DLTX 67 Throttle Stop Screw/Spring Setting

Hello,

I was wondering if someone may be able to help me understand how the throttle stop screw/spring is supposed to be set up on a MS DLTX 67 carb? My engine is currently hunting, where it idles down then the governor picks it up but repeats the process. There is a lot of movement going on in the linkage between the governor and the throttle. Would someone potentially be able to post a picture of what your throttle stop screw and spring look like at full throttle position, as well as at low idle position?

Thank you kindly.

When at wide open throttle or "fast idle" the screw should be no more than 1/8" off the spring. This is at wot sitting still/no load. When at slow idle the screw will be pushing against the spring and even bending it a little. When you want to shut down, the throttle all the way back and the stop on arm should be against stop pin on carb by spring. This setting has nothing to do with surging or hunting. While idling and surging, slowly close choke little at a time and see if it smooths out. If it does , you have internal carb problems. Choke does not help if it's a gov problem. If choke helps , here is another test to prove it is carb problem .Open both mixture screws 2 turns and start and throttle up to wide open or at least 3/4 open throttle. Now close load needle until seated. If tractor stops, you need carb rebuilt. Lean mixture causes surging/hunting. Either not enough fuel or air leaks in carb.

Guess I better explain, those settings were with tractor running....I assumed that is what you were asking for since that's all that really matters. RB

Thanks for the feedback. Is the idea with that test that when you screw down the load needle and if the engine shuts down, your idle passage is not clear? It should continue to run (although probably not at full speed) with the load needle tightened correct?

I am suspecting the idle circuit on this carb. Do you have any advice/hints for cleaning it?

Thanks.

The adjustment of the rod from governor to carb throttle lever is
Often responsible for hunting and surging.
With engine stopped, throttle in full speed, Rod should be adjusted
To be ? hole (⅛") short of dropping into the throttle lever on
the carburetor in max open position.
MikeS.

Yes, it is a test to determine that. Engine at full throttle (fast idle) and both needles 2 turns out. Slowly close load needle, it should make no difference in speed or running as at fast idle , all the fuel supplied from idle circuit. That's why I say to use the choke test first. At slow idle (when it lopes) slowly close choke little at a time. If it even out then that means it is running lean. Either from lack of fuel (plugged passages) or too much air leaking around throttle shaft/blade from wear. If it can suck air , it will not suck fuel. So do the choke test first and then the fast idle/shut load test. If tractor stops then you probably have plugged passages. You can either send it out or get the video from Roberts carb and the drill bits and bushing driver and learn the theory of operation and do it yourself. Also they wear a groove in bottom of throttle bore from blade wear and lets plate sit too low in bore and leaks air around top. All too involved to explain here.Be glad to build it for you if you go that way.

This post raises some questions and from my research I found the following: As I recall the 67 was a gas only carburetor for the "B". I have 4 of these B's and noticed that the stop not the adjusting screw was bent as to allow the butterfly to stay cracked on low idle. In my examination of the original factory offering this was not the case. When you pulled the throttle all the way to the rear the butterfly was supposed to close shutting down the tractor. I supposed this was the safety feature, however it appears with operators frustration with inappropriate shut down they bent the stop to prevent this. Now having said this "your hunting" has nothing to do with this. You are fuel starving the engine and it is going to governor opening to partial opening to get fuel from the secondary or main jet nozzle. You need to have the carburetor properly cleaned, all the passages and there are many videos on this. You high and low jet adjustments with tweet the fuel mixtures when the carburetor is cleaning. Also check for vacumn leaks at your intake as a bad intake/exhaust manifold can cause fits as well as bad valves or valve adjustment. My first approach is to check compression then following the air flow back to the carburetor and also check the air intake. One can't put a bandage on serious problems as they have to be corrected for correct operation. I can tell you for a fact these engines will idle on the impulse 100-200 rpm when right (this is high recommended) but they are low speed operation engines. When you full throttle you are not on the load side just the high idle....load doesn't actually occur unless under a pull. Good luck.