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...