PT422 Engine shaking / sputtering

[washita]

here is a thought, figure the volume the cylinder is capable of holding, remove sparkplug and fill will oil, if it will accept full volume of oil and discharges it out of sparkplug hole while rotating the engine that would narrow it down to a head problem. but if the oil level in the crankcase increases when you do this test it means a hole in the cylinder, if the volume accepted into the cylinder does not change as engine is rotated then piston is disconnected from connecting rod =broken rod or wrist pin, this test may save you time and help to diagnose where the problem is. please disconnect the power to the coil to avoid ignition of the oil if it sprays from the cylinder head when doing this test

 

[KMA]

I made a simple leak down tester per duane's suggestion. I put a socket on the flywheel so I could rotate the piston to TDC before testing. I placed a dowel into the spark plug hole to see how the piston was moving... it wasn't. The dowel moves up and down as expected in the "good" cylinder. I don't think its possible for the piston to be "frozen" without something being broken (e.g. connecting rod).

I'll have to pull the engine and take it somewhere to be fixed. Anyone have an idea of what the ball park cost might be? Reason I'm asking is that I always thought I would swap in a different/better motor if the Robin had troubles. Anyone have a recommendation on a high quality, reliable, (liquid cooled?), 22hp-ish engine that could be shoe-horned into the PT422? I think I can handle the engine swap, but I'm not sure about the shaft diameter/shapes, etc. I also think I could figure out how to mount the radiator if it was liquid cooled.

Maybe something like this:
http://www.smallenginewarehouse.com...1/8" Shaft, Fuel Pump, Oil Filter, Oil Cooler

or this:
http://www.smallenginewarehouse.com...94" Keyed Shaft, Electric Start, OHV, Muffler

Let me know what you guys think (about the frozen cylinder and/or the swap). Thanks!

 

[KMA]

I'm not sure about the shaft diameter/shapes, etc.

Is it a 1" keyed shaft? Anyone know the length or how to find out? If I decide to swap the engine with a different model, does anyone have experience with a particular model that starts better in the cold weather? or runs less hot?

Thanks again.

 

[3238dpw]

You could always call this guy for advice. I have no experience with him, but have read his web site pretty well and always thought I would call him if I was ever in your situation. He will recomend a Vanguard for the reasons listed on his website. He has done Vanguard conversions for smaller skidsteers so the hydraulic system is similar

Used Lawn and Garden Tractors - Mowers - Small Engines - Jim's Repair/Jim's Tractors

 

[stray]

well if your are lucky may be all you will need is to replace the connecting rod (Piston to crank).

 

[MossRoad]

I made a simple leak down tester per duane's suggestion. I put a socket on the flywheel so I could rotate the piston to TDC before testing. I placed a dowel into the spark plug hole to see how the piston was moving... it wasn't. The dowel moves up and down as expected in the "good" cylinder. I don't think its possible for the piston to be "frozen" without something being broken (e.g. connecting rod).

I'll have to pull the engine and take it somewhere to be fixed. Anyone have an idea of what the ball park cost might be? Reason I'm asking is that I always thought I would swap in a different/better motor if the Robin had troubles. Anyone have a recommendation on a high quality, reliable, (liquid cooled?), 22hp-ish engine that could be shoe-horned into the PT422? I think I can handle the engine swap, but I'm not sure about the shaft diameter/shapes, etc. I also think I could figure out how to mount the radiator if it was liquid cooled.

Maybe something like this:
Small Engine Warehouse: GX690TDW - Honda engine 22.3HP 690cc Horizontal 1-1/8" Shaft, Fuel Pump, Oil Filter, Oil Cooler

or this:
Small Engine Warehouse: FH680D-S01 - Kawasaki Engine 23hp Twin Cylinder Horizontal 1-1/8"x3.94" Keyed Shaft, Electric Start, OHV, Muffler

Let me know what you guys think (about the frozen cylinder and/or the swap). Thanks!

You do not want to shoehorn in a liquid cooled engine. It will be a nightmare project and require much fabrication and relocation of just about everything in the engine bay.

In my opinion, you have a few good options.
1. pull the engine and either repair it yourself or have it repaired. Hopefully only the rod is broken and not the crank shaft.
2. buy an identical engine and do an exact swap. Then repair the first engine and keep it for a spare or sell it or keep it as is just for parts. Go karters do this all the time. They get an engine running sweet, then pull it out and put it on the shelf for use later.
3. try finding a Kohler with the exact same shaft dimensions, but you may be hard pressed to get the pump brackets to line up or you may have to modify them for length, etc...

 

[KMA]

Any know the shaft dimensions on these motors or someone who's swapped one out?

I will have to pull the engine regardless, and will probably get it looked at either way. But if I'm going to buy a new engine, it's not going to be another Robin/Subaru... I don't think they are the worst ever, but definitely not the best either. I guess i could measure up the shaft, etc once I get it pulled, but it would be nice to know it ahead of time so I can start researching my options. I'd like to get either a Honda or Kawasaki as my 1st and 2nd choice. Kohler would be 3rd.

Thanks again for everyone's input.

 

[KMA]

You do not want to shoehorn in a liquid cooled engine. It will be a nightmare project and require much fabrication and relocation of just about everything in the engine bay.

Oh I don't know if it would be that severe. I'm thinking the motor itself is roughly the same size, but the radiator would need to be relocated. My idea would be to move it out on the backside of the tractor since I don't use the rear hitch and it would allow for short hoses. A bracket + shroud would need to be fabricated.

Here's a Kawasaki:
Kawasaki Engine , FD661D-DS00, FD661D-CS00, FD661D-BS00, FD661D-S00 on sale from Tulsa Engine Warehouse

 

[Marks481]

Scarg replaced his PT422 engine with a liquid cooled 29hp engine. Search back and you can read a number of threads on his conversion.

http://www.tractorbynet.com/forums/power-trac/110268-pt-429-project.html

Here are some other threads that discuss engine replacement. Scarg discusses some engine alternatives here:

http://www.tractorbynet.com/forums/power-trac/106815-422-robin-engine-blew-up.html

http://www.tractorbynet.com/forums/power-trac/159468-engine-swap.html

And here is a step-by-step PT422 engine removal and installation thread:

http://www.tractorbynet.com/forums/power-trac/150760-robin-422-engine-main-bearing.html.

There are one or two threads that I remember that discussed shaft size and replacement motor model numbers, but I couldn't find them in the time that I had to look.

 

[Gravy]

Kevin,

I've spent way too much time researching replacements for my Robin engine. I've come to the conclusion that the Robin is the most compact engine in it's horsepower class. Anything but another Robin will likely require some serious re-engineering.

Fortunately for me, my poor abused Robin has refused to die. I think the rings are actually re-seating.

If you decide to re-engineer, remember the corollary to Murphy's Law that applies to estimating time for a new project:

Figure out how long it should take. Multiply that by two. Then raise it to the next higher unit.

If you think it *should* take 2 days, it will take four weeks.

And that only applies to stuff that you have some experience with. For this stuff, there's another multiplier between 2 and 10...

 

[stray]

Kevin,

I've spent way too much time researching replacements for my Robin engine. I've come to the conclusion that the Robin is the most compact engine in it's horsepower class. Anything but another Robin will likely require some serious re-engineering.

Fortunately for me, my poor abused Robin has refused to die. I think the rings are actually re-seating.

If you decide to re-engineer, remember the corollary to Murphy's Law that applies to estimating time for a new project:

Figure out how long it should take. Multiply that by two. Then raise it to the next higher unit.

If you think it *should* take 2 days, it will take four weeks.

And that only applies to stuff that you have some experience with. For this stuff, there's another multiplier between 2 and 10...

WHAT HE SAID!

 

[MossRoad]

Scarg replaced his PT422 engine with a liquid cooled 29hp engine. Search back and you can read a number of threads on his conversion.

http://www.tractorbynet.com/forums/power-trac/110268-pt-429-project.html

Here are some other threads that discuss engine replacement. Scarg discusses some engine alternatives here:

http://www.tractorbynet.com/forums/power-trac/106815-422-robin-engine-blew-up.html

http://www.tractorbynet.com/forums/power-trac/159468-engine-swap.html

And here is a step-by-step PT422 engine removal and installation thread:

http://www.tractorbynet.com/forums/power-trac/150760-robin-422-engine-main-bearing.html.

There are one or two threads that I remember that discussed shaft size and replacement motor model numbers, but I couldn't find them in the time that I had to look.

Radiator, Muffler relocation, battery, fuel tank, hydraulic cooler, the swing of the engine cover, length of existing hydraulic hoses, engine shaft diameter, length, adapter for engine to pumps, cooling hoses, etc...

Yes, it can be done. My guess is you will end up removing the engine cover and cutting the rear out of the engine tub, mounting the engine, pump, radiator and battery to one big tray, slide it in as a unit, bolt it down, hook up all of the hoses, then put the engine cover and fuel tank back on, fabricate a new rear end to the engine tub, then hang a muffler out the back or side, which will promptly get ripped off or smashed on a tree. At least, that's what would happen to me! :laughing:

 

[KMA]

Radiator, Muffler relocation, battery, fuel tank, hydraulic cooler, the swing of the engine cover, length of existing hydraulic hoses, engine shaft diameter, length, adapter for engine to pumps, cooling hoses, etc...

Yes, it can be done. My guess is you will end up removing the engine cover and cutting the rear out of the engine tub, mounting the engine, pump, radiator and battery to one big tray, slide it in as a unit, bolt it down, hook up all of the hoses, then put the engine cover and fuel tank back on, fabricate a new rear end to the engine tub, then hang a muffler out the back or side, which will promptly get ripped off or smashed on a tree. At least, that's what would happen to me! :laughing:

I'm not sure why you are saying all of that needs to change... am I missing something? The pumps, etc mate to the "front" shaft side on my PT422 so the engine is mounted at the back of the tub and everything else is in front of it. The location of the muffler, battery, fuel tank, etc should not change (in theory). I'll have to take some pics and post them here. Of course, this assumes the actual engine block size is similar to the Robin. For a liquid cooled engine, the radiator would need to be moved outside. Of course, a new muffler would need to be fabricated regardless, but that is probably a positive thing.

This isn't a particularly good pic, but you can see the engine is at the very back of the tub and the muffler is mounted outside the cover. The black metal thing on the right side is the heat shield between the exhaust pipe and fuel tank.

 

[KMA]

Kevin,

I've spent way too much time researching replacements for my Robin engine. I've come to the conclusion that the Robin is the most compact engine in it's horsepower class. Anything but another Robin will likely require some serious re-engineering.

Fortunately for me, my poor abused Robin has refused to die. I think the rings are actually re-seating.

If you decide to re-engineer, remember the corollary to Murphy's Law that applies to estimating time for a new project:

Figure out how long it should take. Multiply that by two. Then raise it to the next higher unit.

If you think it *should* take 2 days, it will take four weeks.

And that only applies to stuff that you have some experience with. For this stuff, there's another multiplier between 2 and 10...

My goal is to find one that fits pretty close. Width seems to be where I have the least wiggle room on my version. I have a inch or two behind the Robin, and height shouldn't be a problem since the engine is currently sitting atop some spacer tubes, and I think I have some decent room above the current air filter. Depth/length is actually the biggest challenge since the Robin is particularly small in this dimension... so finding a replacement that fits depth-wise will be tough. As crazy as it sounds, the liquid cooled Kawasaki I linked to earlier might give me the best chance of fitting without modification (other than moving the radiator outside).

Regarding the time estimates... since my Robin didn't like to start below 55 degrees when it was running "good", I've gotten used to not having it available over the winter. So that leaves me roughly 6 months or so to work on it. If that's not enough time... I'm definitely in over my head.

 

[KMA]

Here's an interesting update from Terry at PT... he says there is absolutely no issue with dropping in a 25hp EH72 Robin in place of the original EH65. I asked him if I should be worried about the pumps, etc and he said "not at all". In fact, he seemed to recommend going for the EH72 instead. In case anyone is wondering, here are the two spec numbers for the engines:

EH720-DS0032
EH650-DC0303 (need to verify if that 'C' is supposed to be a 'Z'... Terry's accent got the best of me I think )

I think I can fit this Kohler Command 25hp:

http://www.smallenginewarehouse.com...16"x4-29/64" Keyed Shaft, OHV, Electric Start

What do you guys think about the trade off between that engine (which probably costs about $250 more than the Robin) and the "drop in" EH72 choice? I'm not particularly happy with the Robin and I'd really like to go for a better engine, particularly one that starts in colder weather and maybe even runs quieter. It appears the engine should be around 25hp and have a 1 7/16" shaft. I'm not seeing options from Honda or Kawasaki that would fit... Found this site for the EH72 with free shipping, still need to see if I can find a better price.

http://www.equipatron.com/subaru-horizontal-engine-sub8011.html

 

[Marks481]

Not to surprising that the 25 hp robin fits... It is the same engine. :laughing:

Different carburetor, and an external oil filter. Smaller diameter cylinders. Same engine block.

The advantage of the EH72 is that you can get a fuel injected version. That way when it quits working, none of our small engine repair knowledge will get it going again.

As long as you are thinking about the FI version, maybe you can get the low profile 28 hp EH72 to fit. I think an extra 6 hp would really help.

 

[KMA]

Not to surprising that the 25 hp robin fits... It is the same engine. :laughing:

Yeah, I knew that... I was more surprised about the fact that there is apparently no issue with the extra power on the pumps, etc. I was under the impression we had to be careful about jumping up to 25hp.

The advantage of the EH72 is that you can get a fuel injected version. That way when it quits working, none of our small engine repair knowledge will get it going again.

As long as you are thinking about the FI version, maybe you can get the low profile 28 hp EH72 to fit. I think an extra 6 hp would really help.

Even the "regular" EH72 FI version appears to be 28hp. Going up 6hp would make me pretty nervous about reliability, although more power + fuel injection does sound pretty cool. :licking: I'm with you on the fact that FI will give me even less chance at being able to fix these darn things.

Swapping out the EH65 for the EH72 is a no brainer since the cost isn't much more. Spending another few hundred dollars more at least to get a potentially "better" brand (e.g. Kohler Command) is a tougher decision, especially until I know I can get it to fit. Rest assured, I won't be buying anything until I get as much of it figured out as possible. :thumbsup:

 

[Gravy]

As far as I can tell, the 28 hp Robin gets it's extra power by revving to 4000 rpms vs the standard 3600. At 3600 rpms it makes about the same power as the 25 hp. I don't know if the pumps will take 4000 rpms.

 

[BobRip]

What do you guys think about the trade off between that engine (which probably costs about $250 more than the Robin) and the "drop in" EH72 choice? I'm not particularly happy with the Robin and I'd really like to go for a better engine, particularly one that starts in colder weather and maybe even runs quieter. It appears the engine should be around 25hp and have a 1 7/16" shaft. I'm not seeing options from Honda or Kawasaki that would fit... Found this site for the EH72 with free shipping, still need to see if I can find a better price.

720cc Subaru Horizontal Engine EH720DS0032

I think the main reason the Robin engine has trouble starting when cold is that the starter must rotate the pumps and the engine. Is there any information to support that the Kohler will start better when cold? I think the fuel injection would help no matter who makes the engine. I am speculating here, so if anyone has seen a Kohler on a PT start reliably when cold (say below 32f) please less us know. If you are afraid of too much horsepower then reduce the top RPM.

 

[KMA]

As far as I can tell, the 28 hp Robin gets it's extra power by revving to 4000 rpms vs the standard 3600. At 3600 rpms it makes about the same power as the 25 hp. I don't know if the pumps will take 4000 rpms.

I think the main reason the Robin engine has trouble starting when cold is that the starter must rotate the pumps and the engine. Is there any information to support that the Kohler will start better when cold? I think the fuel injection would help no matter who makes the engine. I am speculating here, so if anyone has seen a Kohler on a PT start reliably when cold (say below 32f) please less us know. If you are afraid of too much horsepower then reduce the top RPM.

Thanks guys. I'll have to give the EH72 FI some more thought. I guess I could adjust the stop on the throttle cable connection so that it only revs up to a point. Anyone find a place that sells them online? I can't seem to find the fuel injected model.

Regarding cold starts, I agree that the biggest problem is turning the pumps with all that cold hydraulic oil, but I couldn't even get the engine to start when it was 50-55 degrees out. I would have to put a heater on the hydraulic oil tank AND make sure the battery was fully charged to even stand a chance.

Thanks again for everyone's input. :thumbsup: I'll keep you posted.