two different cylinders for these... the latter being 44.7mm and at nearly 1/2 hp less than the predecessor MS260, a dog. Thanks EPA) typically runs 165+ psi compression from the factory.

lakeside53
05-30-2012, 12:56 PM
I know this will not help on the carb problem but several years ago after having the same problem I gave up and bought a propane unit.

I no longer worry about octane, dried carbs or mixing oil.


Just remember to change your sump oil :)

lynnl
05-30-2012, 12:56 PM
One thing not mentioned is the fuel filter on the end of the hose inside the fuel tank, make you a wire hook and fish it out the fill hole, either clean it or replace it if plugged.
James

I was recently having the same problem with a Stihl chainsaw; would die when I opened the throttle to cut. ...as if it were afraid of the wood. :)

Replaced that fuel pickup filter and the rubber fuel line from tank to carburetor, and it worked great thereafter.

That's what I'd try first, before getting into the carburetor.

Incidentally, my filter looked to be clean and ok. I would just replace it.

lakeside53
05-30-2012, 01:11 PM
Fuel lines get leaks and suck air (and crud). The Stihl 029-390 (and MS versions) are horrible for this - the sunlight gets in just under the air-filter cover and rots the line. Later lines are now UV resistant.

Take a small pressure bulb (like you use on a blood pressure monitor) or whatever, and apply 5 psi to the end of the fuel line after removing the filter. it should hold pressure. At about 8-15psi, the inlet needle valve in the carb will start to leak. If the fuel line leaks at 5psi, as part of replacing the hose, take off the pump side end cap of the carb (one screw on zama and walbro) -the inlet filter will likely be full of crud.

Boot
05-30-2012, 05:47 PM
Thanks fellas. I'm going to try all those suggestions before I throw it in the scrap bin. Need to pick up some carb cleaner this week.

Forestgnome
05-30-2012, 07:25 PM
Didn't read all the posts, but did you try a fresh batch of fuel? That's the most common cause of two-stroke problems. Like someone else stated, use premium.

madman
07-11-2012, 10:15 AM
Never run any gasoline with alcohol in the weed whippers, The tiny openings in the carbs jets will just plug up, if you run premium without alcohol it will like that a LOT better, The aluminium housing gets a corrosion caused by the alcohol content, secondly if you know someone with a ultra sonic cleaner give the carb a bath in it with cleaner, the openings in the carb are like 4 or 5 thou in diameter, (some even smaller) The shops use ultrasonic carb cleaners for there weed whipper carb cleaning and it helps a lot, Lastly check the diaphragm if its hardened up and doesn't flex very well that also can cause troubles Good Luck Mike

atty
07-11-2012, 11:20 AM
Never run any gasoline with alcohol in the weed whippers, Lastly check the diaphragm if its hardened up and doesn't flex very well that also can cause troubles Good Luck Mike


#1 on all of the above. I finally emerged victorious after a long battle with a Ryobi weed trimmer. Replaced the diaphragms, which were stiff as a board, and went to 100LL Avgas. What an amazing difference with that gas. Takes a little while for it work its way through the carb and settle in enough to get H and L adjustments right. I know that makes no sense when you start off with a clean carb, new fuel filter, and a clean gas tank, but that's the way it was. May have something to do with the residual in the crankcase. Anyway, it's running like new now.

Also, not to be outdone by a friend of mine in N.C., I temporarily ditched the string attachment for a 7 1/4" saw blade. You have to be careful about rocks, but that thing does a great job clearing brush, as well as grass. Just be careful where you're swinging it.

kbertoson
07-11-2012, 12:58 PM
Anyone with a Ryobi 2 cycle string trimmer. My fuel lines and primer bulb had rotted away. Home Depot sells a kit with a primer bulb and 2 fuel lines and a curved puller wire. The cost is about $8.00 here in North Georgia. Replaced those now my starter is bad.

atty
07-11-2012, 06:12 PM
Mine is a Ryobi 720R, and I had to do the bulb and fuel lines as well as the carb kit. I'm keeping my fingers crossed on the starter. I also figure it's next on the list.

madman
07-11-2012, 06:56 PM
Firstly none of us want to weed whip BUT when finally that time comes its nice if the thing starrts up . I learned a bunch from the posts and mainly my personall exoperiences. I always thought I knew more about engines than most people but the weed whippers suck period. Now i seem able to get mine to start and unfortunately in my neighbourhood I get a Lot of requests to get there **** going also. sucks to be me I guess

Forestgnome
07-12-2012, 10:05 AM
You just need to stay away from big box store weed trimmers. I have a Shindaiwa that starts up every time. No special care, old gas, never adjusted or cleaned in years.

firbikrhd1
07-12-2012, 10:20 AM
You just need to stay away from big box store weed trimmers. I have a Shindaiwa that starts up every time. No special care, old gas, never adjusted or cleaned in years.


I agree that the Shindiawa is a better trimmer than most big box store trimmers. I too have a Shindiawa (T-25) but it has had fuel related trouble too. Ethanol in fuel is an equal opportunity destroyer of small engines, particularly the soft parts in their carburetors. Particulate matter is an equal opportunity clogger, as well.

One solution would be to use fuel without ethanol, but that is difficult to obtain in my area, so, I modified my Shindiawa, after replacing the rubber fuel pickup for the second time in six months, so it could withstand ethanol. To prevent particulate matter from entering the fuel tank I began using a funnel designed for Coleman lanterns to fill the tank. Gas lanterns are picky about particulate matter so funnels designed to fill them are quite good at removing it.

Since making these two changes my Shindiawa has started every time for several years now.

atty
07-12-2012, 11:13 AM
Good idea on filtering before the tank. I've been looking at another option to filter the fuel just before it enters the carb, and it's one of those 1/8" inline filters, like this one. http://www.adaracing.com/scooter/fuel-filter-billet-inline/ff-1
I haven't checked Home Depot, Lowes, etc., but I'm sure they have something similar.

I know this is a bit of a pain, but if you can't get to a source of gas without ethanol, there is a way to remove it. I'd work with about a gallon since more than that becomes a big hazard. As crazy as it sounds, just add about 20-25% water to the gas. Shake it up and let it sit for several hours. The water binds to the ethanol and both settle to the bottom of the container. If you're using a glass container, you will see a well-defined line of separation. Simply siphon off the gas above the line, and you're back to pure gas. It's a little tedious, but since we're talking about small engines, a gallon should last for a while. I'd personally recommend a trip to the local airport instead, but this method will do in a pinch.

lakeside53
07-12-2012, 11:42 AM
Just buy a quality fuel filter. There are a few sizes with different hose connector nozzle sizes. Stihl filters do not suffer damage with ethanol. They are only $5 or so; on one size you can just replace the inner core for less then $2.

If you are having trouble with box-store (or old quality brands) fuel trimmer system parts, replace the hoses with Viton or similar. They will last forever. If you have a Stihl dealer nearby, Stihl has many sizes of fuel hose (dealer may not stock them though!) that work fine.

10% Ethanol gas works fine. Just don't leave it in your can or trimmer more than 30-60 days, and use a quality synthetic mix oil to lessen the chance of separation in the presence of water. If you use Avgas, it can stay in the can and trimmer for a couple of years - be aware though that even 100LL it has 7x the lead than 80's automobile gas.

kbertoson
07-27-2012, 07:46 PM
Ryobi String Trimmer update. I ordered a new carburetor assembly, gasket, air box cover. filter, filler cap and starter grip. Total with priority mail, $38.28. Ordered from ereplacementparts (no connection, happy with the service). The trimmer now runs. There is no parts kit for the carburetor only replacement. I now see I was missing the choke plate as well. Somebody needed a replacement? The carburetor was $18.77. I do not use this day in and day out. For money spent it is worth it. A Lawn Care business buy a real top line model. . Anybody with a Ryobi trimmer, ereplacementparts also has repair tutorials, a big help.They may have other makes tutorials as well.

Bill736
07-27-2012, 08:20 PM
I've usually found on these all-position diaphram carbs ( cursed little Walbros) that the little needle under the diaphram is gunked up. Sometimes, however, you can clean them out if you can get the fuel flowing again. Keep the engine running using starting fluid for about 30 seconds or so, and richen up both the low and high speed jets if you can. Sometimes, getting a jet cleaned out is as simple as turning it all the way in so it's closed, ( but gently), and then backing it out to the run setting, or richer. Granted, many of them are hard to adjust nowdays. Storing these little engines with stabilized gasoline in the tank may help you next season.

J Harp
07-27-2012, 10:48 PM
Make sure the check valve in the priming pump (the small flexible bulb) is working as a one way valve. My Echo had that problem a few years back. The carb was sucking air, so the engine wouldn't run above idle The fix was to splice another generic priming pump into the pump discharge line inside the fuel tank to stop air being pulled back. It's still working.

J Tiers
07-27-2012, 11:06 PM
Whoever (not the OP, I checked) said they are not sealed........ are you sure about that?

Seems that a lot of newer carbs have no adjustments, Kalifornia EPA requirement..... don't let anyone work on them, nor change most settings, might increase emissions...... A couple I have seen were just "blocks" with the usual adjustment places filled with plugs.

If it's an older unit, that may not apply.

Ron of Va
07-29-2012, 07:56 AM
Ethanol Free Gas by State.
Click the State at the bottom of the page.
http://pure-gas.org/index.jsp

jnissen
07-29-2012, 11:09 PM
Ditto on the 100LL. Get it at your local small airfield. The field I purchase it requires you to put a tail number in the log sheet. I just put in whatever plane is nearby and the guy selling doesn't complain! I buy it 5 gallons at a time and will use it in my yard gear as well as my remote control model 2 cycle engines. Works wonderfully in the race boats.

As for the Ryobi, you would have been better off saving your money for a good brand. Shindawa's and even Echo's are fair. The Ryobi has a stamped steel connecting rod and in general is hardly worth replacing parts on these things. I rebuilt one for a neighbor but it trashed the starter and the lower crank bearings started to make noise. Told him to toss it as I wouldn't even try to rebuild it after that. He could buy two of the low dollar type trimmers new for the price of the replacement parts alone.