engine performance question: model 19 (UPDATE)

[wminmi 0]

ok, so maybe i should have said "questions" instead of "question" I'm just about at my wits end here......so someone give me an idea of what to try next :( 1959 WonderBoy 700 Briggs Model 19 7hp engine Alrighty, here we go (this may get long.....) #1 changed the head gasket today, as i noticed puffs of smoke from between the head and block. Noticed once the head was off that the piston is .30 oversized and can still see cross-hatch in the cylinder wall. Cylinder and piston look EXCELLENT, but they was some serious carbon buildup around the valves. Cleaned that all up and put the new gasket in. Torqued to specs. #2 i lucked out this morning and got a rebuild kit for the carb off the shelf at the local briggs dealer. Got that in there and geeeee, no more flooding :D Got the settings at stock right now and she seems to run fairly well. About the same as before the carb kit but without all the fuel hassles i had before. SHE STILL BACKFIRES AND DIES OUT AT IDLE :(! Points maybe? Coil? I'll be honest, i didn't even take a peek at the points.....she ran absolutely perfect at high idle, wide open throttle and lower RPMS, but when i went to idle her down and set the idle itself she started backfiring, sputterring and then flat out died :(! If you guys do think it's the points/coil/whatever, is there any certain thing specific to look for?

[RayS 80]

Is it possiable that you have a burnt valve? Or even a sheared flywheel key?

[wminmi 0]

i kinda doubt a sheared key, i would think if it was indeed sheared or half-sheared, it would run like crap no matter what i did. I could be wrong though, and will check it out. Burnt valve is possible.....stupid question time: how would i check it to know for sure? I know when i wire brushed everything when i did the gasket everything looked brand new and appeared to work perfectly ?

[RayS 80]

http://autos.yahoo.com/maintain/repairqa/engine/ques053_1.html

[wminmi 0]

thanx Ray.....even though i kinda feel stupid now! I've done compression/leakdown tests on automobiles before.....talk about a major brain fart :I

[BLT 725]

Even tho Briggs doesn't advertise it, you can take a compression check. If you get 80-90 PSI on a cold engine, you should be OK. My 32's are all about 100.

[D-17_Dave 12]

You've done everything right up to the part of running it after a carb rebuild. You need to set the fuel screws for the right mixture. Then if any problem persists start lookling elsewhere.

[wminmi 0]

dave ~ i don't mean to sound stupid, but what do you mean "set it for the correct mixture?" I set it at the starting points and then adjusted per the manual and she still backfires and craps out at idle........

[D-17_Dave 12]

In your prior post you stated you set it at the starting settings and that's where you ran it. As you later stated you adjusted per the manual while running after starting it at the initial settings. I still feel like your idle mixture is a bit lean. This will cause the bad backfireing when going from high idle to low idle and then will starve it to die. If you have a good clean spark then there isn't much need to worry about an ignition problem unless it runs well when cold and deteriorates after it gets warm. This posibly indicating a bad condenser or more rare a bad magneto. I still think your problems are in the carb. When adjusting the idle screw do you have a full range of flow? Meaning can you lean it up enough for it to die unless you apply the choke, and can you richen it up enough to pass the "sweat spot" and begine lopeing as you get on the too rich side of the mixture. If You can't get rich enough then maybe there is something restricting the fuel flow to the idle screw. These are guese's, but these conditions should be able to be reproduced. A proper carb adjustment may take several attempts since as you change one adjustment it may have an effect on the other adjustment.

[Ketchamized 2]

William, This may be useful to you... [img]/club2/attach/ketchamized/carb adjustment.jpg[/img]

[BigSix 0]

William: I'm leaning toward carburetion, as has been discussed. However, Re:

quote:

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i kinda doubt a sheared key, i would think if it was indeed sheared or half-sheared, it would run like crap no matter what i did.

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A couple things to consider: 1. Sometimes, when you have a sheared flywheel key, the flywheel will actually "walk" or change it's timing as you throttle up and down, so that it could be running perfectly if it happens to line up properly. And then a sudden load (deceleration) or acceleration could cause it to shift, changing the timing and running. I've had this happen. 2. If it's only a half a degree off, say, (like if the key mushroomed rather than sheared right off) it's gonna run like it's only a half a degree off, i.e., not that bad. You just might find more there than meets the eye. Good luck with it. Peter

[wminmi 0]

Dave~ yes, i can adjust her out both ways to where she leans out and dies and to where she starts "missing" i set it "in between" like the instructions suggested, but i'll try it again. Erick~ That's one of the refferences i printed out and used. BigSix~ I'll try the carb adjustment thing once more than start digging into the keyway idea. You may be right though, the keyway may have "shifted" or "mushroomed" Thanx for the info guys, i'll get her going good one of these days ;)

[wminmi 0]

I've searched both the "19" manual and the "700" manual, and i can't seem to find the flywheel key part number......is this just a standard half-moon style key or no? Figure i'd go ahead and get one, no sense in tearing into her that far without one on hand

[MPH 12]

You said earlier you hadn't even checked the points because it an perfect. Seems it be easier to double check them before you tear the flywheel off. Just my first thought for the morning

[gregc 3]

quote:

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Originally posted by wminmi
I've searched both the "19" manual and the "700" manual, and i can't seem to find the flywheel key part number......

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That's because there's not one. The Model 19 engine doesn't use a flywheel type ignition. It uses the Magna-Matic ignition. In the Magna-Matic ignition the magnets are in the rotor located on the crankshaft behind the flywheel. The rotor is alined on the crankshaft by using the woodruff key. You might want to get this manual: http://shop.briggsandstratton.com/BShopProductPage.asp?CatalogID=56B2B9AA-283C-11D4-8886-00B0D0203414&MECID=100&SessionID=D9896790-54FF-4C97-B379-C9C6EFC2010E&CategoryID=&lrid=1&ProductID=56B2BB53-283C-11D4-8886-00B0D0203414

[Ketchamized 2]

Gregc, If that's true, then a Mega Fire electronic Ignition module won't work with this engine right?

[HubbardRA 19]

Check the carb and intake gaskets. When the throttle is closed, it makes a much higher vacuum in the intake than with the throttle partly open. This could be causing a sudden lean-out which can sometimes cause a backfire. Test all the intake gaskets with carb cleaner, starting fluid, or WD 40, while the engine is running.

[johnmonkey 4]

quote:

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Gregc, If that's true, then a Mega Fire electronic Ignition module won't work with this engine right?

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This is the question I would like to know. I have a model 19 (magnamatic) and a model 19d. Will the mega fire work on either one? JH

[Roy 0]

I have an electronic ignition module on the Magna-Matic in the Model 19 on my B-1. Works fine when running but has weak spark when starting and the engine wanted to kick backwards when trying to start. Suspect my timing was advanced too far for whatever reason. Last time I used the B-1 it backfired and blew the head gasket for the third time as I was pulling into the garage. Have been told it isn't supposed to work but it does on mine provided the timing problem is not due to the module.

[wminmi 0]

quote:

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Originally posted by Roy
I have an electronic ignition module on the Magna-Matic in the Model 19 on my B-1. Works fine when running but has weak spark when starting and the engine wanted to kick backwards when trying to start. Suspect my timing was advanced too far for whatever reason. Last time I used the B-1 it backfired and blew the head gasket for the third time as I was pulling into the garage. Have been told it isn't supposed to work but it does on mine provided the timing problem is not due to the module.

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Hmmmm....i JUST ordered the module Erick is talking about for my 700.....well, if it doesn't work maybe i can use it on the B-12?

[wminmi 0]

quote:

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Originally posted by HubbardRA
Check the carb and intake gaskets. When the throttle is closed, it makes a much higher vacuum in the intake than with the throttle partly open. This could be causing a sudden lean-out which can sometimes cause a backfire. Test all the intake gaskets with carb cleaner, starting fluid, or WD 40, while the engine is running.

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will give it a shot Rod, thanx for the idea!

[gregc 3]

Erick and John, I don't know of any reason why an electronic ign. module wouldn't work on the 19 or 19D.

[Nick 0]

quote:

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Originally posted by wminmi
Hmmmm....i JUST ordered the module Erick is talking about for my 700.....well, if it doesn't work maybe i can use it on the B-12?

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Yes you can.

[BLT 725]

I wired the Mega Fire on my 7010 by using the points as the firing device. This definitely eliminates any back fire on start as you are only firing on every other revolution the way it was versus firing every revolution using the electronic device. I have had this arrangement for over 15 years without a problem. You don't need a lot of point action to make it happen. I think I have only a .004-.005 gap.

[wminmi 0]

This may be a stupid question, but after reading BLT's reply i figured i would ask: doesn't the mega fire or whatever wire to the points or is there 2 ways to wire it? For what it's worth, here's the ignition i bought: [url]http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ih=008&sspagename=STRK%3AMEWN%3AIT&viewitem=&item=180045471650&rd=1,1[/url]