Just scored a 1997 520H - looking for a recommendation...

[Brian K WheelHorse 28]

Hey guys - new to the forums here. I purchased my first WHeel Horse new back in 2000 - a 314 Classic gear slammer. Just sold that one to help finance my new aquisition - a nice 520H with the Onan twin, with only 380 hours on it. Has a 48" deck and I got the factory wheel weights with it.

The sellers were "thoughtful" enough to top off the battery and not tell me the voltage regulator was smoked. I replaced that, the fuses (after I plugged in the wire they hid, it wiped out the fuses for the charging system), all fluid and all filters, spark plugs, 1 sloppy tie rod end, both front tires, etc.

Motor runs great. For whatever reason, the folks I got it from had it idling at over 2000 rpm. I adjusted the governor/low idle screw down to 1100 warm. It idles and runs super, BUT the exhaust smells like its running a bit rich. I mowed the lawn Friday (2.75 acres) and it took more than a tank of gas so there seems to be a definite carb issue.

It's using a lot of gas - here's my questions:

1. What type of carb maintenance should I be performing at this stage? I haven't tried any carb cleaner or fuel treatment yet, and I have some concerns about buildup due to cruddy ethanol gasoline.

2. Where can I get a carb kit if I need one? The local dealer couldn't even tell me what comes in the kit when I gave him the Toro # I got from the Toro site that had the Parts Manual.

3. I know the Onan twin is a good motor from what I've read, but also comes with some concerns. Given that this seems to be an authentic low-hours motor, what maintenance issues should I look for? Is it too early to worry about valve lash if I don't really have issues with hard starting or fuel burping out of the carb?

Thanks for the help - I've been a big fan of Wheel Horse fro 12+ years and it was a shock to me when they finally stopped making them altogether.

Brian

[stevebo-(Moderator) 8,527]

Brian,

Welcome to the forum. Congrats on your new purchase and be ready to hit the gas station often with that Onan. I have an 88 520HC that I run a 60 inch deck on and it burns twice the amount of gas as my kohler single. In terms of the carb kit, if it is running smooth then do not mess with it. IMO that is a downfall of the Onans is that there is not much adjustment on them. Typically they get cleaned by taking the top off and cleaning them out. When the carb is dirty the govener will search or surge at lower rpm. I just mowed with mine on Sunday and the week prior it ran mint then on Sunday it was surging so much that I needed to keep the rpms up when not mowing. Once I started to put a load on it at wot it was fine.

The other thing that i find is common on these is the voltage regulators go bad often. Sounds like you found that out. Good luck with it and let us know how you make out. Oh yeah... the members around here love pictures... :hide:

[Foozerush 40]

Welcome to RS!! Congrats on the new 520... I have a 416-8 that is a step under yours, keep the fluids changed and keep engine free from grass/leaves on the flywheel screen and the cooling fins on both heads. I sometimes let the back yard get a little longer so the Onan can get a nice workout ( love the sound of it ). Might want to do some research on decarbonizing the heads, there are some threads here talking about it to Onans, as I plan on doing it before I get it ready for snow duty this winter. And yes Stevebo said it all by... We love pics!! fooze

[AMC RULES 37,195]

[zieg72 209]

Welcome to the 520 club, I got 2... Keep em clean and fluids changed as recommended and it'll last you a long time.

[Ken B 3,189]

My 88 520 just cracked 202 hrs. It is the best Wheel Horse I've owned for doing all of the chores. I'm only running a 42 in side discharge on mine so the fuel consumption isn't too bad. Even in tall grass the governor doesn't need to kick in.

[Brian K WheelHorse 28]

Thanks guys. Seems like this forum is a great resource with friendly folks! I'll get some pics up soon! By the way - ran some carb cleaner in it today and added some Sea Foam to the gas. When I ran the tractor with the air cleaner off I did notice a little gas coming up through the carb when I slammed the accelerator so I think it's time to check the valve lash...it isn't really noticable under slower acceleration.

[Fordiesel69 271]

My recommendation is to make a video of it idling. If it is running smooth, then I agree with the others that the carb will be fine. The kohler command on your 314 is quite a bit more fuel efficient, per HP. Keep in mind running the hydro pump sucks fuel a bit.

Here is an example of a twin briggs needing carb work:

Notice it hunting, then stumbling, thats not me doing that. Your onan should be smooth.

As far as maint concerns, you should do the valves & decarbon now. As well as clean the cooling fins to avoid the valve seat issue before it surfaces on you. The valve seat issue is brought on by dirty fins, and incorrect valve lash.

Enjoy the new 520............

[Brian K WheelHorse 28]

I haven't checked it out yet, but do I have to "move anything out of the way" to adjust the valve lash? I want to do this right away and then de-carbon the heads after the mowing seaeson.

[Brian K WheelHorse 28]

I haven't checked it out yet, but do I have to "move anything out of the way" to adjust the valve lash? I want to do this right away and then de-carbon the heads after the mowing seaeson.

OK - got the manifolds out of the way and the valve covers off. Not too bad but it certainly isn't like a single Briggs - lol. Do I have to take the side cover off the flywheel to line up the timing marks? The manual is a litte non-descript about this...the rest looks pretty straight forward.

[jusjeepn 59]

For 380 hrs it must have been pretty severly abused to have so much wrong with it. I'm not suggesting a rebuild, but I'd certainly go over it with a fine tooth comb.

[Brian K WheelHorse 28]

Actually - looks pretty good ( yes - I will post some pics) but I'm going to error on the side of caution because the sellers didn't tell me about the regulator. Valve lash/tappet adjustment is recommended every 200 hours on the Onans so I'm assuming it was never done. The hydraulic fluid didn't look bad but that's the way I'm going to approach all the maintenance items on it. Change everything - adjust everything. I already ordered new manifold gaskets and I might go ahead and pull the heads off to de-carbon them. After removing the valve covers I was pretty impressed - you can still see the metal on parts of the valves and the build-up is minimall. No sludge or deposits on the springs at all. Looks real good and it seems to indicate the motor truly is low hours.

[bobert94 38]

Welcome to the 520 club . Mine is used for winter snow removal with a 44" 2 stage blower running wide open the tank does not stay full for long. But it loves chewing through 2' of snow hardly slows it down. The newer 520's have a accelerator pump on the carb thats probably were the gas shooting in the carb is coming from. Enjoy your new toy & welcome to Redsquare!

[Brian K WheelHorse 28]

Thanks - I have the carb off now - is the accelerator pump an easy fix?

[Brian K WheelHorse 28]

OK - pictures in order, more or less...

I didn't think the buildup is too bad but the heads definitely need to be de-carboned. I forgot to take pics of the heads. Now that i have the belt guard off I think I'm going to mill vent slots in it to aid in the engine ventilation. I thought about adding a 12vdc pancake fan to the gurad but I think it would just get clogged up too fast. The gaskets, new bolts, etc are in the mail from Parts Tree so I'm about a week from total completion. what you see is what I have done since last night so I am pleased with my progress. I have already bead-blasted/sanded the top guards and the muffler and painted them with high temp engine enamel. I have also cleaned up the intake manifold and carb (nothing too invasive) so I'm chugging right along. I will have everything ready to go back together when the parts arrive.

[JackC 617]

Use a torque wrench when you put it back together to avoid stripping threads in the soft aluminum block.

[Brian K WheelHorse 28]

Thanks Jack - I printed off all the specs for the tappet adjustment and torque rating.

[Brian K WheelHorse 28]

OK - got it back together. Here's some more pics:

Heads before:

Heads and valve covers cleaned up:

The belt guard milled for more engine air flow and re-painted:

One of the heat shields cleaned up and repainted:

Back together:

It went back together nice. Carb is still not perfect but the valve lash and carbon removal did need attention. Runs real nice even with the fuel not being properly vaporized. Filled the tank again and added more Sea Foam. I know it's not recommended but it still seems like the carb need to be taken apart and be cleaned up and evaluated. Thanks for your input guys. It's been quite helpful.

[Foozerush 40]

I know you have one happy 520h there!! Looks great!! Belt cover looks factory!! Good job!! Hope it gives you 20 years trouble free service!!

[krazy_horse 59]

Looks great and I like the belt guard.

[varosd 1,185]

Looks great, How did you do the belt guard? looks like neat!!

[Brian K WheelHorse 28]

To do the belt guard, I put the sturdiest 90 degree fold of the metal into the table vise on an old Bridgeport milling machine. I supported the overhanging part with some wood and held it with my free hand. I used a single 1/2" end mill and plunged through and made single passes. Filed the edges and de-burred the slots. I've seen other guys do something similar and I thought the slots would not only be functional, but add a cool louvered look. This tractor is a grass cutting beast and in great shape so I want to keep it nice.

[520h driver 0]

Looks great!! More pictures!!! ;9

[520h driver 0]

Do you have the Toro # for the PTO Shield? Looks awesome ;)

[Brian K WheelHorse 28]

Do you have the Toro # for the PTO Shield? Looks awesome

Thanks. I actually milled out the side shield for more air flow. I used an old Bridgeport milling machine. It was tough to get it secured in the vise but I got it to work.