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Advice - Honda HR21-5````

Started by Swissqp, October 24, 2020, 09:03:10 PM

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Hi all,

Right, an admission. I am obsessed with the HR21 and HR21-5. I won't bore you with details but it has lovely childhood memories. Having restored a HR21 I came across a sad HR21-5 on FB Marketplace and managed to secure it. The engine is fine and doesn't smoke. However, looking at the blade and oil pan, there was more oil knocking about than a Thai massage. There was a leak from the lower crank shaft and the trochoidal oil pump gasket and cover. I replaced the gasket with a new one but unfortunately that did jack all good. So first question....you reckon Hondabond will sort this problem? Let's see!

Next up the crankshaft oil seal. When I remove the old one I found another one rammed in upside down. Both were removed and a new OEM one installed. So firstly the trochoidal gasket leaked and so did the crank shaft oil seal. It was weeping oil ever so slightly on the crankshaft. A new seal has been fitted with a little HB added for good measure. Let's see if the leaks stop.

All in all a brilliant mower and testament to Honda's total dominance of the mower market in the mid-80s.



That's an oldie Tim, hopefully you'll post a photo when you have it all back together again. 

Not sure why the oil pump cover is leaking with a new O-Ring fitted, you sure it's not leaking down one of the bolt holes.  I'm sure a light coating of Hondabond will seal it up just fine otherwise. And regarding the lower crank seal, the new seal should be fine as long as the crank is straight and has no movement in the lower bearing. 

Keep us posted, and don't forget the photo.  ;)   


Mick, here are the photos. I cleaned up the oil cover and added some Honda bond. The new crank oil seal has gone in. It says to have a recess of 2mm but I put it in a little further. Will report on progress.


So an update...dry as a bone under the mower so fingers crossed the problem is solved. The deck needs some love but that's a job for winter. I've changed the throttle, clutch and drive cables and the drive belt. New wheel bearings required.


Oil leak under control then Tim, nice work.  ;)

So in the winter, are you stripping it down again to refurb the deck, or shelving the whole project till then?


Mick, I will strip it down....and bad news, I ran her for a bit and she's leaking again. I think there is an issue with the shaft......got a couple of new seals coming. That there was 2 in there to start with means there was likely an issue.


So changed the seal again. It's better but still leaking. The problem is a small gouge in the crank. Nothing will solve that other than a new crank..which I found on eBay in the US. So a winter project to swap that out. In the meantime, I'll restore the deck.


Ok so to close this off, I found the reason the that crank seal was leaking despite changing it twice. Someone had gouged the crankshaft right where the seal lip sits. I managed to get a new old stock crank from the US (not bad for a 35 year old machine!), so swapped it out. All working fine and no more oil.HR21 crank.jpg


You keeping this mower Tim, or selling it on. Just curious how many mowers you have lol...  ;)