Robin 425 Engine Problem

[TheBigHeadKid]

I recently (week ago) completed a tram pump replacement on a PT-425 with 500 hours on it. Got the pump back from Terry and installed it and all looked good.
Mowed with the unit for nearly 2 hours without any issues, Lots of power back on the wheel motors and everything looked good.

Mowed today and got 5 minutes in and lost engine power quickly over 1 minute time. The engine was running but skipping and popping alot. It finally quit on its own and when I tried to re-fire the engine all it will do is pop and backfire through carb really bad.

I went and checked the compression on each cylinder to see if I broke a valve or something and got very good numbers 150# plus. Exactly what I saw a month ago while I was troubleshooting power loss on wheel motors.

I have seen many post about floats sticking in the carb so I checked engine oil and level looked fine and smelled normal. I have a Quick Disconnect fitting in my fuel line so I can remove gas tank easily. So I disconnected fuel line to prevent fuel from dumping in like many others have had.

When I first pulled the air filter it had a little extra gas and oil on the metal cover. After several attempts to start I have alot of black oil now on the cover.

Any thoughts.. Where do I start ?

 

[washita]

mine will do the same thing with a plugged air filter-snap /crackle /pop 178 hours on my motor

 

[Marks481]

Oil in the air filter?

Possibly a malfunctiong PCV (positive crankcase ventilation) valve? The PCV valve allows the air intake to keep a suction on the crankcase to keep it under a vacuum during operation. This prevents gas fumes or exhaust fumes from building up in the crankcase. Robin calls this the "breather plate".

The PCV valve essentially acts as a check/float valve to keep from sucking oil out of your crankcase. If it failed, it could allow oil to spray into your air filter. If clogged, it could also possibly affect the operation of your manual fuel pump, which relies on pressure/vacuum pulsations in the crankcase (caused by the moving of the pistons up and down) to operate.

In the picture below, you can see the "breather pipe" which connects your carburator to the "breather plate" (PCV) on the cylinder head.

 

[woodlandfarms]

PCV could be malfunctioning, but with a restricted air filter the engine would create a vacuum under the air filter and attempt to draw from the crank case. It would have to work hard at that...

I just saw a product (from one of the other sections) that is a guage to let you know when your air filter is plugging up.

$20 to $35....

Air Filter Service Indicators | K&N Filters | StreetPerformance.com Page | 1

 

[SpringHollow]

Carl,

Doesn't ours have an indicator on it?

Ken

 

[woodlandfarms]

Ohhh Please tell me it doesn't.... I remember seeing that little burping thing that lets out debris that is supposed to collect on it... Don't remember any indicator...

But with that great manual I got, I wonder how I could have missed it if it does exist...

Let me know what you find before I place an order.

 

[Bob999]

Ohhh Please tell me it doesn't.... I remember seeing that little burping thing that lets out debris that is supposed to collect on it... Don't remember any indicator...

But with that great manual I got, I wonder how I could have missed it if it does exist...

Let me know what you find before I place an order.

My 1845 has an indicator.

 

[ponytug]

Dear Carl,

It should be around the corner from the one way "burping thing". Red line on a clear and yellow vacuum indicator. The Deutz engines should all have it. (and you should reset it when you change your air filter).

One could probably add one to any of the green engines, but one would want to set the vacuum spring appropriately.

The concept is called a "filter minder", but there are lots of variants.

All the best,

Peter

Ohhh Please tell me it doesn't.... I remember seeing that little burping thing that lets out debris that is supposed to collect on it... Don't remember any indicator...

But with that great manual I got, I wonder how I could have missed it if it does exist...

Let me know what you find before I place an order.

 

[TheBigHeadKid]

Terry had it. Even though I had 150# compression he still had me pull the valve covers. Sure enough Cylinder #2 exhaust valve rocker arm was loose....loose....loose.

The pivot bolt stud had backed out of the head. I was surprised to see it backed out and not broke off. Terry had me call Robin to confirm next step of action and Robin just said, "Apply red loctite and torque to 15 ft lb and then do valve adjustment and should be fine."

I performed those steps and started right up.
I will send pictures of the valve arrangement for those who do not have service manuals.

Thanks to all who commented.
Dave

 

[woodlandfarms]

Bob, what year is your PT?

Nope, Mine does not have one as far as I know...

Now for the $64 question. What is the proper pounds meter that I should buy? The come in various flavors and I don't know how to guage it.

I would guess smaller is better, nothing hurts have a freshly cleaned filter....