dltx10 problems

RyaninKS

Member
trying to diagnose a problem with my b. I"ve narrowed it down to a carb problem. It starts and idles great but as you start to give it gas it starts to run rough and cough. Taking off the throttle linkage makes no difference. I"ve put in a new needle and seat. Checked the float level multiple times. No change. I did notice that at an idle I can close the load needle and it makes no difference, but while it"s running WOT if you close the idle needle it tries to die. Is this normal? Any ideas?
 
The engine should die with the idle mixture screw closed.
If the passages in the carburetor are clean, the tractor should run at WOT with the idle mixture about 1-1/4 to 1-1/2 turns open.
The IDLE mixture adjustment does not mean idle RPM.
It means "unloaded" at any RPM, and should be open enough to stop governor surging at WOT, but not open enough to give black smoke.
However, adjusting at WOT may be too rich at slow RPM, so,your final setting may be a compromise between top and slow RPM setting.
Engine should be warmed up pretty good for adjusting.
On most B's, the load needle will be right at 3/4 to one turn out.
MikeS.
 
ok, now that i'm at a computer and not a smartphone, i'll actually type up everything i've done so far.

-No air stack on it at this time.
-Drilled EVERY passage in the carb.
-NEW nozzle
-Float set by both measuring from the top of the bowl and verifying it with a piece of clear tube.
-Head has been rebuilt by a reputable machine shop with new guides, valves, and springs.
-All valves adjusted according to spec.
-Good compression on both cylinders. (I don't have any actual number for yall but it takes quite abit to crank her over and i'm not small fella)
-I can unhook the carb from the governor and run the butterfly by hand and it makes no difference.
All bushings and throttle plate have been replaced.

-Both needles do seem to be working, i can find a sweet spot where it runs "better" but not right by any means. (this isn't my first john deere so i do know how they are supposed to run) I swapped mags with my 50 A (Wico X) and I get the same results.

I've bought all the videos from roberts and have watched them so many times i can see them in my dreams. The only thing i have noticed on the carb but from what i understand it shouldn't make a difference is that the bowl vents have been removed. (The tractor is sittin on a stand in the shop right now so i don't see this making a difference, feel free to correct me if i'm wrong though)

I'm truely at a loss over this thing.
 
You should be able to keep the engine running with either the idle needle closed and the load open or the load closed and the idle open. Throttle plate will have to be opened up off of idle position though for it to run on the load circuits. If you can't do this then something is still plugged up in the carb.
 
New set of Copper Core plug wires. I DID however order a new set of plugs yesterday. I'm going to try some autolites instead of the champions i'm running now, the champions are new but i've read a number of people recomending the autolites. Hopefully i'll have an answer by tonight
 
You have systematically ruled out everything accept possibly the two things that will cause a rough run/ cough. Ever notice if you choke a warmed up engine that it will not "cough"?? It will slowly just die from flooding. BUT... if you run an engine too lean it will backfire / cough and run rough. So what all would cause a lean condition that you havn't allready checked? We are assuming you tried choking it a little when throttling up to see if it made it better or no change. Check for air leaks at all intake tract mating surfaces. What kind of intake manifold does it have? Some of the "all fuel " ones have the intake runner going through and cast right into the same casting as the exhaust so there is a remote possibility that a crack inside could let intake pull diluted exhaust air just as an outside gasket leak would. Just thinking out loud here. You are either leaking air or starving for fuel...lean!Another thing that will cause your problem is a flake of rust in the small orfice on the top of sediment bulb protruding into bottom of tank. You can have a perfect carb job and float level will show correct at idle but will still lean out when throttle is opened up and I know from personal ex that it will make it cough and pop and sometimes even intermittantly. I would say a weak/junk condenser will do same but you said you eliminated that with diff mag that I assume worked good on donor tractor. Let us know what you find.
 
Update:
Back on the dang smartphone again do bear with me.

Went and got a new set of LONG reach plugs and it seems to have fixed most my problems. I played with the plug gap a little and found it runs best at 35 thousandths. now it runs smooth at all engine speeds but it coughs and studders when you pull the throttle quickly. If I open it slowly its fine. I made sure all my linkages were free and straight, and it does only have 1 governor spring. any suggestions to try next?
 

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