Tool Talk
General Category => General Discussion => Topic started by: 1930 on September 12, 2011, 12:23:45 PM
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or know of a good site that I can ask a question, thanks
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I have repaired a few. questions are easy answers are hard sometimes. bob w.
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I see you are online Jason, so I will back-up Bob, What Do Ya Got???????????
Wayne
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Thanks, I think it is a pretty common problem as I have had lawn mowers do the same thing. I have a walk behind edge trimmer that surges up and down on its own no matter where the idle is set.
In the past in looking at lawn mowers with the air cleaners off I can see a linkage that is attached to the carb and goes to another unknown destination and that linkage is being moved back and forth somehow and I am assuming it is being moved from the end that I cant see.
I would like to know how to fix this and why its happening.
I would like to take a course in small engine repair but there is not one offered here locally that I know of.
I can post pict. if neccesary, thanks
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Ok, (and back me up on this Bob)! The up and down RPM is caused by the Governor action! The action of the Governor is to speep-up the engine RPM, as the load requires it! The first thing you want to do, is check to see if you have a full tank of gas, then, pull the carb. float bowel, and run a small wire, (or a welding tip cleaner will work), thru the main jet, to see if it is not plugged. Also, make sure the Carb. bowel is clean from anything that may float within the bowel, and clog the main jet opening, in an intermittent manner, when the engine is running!
Wayne
edit: to make spelling gooder !!! Lol
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Wayne is right on the money the governor is trying to keep the rpms up to satisfy the load. During the cleaning process check the holes in the carp that allow the air to exit as the carb fills with fuel .the holes are small and above the normal level of the fuel. if the holes are plugged the air pressure will not let the fuel in.IN AN EMERGENCY YOU COULD BLOW INTO THE FuEL TANK FILL NECK CAUSING THE FUEL PRESSURE TO BE GREATER THAN THE TRAPPED AIR. you might check the fill cap to make sure the air is replacing the fuel in the tank. good luck them little rascals can cause a lot of problems cleanliness is a must
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If it is a new engine , they have leaned out the fuel mixture to meet the E.P.A. clean air standards
to a point where the engine just runs. One indication of lean fuel mixture is engine surge.
You can try running it with the choke partially closed, or drill the main jet a few 1/1000 of an inch larger.
Ray
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I am working on getting pict, and a reply so will have more in a few minutes, thanks
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Lets see if this works
Ok looks like I will have to attach one at a time until I figure out this resizing debacle again, just in case it was not clear this is the rod that moves back and forth that is in question, I am pretty mechanically inclined but I dont see a float bowl?
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This little spring was completely un-attached on the one side I noticed when I pulled the air cleaner off, putting it back on did not help
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And this little piggy shows a little more of the carb, dont see a float anywhere, looks like it is directed into cylinder directly, will await further instruction :)
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Its not too new but I am pretty carefull about taking care of my stuff so it stays like new, the machine is prob. at least 10 years old
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I have the same one. 3 hp.
I cured the exact same problem by changing the carb diaphragm. it is inside the bottom of the carb bowl.
I see you took the carb OFF of the edger.
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Hey Chuck, I am runnin with the big boys at 3.5 H.P
I am not sure where this is .........it is inside the bottom of the carb bowl
I dont understand this .........I see you took the carb OFF of the edger.........This is the way it came new, it is a Mclane model 3.5 big ones :)
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I am going to jump in and ask a question no seems to have asked yet. How old is the gas in that thing? if it has been sitting more than 3 months, you should dump the gas and put new gas in it.
Cruddy gas will cause the symptoms you are describing as well. Modern gas has a very short shelf life.
Beyond that, stuck choke, bad gasket in the carp, gunk in the carp as before mentioned...
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I see you took the carb OFF of the edger.
No, No, No, He took the "AIR CLEANER OFF"! Now then Jason, the top of the carb. is the thing with the butterfly valve, in the picture. The float bowel is underneath it ! BUT, if you found the govenor spring off completly, did you reattach it, and does it work now???????
Wayne
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I empty out all my units at the end of the season and let them sit for a few days with the cap untightened so that whats left can evaporate. If someone can show me where this carb bowl is that would be helpfull. Mr chuck, can you take my picture and draw a circle around what you mentioned and then repost so I know where this part is that you mentioned.
Is yours a Mclane as well, I know I had the option of the 3 or 3.5 version when I purchased the unit.
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Yes I know what a butterfly valve is, ( I am a mechanic when I want to be ) there is no bowl under that, I will post more pictures in a few, thanks
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Here are a few more pict of the carby
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Yes I know what a butterfly valve is, ( I am a mechanic when I want to be ) there is no bowl under that, I will post more pictures in a few, thanks
Best of Luck to You!
Wayne
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If you look straight down into the butterfly there is nothing at the botom except the throat casting that takes a wild turn heading for the cylinder.
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Quote...Best of Luck to You!
Giving up already Wayne?
I did mention in a previous post that I re-attached spring and it did no good
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Wow, I havn't seen one of those in a while. The carb has a dip tube that sucks the gas right out of the tank that it is sitting on. no bowl, no float, no needle valve. just a venturi.
They are totally idiot proof. Except for crappy gas, and junk getting stuck in the dip tibe or venturi.
And the gas cap getting a plugged up vent hole....
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OK well that answers that then no float ect, Rusty can you embelish on how this works, I am familiar with most aspects of how automotive engines operate but even cars that I own or have owned ( going back to late 20s ) have had a bowl with the float on them.
How does this dipping system work, when you say dipping you make me think of cranhshaft dippers before force feed oil systems were used.
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Quote...Best of Luck to You!
Giving up already Wayne?
YES!,I stop when I have nothing else to offer you. Even If it has no float, and it has a dip tube system, I still think it has to have a main Jet, orfice, or what ever you want to call it. Be it .040, .060, or any size in diameter. I thought it was getting crowded , so I backed out, but I'm back now, Happy? Lol What have you found since I fed the dogs, and went to the store? Is it running now that you hooked the spring back up? Do you have a can of either, to help you start it? The next time you get it running, bounce the S.O.B. up and down a few times for me! Let me know how you stand at this time, and I will dig out my thinkiing cap again if needed.
Wayne
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Playing around with it a litttle more I notice that it runs smooth as a kitten when I restrict the airflow to the carb choking it almost closed so I guess that again its not getting enough fuel for some reason.
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Yes I would also think that it has to have some way of metering the fuel but again I am not sure where to look and that is what I was hoping someone here could tell me. It has no problem starting and it never has and believe me it bounces around on its own plenty while it is running due to solid tires and no rubber mounts to the frame.
I hate to pull the carb off only to realize that it was not what was needed.
No the spring being re-attached did no good
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Glad you got it running Jason! Trim the crap out of the grass, and move on to your next project, untill we have an actual lawn mower engine specialist member to chime in! Lol
Wayne
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Can you see in the tank well enough to see if there is any rust in there? That's ther other thing that happens to old engines...
I suspect you are going to end up taking the carb off and giving it a cleaning. Yoiu will probably need a new tank gasket to do that tho, last time i tiook one of those off I had to beat it sensless to get it to let go...
Youu could try an oz of dry gas or fuel stabilizer, just in case it's goo, but I doubt it will fix anything, it never has for me, it always ends up being varnish or bits of rust stuck in the jet.
>main Jet, orfice, or what ever you want to call
Yes, it has only the part that in an automotive carb would be for high speed...
Most don't even have any metering adjustment, idle is set via a throttle stop screw.
There isn't a lot you can muck up with them, which is nice, but they don't work well in cold weather, which is why you don't see them on snowblowers, and they are kinda inefficient for large engines, they need a restricted airflow to make high velocity air to operate the venturi, which reduces the hp available from the engine rather a lot.
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Well now that rusty has re-opened this can of worms (no offense intended rusty), pour a little chemtool in the fuel tank to clean out the varnish that builds up over time.! A little, Not Allot, and make sure you either run it thru, or it sits for a week or so, then drain the whole fuel tank, and add new fuel! Thats ALL I got, so again, the Best of Luck to you!
Wayne
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One comment tells me all I think we need to know-
it runs smooth as a kitten when I restrict the airflow to the carb choking it almost closed
This means that the fuel passage is partially blocked and you are not getting a free flow of fuel to the intake. On regular carbs, this usually means the idle jet is clogged and by blocking airflow, you are enrichening the mixture. Usually won't happen on a "dip tube" type, but seems certain that this is your problem. By the way, the "dip tube" works on the very simple Bernoulli's Principle, the faster speed of the air along the top of the tube leads to reduced air pressure there and hence produces a lift of the fuel below it. When you choke the carb, you cause the air coming in to enter at a faster rate.
Your problem is most likely as mentioned above- crap in the gas or the nozzle entering the intake.
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One comment tells me all I think we need to know-
it runs smooth as a kitten when I restrict the airflow to the carb choking it almost closed
This means that the fuel passage is partially blocked and you are not getting a free flow of fuel to the intake. On regular carbs, this usually means the idle jet is clogged and by blocking airflow, you are enrichening the mixture. Usually won't happen on a "dip tube" type, but seems certain that this is your problem. By the way, the "dip tube" works on the very simple Bernoulli's Principle, the faster speed of the air along the top of the tube leads to reduced air pressure there and hence produces a lift of the fuel below it. When you choke the carb, you cause the air coming in to enter at a faster rate.
Your problem is most likely as mentioned above- crap in the gas or the nozzle entering the intake.
Very Well said Boss !
Wayne
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The engine has never stopped running so there was no getting it running again and it has been running the way it is running now for prob 3 seasons no change but I simply have not bothered to look into it because I use it for 10 minutes every 2 weeks or so and then put it away with other projects on the plate.
Yes when I said this......... it runs smooth as a kitten when I restrict the airflow to the carb choking it almost closed so I guess that again its not getting enough fuel for some reason........ my next thoughts were .........so I guess that again its not getting enough fuel for some reason.
Hopefully this does not sound sarcastic
Quote........Usually won't happen on a "dip tube" type..........
I am/was hoping that someone can tell me exactly why, I was hoping that maybe someone here has had the same problem with the same sort of carb.
Bottom of the tank is shined like a mirror almost and yes I don't have any thoughts of fuel additives fixing the problem but I have some laying about so I will try this before I pull the carb off to blow out and clean.
BTW you may already realize this Rusty but making gaskets is easy using an old cereal box, I hope it does not come to that because I am thinking that partial exhaust removal might be necessary and those nuts might not budge easily.
Thanks for the explanation on the dip-tube, now that it is explained to me I am quite sure that I remember some autos a bit older ( mid twenties and before ) than what I am used to messing with using this type of system, only read about it though and have seen schematics but have never had one apart.
Thanks again to everyone that has made suggestions, I will work it out and hopefully report back what I am able to find, if not than I will have one gently used working like brand new edger for sale on e-bay : )
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That type of carburetor has a built-in fuel pump, in order to pull the gas out of the gas tank. It does not have a fuel float bowl, lots of check valves and springs. Try running some carb cleaner through it.
I have taken the bolt that holds the air cleaner on out and while the engine running putting the palm of my hand over the air inlet and choke the engine till it almost dies, a few time to pull any dirt out of the carb
Ray
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Thanks for the tip, I am in the process of running cleaner thru it, I poured some in yesterday ( alot ) and after finally getting it to re-start it did seem to run better. I let it sit and did the same, trying to get the cleaner thru the carb and then let it sit to do its thing.
I will see today what progress I have made.
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PB BLASTER has a product called lawn mower tune up in a can. I usually get it at Lowes for less than five dollars. Buy some, follow the instructions on the label, spray some into the carb throat while running every now and again, be happy with the results!
I've been working on small engines over 40 years and this stuff is a great time and effort saver. I've used it to start 2-cycle engines needing carb rebuilds until I take the time to fix them. It's difficult to dose automotive cleaning products properly for small engines- this takes the guesswork out of it. Also, make sure that the air filter is clean. This almost always helps neglected lawn equipment. I clean all of mine several times a year. Good luck, Gene