520-8

[dgjks6 6]

I am still looking at getting another wheel horse and they keep getting closer. There is a 520-8 close to my house. I t has 1100 hours. I know for the body this does not matter, but what about the engine. Is the Onan as good as the Kohler Magnum?

As an aside - I also was reading new tractor reviews and they said the new tractors at the big box stores were desgined to last about 250hrs.

[nylyon-(Admin) 7,121]

I would love to see that article if you could find a link. In my opinion, the Onan is a great engine, but I have heard that sometimes the valve seats will come lose causing engine problems. I am not sure if there is preventitive measures, but I believe that you need to be sure that the cooling fins are clear from debris which means taking off the enfine shrouds and cleaning it up good.

My 416-H has an Onan and I love it. Very smooth and powerful engine which for me (knock on wood) has been trouble free since 1994.

[T-Mo-(Moderator) 4,345]

I also would like to see this article. From the things I've read, the cheaper tractors were designed to be 5 year or 500 hour machines.

I think 1100 hours on an Onan is not too bad. But parts can be expensive I've heard.

[TT-(Moderator) 1,128]

The 520-8 you speak of must be the one currently on ebay.

You will find that it will go for a much higher price than a 1990 520H in the same condition because of the very low production number (225) of the gear drive unit.

That particular tractor was not a well maintained machine, or it wouldn't look like it does. It might have had the drivetrain serviced on occasion, but the rest of the tractor was badly neglected. 1100 hours on an Onan twin isn't bad, but the remaining lifespan would depend on the frequency of oil changes and general upkeep history.

[dgjks6 6]

I can't find the article that said 250 hours. I think it was consumersearch or something like that. I will keep looking. I hope no one tells that guy that he has a limited productin tractor.

[TT-(Moderator) 1,128]

I hope no one tells that guy that he has a limited production tractor.

The low number of 520 8 speed tractors wasn't intentional.... it's just that nobody wanted them. Everyone seemed to like the extra gauges, chrome, and the hydro transaxle with hydraulic lift on the 520H a lot more.

They are basically just a 416-8 chassis, a 518H hood stand / dash (and hood), and a 520 engine (minus the chrome goodies) and "swept forward" front axle assembly. (no reduction steering in 1990)

[dgjks6 6]

I think I like the manual transmission. I think it has less problems, though I don't know if this is really true.

[Sparky-(Admin) 19,587]

In my opinion, the Onan is a great engine, but I have heard that sometimes the valve seats will come lose causing engine problems.

The funny thing is that all the valve seat stories I have ever heard or read on a tractor forum/group, and there are plenty, were about the 20hp Onan and not the 16hp .

Anyone have thoughts on that?

Mike............

[DMESS 24]

I think I like the manual transmission. I think it has less problems, though I don't know if this is really true.

The problem on the 520-8 is lifting "520 size" attachments with the ol' arm stick instead of that handy "lazy lever". Infinite ground speeds are certainly nice too since 1st always seems too slow and 2nd always seems too fast for normal mowing. I'd take the H over the 8 in a 520 any day unless I was going for "collector value" or wow factor. B)

[TT-(Moderator) 1,128]

Less "meat" between the cylinder bore and the valve seats on the P-220's could be the cause. (increased thermal expansion/contraction)

D..... second is too slow and third is too fast, except for some guys who probably wish they had a fourth. (or a fifth! )

[Nick 13]

Dustin, Was the production of 16hp tractors near that of the 20hp? I would assume there are a lot more 20s out there but thats a guess. Another guess but more 520s could have been used commercially and had more hours and abuse.

Now how about the KT17 and KT19. We hear about the 17 problems but not 19s. Was the 19 that much different or is it just so few of them? B)

[DMESS 24]

Less "meat" between the cylinder bore and the valve seats on the P-220's could be the cause. (increased thermal expansion/contraction)

D..... second is too slow and third is too fast, except for some guys who probably wish they had a fourth. (or a fifth! )

LOL, yeah, that is what I was shooting for. 1st is WAY too slow! Although sometimes in heavy grass 2nd is a bit too much for my 310.

Nick, the 19's are just stroked 17's and have their problems too. I could show you a DOOZIE! :whistle:

[wh500special 2,055]

I don't recall why this sticks in my mind - perhaps there is a mention in an owner's manual or something - but isn't part of the valve seat issue in these Onans resultant from incorrect valve lash adjustments? Seems like I recall a manual and a dealer somewhere/sometime directing that the valves MUST be adjusted every 200 hours or disaster may befall the engine...I'll see what I can find.

I am not a mechanic, so am just repeating info here...I suspect any valve seat issues would be mostly a consequence of overheating though and differences in thermal expansion between the aluminum block and steel seats but perhaps if the valves aren't closing properly it could cause problems too.

again, not a mechanic....

Steve

EDIT: OK, found in the manual for the 724 that the valve tappets need to be adjusted every 200 hours by an "authorized dealer". Adjusting valves isn't tough to do, but probably rarely gets done by most owners.

Also, I think most Onan valve troubles develop on the back cylinder in the WH configuration. I guess that part of the engine doesn't vent as well and maybe is more susceptible to grass/chaff buildup and hence heats up more.

Finally, I had a 16 Onan BF in a D160 that had dropped a valve seat. I gave the engine away and scrapped the rest of the tractor for spares. Aluminum has a higher Coefficient of Thermal Expansion (CTE) than steel so the valve seat can sometimes loosen if the engine is allowed to get too hot. Oversized seats are/were available.

Onans are smooth operating engines and are certainly some of the quietest engines WH ever used. I have had good ones and bad ones in about an equal proportion, so I think their long term reliabilty is - as TT pointed out - highly dependent on their maintenance history. They DO seem to use a lot of fuel though compared to my other tractors, but are said to put out a little more torque than like-sized Kohlers.

[bambooheels 0]

i myself bought two mowers with the onan 20hp years ago both i still have with way over 1500 on the one, never an problems. but i kept my stuff clean, very clean and the oil changed all the time. you have no idea what your buying, my advise would be if it runs good now, clean it well the fins and any dirt and grime tat build up around that engine causing it to heat too much, then change the oil onans are excellent engines.

in regards to the comment 16 Vs. 20 , simply put i dont think as many people use dthe 16 for much! think about how many homeowners buy this equipment then it just sits neglected or they neer change the oil or wash there equipment. iiots B)