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Red hot exhaust


Frank Knox's Avatar
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03-26-03, 04:42 PM   #1  
Frank Knox
Red hot exhaust

I just did a rebuild on a Briggs and Stratton 12 hp engine. New Rod, new rings, new timing key in the flywheel. The cam and the drive gear are absolutely lined up, magnet looks to be in the right spot to fire the plug looking at the piston and valve position with the head off.
When I try and run it it is hard to start. When I get it started the exhaust flames and the muffler glows red. Obviously I don't run it for very long that way. What am I missing?

Thanks in advance.

 
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03-26-03, 05:23 PM   #2  
ALMOST
red hot exhaust

sounds like that exhaust valve is opening a bit to soon , and is blowing out the fire in the hot cyl ,so maybe is is advanced a little to much on the timing, just a thought

 
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03-26-03, 05:28 PM   #3  
ALMOST
red hot exhast

did you have the valves refited , sometimes the valves are to long after the engine is older and need to be reground and the valve seats trued up , mite check this out to

 
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03-26-03, 05:43 PM   #4  
Frank Knox
I have not done anything with the valves other than pull them out, clean them off and put them back. I picked up 2 lawn tractors that I needed to cabbage the engines from. One was a gem one, this one, was a dog.

It ran but when I got it, but the float was sticking open and dumping gas when the engine was off. But it did run and run decent. About 15 minutes into the endevour it threw the rod. So at least before the rod went the valves were working okay before the rebuild.

I agree with your thoughts on the timing. How do I adjust it? it seems electrical not mechanical. I can't see anyway to adjust the coil or the flywheel. Flyweel is keyed to the crank, coil is slotted but doesn't seem to be enough to make any real adjustment.

I really appreciate the help on this. it has me stumped and I feel like it's got to be something obvious I am missing.

 
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03-26-03, 05:57 PM   #5  
mikejmerritt
Shot in the Dark......

......Look for an exhaust valve with to much clearance and a carb running to lean.....Mike


Last edited by mikejmerritt; 03-26-03 at 06:39 PM.
 
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03-27-03, 12:29 AM   #6  
I agree...valve problems or lean running.


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

God bless!

 
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03-27-03, 02:55 AM   #7  
Frank Knox
Valve?

I will check it out. What do I look for on exhaust valve clearance? How do I check it?

Thanks.

 
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03-27-03, 09:50 AM   #8  
Oil Doc
Pull the breather cover and check the clearance on the vavles with a feeler guage. I use to set the intake at .006 and the exhaust at .010.

I always did the valves when doing a rebuild no matter how they looked. That means cutting the valves and the seats doing a 3 angle so the valves ran cooler, not just lapping them. The narrower the contact area, the cooler the valves run.

I bought all the tools to do the job after a short time in the business but when I first started I sent them out to a couple of machine shops .

Also they can plug guage the valve guides for you to make sure they are in spec so the valves aren't wobbling in the guides causing more problems.

 
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03-27-03, 02:14 PM   #9  
Frank Knox
Thanks

Thanks a lot guys. I appreciate all the help. I will tear back into it this weekend.

Again thanks!

 
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03-27-03, 08:11 PM   #10  
You can probably get away with just grinding the valve stem until the desired clearance is reached if the seats and valves look good, but a good valve job would be nice. To do this, check with feeler gagues until you find the one that fits. Lets say that you have .002" clearance on the intake valve. You need .006", so you must remove .004" from the valve stem length. Too much removed is not good either, so be careful...take the valve to a machine shop and tell them how much you need it shortened. If you cannot even get any feeler gagues to fit, there is no clearance at all, and you will have to adjust accordingly. Do this test with the engine at TDC.


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

God bless!

 
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03-28-03, 04:30 AM   #11  
Frank Knox
One more question Cheese

I want to check the valve clearnace between the push rod and the valve stem right? Just turn the fleewheel until it's at TDC and then slide the feeler gauge between push rod and valve stem?

Thanks again!

 
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03-28-03, 06:53 PM   #12  
Fisher
Check the flywheel key again, and then when you replace it,
properly torque the flywheel nut.
Fish

 
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03-28-03, 08:53 PM   #13  
I like your thinking Fish...sounds like a key could be slightly "pushed", in moderator words...thereby creating preignition, or is that detonation?..lol...are you using synthetic oil?...(inside joke)...lol...seriously...the key could be possibly "pushed" or sheared and you have a timing issue. It can be that simple.

 
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03-29-03, 07:28 AM   #14  
Frank Knox
Timing key

Nope not the key. It was sheared off when the rod went. I have had the flywheel off and have replaced the key.

 
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03-29-03, 04:17 PM   #15  
Fisher
Look at it again.... One must not assume too much....
How did you tighten the nut? It is most likely sheared again,
due to insufficient torque. But I am usually wrong, so do not
check and see if I am right.
I usually am way off base, so disregard anything I have said or written.
Why did you do the ring job in the first place?


It is awfully cheap to check the flywheel key again, as it is
likely sheared.

I ask the folks on the forums to check the cheap possibilities
rather than spend a lot of cash first.

Trust me, recheck the flywheel key.

Ask anyone on this forum, I am usually wrong, but humor an old man, before you expend a lot of time and money, and look at the
sheared key.
I won't post again, since I am likely wrong.

I am usually wrong, so disregard my earlier posts about the
flywheel key, even if you have recently replaced it.

But just for giggles, check your "new" flywheel key for partial
shearing. I am usually wrong though.
So ignore me.
fish

 
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03-29-03, 04:18 PM   #16  
Fisher
Or it could be the flywheel key.......


Fish

 
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03-30-03, 02:19 AM   #17  
Fisher
Just teasing you a little. Replacing the key when you rebuilt the
engine, does not mean that it is still OK. If, upon reassembly,
you did not torque the flywheel nut enough, it could have
easliy sheared again. While it very well could be another problem,
this, with the proper equipment, is easy to check. Without the
proper equipment, removing and reinstalling a flywheel is
extremely difficult, thus making the flywheel key even a more
likely suspect, and since your engine has one of the symptoms
of a sheared key, it might be worth a look.
Just trying to help,
Fish

 
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03-30-03, 06:03 AM   #18  
buttlint
Frank,

Fish is right........He is usually wrong But I would check the key again anyway. But then again, I am usually wrong most of the time too.

You mentioned earlier that you had a problem with the float sticking. Did you clean and rebuild the carb at that time? How did you stop it from leaking? Did you change the float setting possibly? Is it possible that its just running super lean now because of crap in the carb?

What prompted the rod replacement in the first place? Was it blown or worn? If blown, it could have been caused by over reving. If it was overreving then-was that problem taken care of?

I know I am making a lot of assumptions and guesses, but all of the usual suspects seem to have been covered. Knowing the history of a machine helps sometimes. I need some more info, so I can make some more guesses. 'lint.

 
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03-30-03, 08:40 AM   #19  
Frank Knox
I hate it when that happens

Under great protest I pulled the flywheel again, only to find that the key had been sheered again and the fleewheel shifted over about a key's width. I replaced it but when I went to install the flywheel again, I found the flywheel was cracked all the way through right behind the key.
I applogize Fish. I think I only pulled it again so I could tell you to go fly a kite. :>)
Anyway it seemed electrical the whole time but I could make no sense out of how it could be since I had replaced the timing key which was in my mind the only way to cause it to fire out of time with the cylinder and valves.
Anyway thanks a lot guys, and sorry Fish.

 
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03-30-03, 11:03 AM   #20  
Fisher
What state do you live in? I have a few flywheels laying about.
I would be glad to give you one if you pay shipping or come
get it. The price of a new one is quite high.
Fish
I am in Ky. No hillbilly jokes please. Also, I hate kites. But you
were likely going to suggest something else anyway.

 
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03-30-03, 12:14 PM   #21  
Frank Knox
Fish

Indiana, and I wish I had read your post before I started back in on it. I had no real purpose for the motor, I bought a couple of interstingly trashed out riding lawn mowers. I needed an engine for a splitter I was building, these were much larger than I needed but they were very cheap and I thought it would be neat to have an electric start splitter. The engine I used for the splitter was a 14.5 hp over head valve that was in perfect condition, except that this guys wife had run the entire riding tractor over with a 9N Ford! Really funny. Engine was only a year old. The other was this little possesed 12hp. Both much larger than I needed but what the hey. The latter was used by this guys son as a go cart. He just took the deck off the tractor and let his kid trash it. It was a disaster. Kid had run into lord only knows what. I had to weld up a hole in the aluminum hosing, the starter was all but destroyed, had to epoxy the bottom of it back together. Cleaned a mess of melted fule line out of the carb. I got it running and was trying to figure out why it wasn't running right when it threw the rod. I think the govenor had been messed with it over reved. This guys family must be really hard on the equipment.
Anyway I can't stand to have anything lying around that doesn't work purpose for it or not. I'm a little neurotic about sutff like that. I would not recomend this fix, and would not own up to it except that you have graciously offered to send me a fly wheel. I used a high strength rod and welded the sucker on there. Yes I know what will happen if I ever use it and it hits something solid or it throws a rod, No I can never take the crank out or get to the alternator. But I really just had to have it run so I could sleep and so my wife could live with me again. It long ago became a contest between me and the machine and the damn thing just was not going to win. It was going to run one way or the other and it does now all though I don't know what I would ever do with it.
Anyway thanks a lot Fish, I really appreciate that offer and would have taken you up on it if I hadn't all ready gone mental on it. I do have an new question for you though. Funny how these things snow ball. I have a very old 5 hp tiller here I just pulled out of my father-in-laws fence row. Rod's blown, piston was broken when the rod smacked the side, put a whole in the housing. Things been sitting for years. I welded up the housing but I am looking at this thing and there appears to be hair line cracks in the housing. Looks like corrosion cracks if I had to guess. It has been sitting outside with a whole in the hosing for years. Ever seen anything like that? They appear to be shallow and I am now trying to decide if it's got any life left in it or not.
My original plan was to buy a motor for it, but then we go back to me being neurotic and before I knew what I was doing I had gone from taking it off the tiller to taking it apart.

 
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03-30-03, 01:01 PM   #22  
Fisher
Hairline cracks now=big cracks later.

Do not waste time on the block.
Fish

 
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03-30-03, 01:18 PM   #23  
Frank Knox
cracks

Have you seen a block do that before? Nothing in the cylinder, seems to be just the top section where the oil had drained off and condensation was on it, but that's just my theory.

 
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03-30-03, 06:19 PM   #24  
Hey...good job Fish, I didn't think of the flywheel key. Glad you got it straightened out Frank.


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

God bless!

 
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03-31-03, 05:30 PM   #25  
Oil Doc
Good call Fish.. Soon as I saw your post it was like dejavu... amazing how you forget the simple fixes to look for when you have been out of the biz for a while...

 
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03-31-03, 06:17 PM   #26  
Shoot, I'm in the biz, and still can't see the forest for the trees sometimes. I call it "brain flatulence", lol. Sometimes I come in and breeze through the posts and don't spend as much time as I should thinking about the problem before answering.

Thanks to all of you who contribute to this forum with your expertise. It is needed and appreciated!


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

God bless!

 
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04-01-03, 08:14 AM   #27  
Frank Knox
THANKS

Just thanks everybody. Really appreciate it. Thanks!

 
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04-01-03, 06:24 PM   #28  
ALMOST
red hot exhaust

boy that one threw me when he said he replaced the key on fly wheel i thought that was a fix , good find there fish ,and good find there red hot exhaust , checking the fly wheel befor you put this back together after fish mentioned the key , did'nt think about a cracked fly wheel either

 
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