# Briggs V Twin runs rough



## borgward (Dec 2, 2007)

Briggs and Stratton V20 HP v Twin runs rough on one cyl. One spark plug looks perfect. The other is wet with fuel. Air Filter is clean. Is spark plug wire replaceable? How to get to the other end of spark plug wire to replace it?


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## K-B (Oct 24, 2005)

Please get the model, type and code numbers from the engine and post them here so that we can help you better.


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## borgward (Dec 2, 2007)

K-B said:


> Please get the model, type and code numbers from the engine and post them here so that we can help you better.


Model: 407677
Type: 0229E1
Code: 020816YG

Model Series 4000000, 440000


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## Basementgeek (Feb 7, 2005)

Have you tried swapping plugs with the other cylinder ?

BG


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## borgward (Dec 2, 2007)

Yes, same result. So, are the spar kplug wires replaceable? If so, how do you get to the other end of them?


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## Vatar (Oct 12, 2009)

Turn the engine over with the spark plug in wire but out of the motor and look to see if you have spark if you do its a carb, exhaust or valve issue. If you have no spark one windings on your ignition coil is probably bad I would go to a tractor supply store or a dealer and order a new coil. Plug wires are almost never your problem in small engines because the reason you would replace them in your car is that they are arcing. You have the opposite problem you aren't getting spark to the motor. If you need a short term fix I would cut the wire off the bad leg and tie it into the good leg at the coil.


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## K-B (Oct 24, 2005)

borgward said:


> Yes, same result. So, are the spar kplug wires replaceable? If so, how do you get to the other end of them?


The spark plug wires are none-replaceable, officially. (I'm sure if you were desperate you'd find some way to at least partially replace them). However, unless the wire are visibly damaged (missing insulation) there's not much point in trying to replace them. Chances are it's the coil. Replacement coil part number is 691060.



Vatar said:


> Turn the engine over with the spark plug in wire but out of the motor and look to see if you have spark if you do its a carb, exhaust or valve issue. If you have no spark one windings on your ignition coil is probably bad I would go to a tractor supply store or a dealer and order a new coil. Plug wires are almost never your problem in small engines because the reason you would replace them in your car is that they are arcing. You have the opposite problem you aren't getting spark to the motor. *If you need a short term fix I would cut the wire off the bad leg and tie it into the good leg at the coil.*


I'm pretty sure that wouldn't work. This engine uses 2 coil packs, one for each cylinder. Running both cylinders off of the same coil would probably throw one cylinder out of time.


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## borgward (Dec 2, 2007)

Vatar said:


> Turn the engine over with the spark plug in wire but out of the motor and look to see if you have spark if you do its a carb, exhaust or valve issue. If you have no spark one windings on your ignition coil is probably bad I would go to a tractor supply store or a dealer and order a new coil. Plug wires are almost never your problem in small engines because the reason you would replace them in your car is that they are arcing. You have the opposite problem you aren't getting spark to the motor. If you need a short term fix I would cut the wire off the bad leg and tie it into the good leg at the coil.


I am thinking that if it were a carb problem, both plugs would be fouled, unless it has dual carburetors.

I have read lots of comments about valve problems in the Briggs and Stratton engines. Must be a manufacturing or engineering problem. Most auto engines that needed valve adjustment needed it on about 100 to 200 hours of operation (3000 to 6000 mi.) Say an air cooled VW for example. How often do they need to be set on this engine? (it's my neighbors!)


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## Vatar (Oct 12, 2009)

Does the plug in the bad cylinder have any spark at all?

PS: Unless your running your motor without a governor I wouldn't think you should have any valve problems, but if you run the engine for over an hour and shut it off with out idling it down for a couple of seconds you can kill the valves on the motor.


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## k2skier (Sep 30, 2008)

Vatar said:


> Does the plug in the bad cylinder have any spark at all?
> 
> PS: Unless your running your motor without a governor I wouldn't think you should have any valve problems, but if you run the engine for over an hour and shut it off with out idling it down for a couple of seconds you can kill the valves on the motor.


How does/can this happen????


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## Vatar (Oct 12, 2009)

Well the valves on Briggs motors aren't the greatest and if you don't idle them down and let them cool off they have a tendency to break off at the stem. It happened to me while I was at a tractor pull, it wasn't fun.


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## borgward (Dec 2, 2007)

K-B said:


> The spark plug wires are none-replaceable, officially. (I'm sure if you were desperate you'd find some way to at least partially replace them). However, unless the wire are visibly damaged (missing insulation) there's not much point in trying to replace them. Chances are it's the coil. Replacement coil part number is 691060.
> 
> 
> 
> I'm pretty sure that wouldn't work. This engine uses 2 coil packs, one for each cylinder. Running both cylinders off of the same coil would probably throw one cylinder out of time.


Found out the engine uses 2 Magneto Coils. These are not like ignition coils usually found on automobile engines. 

I do not think connecting both plugs to one of the coils would work, assuming that the cylinders cycle 180 degrees from each other. The magneto is energized by a magnet in the flywheel. It is going to fire everytime the piston comes up, once on the compression stroke, and once on the exhaust stroke. There is no distributor as in an auto engine. 

While one piston is at the top of the compression or exhaust stroke, the other piston is going to be at the bottom of its the compression or exhaust stroke, and the spark will be wasted.

These engines would be much more efficient if they used either a mechanical or electronic distributor, that could advance or retard the spark as needed. An electronic (solid state) distributor would be easy to convert to as it would require no re machining to provide gearing and shafting for a mechanical distributors shaft. All that is needed is a sensor energized by an actuator connected to the crankshaft. 

This scheme would use one ignition coil per cylinder energized by the ignition controller. This method is pretty common on cars and motorcycles nowdays

As for valve problems due to shutting the engine off w/out letting it idle, that sounds like a design problem. I have heard of valves warping on race car engines after the engine is turned off. This is due to cool air rushing in thru the intake or the very short exhaust and the valve cooling off too fast. These engines have no air cleaner to restrict cool air from reaching the valves. Cool air also can come in thru the short exhaust manifold. It is common practice to stuff rubber balls or rags, etc in these points of entry
d


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