Repowering our 520H

[leeave96 487]

I adjusted the valves about a year and a half ago when the front cylinder puked the valve seat and I needed to repair it. Being a 22 year old motor I just feel more comfortable replacing it with something that will, hopefully, be less fussy. I think the Honda will work out well.

 

Red

 

I'd say if you want to repower - more power to you!  As these fine old tractors, it's helpful to see repower experiences and hopefully you can share this with the forum.

 

My Brethren over at the Simplicity forum with Kohler Command and Kohler Triad twin cylinder engines don't seem (IMHO) to hesitate to repower vs rebuild those engines.  Several have repowered with Honda engines with great success.  It's interesting to hear the Honda engines are more fuel efficient than the Onan - don't know how thay compare to that classic Onan engine sound...

[Keith 21]

The BMW motorcycle "airhead" boxer is also known for valve seat failure.  The BMW seat failure is because of valve guide wear.  The horizontal valves wear the guides unevenly.  When the valve doesn't center in the guide it begins to pound the valve seat, which eventually loosens. It is easier to do the preventative maintenance on the ohv BMW than the Onan.  The later BMW have oil cooled heads. I think the newest models are water cooled.  There can be valve failure on the BMW when the bike gets stuck in heavily congested traffic for only a few minutes, but the repairs are generally not super costly.  The Onans don't appear to be easy to service in a garden tractor.

 

I would venture that the exhaust valve guides of the Onan probably don't get enough oil.  Many Onans are reliable for years of service in RV generators.  Maybe grass clipping on the cooling fins contributes to the valve problems.  From what I can see the Onan is robust and automotive grade. I wouldn't like to do annual valve preventive maintenance.

[JackC 617]

"Maybe grass clipping on the cooling fins contributes to the valve problems."  

 

When mowing, grass clippings get sucked onto and collect on the fly wheel screen which greatly reduces cooling air flow to the aluminum block.

Overheating and warping can be the results especially if mowing on a hot day.

 

[Brian K WheelHorse 28]

I have handled the Onan on my 520H with "kid gloves" after reading all the posts last yearWhen the day comes for a repower - It will be a big Briggs Vanguard 23HP from Small Engine Warehouse, Direct replacement and the Vanguard Series has proven to be reliable...

[Keith 21]

Does the P series Onan have an aluminum block?    An alloy block could be more susceptible to losing valve seats during overheating because of the expansion of the alloy.  From what I have read the older Onans had a cast iron block and didn't have this problem.  If the Onan has an alloy block then cooling fins should probably be cleaned with compressed air almost every time the tractor is used.  Failed valve seats is a design flaw, but keeping an air cooled motor clean with an adequate oil level could help prevent failures.   The Honda GX probably would have few problems over a long life of use.  

[Red-Bovine 309]

The overhead valves engines just seem to be a better design. While the Onan is a well constructed engine, it is old school technology. The solid lifters that need maintenance are not something the average owner cares to or can do. Not to mention that they aren't very easy to access. The V design with OHV's and hydraulic lifters is much more appealing to me. I will start posting as soon as I start the conversion. The engine and kit are scheduled to be delivered on Monday.

 

Red

[Keith 21]

OHV motors have an oil pump, even those which are otherwise splash lubricated.  The oil pressure to the head also helps in cooling.  The splash lubed Chevy stovebolt sixes use an oil pump for the valve train.  As per the Onan P series, either the engineers or the cost analysts came up short, an internal memo likely documented the risk.  The Honda is a long lasting design, but nothing in this class matches the boxer twins for smoothness.

[Red-Bovine 309]

OK !!!! I received the GX630 Honda engine from Repower Specialist in Oregon this afternoon. The unit arrived in perfect condition and included the muffler and parts necessary to mount it into my 520H. There is a new mounting plate that places the shaft correctly for and aft and at the correct height. Slots are provided in the mount for aligning the pulleys. I pulled the old motor off today, mounted the new mounting plate to the tractor and set the new motor on place. I needed to grind a little cutout in the plate to clear the lower PTO clutch mount. The pully was a bit of a bear to remove off the old motor, but a little heat and penetrating oil loosened it up. A bear claw puller worked fine here once heated a bit. Other than that it seems to be a no brainer. I will set the pulleys tomorrow, bolt the motor down, and begin modifying the upper clutch bracket. I need to lengthen the fuel line so I will be replacing the line all the way back to the tank. There doesn't seem to be a temperature probe, a manifold pressure tap fo the power gage, and I'm not sure where the tach is integrated in to the wiring. The motor I received has a fan screen with a hole for a PTO shaft. I'm checking with Repower on rectifing that.

 

I'll post more tomorrow on the clutch mod.

 

Red

[sorekiwi 761]

That Honda looks good in there!

[leeave96 487]

Looks great!  Keep the pics coming.

[Don1977 604]

Why are you modifying the upper PTO bracket.  Does the top of the loop not line up with the bottom on your tractor. They make a couple of different PTO loops. Mine the top and bottom lined up and I just need a couple of washers behind the bracket. Kelly one of out vendor might have  what you need. Tell us what you need it may make the repower easier.

 

This is the one I used came on my C-120.

 

[Ken B 3,164]

That looks pretty good on there. You'll have to take a video of it in action when it is all done so we can hear it.

[Red-Bovine 309]

Why are you modifying the upper PTO bracket.  Does the top of the loop not line up with the bottom on your tractor. They make a couple of different PTO loops. Mine the top and bottom lined up and I just need a couple of washers behind the bracket. Kelly one of out vendor might have  what you need. Tell us what you need it may make the repower easier.

 

This is the one I used came on my C-120.

I need to modify the bracket to match the tapped holes in the new motor block and make sure it is at the correct height and make sure the hole in the lever for the upper part of the loop  lines up correctly. I think this would be easier than trying to find a different loop.

 

Red

[Red-Bovine 309]

I finished the conversion yesterday and am happy with the results. The motor runs great and the PTO functions perfectly.

 

The first thing I did was to temporarily slide on the main pully and set the motor position to align the pully to the belt. The motor was then bolted down and the belt placed on the pulley. The next picture shows the split collar that converts the shaft from 1" to 1 1/8". A new, thicker, key is provide to compensate for the collar. This needs to be trimmed to the correct size so it does not protrude beyond the bolting collar on the pulley. The next picture shows the key in place and the pulley secured.

 

I made an adapterfor the PTO bracket from 1" X 1/4" bar stock. It was drilled to match holes in the motor block that most closely match the position needed for the PTO upper bracket. Once I was satisfied with the positioning, I welded the bar stock to the bracket. The next picture shows the PTO and linkage attached. The motor adapter plate provided does a good job of setting the correct height of the motor and the correct fore and aft position. Slots in the plate allow you to move the motor in and out to adjust for overall postion. I needed to move the main pulley out 1/4" from the block to properly set the PTO loop to line up with the bottom hole on the frame the PTO loop engages.

 

The choke cable was jogged over from left to right and fasten to the choke. The throttle cable was wrapped around the motor and secured to the motor throttle linkage. I may shorten that cable later to make the connection more direct. The linkage on the motor provides two postions for each cable so you can run them fore or aft, depending on your needs  or preference.  The next pictures are the completed conversion with venerable hubby trying it out.

 

Wiring was pretty straight forward. The yellow coil wire was attached to the ignition wire on the motor. The light blue wire from the old solenoid was attached to the spade connector on the new starter solenoid. The main red wire and the positive battery cable are attached to the lug on the starter. A new voltage regulator is mounted somewhere convenient on the tractor. I mounted mine on the bracket that hold the front of the main belt guard. There is a loom and plug on the new motor that plugs directly to it. There are two wires that went to the oil pressure switch on the old motor. The dark blue wire goes to the new oil pressure switch. The black wire can be grounded to keep the hour meter running. The white wire that went to the temperature switch is not used unless you care to install a sender on the new motor. The red wire that was plugged into the old voltage regulator is not used nor tis the grey tachometer wire.

 

The only real issure I had with the whole deal was the muffler (does not appear to be a Honda part)) fits the motor just fine, but interferes with the PTO linkage. Lowering the upper bracket is not an option. What I wound up doing was to trim the top of the loop and the bushing and bolt for the lever pivot and making a small dent in the bottom of the muffler so everything would clear. Not a big deal, but annoying. I may look into getting an OEM muffler to see if that makes a difference. I slight smaller diameter would have helped. I still need to adapt the heat shield to the muffler and I want to get an elbow to direct the exhaust away from the belts better.

 

Red

 

 

[Red-Bovine 309]

Here are the completed pics of the Honda Wheelhorse. I ran out of space on the last entry. There is a utube link to the video, as well. The squeeking noise in the video is the deck wheels scrubbing on the driveway in the turns. My venerable hubby gets his turn to drive. We don't normally leave the tractor so dusty. I haven't had time to clean it off this spring from the dusty winter projects.

 

http://youtu.be/v2DJ2mWTC44

 

Red

 

100%

 

[papaglide 542]

Good job! Doesn't sound like it was hard at all.

[Red-Bovine 309]

Thank you!! It was easier than I feared. Only took about 12hrs and I am a bit putsy. I also nee to get the PTO hole in the fan screen covered up, yet. No big deal.

 

Red

[leeave96 487]

That is an AWESOME job and QUICK too!!!!!!

 

Might I suggest - next up a foot control kit from Matt and a cup holder...

[Red-Bovine 309]

Is there a link to Matt's foot control? I'd like to check that out. The cup holder sounds like a good idea, too!!

[leeave96 487]

Is there a link to Matt's foot control? I'd like to check that out. The cup holder sounds like a good idea, too!!

 

http://www.wheelhorseforum.com/forum/103-matts-custom-hydro-pedal-kit/

[Red-Bovine 309]

Thank you!!

[bean 85]

it will be interesting to get your thoughts on power comparison and fuel consumption. I think the honda will fare very well.

[leeave96 487]

it will be interesting to get your thoughts on power comparison and fuel consumption. I think the honda will fare very well.

+1

This would be great info to have.

I think that regardless of hydro or gear drive, Kohler or Onan, at the end of the day, the engine is the weak link in these tractors. It would be good to hear your experiences with the Honda engine.

[Red-Bovine 309]

When I cut the grass later this week I'll have an idea of the economy of the Honda and how well it performs. So far I am happy with it. I was happy with the Onan until the valve seats started acting up. The Onan was very well built but was also very old technology. That type of valve in block system is just a PITA to work on.

 

I did look at getting an OEM muffler that would fit better and have the heatshield on it. Problem is they are either too high and would necessitate cutting up the hood or they are too low further interfering with the clutch. The mods I made are working fine so I will be leaving that alone and modify the Onan shield to fit the new muffler.  Repower Specialists  is sending me the flywheel screen that does not have the hole in it for a PTO. As far as the tach, I will verify the RPM and forget that. The manifold pressure Power Gage I will not hook up and the cylinder head temp will not be hooked up either. Everything else seems to be just fine.

 

Red

[Ken B 3,164]

Super clean job.  That 520 should be good for another 20 yrs. Money well spent.