Repowering our 520H

[Red-Bovine 309]

Hello, I'm new to the forum. We have a 1991 520H with the Onan engine. I have had to repair loose valves seats in both cylinders over the last 5 or so years. Again, the motor is running poorly and compression has dropped from 125 to 75 and 35. The worst on the aft cylinder. The engine has 800+ hours now and I am tired of pulling it apart. I have decided to re-power with a Honda 630 motor. Repower Specialists, LTD, in Oregon has a conversion kit that I have ordered. It's pricey at $1995.00, but the tractor is really nice and we have a 48" mower, a grader blade, and 44" two stage blower for it, so we want to keep it running. Toro Wheelhorse does not seem to offer a replacement tractor that will utilize the accessories we have, so keeping this one running is our best option.

 

Over the years I was able to stake the valve sets in with success. I know both my husband and myself have not always be diligent about cooling down the motor after hot runs, so we are partially at fault for the early demise. Hopefully the V2 Honda will cool better. I will post pictures of the conversion and my thoughts regarding it and the components received. 

 

We are in SE-WI. If anyone is interested in the old Onan core, I will sell it for a reasonable price.

 

Red Bovine

[Chevydave 25]

I have a 416-8 repowered with GX-670.

You will be happy with the motor, and I'm sure your fuel consumption will drop.

I have had it in for about 3 years used it for mowing two acres, snow blowing and tilling.

[Red-Bovine 309]

Thanks for the encouragement!! We also have about 2 acres to mow and a large 150 ft driveway to clear. I would really hate to have to pay full replacement of all our equipment. After 22 years, 2 grand is cheap. I think we have around 7 grand invested in 1991 money. These 520H's are really work horses. Too bad Onan had some problems and went out of business. When the Onan was running right, it was GREAT!! Just don't have any faith or inclination to repair it again.

 

Red Bovine

[leeave96 487]

Please post pics of your install.

 

BTW - great tractor you have.

 

Thanks!

Bill

[Don1977 604]

The most important thing on any repower Is the location of the crank shaft. Be sure to measure the exact location of the Onan crank shaft height from the frame and centered on the clutch bracket. They should have already done this but check it anyway, so all the belts work and the belt cover will bolt up. I looked at the Honda when I repowered my C-120

but there was not enough room with my gas tank under the hood. Went with a Briggs Vanguard.

 

Chevydave how about posting some pictures of you repower.

[Red-Bovine 309]

Good tip, Don!! Will do and I will post pics of the process.

 

Red Bovine

[AMC RULES 37,130]

Thanks Red...this will make for a great thread to follow.    

[decksetter 50]

Sorry to hear of onan problems, if I were closer I would gladly take it off your hands! Mine have been pretty reliable.

[bean 85]

you won't be sorry with the honda. expect 2000 hrs of reliable service life. the vanguard is also a good choice. we have had great success with them in the commercial roofing industry.

[Wheel-N-It 2,969]

Good luck and please post alot of pics. I have a 520H that needs to be repowered after all my other Wheel Horse projects are 100% complete. Believe it or not I am making progress on that LOL. I bought the 520 not running, and it has 735 hours on it.

[Red-Bovine 309]

Thanks, Bean. It is comforting to hear positive endorsements. The Onan has been a good motor but they apparently had some issues with the valve seats getting loose. Having the valve arrangement in the block instead of the head makes it difficult to properly repair. When the seats were loose I had zero compression in the affected cylinder. After repairing I regained the compression to 125 psi. The motor recently was becoming difficult to start. Checking compression showed 75 in the front and 30-35 in the aft cylinder. I don't think this is an indication of loose valve seats again. It wasn't burning oil, so I think maybe the valves are just bad and it needs a good valve job. I don't feel spending anymore time or money on this motor is a good investment. To have someone repair this one would probably cost nearly as much as what I am spending to re-power with the Honda motor. I just don't have the proper tools to repair it myself. Someone with the skills and tools might be interested in the Onan core and rebuild it. It is available for local pickup for $100.00.

 

Red Bovine

[MalMac 1,331]

I know of a member on here that re-powered one of his 520's with a Honda that was supposed to be ready for the 520 conversion. It came from one of the well know en Web site's that promoted the Honda conversion. Short story- it was anything but. He had to do or I should say undo their attempt at wiring, Refab some of PTO stuff. It ended up being a good motor for his 520 and he likes the power. It just not all what the advertised just drop in and go. He talked to the place where purchased it and they were no help at all. Just be careful what your getting into.

[Red-Bovine 309]

I expect there to be a certain amount of fabrication with any conversion. Repower Specialists has said that the PTO linkage brackets will need to be modified and I don't think the wiring will be a big deal. The trick will be to make sure the shaft is properly lined up so the PTO and linkage will be lined up. I have built two airplanes and two boats, so I'm pretty sure this will be doable.

[Chevydave 25]

I know of a member on here that re-powered one of his 520's with a Honda that was supposed to be ready for the 520 conversion. It came from one of the well know en Web site's that promoted the Honda conversion. Short story- it was anything but. He had to do or I should say undo their attempt at wiring, Refab some of PTO stuff. It ended up being a good motor for his 520 and he likes the power. It just not all what the advertised just drop in and go. He talked to the place where purchased it and they were no help at all. Just be careful what your getting into.

 

I agree, I did not do the repower myself, I had a Kohler guy do it.

All of the mechanicals were fine, but had a heck of a time with the wiring, primarily to get it to charge.

If you read my past posts on the Honda this repower was not problem free.

I would recommend having a Honda shop do the repower.

If by chance anything does go wrong, you will be covered as far as the warranty goes.

If you decide to do it yourself, beware, I got no help from Honda unit it went to a Honda shop.

 

All that said it is an excellent, fuel efficent motor, I am glad I went with it.

[Red-Bovine 309]

Chevydave, who did you get your Honda motor from and what model was it?

 

Thanks,

 

Red

[Don1977 604]

If you buy an engine with the 20 amp charging system and key switch already in stalled extend the wiring and hook up the gauges and safety switches. You will need the right key switch anyway. I only hooked up the amp gauge and added an oil pressure gauge. I'm the only operator of my tractor and I skipped the safety switches. I would hook them up if I had kids around. My youngest is 35 and it don't look like we will have any grandchildren so I'm good.

[Red-Bovine 309]

The one I'm getting is the GX630 without the little control panel built on the side. It supposedly has the 17.5 amp charging system on it. There is an adapter to adapt the 1" Honda shaft to the 1 1/8" PTO clutch and main drive pulley for the Hydrostatic drive. I'll ring out the electrical system on both the tractor and new engine to make sure all the wire connections are correct. I have had lot of experience with both AC and DC wiring systems, so I should be fine with getting everything hooked up correctly. I should be getting the motor next week and will start on the conversion then.

 

I appreciate the tips and insight. Keeps me thinking and apprised of any "gotcha's".

 

Red 

[Chevydave 25]

Red,

 

I got the unit from Small Engine Warehouse, in Indiana I believe and it was a "drop in" unit.

I encourage you to search my old posts from the time of the installation.

Did you conside the larger GX-690, I believe it's a little over 22 or 23 HP, maybe closer in power to the Onan.

Keep in mind you don't have to go with the lower HP for fuel usage, they are very efficient.

[Red-Bovine 309]

Thanks, Dave. Repower did not offer that particular motor. I think the 630 should be OK, though. It may have been something to do with the shaft sizing and how they make up their kits.

 

I can't seem to find the thread about your conversion. Could you point me in the right direction?

 

Red

[Chevydave 25]

Red,

I forgot I did the repower before I was a member of Redsquare.

If you search Mytractorforum.com for GX-670 you will find the story.

Mytractorforum has a special section for Wheelhorse

Al my posts are under Chevydave in that forum also.

[Red-Bovine 309]

Thanks Dave!

[ericj 1,578]

i have had valve seats redone in 2 onan motors 1 was just the intake seat the last 1 was both intake and exhaust seats. the intake only cost about $50.00 for the machine work at napa and $ 50.00 for gaskets. the last 1 i did i had to do  like i said intake and exhaust seats and that cost me about $ 130.00 so it is not outrages to have new valve seats put in if you can do the tear down and put back together yourself

 

eric j

[Keith 21]

i have had valve seats redone in 2 onan motors 1 was just the intake seat the last 1 was both intake and exhaust seats. the intake only cost about $50.00 for the machine work at napa and $ 50.00 for gaskets. the last 1 i did i had to do  like i said intake and exhaust seats and that cost me about $ 130.00 so it is not outrages to have new valve seats put in if you can do the tear down and put back together yourself

 

 

 

That's good to hear.   I think Onans should have valve service done once every other year or so.  Clean the carbon and inspect the valves.  Waiting too long for valve service might be the costly Onan mistake.  From what I have seen of the Onan the motors are built very well.   

[decksetter 50]

Just curious, but how recently were your valves adjusted? I am in process of going through an onan that had 70 psi in the front cylinder and under 5 psi in the rear, and the major problem was that the valves weren't set right. Both intake valves were adjusted too tight and holding the valves open enough that I could spin them around and around with 1 finger while they were supposed to be shut tight.

[Red-Bovine 309]

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