Throttle issue on 450 Series 148cc - thoughts?

[rustymidget]

Hello all, my first question on LMF, so please bear with me! I have the above engine on a Lawn King self propelled mower, that was given to me so I could get it running properly and learn along the way. It starts 1st or second pull, and ticks over quite happily. There is a fuel leak from somewhere, as when its running, petrol starts to pool up in the channel / valley of the deck. I'm guessing its related to the gasket / diaphragm, so will pull the carb to investigate further. And I know the reason the self drive doesn't work is that there's no belt! The original part no. isn't listed anymore, so I thought I'd use some rope to estimate length, and then just buy the closest generic one off ebay.

Now, to the actual question itself. The throttle cable, though moving very smoothly/freely, and moving the metal plate at the carb end, has absolutely no effect on engine speed, whether its at the tortoise end or the hare/choke end. However, if you push the triangular shaped plastic throttle piece (butterfly?) it revs up and down as it should (well, I'm assuming thats what it should do, only with the cable controlling it rather than my finger). When I look at the throttle plate thing that the cable attaches to, the axis on which it turns, barely changes, irrespective of what position the cable is in - see the pic with the red circle annotated on it - that one is at full throttle, the first pic is at the stop position. So, I'm wondering, is my problem related to this plate and the perhaps the tension of the bigger governor spring? Or could it be down to the length of the cable? Or could it be something jammed up inside the carb? Some thoughts on where I should be concentrating my efforts would be much appreciated. Thanks.

 

[Rivets]

Ok, give this a try. Everything I’m talking about will be in the #2 picture with the red circle. First, set the throttle cable to the fastest position. Second, now loose the throttle cable screw and pull the cable back as for as possible, then tighten the screw. Third, start the engine and see if it solves the problem. Fourth, problem not solved, with a needle nose pliers grab the arm which has the governor spring attached to it. Pliers should go into the hole and engine needs to be running. Slowly bend this arm outward and you should see the spring start to pull on the throttle plate. Keep pulling until until you reach the proper RPMs, about 3200. Post back and let us know if it solved the problem.

 

[rustymidget]

Thanks I'll give that a go. Just to clarify, the throttle cable screw, you mean the little bracket/screw that holds the cable against the side of the engine cover / recoil starter assembly? There is no adjuster higher up at the throttle control unit, which is sealed plastic. And pulling the cable back as far as possible, I take it you mean pulling it towards the front of the mower, thereby taking out the slack in the cable at the handlebar end? And re the arm that has the governor spring attached, do you mean the exact one that I circled in red, that the bigger of the two springs attaches to (are they both called governor springs, or just the bigger one?)? If so, I just insert the pliers into that ovalized hole which the larger spring is attached to, and bend it out / upward (towards the right front wheel)? Sorry, my questions may seem daft, but this is my first go at all this, so just want to be sure I'm doing exactly as you mentioned. Thanks

 

[Rivets]

Yes to both your questions. We want to make the adjustments with the throttle control at it’s highest speed and adjust the arm to put more tension on the larger governor spring.