Thinking about 520H Repower

[r1jakecfd 51]

Hi Guys,

The Onan in my 520H was running poorly so last month I took the heads off, decarboned, cleaned/reseated the valves, checked valve seats and reassembled with new gasket set. When installing intake manifold, I realized last year (carb cleaning) I forgot to hook up vacuum line from manifold to gauge. Hooked it up correctly this time and ran great. First blizzard yesterday and started snow blowing. After about 15 minutes the became noticeably louder with less power.

I was wondering firstly if anyone has any idea what went wrong?

Also, I was thinking about repowering with a Honda or Vanguard and would love opinions on which way to go? Also, should I go with an engine or kit and which company? I’m good at fabrication, etc.

 

Thanks in advance!

Happy NewYear

[Desko 607]

You might have Ice or snow plugging your air cleaner and the loudness could be the blower? I would fix the onan as it'll be the best engine to have in that tractor in my opinion. But a Honda would be a better repower over the briggs but some wiring altercations will have to be made. 

[cafoose 3,354]

Check this thread:

 

 

[Mike Johnson 9]

I repowered my B-100 about a year ago with a 22HP Honda twin that came in a kit from Repower Specialists.  It comes with a 3 year warranty and so far I have been delighted with it's performance.  Installation was relatively easy, and would be even easier on your 520 since it is a larger framed tractor.  You can see pictures and more details by doing a search on "B-100 Repower" in the customs forum.

[WVHillbilly520H 10,373]

You want cheaper? but seems durable so far, try the 22hp Predator basically a Honda clone many threads on here if the conversion, check out this video of @fast88pu modded predator, Jeff.

VID_20171104_172556_edit_0.mp4

[r1jakecfd 51]

8 hours ago, Desko said:

You might have Ice or snow plugging your air cleaner and the loudness could be the blower? I would fix the onan as it'll be the best engine to have in that tractor in my opinion. But a Honda would be a better repower over the briggs but some wiring altercations will have to be made. 

Good idea! I didn’t think of the air cleaner. I’m also going to check the torque on the intake and exhaust bolts. I just redid the top end and used the $30 gasket kit vs Onan OEM. The gaskets look different than OEM ones so I wonder if that has something to do with it? 

I definitely won’t find out today as it’s 12 degrees right now, going down to negative numbers tonight and I have an unheated garage!

[Desko 607]

That might be the issue I used those $30 ebay special gaskets and they leaked so bad around the intake and exhaust it sounded like a bad tick but it was the exhaust blowing past the gasket 

[r1jakecfd 51]

1 minute ago, Desko said:

That might be the issue I used those $30 ebay special gaskets and they leaked so bad around the intake and exhaust it sounded like a bad tick but it was the exhaust blowing past the gasket 

Now that I think about it, after I started it for the first time, my vacuum gauge was reading about 28-30. When it started running poorly, it was reading about 20. I think I may have found the problem! I guess you get what you pay for!

[fast88pu 3,324]

18 hours ago, WVHillbilly520H said:

You want cheaper? but seems durable so far, try the 22hp Predator basically a Honda clone many threads on here if the conversion, check out this video of @fast88pu modded predator, Jeff.

VID_20171104_172556_edit_0.mp4

That's the stock engine with header pipe

 

[littleredrider 409]

If the Onan goes  on my 520 I plan on getting the HF 22 horse motor. Love to put a V-twin diesel, but can't afford one right now...

[r1jakecfd 51]

On 1/7/2018 at 8:33 AM, fast88pu said:

That's the stock engine with header pipe

 

 

On 1/6/2018 at 1:33 PM, WVHillbilly520H said:

You want cheaper? but seems durable so far, try the 22hp Predator basically a Honda clone many threads on here if the conversion, check out this video of @fast88pu modded predator, Jeff.

VID_20171104_172556_edit_0.mp4

At this point seriously looking at the Predator! Getting frustrated troubleshooting.

[r1jakecfd 51]

OK guys, here we go again! I decided to test the compression and have no compression in the front cylinder. I know it’s usually the rear cylinder that has issues but that has over 90 psi. Like I said in my first post, I decarboned the heads/valves, reseated and adjusted the valves, new (non-OEM) gaskets and new plugs. Running really rough and loud with misfires and loss of power. Any advice or recommendations before I convert it to a boat mooring?😂 

Any input/advice would be greatly appreciated!

Thanks Guys!

John

[fast88pu 3,324]

Loose valve guide or seat. Mis adjusted valves. Bad plug. Dirty carb

[WVHillbilly520H 10,373]

11 minutes ago, r1jakecfd said:

OK guys, here we go again! I decided to test the compression and have no compression in the front cylinder. I know it’s usually the rear cylinder that has issues but that has over 90 psi. 

During your compression test did you try a couple teaspoons of motor oil and try again, this will let you know if it's rings/valve guides/seals (compression comes up) or no increase valve stuck open no piston movement ect, both cylinders fire from the coil at the same time, easier way to check fire is a $10 inline spark tester, try these first if you havent already, Jeff.

[r1jakecfd 51]

17 minutes ago, fast88pu said:

Loose valve guide or seat. Mis adjusted valves. Bad plug. Dirty carb

Great point. I think I’m going to check the valve adjustment first and while I’m in there make sure I didn’t lose a valve spring retainer. I just read about that on another feed for the same symptoms I’m having. I’ll keep you updated on the progress/problem found.

Thanks everyone!

[WHX?? 48,703]

Any chance that head gasket  blew & how many hours on it? If it's got no compression on that front  something bad must have happened. Since that's the easiest jug to get at I would at least pop the head off. Maybe just a stuck valve.  I'm kinda in the same boat anchor  as you John in that I have one that smokes worse than I do & eats plugs. Haven't  got past the carb cleaning stage yet but afraid to even stick a decarbon gasket set in it. Jeff just beat me to the stuck valve diagnosis.

Edited January 9, 2018 by WHX14

[r1jakecfd 51]

4 minutes ago, WVHillbilly520H said:

During your compression test did you try a couple teaspoons of motor oil and try again, this will let you know if it's rings/valve guides/seals (compression comes up) or no increase valve stuck open no piston movement ect, both cylinders fire from the coil at the same time, easier way to check fire is a $10 inline spark tester, try these first if you havent already, Jeff.

Haven’t tried oil yet and I do have spark plug tester but also had a good spark when I removed the plug to test compression.

[r1jakecfd 51]

3 minutes ago, WHX14 said:

Any chance that head gasket  blew & how many hours on it? If it's got no compression on that front  something bad must have happened. Since that's the easiest jug to get at I would at least pop the head off. Maybe just a stuck valve.  I'm kinda in the same boat anchor  as you John in that I have one that smokes worse than I do & eats plugs. Haven't  got past the carb cleaning stage yet but afraid to even stick a decarbon gasket set in it. Jeff just beat me to the stuck valve diagnosis.

I’m going to take the valve cover off first to check adjustment and if I threw a spring/retainer. If things look good I’ll take the head off to check that. I just decarboned and put a new gasket set in about an hour ago. I torqued everything to specs so it should be good but I am human!

[ericj 1,578]

my cousin's daughter called me last summer and said that their 520's deck had a loose blade and she had just tightened it and it was loose again, I told her to bring me the deck to look at, instead of bringing me just the deck she brought me the whole tractor and deck. So when I started the tractor to pull the deck off I right away said something didn't sound right on the tractor. diagnosed the deck as a broken bearing housing. then looked at the tractor. Checked the spark plug and while out decided to do a compression check and found low compression on the back cylinder. Pulled the motor and stuck a spare on it and gave them the tractor back to use. When I checked the motor couldn't find a problem at first. Finally pushed on the valve seat and found some movement. My guess is the seat had just came loose and didn't have a chance to were to bad. Seat was still fairly tight in the block, just not tight enough to run as is. So what I'm saying is to check the seat closely, might have to push on the inside of the seat or even tap on it LIGHTLY to detect any movement. sounds more likely that either your valve keeper came apart or something foreign is holding the valve open. good luck. 

 

 

 

 

eric j

[r1jakecfd 51]

Well, I’ll let my new head gasket speak for itself. I’m not sure what happened... was it installer (Me) error, old head bolts that backed out. Not sure. I’m definitely ordering a new OEM gasket kit and new head bolts. I’ve also bought High temp Threadlocker to install this time around. I’ll let you all know how it works. Very relieved it’s not a valve seat! Thanks to everyone for their input!

[lynnmor 7,294]

That gasket does look like inferior material.  Do you know if the head is flat?  I don't think you are to use thread locker on the head bolts, usually you use a drop of oil.

[WVHillbilly520H 10,373]

8 minutes ago, lynnmor said:

I don't think you are to use thread locker on the head bolts, usually you use a drop of oil.

This is what I used on my SBC head bolts, ARP thread sealant...

[Howie 886]

Yeah but that is because the head bolts go into the water jacket on the SBC!

[r1jakecfd 51]

2 hours ago, lynnmor said:

That gasket does look like inferior material.  Do you know if the head is flat?  I don't think you are to use thread locker on the head bolts, usually you use a drop of oil.

It’s a good lesson in buying OEM parts. Material is completely different material, not aluminized. OEM set on order

[WVHillbilly520H 10,373]

 

7 hours ago, Howie said:

Yeah but that is because the head bolts go into the water jacket on the SBC!

If it's a factory block with through holes the aftermarket blocks have blind holes,  plus this sealer is for the steel to aluminum so the threads don't gall up and you can remove them without breaking the bolts off plus helps get the correct torque reading when installing, Jeff.