MTD / Yardman snowblower engine

[Cfs]

I am trying to help a neighbor with his Yardman model 31AS62EE708. It has a MTD engine 265-SU serial 1005284B0327. It's 15 yrs old. I assumed it was a typical old gas dirty carb situation. Owner said it would start and die after a few pops. Now after cleaning the carb, it will start after 6-8 pulls and runs super slowly about 1pop a second..super slow it cannot gain any speed and smokes a lot. Taking it off choke or moving the throttle to a higher or lower speed doesn't increase the speed and the engine will usually die after 30 seconds or so. I have pulled the carb and cleaned both jets.. high speed and low speed as well as the emulsion tube. I have cleaned and repaired a lot of these 'Honda' style carbs and I am sure it's done correctly. It seems to have good spark as far as I can tell using tester that lights up when it gets an impulse. I have installed a new spark plug too. I have set the valve lash to .006 for both. Maybe .008 would be better for the exhaust valve. I have not tried to check the compression but I will tomorrow. I am assuming that the coil is good since I have spark...do coils ever breakdown and only spark half of the time or less? Maybe the 6-8 pulls builds up enough compression maybe from the excess uncombusted gas in the cylinder? But due to low compression it will not run anywhere near full speed?

A couple of asks...Does anyone have a shop manual for a 265-SU
What results should I expect to see for compression for this single cylinder horizontal 4 cycle OHV.

I welcome any and all ideas and comments on what I should try to troubleshoot and hopefully repair this snowblower...I am really stumped but I am hoping its something simple that I have never run into

Spit

 

[StarTech]

 

[Auto Doc's]

Don't use a "Christmas light" style spark tester, use and open air one with the adjustable air gap. With the gap style you should see a consistent bright blue spark and that will verify the coil operation.

I know you set the valve lash, but did you verify both valves are opening about the same about?

Do you have more than 50 PSI compression?

 

[slomo]

Don't use a "Christmas light" style spark tester, use and open air one with the adjustable air gap. With the gap style you should see a consistent bright blue spark and that will verify the coil operation.

Agree with Auto Doc's.

There are cheaper tools out there than the below one. IMO, that is the best out there.

 

[Auto Doc's]

Agree with Auto Doc's.

There are cheaper tools out there than the below one. IMO, that is the best out there.

View attachment 72463

I use a Thexton 404 most of the time for small engine and automotive.