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  #1  
Old 05-11-2011, 09:23 PM
2old2shovel 2old2shovel is offline
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Default Repowered walk behind

I dragged a 48”Giant Vac walk behind mower home from the junkyard a couple of months ago because except for the partially disassembled engine, it was in remarkable shape. The engine was an 11 HP B&S single. I got it running and everything was fine until a couple of days ago when the rod went through the case. I had an 18 HP B&S Twin sitting around doing nothing so I mounted it on the walk behind.
It runs great and the mower cuts just fine. The only problem I had was the exhaust. I had none. I had the original exhaust flanges and a few bits of exhaust pipe so I bought two $5 mufflers and made a dual exhaust system for it.
It sounds and cuts great, except for the popping from one cylinder, but before too long I am going to change it so that it all goes into one good muffler.
For now I am using the manual PTO lever that came with the walk behind. I cannot see any reason why the electric PTO that came with the engine won’t work. The electric PTO is about a 5” pulley and the pulley that is on there now is about a 6” pulley.

Anyone see a problem with the pulley size change? I'm assuming a belt change is going to be in order.
Will running the machine on that exhaust cause any damage?
Is there anything else I should be looking at to make this thing last a while?
This is my first walk behind and I am amazed at how maneuverable it is. I cut about 4 ˝ acres and I don't even mind the walk...for the time being.
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  #2  
Old 05-12-2011, 07:43 AM
SpudHauler SpudHauler is offline
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Would be great to see a picture or two. But otherwise, yes a muffler is required. May burn the exhaust valves eventually and the noise will begin to wear thin after awhile for both you and the neighbors. No muffler means harder on fuel as well so get something hooked up. Pulley will reduce speed when downsizing the drive pulley on the thing it drives. So you will have a little less speed on you blades if that is what it drives but a little more power. May be just fine. Sounds like you have a win/win.
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Old 05-12-2011, 08:13 AM
2old2shovel 2old2shovel is offline
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Default Picture of repower

Well, hope this works.
Repowered.jpg
Guess I'll find out. After I finish this coffee, I'll actually read some instructions on how to post a picture.
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Old 05-12-2011, 10:53 AM
SpudHauler SpudHauler is offline
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I missed that you had mufflers. And they look fine for the price. The popping may mean a small air leak in the exhaust system itself. Switch mufflers from side to side and see if the popping moves to the opposite side. Seal the flanges between the engine and muffler pipe and seal the mufflers on the exhaust pipe as best you can and see if it stops.
And you may need to clean the carburetor as you did say it was sitting around for a long time, or just drain the bowl and see what you get. If it's dirty, continue and clean the entire carb, otherwise reinstall the bowl and cut grass.
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Old 05-12-2011, 02:02 PM
2old2shovel 2old2shovel is offline
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I thought it might be an air leak. I think a flange got a little beat up in the process and I didn't spend a whole lot of time checking it over. Soon as I get my other two machines running again, I'll pull it off and go over it again. You think the dual exhaust is ok? It looks cool but I wasn't shooting for cool. I was shooting for functional. I don't need to go into a single exhaust?
After two years, I was surprised the 18 HP even started to be honest. The frame was shot on the mower but when I had need for the engine, I went down, shot a little starting fluid in the carb and it fired right up. I didn't even charge the battery.
About every 15 or 20 years, I get lucky. Now I have to wait for another 15 years.
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Old 05-13-2011, 08:35 AM
SpudHauler SpudHauler is offline
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Other than someone touching them and burning their fingers I think they're cool too. Should work perfect just the way they are. Warp with exhaust wrapping if you want to safe guard the kids and cover your belts an pulley for safety too. Just my opinion. And for $5 you must love the price.
Enjoy!
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Old 05-13-2011, 09:06 AM
2old2shovel 2old2shovel is offline
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Yeah, the price was right. The electric PTO just became very attractive. PTO linkage just fell apart. After the rain passes I guess I'll start that little project which means I'll have to convert the PTO pulley to a spring tension pulley. Hope I don't have to buy a new belt. So far I have $10 invested in this machine so I guess the price of a belt won't kill me.
Oh jeez, that means pulling the engine again. Well, I guess that means I'll be able to get a real good look at the exhaust and make sure they are bolted up good and tight. I'll probably clean the welds up some, too.
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Old 06-26-2011, 09:58 PM
2old2shovel 2old2shovel is offline
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Default Popping

Quote:
Originally Posted by SpudHauler View Post
I missed that you had mufflers. And they look fine for the price. The popping may mean a small air leak in the exhaust system itself. Switch mufflers from side to side and see if the popping moves to the opposite side. Seal the flanges between the engine and muffler pipe and seal the mufflers on the exhaust pipe as best you can and see if it stops.
And you may need to clean the carburetor as you did say it was sitting around for a long time, or just drain the bowl and see what you get. If it's dirty, continue and clean the entire carb, otherwise reinstall the bowl and cut grass.
Sheesh, these engines are really sensitive about air leaks in the exhaust, aren't they. 3 or 4 times I've had the exhaust off because of backfiring and popping when it isn't under load. I checked and double checked the welds, ground them down anyway and rewelded, put new exhaust gaskets in, flattened the flange as perfect as I can possible make it and used new bolts and lock washers. Hope this does it. I haven't looked at the carb but so far, so good. It runs like a champ and it is fast even pulling me on the sulky I made.
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Old 06-27-2011, 07:50 AM
SpudHauler SpudHauler is offline
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You may just have to live with it. Very hot exhaust and a little unburnt fuel being dumped in when idling down will also cause popping. If it works that good, I'd ignore the issue and cut grass.

Here is another explanation for popping. http://www.hmfracing.com/forums/showthread.php?t=3927
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Old 08-01-2011, 11:59 PM
2old2shovel 2old2shovel is offline
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Default I'm accustomed to it now.

Quote:
Originally Posted by SpudHauler View Post
You may just have to live with it. Very hot exhaust and a little unburnt fuel being dumped in when idling down will also cause popping. If it works that good, I'd ignore the issue and cut grass.

Here is another explanation for popping. http://www.hmfracing.com/forums/showthread.php?t=3927
It only does it when it's sitting there idling anyway so I got over it. I am in the process of making a new set up out of new pipe anyway. The other ones I pieced together out of some pretty crappy looking exhaust from another mower and the handles off of an old hand truck. I asked this question somewhere else but I guess they must have thought I was stoopid or something but does it really make any difference which way you mount those little mufflers that have pipe thread on one end? Or should I start another thread with that one?
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Old 08-02-2011, 07:36 AM
SpudHauler SpudHauler is offline
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Not sure but I believe some mufflers are directional, but how you tell with these I don't know. Check with your supplier. For me if they were straight through, direction makes no difference, because it the holes in the through pipe and the surrounding baffling that does the work and that should work in either direction. But if you can't see through from end to end then there is probably a right and wrong way. Threads could be for the extension or the mount to the engine.
I'd put them back on the way you have them now, they are working, so install them the same way.
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Old 08-02-2011, 10:13 AM
2old2shovel 2old2shovel is offline
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Quote:
Originally Posted by SpudHauler View Post
Not sure but I believe some mufflers are directional, but how you tell with these I don't know. Check with your supplier. For me if they were straight through, direction makes no difference, because it the holes in the through pipe and the surrounding baffling that does the work and that should work in either direction. But if you can't see through from end to end then there is probably a right and wrong way. Threads could be for the extension or the mount to the engine.
I'd put them back on the way you have them now, they are working, so install them the same way.
Yeah, that's what I ended up doing. It was just that the pipe I was cutting up to make the exhaust was flared in such a way that it made it easy welding together if I put the muffler on backwards. I found a piece I could use as an adapter so that's what I did.
I get it all done and someone came by and said dual exhaust wasn't good for the engine. Both cylinders should go through one muffler. They said the B&S 18 hp twin required a certain amount of back pressure and I could damage the valves running dual exhaust. I felt like slapping him for throwing that into the equation.
Could there possibly be any truth to his comment? Someone stop me if I should move this to a new post.
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Old 08-02-2011, 10:15 AM
bczoom bczoom is offline
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bczoom is just really nicebczoom is just really nicebczoom is just really nicebczoom is just really nice
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"Someone stop me if I should move this to a new post. "

Keeping it in this thread is fine.
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Old 08-03-2011, 07:45 AM
SpudHauler SpudHauler is offline
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Most BS engines have fairly open exhausts so I would not be worried about your setup. Looks fine the way you have it. Your not dealing with a big budget race engine. I think your solutions should work just fine. Cut grass!
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Old 04-05-2012, 03:39 PM
2old2shovel 2old2shovel is offline
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I bought those cheap little bullet mufflers(or whatever they are called) but I kept blowing them in half. Ended up making my own out of 3" pipe. Wish I had a tubing bender. It would have come in handy.
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Old 04-05-2012, 05:47 PM
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you'll need to repaint it and add flames, then we can call you "Lawn Mower Man"
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