Jump to content
TC10284

520H High RPM

Recommended Posts

TC10284

I have a 1991 41-20OE02 520-H.

Recently got it running and it runs pretty dang well. 

 

The only engine issue I may have is that the RPM at full throttle seems to be too high. I had to replace the throttle and and cable with one from a parts-only 520H because the one that came on it was messed up. 

Compared to my other 520H's, this one seems to be closer to 3800 to 4000RPM. I cannot tell exactly because the tachometer isn't working on this one (just my luck huh). The replacement throttle seems to creep back down a little to the "normal" RPM range and stop there. But I wanted to make sure it's good and I'm not pushing it too hard.  

 

What can I check to verify this? 

Share this post


Link to post
Share on other sites
 
WHX??

Get yourself a handheld photo or contact tach. to verify. Was just a thread on them a bit back see if we can find it. Not sure if there is a high end throttle stop would have to check the manual. I wouldn't go by the dash tach, all three of mine read different when set @ 3600.

Share this post


Link to post
Share on other sites
 
TC10284

Thanks.

This looks like a good candidate:

https://www.amazon.com/HDE-Professional-Digital-Infrared-Tachometer-x/dp/B00850ZCRI/ref=sr_1_3?ie=UTF8&qid=1540409350&sr=8-3&keywords=handheld+photo+tach

 

I did some research prior to posting this and what I read was a normal max RPM for the P220G is 3600RPM. 

Edited by TC10284
  • Like 1

Share this post


Link to post
Share on other sites
 
pfrederi
7 minutes ago, TC10284 said:

Thanks.

This looks like a good candidate:

https://www.amazon.com/HDE-Professional-Digital-Infrared-Tachometer-x/dp/B00850ZCRI/ref=sr_1_3?ie=UTF8&qid=1540409350&sr=8-3&keywords=handheld+photo+tach

 

I did some research prior to posting this and what I read was a normal max RPM for the P220G is 3600RPM. 

 

That is the one I use

Share this post


Link to post
Share on other sites
 
lynnmor

You bend the throttle stop to adjust top speed, download the Onan manual on this site.  If you have runaway high speed that the governor can’t control, then the ball spacer in the governor is loose, a not uncommon problem.

  • Like 1

Share this post


Link to post
Share on other sites
 
TC10284

I was wrong. It doesn't have a tach. It has the load gauge instead. I adjusted the throttle cable. Tested it and the load meter stays right below 100%, around 90% in the green, and sounds better, so I think I'm good now. 

Edited by TC10284

Share this post


Link to post
Share on other sites
 
lynnmor

Doesn’t make sense to me, your tractor should have a tachometer and the power percentage should only reach 100% when working hard.  You don’t adjust maximum RPM by adjusting the cable, rather you adjust the cable so that the throttle stop is reached and that stop sets the maximum RPM.

Share this post


Link to post
Share on other sites
 
elcamino/wheelhorse

Don't mean to steal the thread , but when adjusting the carb to max rpm (3600) should the max rpm be adjust under load " Example  have mower powered so when the governor kicks when PTO is on?

Share this post


Link to post
Share on other sites
 
lynnmor

It should only make a little difference in RPM when the engine is under normal load.  If there is a great difference, or the speed is hunting, see the manual for instruction about that.  If there is a need to move from the factory linkage settings, there most probably is something else amiss.

Share this post


Link to post
Share on other sites
 
TC10284

This problem has resurfaced. I started her up this evening to clear off some leaves from the driveway. Was running for approximately 10 to 15min. Throttle all the way up. Ran good @ 3600RPM for most of the time. Then suddenly shot up over what sounded like over 4000RPM. I had to lower the throttle position to around 75% to get it back to where it sounded like it should be. Of course my tach on the dash doesn't work. It does have a tach. I was wrong in my previous posts. The engine load gauge does work. So in the initial few minutes of operation, it was right under 90%. When the RPMs increased, it would shoot up over 100%, as far as the gauge would go. 

 

I've got three working 520H's and one working 520HC. I've never heard any of the others run this loud and hard. 

 

I didn't have time to try the tachometer I bought to see the actual RPM. But I know for sure it's off. 

 

I do know the throttle is pretty sensitive. A quarter of the way up sounded like 50% throttle. But I don't get why it was correct RPM in the beginning few minutes. The only other time I've had a slightly similar situation was when I had cracks in the fuel line in another 520H but that included a lot of surging as well (don't ask me how the high RPMs happened)

 

Is there anything else I can check, such as cable positioning, etc? 

 

Edited by TC10284

Share this post


Link to post
Share on other sites
 
lynnmor

What is happening is that the plastic governor ball spacer begins to slip when the engine warms up.  The fix is to either get an old metal spacer, or one of the newer ones with a tang that is a positive driver.  In either case, they need to be super glued in place.  Here is the fix: FIX

 

Contact Boomer for parts and help. Boomer

Share this post


Link to post
Share on other sites
 
TC10284
3 hours ago, lynnmor said:

What is happening is that the plastic governor ball spacer begins to slip when the engine warms up.  The fix is to either get an old metal spacer, or one of the newer ones with a tang that is a positive driver.  In either case, they need to be super glued in place.  Here is the fix: FIX

 

Contact Boomer for parts and help. Boomer

Doesn't look too bad. Just got to get the right parts. 

Share this post


Link to post
Share on other sites
 
TC10284
On 11/7/2018 at 7:30 PM, lynnmor said:

What is happening is that the plastic governor ball spacer begins to slip when the engine warms up.  The fix is to either get an old metal spacer, or one of the newer ones with a tang that is a positive driver.  In either case, they need to be super glued in place.  Here is the fix: FIX

 

Contact Boomer for parts and help. Boomer

 

Can the process in your "FIX" link be used with the original plastic flyball spacer and loctite?

Share this post


Link to post
Share on other sites
 
ericj

I have had several onan's do this to me after running awhile the governor wants to let the engine run away with itself. I have found that after using the unit for awhile, making sure that the motor doesn't over rev too bad, they have gotten better  and don't do it anymore. It seems to happen to motors that sat for long periods of time. My recommendation it to use it before tearing it down and see if it gets better, ain't got nuthin too loose, unless you over rev the motor and scramble it :hide:  good luck

 

 

 

 

 

eric j

Share this post


Link to post
Share on other sites
 
lynnmor
2 hours ago, TC10284 said:

 

Can the process in your "FIX" link be used with the original plastic flyball spacer and loctite?

 

Maybe, how are you doing with the lottery tickets?  :eusa-pray:

 

Once the bore of the plastic parts has enlarged the results will always be in question.  Some might get lucky and have the bore fuse to the metal from spinning freely then melting fast, but I would prefer the positive drive from the extended tab.

Share this post


Link to post
Share on other sites
 
TC10284

Once again, you guys were right on the money!

Took me a while, but I finally had time to work on this and replace the flyball spacer. I had one that came from another P220G that has the extended tab. This one apparently did not. Hopefully you can see the pics here: https://photos.app.goo.gl/BEpaNvzxBhyYp45s7

Let me know if not. 

 

Anyway, put everything back together. Made sure to reinstall all governor balls, C clip on cam shaft, put the timing cover pin aligned with the governor cup. Made sure to put the key back on the shaft and reinstall the ignition rotor. Put everything else back on. Tried to start and it will not run. 

Turns over fine. 

Pulled plugs. Both plugs seem to get fire. Both plugs seem to be getting fuel (I think I smell it). 
Tried squirting some gas into carb. Still no start. At one point, it backfired kind of loudly when I kept turning it over and unspent fuel got pretty heavy coming out of the muffler. 

Not sure why it won't fire and run at this point. 

Last time this happened on a different 520H, I had to replace the ignition rotor.

Note that this tractor ran prior to the work. Although it over-revved after 15-20min of running due to the flyball spacer. .  

Edited by TC10284

Share this post


Link to post
Share on other sites
 
TC10284

After a little more testing today, I have a feeling it's the ignition rotor. 
Is there a way to test these things? The magnets inside seem fine. 

Edited by TC10284

Share this post


Link to post
Share on other sites
 
lynnmor

The manual is on this site.  manual

 

The ignition information starts on page 8-1.

 

After you run thru the tests, and still have problems, report back.

Share this post


Link to post
Share on other sites
 
cleat

Are you sure the rotor is in the correct position and not flipped over.

 

That may still allow spark but at the wrong time.

 

If it worked before then it must be something that was touched during the governor job.

 

Cleat

Share this post


Link to post
Share on other sites
 
TC10284
6 minutes ago, cleat said:

Are you sure the rotor is in the correct position and not flipped over.

 

That may still allow spark but at the wrong time.

 

If it worked before then it must be something that was touched during the governor job.

 

Cleat

 

Yeah, I actually wondered about that when I took it off. I wasn't paying attention when I took it off (the second time), but I THINK it may have been flipped around. I didn't think about it until after I had put up all my tools. And after I had taken apart the rotor to look at the magnets. 

I asked myself if I remembered seeing the "Flywheel side" text facing me and I don't think I do remember seeing it. 

 

Does anyone know if the magnets in the rotor has to be facing a certain polarity? 

 

I ordered a new one anyway, just in case. 

Edited by TC10284

Share this post


Link to post
Share on other sites
 
TC10284

Update:

Got the replacement ignition rotor. Installed, put everything back together and it fired up perfectly! 

 

Thanks as always, guys!

  • Excellent 1
  • Thanks 1

Share this post


Link to post
Share on other sites
 

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×
×
  • Create New...