This girl was running fine and now it is hard to start and when it does, runs fast, then slow, fast, then slow, etc--can't get it to run steady. It had happened once before, I took the bowl off and cleaned the jets and it looked like the needle was new and the seat was fine too. The float was good at that time also. I cleaned things up and it ran fine, now it is misbehaving again. What would be the likely culprit? I cleaned it just two or so months back.

Sounds like it may be time to get a rebuild kit for the carb.

Both the needle and float looked new, what else might it be?

look for one of these.

1. Dirty air filter.
2. Water or trash in the fuel system.
3. Breaks in the spark plug wire, loose or corroded terminal connections causing an intermittent failure. (Very common for twin cylinder engines.)
4. Misadjusted or malfunctioning governor.

plugged idle circuit will make you pull your hair out also a partially sheared flywheel
key can cause erratic running very common on tecumseh engines mounted on mowers
sometimes this happens just by getting into high grass to fast good luck

Symptoms: Mower starts up and on high throttle, it speeds up, then slows down, over and over again. Interestingly, when I reduce the throttle, it runs smoothly, but does not generate enough torque to be useful. Dies and then cannot be re-started.

I fired this mower up again for the first time this season and am still seeing the same symptoms. I dropped the carburator bowl and inspected. Gasket looks good. I cleaned the bowl up, inspected the float and it is not filled with gas. The needle still looks new. I forgot to inspect the seat for it, though. Operating the float mechanism it moves up and down fine. The nut that secures the bowl, which I believe is the "jet", is all cleaned up, the small holes are clear. I also shot some air up into where the jet feeds the carb and it sounds clear.

I really like this mower, but it may be headed for the trash heap if I can't get it to work reliably. Anything else that I should be looking at? One of the previous comments mentions the idle circuit, where is that and what do I need to do there to write that off as the cause. Also, the governor?

Looking at this diagram of the carb, I don't recall seeing part #11, where is it? http://partsandservice.com/bin/ipl.cgi

The mower did run fine for a few months last year, so I don't think there is anything seriously wrong with it.

That link does not show a parts breakdown (at least not when I clicked on it). What is the spec number off your engine?

These links should work. I'll get the carb number this afternoon. From the manual, it is a series 1 float style carb, with no adjustments.

According to comments here, the “open end” of the clip must point towards the air filter. That means that the long end points towards the front (left) when looking at the mower from the side with carb installed and bowl dropped:

http://www.lawn-mower-shop.com/carb1.htm

But if you look at the Tecumseh service manual, see page 17, it looks like the long end is pointing to the right (turn picture upside down to get oriented as installed) towards the air filter and the “open end” is to the left:
http://www.cpdonline.com/692509.pdf
This is also confirmed on pg. 22 of the manual in the inlet needle and seat paragraph.
Am I getting this wrong? Someone needs to post a photo of the correct installation, I will if I can get it straight.

Also, the proper bowl installation is as shown in the carb1.htm drawing with the deep end of the bowl opposite the hinging portion of the float. Is this correct?

The reason I want the spec number off of your engine is the breakdowns you are looking at are general. There may be something more specific to look at for your carburetor.

The orientation of the spring clip will not keep your engine from running unless it gets hung up and does not let any fuel in or keeps it from shutting the fuel off and allowing your carburetor to flood.

The engine is TVS115-62101A (D). The carb is as shown in photos. I believe it is the Dellorto carburetor, as it has a needle with a viton tip and no adjustments.

I'm going to go ahead and get a carb rebuild kit. I'll start by swapping out the needle and seat in place. If that doesn't work, I'll pull the carb and complete the re-build. Is there any benefit to soaking the carb, are there passages in the body that cannot be gotten to in place? I did replace the float when I got the thing last year, it was flooded.

The mower is a Murray with a 96044 build date, but looks well taken care of, and when it did run, ran very well except for some occassional popping. I got it curbside last year with a broken pull which I replaced and got it working fine for a few months before it started giving all kinds of problems. They began when I was cutting grass on the side of a hill.

I have noticed that I put the bowl on backwards, you can see that in the pic, the deep end should be opposite the hinge on the float.

Here is a parts break down on your specific carburetor. The problem I usually find with these carburetors are the little o-ring seals on the nozzle (ref # 37) they deteroriate and don't provide an adequate seal around the nozzle. This allows air to be drawn up into the venturi (instead of fuel) and prevents the engine from running properly. I would venture to guess that is also your problem. Try replacing these 2 o-rings (oh and but the bowl back on right) and see if this takes care of your problem

:thumbsup: http://www.hobbytalk.com/bbs1/attachment.php?attachmentid=40699&stc=1
632742.pdf
http://www.hobbytalk.com/bbs1/attachment.php?attachmentid=40700&stc=1
632742_List.pdf

This sounds like a good suggestion, I should be tackling the job this weekend at the latest, the lawn is approaching knee height as we speak...

This diagram is indicating the float to be plastic, but the float I have is metal. Is this a problem?

It does not matter they are interchangeable in this carburetor. The plastic floats are more reliable then the metal ones.

I think that I can replace these orings w/o dropping the carburetor. Is there any value in removing and soaking the carb, are there passages in the body that are not shown in the diagram that could potentially be clogged?

Unless the carburetor has a lot of varnish on it, then it probably does not need to be soaked.

I will be a lot easier to remove the nozzle with the carburetor off of the engine, I have tried to do it on before, but you really can't see what your doing with the carburetor mounted. Be careful the nozzle is plastic and is easy to damage.

Replaced the o-rings, they disintegrated on contact. They were replaced with 1/8" ID, 1/4" OD from autostore. Also discovered that I had not properly adjusted the float, was way off. Running fine, thanks for the help.

Thats Great! Glad to hear you got it going again....