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finally got spark ...then BANG ...BANG


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#31 ACmowerguy ONLINE  

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Posted April 24, 2015 - 08:00 PM

The correct gap per the manual is .020"  That's were I go for initial setting on mine and then tweak as required.


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#32 classic ONLINE  

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Posted April 24, 2015 - 08:33 PM

.020 will be the correct point gap. A point gap of more or less will change the ignition timing, same as turning a distributor in a car. I usually change out the coil, points and condenser when I go over these old Briggs engines, since I want them to run without trouble. The armature air gap should also be in spec and the flywheel should be fee of rust flakes. Usually the valve lash opens up with time, mainly the exhaust valve. This wouldn't cause back firing, just a noisy valvetrain. It is possible that the flywheel key is partially sheared in this engine. I just went through an old Briggs that had carbon flakes lodged between the valve seats and valves. I lost compression, but had no backfiring issues. I just cleaned the valves and seats and the engine fired right up.
It's hard to diagnose an engine problem without the engine in front of me. Intermittent spark due to bad ignition components can cause a backfire. The muffler can fill with raw fuel and go bang when the engine does get a good spark. My advise to anyone who relies on their old Briggs, to just tune it up like you would your car. For the cost of a new coil, spark plug, points, and condenser, it's worth it. Also, clean the fuel system completely, and change the fuel line and filter. A new carb kit wouldn't hurt either. Lapping in the valves and setting the valve lash is also important to having a good running engine. Myself, I hate having an engine quit running because I skipped something, and they always quit when you need them most.
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#33 classic ONLINE  

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Posted April 24, 2015 - 08:49 PM

I kind of rambled on in my last post, and didn't really give my opinion on what I think is causing the backfiring. I think the problem is with the coil and I would change it to rule it out.
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#34 trowel OFFLINE  

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Posted April 24, 2015 - 08:52 PM

It happens :D


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#35 ol' stonebreaker ONLINE  

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Posted April 24, 2015 - 10:30 PM

I beg to differ. If the valve can be moved by twisting when closed it means it's worn into the seat far enough to lose the lash ie: .ooo inches


Trowel,read it again. Especially the ".000 inch". Ie: you can't get the thinnest feeler gauge in. Guess I should have explained about grinding the valve stem end.
Mike

#36 trowel OFFLINE  

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Posted April 24, 2015 - 11:26 PM

Trowel,read it again. Especially the ".000 inch". Ie: you can't get the thinnest feeler gauge in. Guess I should have explained about grinding the valve stem end.
Mike

Go back and re-read mines. Or should I haul out all the pictures and information of engines I have rebuilt since I was a child ?

 

I am going to ask you a question then,....if we are agreeing on the same thing, then why did I react to your post the way I did ?

 

Tread carefully, I left MTF over crap like this.


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#37 alec OFFLINE  

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Posted April 25, 2015 - 12:38 PM

Is .18 correct for the points gap ? seems a bit much to me. how did you make out ? get it running ? some of those carbs can be a hassle to get correct especially if they are worn a little. I am building two motors now with that style carb, great when they work not when they don't.

Pete

.018 .lol ! someone told me That for when they are old. It should be twenty by the book .the carb is now soaking probably screwed up the needle shaft .i have another off a blown motor and will soak that one next now that i have a custom screwdriver

Edited by alec, April 25, 2015 - 12:42 PM.


#38 alec OFFLINE  

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Posted April 25, 2015 - 01:13 PM

Classic. Can i use the same coil on the 10hp and 12hp ?
I have 2 of each and they seem to all have the same issues ( no or week spark )
Two have brand new (looking) points . one the cut the wire to the coil (magneto ?)
The other was under a carport. Am wanting to bench test this one (and then the others) am going to build a table for doing this. Any suggestions?

Edited by alec, April 25, 2015 - 01:15 PM.


#39 classic ONLINE  

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Posted April 25, 2015 - 04:17 PM

Alec, I would take the model and type numbers from your engines and see if the coils are the same. I only have one 12hp Briggs on a Simplicity 2012, and I haven't looked at the coil yet.You also need to verify the correct armature air gap, because they do vary on these cast iron engines.
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#40 trowel OFFLINE  

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Posted April 25, 2015 - 06:38 PM

As long as the 10 hp (model 243431) is built after code date 81073100 then yes the coils (magnetos) interchange with the 12 hp.

 

Upload the model, date code and serial for that engines, it will help us help you.


Edited by trowel, April 25, 2015 - 06:40 PM.

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#41 alec OFFLINE  

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Posted April 25, 2015 - 09:24 PM

As long as the 10 hp (model 243431) is built after code date 81073100 then yes the coils (magnetos) interchange with the 12 hp.

 

Upload the model, date code and serial for that engines, it will help us help you.

B110   243431-0123-01-671212  so no then ?

B112   300421-0127-01-6901161

B112   300421-0127-01-6711141

B112   300421-0127-01-69061c   ? that last one is questionable( the number)

 

your tractor looks like it can get stuff done !


Edited by alec, April 25, 2015 - 09:34 PM.


#42 trowel OFFLINE  

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Posted April 26, 2015 - 06:28 AM

Magneto air gap at .010, if you do not have a feeler gauge, another way is to use a one dollar bill folded in half between the mag and flywheel. Loosen the mag screws slightly and lightly push the mag onto the bill on the flywheel, the magnets on the flywheel will help suck the mag onto the bill / /flywheel. Do not press down tightly or the bill will rip and roll up forcing the mag back up. Slowly turn the flywheel in the direction of the fold in the bill while holding the bill with the other hand until it is out. This may take a few tries and better risking a dollar bill then a 20 dollar bill :D

 

There are other methods, some better but this is one I have used for field repairs while my feeler gauge sits in the shop 20 miles away.

 

Correct me if I am wrong, going by memory. Since August 1981 B&S used Magnetron ignitions on all of their heavy-duty and super-duty engines, and then in June 1982 they used it on all their product.The before part is because they had reverse polarity on the flywheel prior to that date for the cast iron long blocks. The Magnatron kit offered was not an option, just a kit they came out with later to by pass the points system entirely therefore which does not apply to the cast iron long blocks, the first 990 to use a solid-state ignition on its engine was the model 142-990A from 1982 so yes, the two leg mags will interchange seeing as the 243431 and 300421 retain the same two magnet flywheels postdating the model 23D three leg mags.

 

If the flywheel key is good, Instead of disassembling the engines for old used mags, if you have a auto type external coil and a battery go that route for testing to confirm it is not the mag, I have switched between three mags with similar problems but when switched to external battery ignition the problem was solved and a new mag ordered for the model 19D (this was before Briggs NLA outright). Below is a wonderful website full of information regarding battery ignition, granted it is for Kohler but both the Kohler K-blocks and Briggs cast iron long blocks has external points so the method applies.

 

My Squire 9 is battery ignited, it was converted in the late 70's or so by the original owner's son. lo, yeah, Squire is a workhorse but the engine needs rebuilding soon so I do not work it hard all the time. The cast iron long blocks at 3,600 rpms are solid workers. I really like the 243431 over the 300421 in a tractor due to it being of smaller bore so it runs cooler and burns less fuel that is if it is not ran at max against the governor all the time mowing over grown yards and fields so as powerful as these tractors and engines are, keep in mind they are old needing total rebuild before becoming daily users again. A common fault I see a lot of people make is the standard of heavy duty now days is pathetic when compared with GTs of the 60's and 70's so people become impressed, feel powerful and begin using the tractors and engines to the point of abuse. Simplicity did not build pullers or race tractors but sensible solid built garden tractors for homeowners and landowners.


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#43 Dayton_King ONLINE  

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Posted April 26, 2015 - 07:49 AM

When I restored my B10, I had the same problem. But I was lucky, since I restored it I has all new ignition parts. The Flojet carb is a finicky pain. I have found in my short life in the Hobbie that super clean is super good. I like to soak my carb for a few days in Lacquer thinner before I even attempt to work on it. I then disassemble it, and glass bead everything. I soak it again and blow out all my orifices. Sometimes I then reassemble with a new carb kit. I attached some pics of a kohler carb. Same process, I am actually doing to onan dd carbs at the moment. Make sure it's super clean

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#44 alec OFFLINE  

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Posted April 26, 2015 - 10:28 AM

trowel ... I seem to have misplaced the link to that wonderful website about ignitions .

thanks for the tips and info . so I can use an external coil without sending the flywheel back to briggs for re-polarization ?

my thought was to buy one mag and if one motor was junk I could use it on the next (until I run out of junk motors to test lol )

I know what you mean about being impressed and feeling powerful !!!!  thats me when I used my belly grader :beerchug:


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#45 alec OFFLINE  

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Posted April 26, 2015 - 10:32 AM

When I restored my B10, I had the same problem. But I was lucky, since I restored it I has all new ignition parts. The Flojet carb is a finicky pain. I have found in my short life in the Hobbie that super clean is super good. I like to soak my carb for a few days in Lacquer thinner before I even attempt to work on it. I then disassemble it, and glass bead everything. I soak it again and blow out all my orifices. Sometimes I then reassemble with a new carb kit. I attached some pics of a kohler carb. Same process, I am actually doing to onan dd carbs at the moment. Make sure it's super clean

the kohler carb is cake to rebuild compared to the briggs . hahaha


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