Really dislike Robin Subaru engines

[Frank Sorbello]

All winter with the new silicon heater my PT-422 would start right up. Lately in 70 to 90 degree weather forget it. I refuse to use starting fluid, tired of setting valves and changing plugs. Decided not to buy a new PT-425 for the sole reason I do not like these Robin Subaru engines. Put a Kohler in it. I'll buy one today. Just sick of all the headaches associated with engine.

 

[Marks481]

wow, that is really strange. I have never had a problem with mine not starting if the temp was above 50.

You could always swap out the engine with a Kohler and Ebay the Robin you pulled out to recoup some of the cost. Not a tough switch from all accounts.

 

[Barryh]

Sorry you are having so much trouble. I know that takes the enjoyment out of owning a PT.. That is strange though, my little PT-180 had the 18 hp Robin never gave me a problem when starting... Even sitting in our unheated garage at 20 degrees. Hope things work out for you..

 

[ponytug]

I'm sorry to hear that it is giving you grief.

Has anyone experimented with 87 vs 89 octane fuel? Brand name (e.g. Shell / Chevron) vs off brand?
I'm just curious if there is something on the fuel side that might help.

I ask only because it made a world of difference on some of my non-PT air cooled gasoline engines. (89 octane from Shell/Chevron). As near as I can make out some of the cooling/ignition characteristics are closer to older 87 octane by using 89 octane. YMMV...

All the best,

Peter

 

[MossRoad]

All winter with the new silicon heater my PT-422 would start right up. Lately in 70 to 90 degree weather forget it. I refuse to use starting fluid, tired of setting valves and changing plugs. Decided not to buy a new PT-425 for the sole reason I do not like these Robin Subaru engines. Put a Kohler in it. I'll buy one today. Just sick of all the headaches associated with engine.

You shouldn't need starting fluid in warm weather. Are you have starting problems with the engine during a cold start at 70 degrees air temp? Or are you having problems re-starting a warm engine after shutting it off when its 70 degrees air temp?

 

[Frank Sorbello]

Having problems starting a cold engine in warm weather. So unpredictable, thats what I dislike this engine so much.

 

[MossRoad]

Not starting cold engine in warm weather aggravates me much more than not starting in cold weather. At least cold weather is a valid reason.

So, air cleaner, fuel/air-mixture/carb adjustments, spark plugs, good spark, and timing. Valves, once set, shouldn't go out of adjustment for 500 hrs.

What are you leaning towards first?

 

[Frank Sorbello]

Not sure. I was looking on brandnewengines.com at new 25hp Kohlers. Around $2200. The question is do i have the knowledge and the patience to install it myself.

If I go that route, I would probably try to thoroughly clean and repaint while the engine is out. I have talked to tech support at Robin Subaru. They are quite familiar with their engines in Power-Tracs. Apparently they do get a lot of calls about problems with engines starting and heat build up.

 

[SpringHollow]

I certainly would check the things Moss mentioned first. Easy to pop off the air filter and see if that lets it start, not hard to replace spark plugs, then valves etc get a little more difficult. With the poor gas these days, I have bought cheap spare carbs for most of my small engines so that I have something to swap out for testing. If the carb is bad, then I can get a rebuild kit if I want. It is worth spending a few hours.

Ken

 

[MossRoad]

Not sure. I was looking on brandnewengines.com at new 25hp Kohlers. Around $2200. The question is do i have the knowledge and the patience to install it myself.

If I go that route, I would probably try to thoroughly clean and repaint while the engine is out. I have talked to tech support at Robin Subaru. They are quite familiar with their engines in Power-Tracs. Apparently they do get a lot of calls about problems with engines starting and heat build up.

What does Subaru say?

 

[MuncyBob]

When I was having my trouble I called Subaru, basically they said their engines are not well suited for PT application.

 

[J_J]

I am going to jump in here and say that you probably got a not so perfect engine.

I doubt that all Robin Subaru engines are bad.

There will be people that don't like Honda, Kohler, Kawasaki, or whatever, and rightly so if they don't perform as expected.

Could be any numbers of things, such as carb, weak ignition, valves, timing, spark gap, type of gas, vacuum in tank, etc.

Recommend tracking all items one by one and see if they are correct.

 

[Frank Sorbello]

JJ
I have put in many hours and spent a lot of money doing all of the things you have mentioned. In 2012 the engine was rebuilt by an authorized Robin Subaru shop outside of Baltimore. The guy who owned it spent more than the cost of a new engine. I saw the receipts.
Since I purchased it in February of 2013, I have had 3 reputable small engine mechanics troubleshoot it when I have problems like starting or shutting down when it gets hot. The valves have been adjusted 4 times. Carburetor has been rebuilt. Fuel pump has been replaced (new). Starter has been replaced (new). New Muffler. New spark plugs at least three times. Timing and gap all checked. I use premium Sunoco gas. New battery and cables. New gas filters, and shut off valve. New choke and throttle cables. New silicone heater. I have checked the compression. I had a mechanic check the timing.
I love this tractor when it is running and stays running. What I hate is the inconsistency with the Robin Subaru engine. Why will it start one day and not the next. I have taken notes on it when it starts good and start or try to start the same way each time. Why does it all of a sudden start backfiring after it has been running smoothly for days. Why all of a sudden does it drop power after it has been running good?
I have talked to Robin Subaru with most of these problems, and have been told more than once they don't like their engines in the the Power Trac tractors.
I was going to sell this tractor and buy a new 425. A man came to look at it but it wouldn't start. That was this Spring. It had been starting like a charm since the winter. Now it is hit or miss.

 

[J_J]

When I had trouble with my Kohler engines, I found the main problem was the solenoid valve on the bottom of the carb which was to prevent backfires.

Even with an inline filter, some scum would get in the solenoid fuel shut off plunger and let a small amount of gas through.

This also made it run rough.

I did not have much trouble starting, and if I did, a shot of starting fluid did the trick.

 

[ernemats]

If I were you I would think I got a lemon, I have a 1998 pt 422 with over 2,300 hours on it and the only thing I have had to do is replace the ignition coils spark plugs and fuel filter. I have not performed all the recommended services such as adjusting valves. It starts fine in warm weather, but when down below 20 degrees it sometimes does not want to start.

 

[davesl708]

Have you tried pure gas in it? The 93 octane works great in my gassers. No ethanol clogging things up.

 

[duane]

Has anybody tried the new coils shown for start-ability. Seems like the -11 have been upgraded again when you search that part number to a -21

 

[coolconnection]

For one don't use preium gas. Preium gas is for engines with high compression. Which means more of a delayed spark not a faster spark which most people think.

 

[Frank Sorbello]

What do you suggest to use for gas?

 

[JimRB]

The spark happens at the same time. That is a function of basic ignition timing. The explosion of gasoline and air is supposed to be caused by the spark plug's spark. Sometimes the gas/air mixture ignites just by compression, kind of like diesel does. In a gas engine that is known as knocking. Not a good thing. Higher octane/lower heptane fuel resists knocking. Higher compression engines tends to knock more than a low compression engine. Dirty combustion chambers may also cause more knock than a clean one. Anyhow, the explosion from a high heptane fuel happens easier than one from a high octane fuel. Fact or Fiction?: Premium Gasoline Delivers Premium Benefits to Your Car - Scientific American Another article Regular or Premium? - Feature - Car and Driver

The issue is that in some states, the premium high octane fuel does not have alcohol in it. Achohol and carbs do not usually play well together even if a carb says up to 10% alchohol.