Overheated Robin EH72-FI (28 hp) in PT-425 solved

[joshlee]

/Users/joshuaromig/Pictures/100_0164.JPG Would a bolt work better with a nylon lock nut work better here instead of the pivot pins? The pins are rolling and wearing the holes open.

The picture didn't go through.

 

[Gator6x4]

Very beautiful work. May I be so bold and suggest protection for the muffler. My luck about the second time I used it I would back up and hit something with the muffler.

 

[Marks481]

Kent, how are you liking your muffler arrangement after a few months with it?

Did you find somewhere that would sell you a short length of 1.25" flex tubing, or did you have to buy the 25' length (which is the only length I have seen sold)?

EDIT: I found a place that sells 1.25" stainless for $4.10 per foot:

.: TAC :. Transportation Accessories Company - Flex Tubing

I am interested because it is time for me to put a muffler back on. My neighbor came over while I was mowing and offered me a pair of noise canceling headphones (in addition to the foamees I was wearing). I think he was hinting that I was a bit too noisy.

 

[Kent]

I have 23+ feet of flex pipe left over from the 25' roll I had to buy, so would be happy to cut off any length you need. The roll was about $50 with shipping, so I figure $2/foot for you, plus my shipping to you. May not be a bad idea to get double the length in case you bend it backing into a tree.

It is Walker 40001 flex pipe, 1-1/4" ID, 1-3/8" OD.

One thing to keep in mind is the minimum bend radius of the flex pipe. The pipe bend shown in my pictures is pretty much the minimum radius. Not all that flexible. But it is sturdy stuff. Though not stainless the flex pipe is galvanized, and is not rusting, just blackish.

Note that I have since directed the exhaust tip to point backwards, not sideways as shown.

I have about 40 hours on the new engine/muffler/fan set up. So far working perfectly! I have not yet backed into anything, so no dents or dings on the muffler or flex pipe. It has been a cold Winter in VT, and as predicted (hoped) the side fan only came on only once, when I used the snowblower (requires full throttle). Otherwise when just plowing (usually at about 3/4 throttle), the fan stayed off, allowing the engine to build up a nice working temperature.

By the way, the garage where I keep the tractor never dipped much below 30 degrees (it is under the house). The fuel injected Robin started up very quickly every time (unlike the original 25 hp which would crank for a while before firing up, occasionally flooding when I mishandled the choke).

 

[SpringHollow]

We have yet to see the ground since December and you are mowing! Snowed again last night.

Ken

 

[Marks481]

I have 23+ feet of flex pipe left over from the 25' roll I had to buy, so would be happy to cut off any length you need. The roll was about $50 with shipping, so I figure $2/foot for you, plus my shipping to you. May not be a bad idea to get double the length in case you bend it backing into a tree.

Thanks for the offer, unfortunately I already ordered from the link I posted. Time to dust off my welder and starting modifying the canopy!

By the way, the garage where I keep the tractor never dipped much below 30 degrees (it is under the house). The fuel injected Robin started up very quickly every time (unlike the original 25 hp which would crank for a while before firing up, occasionally flooding when I mishandled the choke).

Now you are just showing off....

We have yet to see the ground since December and you are mowing! Snowed again last night

I don't think it got below 30F at my house this winter... and not a wisp of snow in sight. My plow blade has sat all lonely in the storage shed for the two years I have lived here...

 

[Raw Dodge]

I guess this explains the engine life problems a few have had...i hope the people at power trac are watching this thread..and make the necessary corrective action on new machines. .

 

[Marks481]

...i hope the people at power trac are watching this thread..and make the necessary corrective action on new machines. .

I can guarantee they are not. The internet only recently arrived at Tazewell... And we are only a small percentage of their business compared to their mining machinery.

The existing evil welded square steel exhaust manifold and muffler have been part of their design for the past 11 years. The exhaust manifold on mine had a steel lip across of about 1/3 of the inlet from one of the cylinders, which couldn't have helped the heat issue. Get rid of the manifold and muffler and your engine will be a lot happier.

Unfortunately adapting the stock Robin exhaust manifold and muffler requires surgery on the canopy (as you can see in Kent's pictures above). But after having monkeyed with my own manifold design, I have decided his route is simpler.

 

[PTWannaHave]

Awesome post, Kent !!

 

[Kent]

Hi - I was asked to post more pictures of the modifications, including the placement of the temp sensor and the wire harness schematic:

https://drive.google.com/folderview?id=0B34rGjNSGixVQmg3Wlc4WmhIVTg&usp=sharing

As an aside, picture 751.jpg shows the connection to the always-hot terminal on the starter solenoid as well as the stock temperature sensor wire screwed into the crankcase (upper right). I forgot to mention earlier that I put a woven fire proof shield around this wire all the way up to the FI module. This was an early attempt to solve the shutdown problem prior to going all the way by installing the stock exhaust header and side fan. I thought maybe the wire was picking up ambient heat in the tub. I just left it in place, figuring it wouldn't hurt even if it didn't help.