Misterclean

But, it started when primed and ran good. That alone eliminates your theory.

Let's not make this difficult. The mower started when hot with starting fluid and ran fine correct? This says ot was mot getting fuel correct? Unless there is more information that we don't know, them the problem is fuel delivery. When the fuel boils it can't pump or even gravity feed thru the filter. The fuel must be boiling. Yes, even if it didn't do this when new. It doesnt.matter why.......it just does. You have cleaned the cooling fins so the only thing left to do in to insulate every fuel component you can between the fuel tank to the intake manifold. This is an air cooled machine and they can get very hot .........Too hot for some fuels. This may be a symptom that isn't repairable but it's worth a try.

That is loose but it won't help your starting problem. Your problem is fuel starvation from overheating.

This thread had convicted me to lower my sodium intake. Reading online about salt substitutes I learned tha MSG has an incorrect bias that we have been taught for decades. I learned that a small percentage of people really have an allergy to it. If one uses it wisely there is almost no chance of any health concerns. The article went on to say that it is wise to eat carbs or protein at the same time to be safe. I'm doing this now.......Just started about a week ago.

Fuel has different blends for different time of the year which can lower the boiling points. Another thing.......an older engine runs hotter than a new engine. The cooling fan blades may be worn after a thousand hours of use. Higher octane fuel runs much cooler than low octane. Reduce the engine speed 50 rpms. Thin oil cools better than thick oil. Just a few ideas and facts.

I could hand deliver the 30 pack in about 5 hours.......hmmmmmm?

Wow Fish, I just got caught up on this thread! I'm very sad to hear about you're stroke but very happy it was a 1. I will miss you and your great humor and perspective on things. I understand all aspects of the political and religious subject. I am a conservative Christian and a conservative on politics. A friend of mine that had a bar said I shouldn't talk religion or politics in his bar forty years ago. LOL I rubbed me wrong at the time but as I grew older I see the wisdom. It is a proven fact that the things that are most important to us are also the most volatile. I personally wish you would reconsider your decision ......at least stay here as a contributor. I would like to confess to everyone that I took a long vacation from this forum because of the Covid subject. Frankly it was hyperbolic in some ways because many if not all of the extreme predictions just didn't happen. I got angry but came back. I would probably leave again if something similar happened again. Fish, again, I really like your contributions ect.......please stay, please. sniff sniff

The aluminum deck is a good idea but the aluminum wears out at the height adjuster making them jump out of the notch. Toro came up with a shim to slip in between but it was just an after thought. They are a little brittle and the steel bolts like to break off in the aluminum threads.

This is good news because it says there is a fuel problem. The fuel is probably boiling in the lines and/or pump. Wrap the fuel lines with insulation and make sure the cooling fins are as clean as possible.

According to your diagnostics the fuel pump will not repair the problem because you said starting fluid doesn't help. I just don't want you to waste money. Please read my suggestions from a few days ago.......this procedure should narrow it down to spark, fuel or compression.

If it runs fine until you shut it off and won't hit with starting fluid it could be flooding after you turn it off. There's a small chance that the coil super heats and quits firing or the valves that were on the edge of too tight get tight during the super heating of the engine. Engines will super heat if turned off after work on a hot day. I always let mine cool down at idle for 5 or 10 minutes. I usually blow or trim during the cool down period. It boils down to this.......you need to be prepared to diagnose your problem when it happens. Mow for an hour, kill it, wait a few minutes, verify that it will not start, spray staring fluid, if it doesn't start check for spark, if it sparks then look for wet spark plugs (checking for flooding) . If that fails then quickly remove the blower housing and spin the flywheel backwards by hand. It should bounce sharply against the compression stroke. This method is the only way to check for true compression because it approaches the compression stroke from the opposite side of the cam shaft lobe where there is no compression release function.

Disabled compression release can burn up a starter, solenoid and wires. It''s very hard on the battery too.

Your can also try to clean the cooling fins and maybe slow the engine speed down 50 RPM's. Overheating causes the fuel to boil. Wrapping insulation on the fuel hoes helps too.

Check your valve lash. If it is too large it disables the automatic compression release causing problems like you mentioned.

I'm exhausted! I just read the whole thing and was hoping for a happy ending........now I'm frustr ated! LOL

That's new information for me. Wide open throttle for two miles! LOL That's hard on an engine! Perhaps the fuel was boiling because of the excessive heat built up in the fuel hose. If you have an inline fuel filter then remove it and just rely on the filter built into the petcock. Fuel does funny things when hot and gravity fed thru a filter media. Also re route and/or insulate the fuel hose. Hope this helps.

Ok but it does not sound logical to me. I'm 62 now and have played with gearing (for fun) for at least 35 years now and have never experienced anything like this. I've geared dirt bikes so tall that they wouldn't top out in high gear. 105 mph on my YZ 250 is a fairly recent example. An old 1978 RM 400 went so fast fast that the unbalanced front tire was literally hopping off the pavement.

If its a fuel flow problem then I would do a flow test at the fuel hose where it connects to the carb nipple and another test out the bowl drain valve. A clogged bowl vent will do this as well. If the valves are too tight it will have these same symptoms. Hope this helps.

When I worked off shore in the olden days we could bring capacitors back to life by submerging them in Naptha overnight. I tried this procedure on an old air cooled yz 250 years ago. Didn't have naptha so I used gas.....it worked!

Concerning the break in procedure.........if it were an OEM top end I would say just run it.........perhaps a little easy on the first cut tho. Since it's aftermarket it's impossible to say because you didn't measure the clearances.....or didn't mention it. Because it's aftermarket, play it safe and do heat cycles and easy cuts etc. for a tank of gas. 38 years doing this and a few years before that on dirt bikes for me.

The first picture in the last post has shiny yellow fuel hose. Chinese hose is shiny and will fail very quickly. Tygon is the only hose I've used professionally. Looks good otherwise!!!!

I've been working on these things for 38 years. I must say those are some odd symptoms. Perhaps its flooding when not running? If it's tight valves I would suspect it would run poorly when hot. Best thing is to check spark when this happens and work down from there. Could adjust valves to be sure. I very curious myself. Please keep us posted.

Better cooling systems, better metallurgy, better machining and better oil is why less oil is needed.

I just read this post and the first few replies. I must ask......how did you own this for thirty years and not know about all the problems?

I've had a twist throttle on every wheeler I've owned. I'm a dirt bike guy and wouldn't have it any other way. All my old dirt bike friends Love it. R I guess you forgot about the huge debates on the old sight. I bought up the sunject way back then in 2014 when I joined. The only problem is leaving it in gear with the engine running. You get off to do something and grab the bar to pull yourself up and twist the throttle instead. Lol it's happened a few times. I warn my friends about this.