Muffler bolts broke off--looking for ideas

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  #1  
Old 06-15-10, 07:40 AM
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Muffler bolts broke off--looking for ideas

Our wheeled string trimmer with a Tecumseh LEV100 had a rusted out muffler and it didn't take much torque to twist the mounting bolts off, right at the surface of the block.

The bolts are pretty much welded into the holes with rust.

I managed to drill out one successfully, and was not able to get an Easy-out to turn it so I have to dig it out (still in progress).
Having an awful time with the other hole, the drill wandered off and boogered up some of the aluminum around it. Seems to be heat-hardened, won't take the drill bit like the other one did.

I don't want to mess it up any further so I'm trying to think of alternative measures to get this mower back in business as fast as possible. I can stand outside and literally watch the grass grow. OK, exaggerating a bit, but here in Wisconsin this time of year we have to dash out and mow patches in between thunderstorms--it's a jungle out there.

One thing I'm wondering is if running the mower without a muffler attached will hurt the motor any, until I get it taken care of. NO worries of sparks starting grass fires here, believe me.

The idea I had was to make an adapter plate, of 1/4" steel, with the same hole pattern as the block mounting. I'm a machinist so that would be no biggie. A center hole for the exhaust and two mounting holes on either side.

One mounting hole would be tapped and serve as replacement for the hole with broken-off bolt still in the block below it.

The other hole would be clearance-drilled for a custom mounting bolt, with longer threads to go through the plate and into the rethreaded block--so it will be what holds the plate, and muffler, to the engine.

If you are familiar with the Tecumseh mounting bolts on mower engines, you'll get the picture. Any opinions on this? Or brighter ideas?

And I gotta fire that mower up today, unless someone says it's a bad idea to run without a muffler (disregarding the noise, of course).
 
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Old 06-15-10, 11:58 AM
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Look inside the big hole where the exhaust exits from the engine. Some of these had threads in them as they used a threaded muffler. If not threaded, you could tap it so you could put on a threaded muffelr.

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  #3  
Old 06-15-10, 03:29 PM
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nope, it's not threaded. The hole is about 11/16", too small for a 1/2 NPT thread, and too big I think for a 3/8" thread.

Possible I could drill it out for a 1/2" npt but I would not want to free hand that. I don't have a milling machine to bolt the engine to. 1/2" would be just about right, without constricting the flow very much.

Can someone tell me if it's OK or not to run this motor without a muffler please? I know it's not good for an automotive engine but this might be different (hopefully).
 
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Old 06-15-10, 04:28 PM
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Originally Posted by kenearl View Post
nope, it's not threaded. The hole is about 11/16", too small for a 1/2 NPT thread, and too big I think for a 3/8" thread.

Possible I could drill it out for a 1/2" npt but I would not want to free hand that. I don't have a milling machine to bolt the engine to. 1/2" would be just about right, without constricting the flow very much.

Can someone tell me if it's OK or not to run this motor without a muffler please? I know it's not good for an automotive engine but this might be different (hopefully).
Your dimensions are not making sense to me. 11/16 is well over 1/2 in fact, almost 3/4. Should leave just about the right room for threads for half inch?
I don't think there is much need for back pressure from the muffler but I also don't know about running it with out one. Specially on these string trimmers where things get pretty messy. Just gonna be leaving alot exposed would be my concern....but...
Sorry I can't be of much more help.
 
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Old 06-15-10, 06:03 PM
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Any chance to pull the carb, fuel line and gas tank. To AVIOD a fire!!
Put a small nut over the broken bolt and weld the nut
to the bolt.
The heat might help to loosen the bolts grip and remove easier.

In regards to drilling into the block for a different hole.
better look into what ever is going to be on the other side of the hole to be drilled.

Re: regards to the muffler, I belive (my personal thoughts) the muffler keeps the air hot as the motor cools down. This way the block and air entering the block get to the same temp. If cold air gets to the valves and under the head thru an open hole (no muffler). There could be warped valves and or head, then $$$ to repair.

Hope you get it running soon!!!
T.J.
 
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Old 06-15-10, 09:01 PM
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BFHFixit: I'm refering to NPT (National Pipe Thread) which is measured in ID. The OD of 1/2" NPT is about 3/4", 1/16" bigger than 11/16".

bmwe0692: as I said in my original post, the bolt is broken off below the surface, nothing sticking out. And good advice on drilling a new hole, there really isn't any good spot to do that.

Not sure I follow what you say about
the muffler keeps the air hot as the motor cools down.
You mean after the motor is shut down? Anyways, I don't want to risk damaging the motor, it's still a good running unit. Shame that Tecumseh went out of business, be hard to get parts for them sooner or later!

Thanks for the replies, guys.
 
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Old 06-15-10, 09:29 PM
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Originally Posted by kenearl View Post
BFHFixit: I'm refering to NPT (National Pipe Thread) which is measured in ID. The OD of 1/2" NPT is about 3/4", 1/16" bigger than 11/16".
I know what NPT National pipe thread - Wikipedia, the free encyclopedia but when you start talking plumbing to a mechanic...well things are gonna get confusing.

Honestly I can not think of any reason it would cause damage to the engine running it without any muffler or pipe, other than what I mentioned already and as you did, concern for fire. If you know about the need for exhaust on auto's n such, for back pressure and proper flow... then take that to point as well. I would apply the same.
Grind the one bolt flat and mount the other and run with it if it were me and I was the only one using it. Personally tho, I would like a plug of some sort in that hole on that piece of equipment because they do and can tear some stuff up and debris is real.
GL
 
  #8  
Old 06-15-10, 11:12 PM
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Could you drill two new holes 180 apart rotated about 15 from the original holes?
 
  #9  
Old 06-16-10, 08:57 AM
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You could probably take it to your local muffler shop and get them to burn it out with a plasma cutter for a small fee, they do it all the time with broken manifold bolts. Have a good one. Geo
 
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Old 06-16-10, 09:39 AM
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ray2047: redrilling isn't an option here, the space is tight and the muffler is shaped to fit right into that space.

geogrubb: will that work for a small 1/4" bolt in an aluminum block?

thanks guys.
 
  #11  
Old 06-16-10, 12:42 PM
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Originally Posted by kenearl View Post
ray2047: redrilling isn't an option here, the space is tight and the muffler is shaped to fit right into that space.

geogrubb: will that work for a small 1/4" bolt in an aluminum block?

thanks guys.
I think it will, I broke a 3/16 drill off in an aluminum bulkhead on a F4 jet(aging myself) and it was burned out, call your local muffler shop I am sure they will know, post back what you find out. Have a good one. Geo
 
  #12  
Old 06-16-10, 05:02 PM
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Center punch the broken bolt in the center,,, Drill it out with left hand drill bit increasing in size each time... If the bolt still dorsen't come out, stop drilling when you get to the size for a Heli-coil... Tap it for the heli-coil, install the helicoil & put it back together,,, I do it lots on all kinds of stuff,, It's a Permenant repair & you can still use the original holes & Muffler
 
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Old 06-16-10, 08:50 PM
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Hopkinsr2 has the best sounding permanent and proper fix IMO.
 
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