Hearthstone II Rebuild, with Questions

  • Active since 1995, Hearth.com is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.

    We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.

    We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.
A couple of years ago I purchased my late grandfolks' place from my dad and aunt. While the house has had many different heating sources over the years, I only remember a 10,000 BTU space heater and the Hearthstone II that has been the centerpiece of the living room since about the time I was born.

It's been clear from the gitgo that the wood burner needed some work, but I only replaced gaskets a few times. In the last few weeks, though, it had finally gotten to a point where I was burning too much wood due to the baffle plate having collapsed. I ordered a new plate.
Hearthstone II Rebuild, with Questions

The old hardware was shot. I broke both baffle support bolts removing the bottom nuts, so that was game over in terms of proceeding with just a rip and replace of the baffle. (The side and rear pieces need replaced, too, but those can wait until spring. I had just run out of patience for being unable to govern burn speed and sending so much heat up the stack and so decided to replace the baffle plate.)

Presently, I have most of the top of the stove off, including the stones and flue plate. I have the new hardware and baffle plate installed and will replace the other cast pieces tomorrow morning after I make a third trip to the hardware store for the correct length bolts.

I have chiseled off nearly all of the old cement from the top of the chassis and top soapstones. The hot-sides of the stones were black with oil and soot and grease; I cleaned them as best as I could with dish soap, rinsed them well. They're now in the oven at 170 overnight to dry and suck most of the moisture out of them, hopefully this will make the break-in period go a little easier on everything.

I'll post my progress, but first, I have several questions.
  • Where I don't have replacement Hearthstone hardware, I'm using grade eight stuff as I hope it tolerates the heat better. I couldn't find grade eight 1/4-20X3" stove bolts, so those are just whatever Menards had on the shelf for the flue plate. Am I wasting a few bucks on the expensive hardware, or is it smart and do I need to go searching for grade eight stove bolts for the flue plate?
  • Is there something else I should be doing to these stones to ensure good adhesion from the replacement cement? The dish soap didn't do much for their appearance, but they do feel less greasy.
  • I imagine 2,000-degree cement is sufficient, or should I get the 3,000-degree stuff?
  • What diameter rope gasket? How often do you replace it? This is my primary heat source. I had hoped I could get away with replacing the rope every other year. This is my third winter here now and I think all of the rope needs to be replaced annually, and I may need to do the side and ash door gaskets even more often than that.
  • This thing has either been overfired or just used too long without an overhaul. All of the cast iron is shot, though the back and side plates can wait for spring. I read elsewhere a theory that chimney sweeping can lead to baffle damage as the sweep knocks all of the soot and creosote down on top of the baffle, where it burns as soon as the next fire goes. Should I be removing my stovepipe and sweeping into something (big garbage can) to prevent this? How often do I need to replace stove and chimney pipe, or have it inspected?
  • What's a good temperature to run this thing at? I usually end up dialling into about 400-450, but I suppose this might change with the baffle replaced.
  • How often do I need to sweep? It runs very nearly 24x7 from late fall to mid-spring, comfortable during the day, a big blast in the evening, and then stuffed and choked as much as possible to get through the overnight without having to rekindle. Today is the first time I've had the stovepipe off and been able to look up from the bottom; there's certainly build-up but I don't know what's acceptable. I'd rather avoid a chimney fire.
  • There's no reason to empty the ashtray unless I'm doing a cold start or otherwise need to improve air intake, right? Sometimes I'm lucky to have good fuel that doesn't leave much ash, sometimes I'm burning junk (wood), but unless I'm doing a rekindle from dead I don't bother with the ashtray.
Thanks everyone, past and present. I've read up a lot here before actually posting anything, and it's all been very helpful. I hope this project provides some useful information for others.


  • Hearthstone II Rebuild, with Questions
    89 KB · Views: 707
  • Hearthstone II Rebuild, with Questions
    172.3 KB · Views: 663
  • Hearthstone II Rebuild, with Questions
    162.6 KB · Views: 731
  • Hearthstone II Rebuild, with Questions
    214.7 KB · Views: 715
  • Hearthstone II Rebuild, with Questions
    102 KB · Views: 630
Last edited by a moderator:
Hardware store grade 5 bolts are fine for all this stuff. It's the iron parts thst generally wear out first anyway, and if something needs to be drilled out later grade 5 makes that easier.

DEFINATELY use Hearthstone cement! Bonds better to the stone and holds up better. Get a 5 lb. tub and you'll have enough for the top stones, to fill in around the flue collar, and to be sure the end of the secondary air tube is plugged. Moisten the under side of the stones and the top frame surface before applying. It seems to work better.

Chronis problem in H II's is the ash pan door. Be sure that it is properly gasketed and closing tightly. They make a replacement ash pan with an integral "door" that you can retrofit. 90% of the time, ash pan door is the reason for overfiring.

Don't overthink this. It's a pre-EPA stove, basically just a stone box. Great heater, not very complicated. You will use more wood than your neighbors with new stoves, btu who cares? Old Hearthstones are just beasts! Love them!

Get the gasket kit from Hearthstone when you order your cement, make it easy, keep it simple.

Regarding sweeping, maybe get a pro in there to have a look. Even if you can do it yourself, it's just priceless to have a chimney professional look it over. Cheapest insurance ever, and a good way to sleep soundly.
Last edited by a moderator:
Conveniently, both my internet and cell were offline the last 36 hours, so I missed this helpful information. Everything but the baffle bolts are grade eight and I used Menards brand cement, which should be cured here in anther four hours or so. Hopefully I did a good-enough job.

Since it's supposed to get well below zero here the next few days, I think I'm going to run with it for now. If we get a warm spell before winter lets out I'll replace the rear plate and get Hearthstone gaskets and cement and redo everything at that point with grade five hardware.

Space heaters are struggling to keep things habitable, let alone comfortable, at this point. But even running small fires viz the break-in procedure should help, but the next few days will be brutal. Thanks everyone for the help; I look forward to ripping it apart again and doing it right. Maybe at that point I'll get a real chimney sweep by to look at things.
Let us know how its performing. Waverly, Ia resident here. Winter has arrived in Iowa! Ouch...
Well, things were going swell until tonight, but with the incoming cold snap (hi, moresnow!) I had cranked the old thing up. With small fires and low inputs, no trouble. But three times tonight I've cranked it up to try and heat the house before I tuck in for the night and I've had secondary combustion in the stack. I've got a damper on the stovepipe about 12" above the top-exhaust of the stove, and three times tonight I've seen flame in the stack there.

Each time I've been able to throttle down the stove at the intake and close the auxiliary damper on the stovepipe and get the flame to go away, but every time I try to turn things up with any sort of flame in the firebox, same result. If I let things get down to hot embers and open it up, no problems, but if there's much flame at all in the firebox I get flame in the stack. Top thermometer spiked to 650* for about 30 seconds at one point before I got everything choked in. I'm feeling like I missed something, but I'll be damned if I know what.

Ideas? I don't have the scratch to have someone come look at this thing, let alone fix it, for at least a week and a half. But it's cold and getting colder out there. At the same time... burning the house down would be worse.
Sounds like flames might be getting around past the baffle. Not sure why if the stove pipe damper is closed off.
Sounds like flames might be getting around past the baffle. Not sure why if the stove pipe damper is closed off.

I've checked that, and it looks good. So far I've only noticed it when I've had the baffle open to open the stove and load wood. I've gotten more careful about turning the stove way down for a few minutes before I open her up, and haven't had as many problems. But I'm still anxious.
This is with the secondary tube intake flapper open, right?

Is this happening with the warped baffle or did that get replaced? Check your secondary burn tube closely and make sure it is not split and failing, somewhere, especially in the middle of the tube.
Correct, begreen, the baffle replacement is what kicked off this whole adventure. The old one was severely damaged. The secondary burn tube is OK, though I need to replace the back plate that it sits on, and the screw that holds it in place broke off in the tube, so I have to reposition it, or at least keep a close eye on it, when loading. I never close the flap unless I need an emergency shutdown (i.e., flame in the stack). I will check that the holes are facing toward the interior of the firebox and the baffle effectiveness.
I've seen a cracked secondary tube on a Hearthstone destroy the baffle. That's why I asked.
Most likely culprits for H II over fire include but are not limited to:

Ash pan door, always a favorite. Whether it
s the spring closure or the cam lock they never seem to want to close easily and tightly, always need some fussing. There is a replacement pan with integral door available from H'stone that is the best solution for this. Pricey, but what isn't these days?

Next up, and you may have done this but I missed it in the post, the 2ndary tube needs to be cemented in lace at the left end. A lot. If it isn't plugged up then, well you see the problem, it's just like having a gaping hole in the side of the stove.

Another thing in many stoves, easily overlooked may be the glass? Does it rattle when you tap it or do you get a satisfying "thud"? Sorry, may seem obvious, but it can let in a surprising amount of air.

Hope this helps? What a great old stove!
  • Like
Reactions: begreen
As always, thanks for your helpful suggestions. The tube is in fine shape, minus the busted screw. It is clear, unbent, etc. etc. I did the ashtray gasket when I did the baffle, and I think it's in good shape. It passes the match test (get a good fire going, stop it down, move a match around the door). I do need to regasket the front door and front door glass. But I think my problem is that when I tore the top stones off I didn't use enough cement when I replaced them, and air is getting in between the baffle and the stack, hence my problem. I'm going to order some cement from Hearthstone and tear the top end apart again, using plenty of cement to ensure there are no air leaks. I'll keep everyone posted. Again, thank you for your help.
Hope your getting things in order! If all else fails you might try calling Darren at Stoneworks in Marion, Ia. He told me he used to rebuild that very stove quite often. Don't have a clue if he still works on them as he is, and has been primarily a BK dealer for some time. Might be worth a chat however. Good luck.