Really dislike Robin Subaru engines

   #1  

Frank Sorbello

Gold Member
Joined
Jul 12, 2011
Messages
360
Tractor
Power Trac PT-422
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.
 
   #2  

tmarks11

Platinum Member
Joined
May 29, 2005
Messages
963
Location
Seattle, WA
Tractor
Power Trac 422 (2005)
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.
 
   #3  

Barryh

Veteran Member
Joined
Jul 5, 2005
Messages
1,480
Location
Harpers Ferry WV - Mountains of Shannondale
Tractor
Former owner of a P T -180 / Kubota BX-1500 .. A Craftsman Yard Tractor / John Deere 140 H-1 / Cub Cadet 108. And now ( Little Red ) a Power Trac 1425
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..
 
   #4  

ponytug

Elite Member
Joined
Mar 27, 2007
Messages
3,506
Location
Bay Area, CA
Tractor
Power Trac PT1445
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
 
   #5  

MossRoad

Old Timer
Joined
Aug 31, 2001
Messages
51,534
Location
South Bend, Indiana (near)
Tractor
Power Trac PT425 2001 Model Year
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?
 
  
  • Thread Starter
#6  
OP
F

Frank Sorbello

Gold Member
Joined
Jul 12, 2011
Messages
360
Tractor
Power Trac PT-422
Having problems starting a cold engine in warm weather. So unpredictable, thats what I dislike this engine so much.
 
   #7  

MossRoad

Old Timer
Joined
Aug 31, 2001
Messages
51,534
Location
South Bend, Indiana (near)
Tractor
Power Trac PT425 2001 Model Year
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?
 
  
  • Thread Starter
#8  
OP
F

Frank Sorbello

Gold Member
Joined
Jul 12, 2011
Messages
360
Tractor
Power Trac PT-422
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.
 
   #9  

SpringHollow

Elite Member
Joined
Dec 9, 2006
Messages
2,512
Location
South of Rochester, NY
Tractor
Power Trac 1850, NH 2120
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
 
   #10  

MossRoad

Old Timer
Joined
Aug 31, 2001
Messages
51,534
Location
South Bend, Indiana (near)
Tractor
Power Trac PT425 2001 Model Year
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?
 
   #11  

Farmall140

Platinum Member
Joined
Mar 17, 2004
Messages
841
Location
N Central PA
Tractor
PT 422
When I was having my trouble I called Subaru, basically they said their engines are not well suited for PT application.
 
   #12  

J_J

Super Star Member
Joined
Sep 6, 2003
Messages
18,927
Location
JACKSONVILLE, FL
Tractor
Power-Trac 1445, KUBOTA B-9200HST
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.
 
  
  • Thread Starter
#13  
OP
F

Frank Sorbello

Gold Member
Joined
Jul 12, 2011
Messages
360
Tractor
Power Trac PT-422
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.
 
   #14  

J_J

Super Star Member
Joined
Sep 6, 2003
Messages
18,927
Location
JACKSONVILLE, FL
Tractor
Power-Trac 1445, KUBOTA B-9200HST
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.
 
   #15  

ernemats

Platinum Member
Joined
Mar 29, 2002
Messages
902
Location
Bolivar, pa.
Tractor
power trac 422, and agco-allis 5660, john deere 550 dozer ,1845 power trac
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.
 
   #16  

davesl708

Elite Member
Joined
Dec 13, 2014
Messages
3,500
Location
Shawnee, KS, USA
Tractor
Kubota BX2200D,
Have you tried pure gas in it? The 93 octane works great in my gassers. No ethanol clogging things up.
 

duane

Gold Member
Joined
Mar 12, 2002
Messages
310
Tractor
Toro 266H and PT422
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
 

Attachments

  • Robin engine coil start upgrade.pdf
    179.1 KB · Views: 105

coolconnection

Gold Member
Joined
Oct 6, 2008
Messages
340
Location
Ohio
Tractor
Massey Ferguson GC1723
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.
 
  
  • Thread Starter
#19  
OP
F

Frank Sorbello

Gold Member
Joined
Jul 12, 2011
Messages
360
Tractor
Power Trac PT-422
What do you suggest to use for gas?
 

JimRB

Veteran Member
Joined
Nov 11, 2008
Messages
1,279
Location
Covington, GA
Tractor
JD 870
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.
 

coolconnection

Gold Member
Joined
Oct 6, 2008
Messages
340
Location
Ohio
Tractor
Massey Ferguson GC1723
You are right Jim. I should have not said spark. The spark is the same but rather I should have said that premium fuel is slower burning for high compression engines. I use regular fuel in all my engines except one which requires premium.
 

duane

Gold Member
Joined
Mar 12, 2002
Messages
310
Tractor
Toro 266H and PT422
I don't think the hard starting problem is the hydraulic tank. If you google Robin engine hard start, you will see service updates for their engines used in welders. A service update is the -11 part number coils. I put a hair dryer on the heads and it will start up. I'm wondering if the new coils will make the hair dryer UN-necessary.
 

joshlee

Platinum Member
Joined
Jul 31, 2014
Messages
582
Location
Beaver Springs, PA
Tractor
Power Trac PT1430 Year made 2016
Ernemats, does the 1998 PT have a Robin Subaru or a Kohler? Just curious, because I'm trying to hear positive things about the Subaru engines:laughing:
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.
 

ernemats

Platinum Member
Joined
Mar 29, 2002
Messages
902
Location
Bolivar, pa.
Tractor
power trac 422, and agco-allis 5660, john deere 550 dozer ,1845 power trac
My 422 has a Subaru engine it has been good for me, I also have a generator with a Subaru engine and I like it also, the only problem with it is it does use a little oil, I don't know if it is common for generators to use some oil due to their constant running at high rpm's.
 

Soundguy

Old Timer
Joined
Mar 11, 2002
Messages
52,238
Location
Central florida
Tractor
RK 55HC,ym1700, NH7610S, Ford 8N, 2N, NAA, 660, 850 x2, 541, 950, 941D, 951, 2000, 3000, 4000, 4600, 5000, 740, IH 'C' 'H', CUB, John Deere 'B', allis 'G', case VAC
You are right Jim. I should have not said spark. The spark is the same but rather I should have said that premium fuel is slower burning for high compression engines. I use regular fuel in all my engines except one which requires premium.

double edged sword.

higher octane, = harder to ignite.. but also less heat for air cooled engines.

tough choice..
 
  
  • Thread Starter
#27  
OP
F

Frank Sorbello

Gold Member
Joined
Jul 12, 2011
Messages
360
Tractor
Power Trac PT-422
Duane, If you call Terry at Power Trac and buy the silicone heater for the hydraulic tank you will never need to heat the heads. When I use the heater in 10 degree weather she fires right up. My beef with the Robin engines is not starting, backfiring while running and vapor locks in the summer months.
 

joshlee

Platinum Member
Joined
Jul 31, 2014
Messages
582
Location
Beaver Springs, PA
Tractor
Power Trac PT1430 Year made 2016
Thats good to hear! I haven't had any problems with mine so far, but I put the fan and different muffler/header pipe on when I first bought it. It has 54 hrs on it. Since your talking about a generator, I have a 13,500 watt Ventrac generator that I'm thinking about putting a hydraulic motor on to run it with the PT. I know it will probably generate about half of the electricity since converting to hydraulic from belt drive. I'm going to make a forum on it in the future to see what everyone thinks?
My 422 has a Subaru engine it has been good for me, I also have a generator with a Subaru engine and I like it also, the only problem with it is it does use a little oil, I don't know if it is common for generators to use some oil due to their constant running at high rpm's.
 

Raw Dodge

Platinum Member
Joined
Apr 8, 2009
Messages
644
Location
Orange County,NY
Tractor
Ventrac 4231,Dixie Chopper XXWD5000
Thats good to hear! I haven't had any problems with mine so far, but I put the fan and different muffler/header pipe on when I first bought it. It has 54 hrs on it. Since your talking about a generator, I have a 13,500 watt Ventrac generator that I'm thinking about putting a hydraulic motor on to run it with the PT. I know it will probably generate about half of the electricity since converting to hydraulic from belt drive. I'm going to make a forum on it in the future to see what everyone thinks?

Good,luck withy our project, I think for field use it may be a handy setup to run if off the PT, for steady use or whole,house use I think you may be a little disappointed depending on what your demands are..as long as you don't as for over 5000 watts you should be ok.Hydraulic power isn't as constant as a belt or direct drive,I'd expect to have larger voltage fluctuations making keeping 60HZ difficult if loads are changing a lot.
 

MossRoad

Old Timer
Joined
Aug 31, 2001
Messages
51,534
Location
South Bend, Indiana (near)
Tractor
Power Trac PT425 2001 Model Year
Thats good to hear! I haven't had any problems with mine so far, but I put the fan and different muffler/header pipe on when I first bought it. It has 54 hrs on it. Since your talking about a generator, I have a 13,500 watt Ventrac generator that I'm thinking about putting a hydraulic motor on to run it with the PT. I know it will probably generate about half of the electricity since converting to hydraulic from belt drive. I'm going to make a forum on it in the future to see what everyone thinks?


For what its worth, I think we (the Power Trac forum at large) calculated the theoretical potential HP at the main PTO of a PT425 at something a tad less than 14HP. You should think about Raw Dodge's comments about fluctuations and what you'd get out of the PTO on the Power Trac. From my own generator, it has a governor. When the load is high, it opens the throttle to boost the gas, to maintain the known RPM that will generate 120V. There's no meter or electronics that control the engine speed. Its just a set throttle of either OFF or ON at about 3600RPM set at the factory.

Your Ventrac generator is belt driven, correct? How do you set the engine RPM for proper voltage? Is there a voltage meter and you increase the throttle until you get your 120V and the engine just holds there? I'd suspect if you drove it off of the PT's hydraulics, you'd just do the same thing. Since a fluid is not compressible and belts can slip, I'd think you'd get more consistent power with hydraulics than belts. But you're going to get substantial HP loss of available power from the hydraulics VS the belt.

The 13,000 watt generators I've seen recently are running 20+HP engines and those are direct drive. You'll never get that out of the PT425 hydraulic PTO.

Using the calculator at this website and plugging in the rated PT425 main PTO pump pressure of 2500PSI and flow of 8GPM you get about 14HP

Hydraulic Calculations | Fluid Power | Advanced Fluid Systems

(2500PSI X 8GPM) / (1714 X 85%) = 13.73HP

For more on what the 1714 is and why 85% efficiency.... OUCH, my brain hurts! :laughing:

1 horse power = 33000 foot-pounds per minute (by definition)

1 US gallon = 231 cubic inch (by definition)

1 psi = 1 pound per square inch (by definition)

In the equation

HP=kΔPF
where F = flow rate in gallons per minute, ΔP is pressure difference in psi, and HP is power in HP, you need a conversion factor. Doing everything in inches:

HP33000∗12∗inch−pounds/min=kΔPpounds/in2flow231inch3/min
from which it follows that

k=23133000∗12≈11714
In other words, "in plain English that a 9th grader can understand, and yet be correct and true to its purpose and place in life to satisfy seasoned physicists":

1714 represents the numerical scale factor needed to obtain pump power in HP given pressure in units of psi and flow rate in gallons per minute. It is not an exact number - only approximate."
 
   #31  

Raw Dodge

Platinum Member
Joined
Apr 8, 2009
Messages
644
Location
Orange County,NY
Tractor
Ventrac 4231,Dixie Chopper XXWD5000
For what its worth, I think we (the Power Trac forum at large) calculated the theoretical potential HP at the main PTO of a PT425 at something a tad less than 14HP. You should think about Raw Dodge's comments about fluctuations and what you'd get out of the PTO on the Power Trac. From my own generator, it has a governor. When the load is high, it opens the throttle to boost the gas, to maintain the known RPM that will generate 120V. There's no meter or electronics that control the engine speed. Its just a set throttle of either OFF or ON at about 3600RPM set at the factory. Your Ventrac generator is belt driven, correct? How do you set the engine RPM for proper voltage? Is there a voltage meter and you increase the throttle until you get your 120V and the engine just holds there? I'd suspect if you drove it off of the PT's hydraulics, you'd just do the same thing. Since a fluid is not compressible and belts can slip, I'd think you'd get more consistent power with hydraulics than belts. But you're going to get substantial HP loss of available power from the hydraulics VS the belt. The 13,000 watt generators I've seen recently are running 20+HP engines and those are direct drive. You'll never get that out of the PT425 hydraulic PTO. Using the calculator at this website and plugging in the rated PT425 main PTO pump pressure of 2500PSI and flow of 8GPM you get about 14HP Hydraulic Calculations | Fluid Power | Advanced Fluid Systems (2500PSI X 8GPM) / (1714 X 85%) = 13.73HP For more on what the 1714 is and why 85% efficiency.... OUCH, my brain hurts! :laughing: 1 horse power = 33000 foot-pounds per minute (by definition) 1 US gallon = 231 cubic inch (by definition) 1 psi = 1 pound per square inch (by definition) In the equation HP=kΔPF where F = flow rate in gallons per minute, ΔP is pressure difference in psi, and HP is power in HP, you need a conversion factor. Doing everything in inches: HP33000∗12∗inch−pounds/min=kΔPpounds/in2flow231inch3/min from which it follows that k=23133000∗12≈11714 In other words, "in plain English that a 9th grader can understand, and yet be correct and true to its purpose and place in life to satisfy seasoned physicists": 1714 represents the numerical scale factor needed to obtain pump power in HP given pressure in units of psi and flow rate in gallons per minute. It is not an exact number - only approximate."
I'm not sure about how much experience you have with working with small hydraulic systems and belt drives,but I can tell you that I own a ventrac,and I have about 15 hydraulic drive mowers and equipment at the golf course..I've been the mechanic and operator there 24 yrs. About the ventrac drive system,the belts do not slip period...if they slip which mine never have its because the belt has oil on it or is ready to fail...They use B series belts on a large 7inch diameter drive pulley,with an automatic tensioner,and a 75 hp rated electric clutch...the rpm will not move more than 50-100 rpm from full load to no load,the engines governor is the same exact one used on those same engines installed in gensets....the efficiency of the belt drive is about 85-90 percent with this system...a hydraulic motor hooked to a small machine working at its maximum rpm and gpm will run around 55 percent efficiency,hence the need for a hydraulic cooler, a lot of power is wasted and turned into heat thru pressurization,restriction, and leakage.As. the pumps and motors wear,the performance starts to drop,and leakage around the pump and motors vanes,and plungers increase,and the speeds will drop as loads increase where as a belt drive will not. In order to have an honest 12 hp at the hydraulic motor you will need about 20 horsepower driving it and still not have quite the rpm control a belt drive only needing a 15 hp engine will... Our older mowers hydraulic drive reels and blades do slow down slightly in heavy growth and especially when used on a hot summer day,where as our older belt drive machines do not have the same issues,just keep the belts tight and in alignment and no rpm loss .I like the reliability of a hydraulic drive ,personally ,even though it's more expensive up front and to repair,no belt failure issues and belt alignment problems...but there is no arguing that a properly designed belt drive will put out more power with less rpm change and way more efficiency..
 
   #32  

DarkBlack

Veteran Member
Joined
Dec 9, 2010
Messages
1,461
Tractor
Massey
I have a Subaru robin engine. It's been real good for me.
 
 
Top