Old engine not running, Craftsman brush trimmer

denchen · Oct 21, 2019

A common fault I have found with this type of engine, is that when they get hot, they cut out and stop and wont start until the cool down. Many time I have found the valve gap too tight. I think the valves get hot, expand, and so do not fully close. As far as the gap, if you carn`t get a manual, I would recommend having a bit too big a gap as opposed to one too tight. How much is plenty, well firstly these are not high tech racing engines, so as long as you leave plenty, say about 15thou. it should be OK. You might find there is no adjustment to the cam followers. The answer is to take the head off, take out the valve and grind a bit off the vale stem. Check the gap whilst putting pressure on the valve head until you get it too your liking then refitting the spring.

RandyT · Oct 21, 2019

TVS90-43022A is the Tecumseh model number for your engine

pripyat · Oct 25, 2019

I checked the valves, .010 intake, .012 exhaust. I ran it some now that I've got heavy duty trimmer line, it starts running poorer as the engine warms up. As it approaches operating temperature, it starts smoking and starts missing on a cycle.

Every 10 or 15 seconds the engine hesitates for what seems like a single cycle, puffs out thicker smoke, and continues to run normally.