I might drag this one back up. Got this thread while googleing to find the valve clearances for one of these.

I have had a bit more to do with the Tecumseh Ultima ULT50 ULT55 motors now, so I thought I should post up some extra info.

I have had issues with carb mounting studs. Stripped out of the block. Not an easy fix, but do able.

The main issue I have found is that the elbow with built in primer does not seat on the face of the carb with enough pressure due to compression of the plastic over time from servicing and over tightening then the carb does not prime properly. The nuts that hold the elbow on bottom out on the threads. Hence you can undo the nut and the stud will screw out, meaning the carb is half on half off and its a pain.
The trick is to make sure the gasket is good. One cut out of a fresh bit of gasket paper with enough clearance around the heads of the mounting studs will do the trick. Then some thin 6mm washers on the studs to make sure the face plate clamps up to the carb tightly before the nuts bottom out.


You can buy new replacement Chinese carbs, Ive stocked up with a couple. But I have not had too many issues with cleaning out the originals as they are mostly plastic and it does not grow stuff like brass, alloy and steel. The clip on bowl type with the self tapper screw in the front. Care must be taken as behind that screw is a spring and a little plastic jet. Hands and knees searching type deal.
Ive heard of a few having the plastic stripped out where the screw goes in, just like on a LM/G4 2 stroke carb.


Ive fixed a few mowers with these motors and sold them on and the customers have been happy. Very willing and smooth running motor, just a bit heavy, they are a fair lump of motor and over complicated to work on. Geez getting the fuel tank off is a pain.

I have two here on commercial Victas at the moment, a 505SP and a 550SP. The 550 is good to go, the 505 has some internal issues I think, it appears that the governor is not working, something is wrong internally. It runs flat out and the governor arm never moves.
I picked up a base with a motor on it thats missing the cowl, so I'm going over it, if it passes the tests and runs right I will swap it out.

Probably should be working instead of posting up on here.
Cheers, Bob.