OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines 1980 B&S Model #110908 0418 - Questions

Hi all,

I've been tinkering with my little project restoring my Scott Bonnar 540 (intro here, some further info here)and have some questions/need some advice.

Firstly

Model...Type.....Code
110908 0418-01 80061924

I have been trying to find some information on the correct air cleaner assembly for this mower, see post -> here

After i found some parts lists/diagrams last nite I also believe I may have the wrong muffler on this thing (I ordered one based on the broken one that was on it - and it's pretty damn loud!). I think it's supposed to have the 'super hushtone' muffler (sales image here. After taking the new muffler off and having a look, I can see there is a bolt broken in the block (pictured below, gave it a little rub to make it more obvious). I'm keen to get the correct muffler for restoration. I think the correct part number may be 391492 for the muffler and 222238 for the deflector (300B in parts diagram)? Can anyone assist in confirming? Or is it supposed to have the one with the spacer (300C - though I don't htink I can see any mounting hole for the spacer ( top right?? ))?



Any tips on how to remove the broken bolt? Will an easy out be small enough to get this one?

Also, took the cowling off and gave it a clean underneath on the weekend, cleaned a heap of crud off the govonor blade and in behind the carby and popped a new plug in.. Now it seems to want to run at 100% the whole time, and I cant seem to throttle it back at all, its either full on or off? Have I done something to the govonor/throttle setup to do this?

Thanks,
Ed.

Hi Ed, I have asked grumpy (our resident B & S guru) to give you some advice on removal of that bolt from the block....I am sure he will give you the correct advice mate.

Thanks Darryl...

Another question, what do you guys use for a tach when tuning? I'm thinking of ducking down to supercheap to grab a Stanley Engine Analyser (50$).. just need to check out that it works with single cyl engines..

Also noted jaycar have an automotive dmm around the same price...

Any recommendations (ideally would like to keep it <100$)?

I use one of these:
http://www.ebay.com.au/itm/Hour-Met...arts_Accessories&hash=item5d2f95b47a

They are sold under many different brands, or no brand at all, the only difference is the graphics painted on them. They don't care how many cylinders there are, because they are just connected to one plug lead, and they have a software switch for 2 stroke (default is 4 stroke). When I got mine I checked it against the stroboscope I'd been using for years before that. They agreed, but the new one rounds to 40 rpm from memory, which I don't much like - I'd prefer 10 rpm, or better still, 1 rpm like the stroboscope.

I'm not recommending these things, they are just what I use because I didn't find anything better or cheaper.

On the subject of removing the broken bolt from the cylinder casting, how difficult it is depends mostly on why it broke. If you look at the broken surface, is it flat or is it a little mountain and valley as you move around the circumference? If the bolt failed in torsion, the shear plane will be at 45 degrees to the surface of the cylinder casting. If it was broken off by a sideways hit, or broke in tension due to over-tighening against the muffler's mounting flange, it will be close to flat across.

If it was twisted off (failed in torsion) it will be quite difficult to remove, and the results will probably be ugly. If it broke in tension it will probably screw out fairly easily.

The process is to file the broken surface flat, and center-punch it very carefully in the exact center. If it was a tension failure, you can then just drill it axially at a diameter about 60% of the outside diameter of the bolt, and try to screw it out with an ezy-out. However if it failed in torsion that will be because it either bottomed in its thread, or rusted in place, and it is bonded to the aluminium casting. In that case you visit a tool shop and get a proper stud extractor, which is a piece of very strong straight rod with shallow longitudinal splines. You choose one about 60% of bolt diameter, drill the longitudinal hole in the broken bolt accurately to the root diameter of the shallow splines, drive the extractor into the hole for its full length, and try to unscrew the broken bolt. If you think it won't unscrew, it will break the extractor, you will have to heat-cycle the broken bolt. Remove the extractor, and use an oxy torch to heat the bolt. Don't apply the torch to the aluminium at this point. Heat the bolt only, to a dull red, and let it cool. Repeat three or four times. Then try the extractor again. If it still doesn't work, leave the extractor in place and heat the aluminium casting near the exhaust port, using a diffused heat source like a propane torch. Try for about 200 degrees Celsius. Then while the casting is hot, try to unscrew the bolt with the extractor. If not even that one works, you would have to drill out the broken bolt, which usually results in destroying the thread. Because there isn't much metal around the existing thread, this will almost certainly be curtains for the cylinder casting, so before resorting to that last step, think about just using a Briggs screw-in muffler in the existing thread in the exhaust port.

Easyout for the bolt will be fine...heat would be better if you have enough to grab onto...Im assuming this is why the smaller bun muffler was fited im guessing. If you havnt used an easy out before,just make sure you step up the drill sizes gradually and get the first drill on centre.(Tungsten Bits are better if you have themthey are like going through wood...EASY.) I use them quite often,but I nearly always get them out and run a helicoil thru to make it stronger. since it is only a 1/4 bolt you might even be able to tap it out once youve drilled if you can get it perfectly centred and not have to by any extra tools,and make sure you re tap the hole before fitting the new muffler.....As for the Tacho,never bothered with one,too costly for one off jobs and your ear is just as good . And I think in a previous post i stated i had an air cleaner assy,If you want it its yours.

Ahh The Master Grumpy Beat me to it....Agreed If your not confident,just put the screw in muffler on less risk of damgaing a good engine. One other thing..NEVER try and remove a stud from alloy when its at red hot temps it will strip the thread straight away and will need to be helicoiled,costing you more money for a kit. always cool before trying to remove,a hit with a flat faced hammer occassionaly to shock it may also help...Youll be fine as I just did mine and also had to remove the screw in muffler thread which was actually harder..man it was in tight!!! lols good luck!

Thanks for the replies, I've got a screw in muffler here but would really like to get it back to it's original 'spec'. I'm unsure why the bolt failed as it was like this when I got it, but I can tell you it has an angled edge all around and almost looks like it's already been center punched (see below).

I've been hitting it with some penetrene every few hours and cleaned the area up a little since the last pic.


I know it's an ordinary shot but it's the best I've got..

To me it looks like it's been twisted off...

I've been tossing up if I should do this myself or just pay the $ to have a pro do it.. I don't want to get it wrong as there is not much room for repair and I'd really like to keep the original engine.

also, Bluegmhtmonaro .. you have PM

It broke because its a 30 year old steal bolt in an alloy housing which has been heated and cooled a thousand times....Its just what happens,im fixing broken studs on manifolds all the time. :)Some one probably already had a go at it....Ill throw a spanner in the works...Even a proffesional can have trouble,ive broken plenty,but ive been lucky and always had a way out some way or another,its hard to give advice when we are not standing there doing the Job, I just want to grab it and fix it lols...ok so there is not enough of the face to grab hold of...would it hurt to linish it down flush,centre it and start drilling? If you get centre you will be fine with at least this part,then reassess it when youve doen that?. Just my thoughts,But trully if your not confident,try and get a pro to do it ke you said....Its just nice to be able to do it all yourself,regardless of the outcome...live and learn right? Although I do have a spare engine if you stuff this one up...Just teasin!

The fracture surface has been filed so we can't be sure what shape it was intially but it looks as if it may have been conical. That is characteristic of a tensile failure, which means it may be easy to fix. However you do have to drill accurately in the center, parallel to the bolt's axis. I've done a fair number of such extractions, though probably fewer than Bluegmhtmonaro, and in most of them I was off center. However, I claim to be getting better, slowly. Strangely enough, I'm gradually homing in on the way the old guys did it when I was a kid. Put the engine up on a milling machine or a large bench drill, use a level on the mounting face to shim it up square to the drill, bolt the engine down rigidly to the machine's table, use a centerdrill at first to dimple the bolt stump lightly, inspect the position of the dimple and move the table if necessary until the second, third, or tenth try gets the dimple dead in the center of the bolt, replace the center drill with a short twist drill-bit or much better, a slot drill, then drill the full length of the broken bolt. If you've got one, use a left-hand drill bit or slot drill, and run the machine backwards so the stump of the bolt is trying to screw itself out, not in. Then keep the table and engine in that position while retracting the drill spindle so you can screw in an ezy-out to see if it is going to be an easy extraction. Change to a proper stud extractor if that doesn't work. When you've gone through the whole process, if you haven't succeeded, use a series of progressively larger drill bits to open up the hole to the root diameter of the thread, just leaving the spiral of steel engaged in thread in the aluminium casting. Then put a center or center-drill in the chuck and engage it in the center dimple in the back of a tap of the correct thread. That allows you to start the tap exactly straight in the thread. With a light pressure pushing the drill spindle downward, rotate the tap with a spanner on its square end, until it just starts to cut (less than half a turn). Then retract the spindle, remove the tap, and see if the thread you are cutting is correctly timed to match the existing thread. If you've got it right, the spiral of steel which is all that is left of the old bolt, will be pushed out of the thread in the aluminium casting. Use a scriber to pull more of the spiral out of the thread, removing as much as you can. If you can get at least a couple of turns of it out before the spiral breaks, you can put the tap back in and push some more of it out of the thread and repeat the process.

That's what I try to do anyway. Sometimes I succeed.

Perfect Grumpy!....There is one more option that does not involve much risk,And ive done this many times when im in a hurry...Again as Grumpy has stressed your drilling must be accurate. Drill the bolt out in its entirety and just helicoil it. Its very common for an exhaust stud/bolt thread to be chewed a little as its a major heat and stress point. Yes its easy for me cause ive got them in stock,BUT if you use this process you can then take it to a Mech or engineer or the like and get him to put in the helicoil. Would be less expensive than buying a whole kit which usualy quite expensive. he may only charge you 25?. The hole should be 1/4 20 from memory and a drilling size for recoil will be 17/64 which you should have in any IMP drill set.. I use helicoils often on Victa 18 handle bar brackets as they are usually chewed out.