660 carb update

[Billybuck]

Sprayed carb cleaner looking for vac leaks. None detected. Dismantled carb. All very clean. Poked every orafice with wire. Made air tube to target main "jet". Satisfied no restrictions in any port, tube or jet. Reassembled, reinstalled, same result. Runs great choke full out, wants to quit or does choke in.

Is buying a new carburetor for $250 the best decision? Guess I could return the new one if it doesn't solve the problem, though I don't like to do things that way.

 

[600ford]

Dont give up---I have took them off & dismanteled them 3 or 4 times in one day before I got it right . Could not see any thing wrong . Just dont give up it is not that big a job. Not like having to take the clutch out . GOOD LUCK
PS I always usr B12 carb cleaner in spray can to blow out all holes

 

[awhtx]

Have you checked your ignition system? Weak spark can lead to the problems you describe such as requiring choke to run.

 

[Billybuck]

awhtx - no. I thought about that. It is 12V and "seems" to have good spark but that's anecdotal. New battery and wiring. Guess I'll pull the center dist. wire and ground it to check the spark quality? Any other checks on that? Pull a plug and check also.

What about exhaust blockage? Any way to check that?

 

[Billybuck]

I know what they say about doing the same thing over and over again and expecting a different result. Insanity. I MAY do it one more time, but that will be it.

 

[JMOR]

(quoted from post at 21:52:17 01/25/11) I know what they say about doing the same thing over and over again and expecting a different result. Insanity. I MAY do it one more time, but that will be it.

n the 'one more' time, be sure a look at venturi.........I put a note on the other thread about your 660 carb.

 

[jim murphy]

I dont know how long this thread has been going or what has been suggested, but I have had some luck taking a squirt oil can, putting gas in it and squirting it in the carb to see if the addition of gas will keep the tractor running without the choke. If it does, it could indicate a gas starvation problem, either within the carb itself, or prior to it, in the gasline, sediment bowl, or even up in the gas tank. Don"t throw that carb. I have had similar problems you describe and gone back and gotten them to work-it took a cooling off period to get over the frustration and take a fresh look at things. Good luck.

 

[Big 86]

Have you opened the main jet with engine running to see if that makes a difference in performance? It should be getting way too much gas with main jet all the way open and smoke black.

I had a similar carb issue, after taking it apart about five times and checking and rechecking, I finally opened the main jet all the way and it ran like it should. After a few minutes of use it began smoking black, so I turned the jet back in to where it is supposed to be and runs fine now.

I fully understand your aggravation on this, took me about a week of taking carb apart and putting it back together before I finally succeeded. Grrr!

 

[old]

I have been where you are before and did replace the carb just to let it sit for a few month then took it apart rebuilt it again and put it on another tractor and it ran just fine. Did you by chance try the heat thing I talked about just to see if that would help?? Ya you have to take off any plastic parts and seals like those in the choke shaft and throttle shaft areas

 

[Billybuck]

I can take the main needle out and nothing changes.

 

[Billybuck]

The fact that I can pull the main needle clean out and she still runs the same lends credence to your theory. I'll blow air into my fuel line and see if that makes a difference in the flow etc..

 

[old]

So with it out the engine keeps running and no black smoke right?? Sounds like the float bowl vent is clogged up. It is if I remember right in the top half of the carb and is one of the small holes in that area. It is also one of the common problems with the M/S carbs. A number of years ago Bob posted a picture of a carb with a wire running in and out of all the holes in the common M/S carb. It was a very neat and helpful picture to say the least

 

[old]

Oh by the way I forgot saying something else. With the air cleaner tube off and engine running about full throttle take you hand NO GLOVES and lay it over the intake of the carb. Do your best to keep from killing the engine when doing that put it on then right before it dies take it off and do that 3-10 times and some times doing that is enough to suck the dirt/rust out and then your good to go. If at all possible do that with out the choke closed so if it does suck it out you will know right away

 

[MarkB_MI]

Clearly the idle circuit is blocked. Take a piece of fine wire and run it through all the passages associated with the idle circuit.

 

[Billybuck]

I'm familiar with this trick and haven't tried it yet. Good idea to try before pulling it, again.

 

[Billybuck]

Correct, runs great, no smoke when choked. I concentrated on the lower half this last time as a result of our main jet discussion. I have seen Bob's picture with the wires. I recall they were white with brown dashes weren't they? Not my carb but helpful. I'll spend all the time needed on the top half this next time.

 

[Billybuck]

JMOR - I read your post to my other post. The diagram you put up is my carb. I've grown too familiar with its passages I did try to get a wire thru the main jet/seat and was able to send it 1/4" in from two directions but never could quite see it. But I also rigged a red spray can tube in the tip of my air compressor nozzle and was able to run air thru that jet and feel it escape thru the nozzle passage and the upper vent hole. I'm satified for sure it isn't plugged. The venturi is in good shape, and only fits the upper body in one direction.

 

[JMOR]

(quoted from post at 10:49:54 01/26/11) JMOR - I read your post to my other post. The diagram you put up is my carb. I've grown too familiar with its passages I did try to get a wire thru the main jet/seat and was able to send it 1/4" in from two directions but never could quite see it. But I also rigged a red spray can tube in the tip of my air compressor nozzle and was able to run air thru that jet and feel it escape thru the nozzle passage and the upper vent hole. I'm satisfied for sure it isn't plugged. The venturi is in good shape, and only fits the upper body in one direction.

ne other experience that I had was air leak between the upper body and the bowl gasket interface........real hard to tell the difference in symptoms between ign & carb on this one.
The bowl venting discussion brought another thought to mind. When the bowl vent is clogged the bowl pressure becomes lower (in direction of a vacuum) & this will lean the mixture, HOWEVER, when you completely removed the main power adjust needle, this now opens the bowl to atmospheric pressure via that hole, which is higher that a properly working carb & should now be overly rich. This tends to pull me away from the bowl vent idea as a problem. As long as we are here, in the picture of my re-pop carb, the orange wire is the bowl vent. Some variations of M/S have vent exactly like this, but some have two vent holes. The idle air is the white with orange wire (same color used for idle fuel thru idle jet hole) & that passage makes a very sharp turn inside the casting (yellow) so you can't likely get a wire around that corner. Other than the bowl vent and fuel inlet, I believe that everything in the top of the carb could be plugged and at high speeds/well off idle, the tractor would run just fine....just saying that so hopes not too high in finding your problem in the top.

 

[Billybuck]

I ran a straight edge down both halves to look for that as a potential problem but could not detect any issue. I do have emery paper so maybe I'll figure 8 the housing halves on that for kicks too.

 

[old]

Been a very long time ago that I saw that picture I just happened to recall seeing it last night so figured I would say something about it. I have had carbs where you could pull that main jet needle all the way out and it was the float bowl vent that was clogged up that was the problem and it is in the upper part

 

[old]

Note I said no glove because you can end up with a gas soaked glove and something odd happen and then have a glove on fire and it will not go out and you going to the hospital. I figured with every thing else you have done to that carb that clog maybe easy to free up doing the hand choke thing

 

[Billybuck]

Here's hoping it is that easy.

 

[old]

Well that air vent is one of those that sound easy but it is small and does not unplug easy or non of mine ever did. Sorry to tell you that but I do not sugar coat things LOL