Another stupid Unstyled question

[Patsdeere]

Well, the friend I was helping has another unstyled A that he claims will start right up. Figuring the first one we played with was refusing to start I helped him drag out the other one. Well tried hand cranking it and it wouldn't go. He said that if we pull it, the thing would run by the end of the drive way. Well after dragging it for 45 minutes we said screw it. So we started going through what we needed. Spark was there, timing was there as it has run well before. However, we seemed to be missing gas. If we put some starter fluid in the cylinder it would pop off and run for a few seconds and then die. Pull the plugs and they are dry (even after running it full choke which should have flooded the plugs). Checked the fuel, it filled and drained out of the carb at a great pace. Pulled the bowl off to make sure that there was no junk in the idle passage. It seemed fine. I am stumped and ------. Where should I start looking?

Thanks.

 

[JDNPC]

Check to see if the float is adj"d properly, or could be a stuck valve in the cylinder head.

 

[John T]

If by checking the carb you meant if you opened its bottom drain cock/valve and turned the gas on she flowed steady for a good while, gas is at least getting to and filling the bowl and even if the float were stuck open she'd get gas and even flood out of course. I guess the float could be set so darn low she shuts the gas off at an extreme low bowl level but I dont thinks thats the problem. You can deternmine by temporarily rigging a clear fuel line out the carbs bottom n see at what bowl level she actually shuts the gas off

If theres no vacuum she cant suck gas into the cylinders during their intake (vacuum) stroke but if both plugs come out dry n she never fires I dont envision having TWO valves stuck at the same time?? You may have to pull the valve covers but before that run a simple compression check on both sides looking for any stuck open valves

If theres a total inlet air restriction in the inlet air pipe or air cleaner that could account for no gas getting sucked in the cylinders as theres no net vacuum !!!!!!!! Id remove some air inlet tube/pipe so youre sure the cabrs getting air n see what happens????????????

Sure the carbs choke butterfly is actually closing relative to where the external rod is locating??

John T

 

[Jake Winn]

I had a B that did something similar once. The manifold gasket had come apart on the intake port, causing a vacuum leak. It was easier to draw air in through the bad gasket then to draw it through the carb. Fixed the gasket and it ran like a top.

 

[Anonymous-0]

I agree with John. I rebuilt a Mag for a gentleman who then decided he had Carb problems. So I rebuilt his Carb. He then wondered why his tractor still would hardly run when everything internally on the engine was correct. Come to find out the oil cup on his air cleaner had not been cleaned forever and was full of a black sticky mess. Cleaned it and ran fine. He didn't figure this out until I told him to take the inlet pipe loose at the Carb. Also when you take the inlet pipe loose be sure the choke blade is closing when you shut the choke. I have seen them broken, wrapped around the choke shaft and other crazy things. You could have some internal passages and main nozzle plugged up. Pull out the spark plugs and put you thumb over the hole while you crank it. It should give a pressurized burst of air that will lift you thumb off the hole on the compression stroke. If not may have a stuck valve. You can put your hand over the end of the carb while cranking it over and see if there is any suction but you'll have to put the plugs back in. Be sure it can't fire because if it backfires your hand may get burnt.

 

[sgtbull]

you've established spark and compression and timing because it will run a few seconds on ether. That also indicates that the engine is getting air and the valves are working. The plugs stay dry even when choked, so gas ISN'T getting into the cylinder. Gas IS getting into the carb though. The logical conclusion is an obstruction in the carb passages. I think that a manifold gasket leak massive enough to offset the intake through the carb would have taken a while to develop and it wouldn't have previously "started great" as stated. It may sound foolish, but are both of your adjustment needles open? Open about 2 1/2 turns is a good place to start.
Is the throttle linkage free? If the idle passageways are compromised, there may not be enough fuel to start if the throttle disc is completely closed. (Seems like I read somewhere that these tractors were SUPPOSED to shut down if the throttle was completely closed, but I can't recall where..)
I would:
1. disconnect the air breather and give a shot of ether through the carb... see what happens.
2. if #1 fails, pull the carb and give it a good inspection and cleaning. Pulling the bowl off and saying "it seemed fine" is not definative.
3. Use fresh gas.

 

[Patsdeere]

Thanks for the suggestions. Tried a few things and then switched carbs and it runs like a top. So now it is a carb problem. Does anybody have a diagram of how the carb works/is laid out? I haven't had to try and clean out any of the passages before and don't know which ones to clean out (or where they are). I believe it is a dltx 8 carb.

Thanks.