briggs 16 hp v twin

[jdog_kustoms 82]

i got a cub for the engine out of it but i think the one head droped a valve seat cuase it only runs one cylinder and brows gass out the carb some is this worth putting money in to or just sell it as is and buy a kohler comand the tractor only has 346 hours on it and i just want the engine for my hot rod

[Sparky-(Admin) 19,592]

Maybe this is a stupid suggestion but can you just open the motor and "peen" the edges of the valve seat to get it to stay put? I thought I had heard about someone doing it with an ONAN and having success.

I could be wrong.

Mike.............

[jdog_kustoms 82]

never thought of that i might have to try that

[Fordiesel69 219]

It is a very common topic among onan/briggs twins. It will work fine but you need to regrind the valve to seat so it matches. MAybe it it is not too loose it can be lapped back in. Another issue is the valve guide could be shot.

[TT-(Moderator) 1,128]

Is this a Vanguard?

Before you dig too deep, pull the rocker cover on the dead cylinder and look for a loose rocker arm pivot stud, broken rocker arm, bent pushrod, etc.

[Fun Engineer 859]

Maybe this is a stupid suggestion but can you just open the motor and "peen" the edges of the valve seat to get it to stay put? I thought I had heard about someone doing it with an ONAN and having success.

I could be wrong.

Mike.............

This worked for me on one of my tractors.

[jdog_kustoms 82]

Is this a Vanguard?

Before you dig too deep, pull the rocker cover on the dead cylinder and look for a loose rocker arm pivot stud, broken rocker arm, bent pushrod, etc.

yes it is a vanguard i will try that and see what i get thanks for your help

[Rooster 191]

WHoa whoa whoa......

What kind of engine is this?

Older Briggs and Onan Flathead twins have seat problems,don't think I have ever seen a V-Twin lose a seat?

Is this a Vanguard?

Before you dig too deep, pull the rocker cover on the dead cylinder and look for a loose rocker arm pivot stud, broken rocker arm, bent pushrod, etc.

Yeah....THAT! LOL

OOPS, nevermind...ya beat me to it, lol

Is this a Vanguard?

Before you dig too deep, pull the rocker cover on the dead cylinder and look for a loose rocker arm pivot stud, broken rocker arm, bent pushrod, etc.

yes it is a vanguard i will try that and see what i get thanks for your help

[jdog_kustoms 82]

i was working on it tonight its not a head issue or spark but the right hand cylinder only fires when it wants to its a very weird thing and especialy under a load or rev it up you loose the right cylinder

[Rooster 191]

Are the plugs good and correctly gapped?

[Fun Engineer 859]

Does this happen after the tractor has been running for awhile? I had a B&S Twin that would cut out after about 15 minutes, once it warmed up. It was a bad ignition coil. Replaced it and it ran fine.

[Rooster 191]

You could check that by switching the coils. If it is a bad coil the problem will move to the other cylinder.

I know you said it was not spark..but you also said it "only fires when it wants to".

A weak plug can work fine at Idle, but as compression in the cylinder increases it quits working.

[Don1977 604]

There are two coils on a Vanguard sound like one bad coil. It could also be a bare kill wire shorting it out.

[Save Old Iron 1,563]

Unless the two coils share completely independent kill wire circuits, one shorted kill wire will kill BOTH coils at the same time.

[TT-(Moderator) 1,128]

Because of the "V" configuration, the coils on a Vanguard twin are isolated from each other by diodes installed in the kill wire harness. If a coil is suspected as being the problem, remove the kill wire from both coils and run the engine. (naturally, you will not be able to shut it off with the switch)

If the dead cylinder becomes "live", the problem is in the harness between the coils or the kill wire connected between the terminal on the engine and the ignition switch.

If the problem still exists with the kill wires disconnected, try swapping the spark plugs and/or coils to opposite cylinders as suggested above.

[Save Old Iron 1,563]

I would think the diodes are there to protect the coils from accidental connection to a 12 volt source - the diodes would protect the coils from drawing reverse current from the battery and frying the coil.

It also matters where you disconnect the kill wire from. Disconnecting the kill wire from the ignition switch would not solve an intermittent short in the kill wires. Disconnecting the kill wire AT THE COIL will prove / disprove the theory the coil is dying from kill wire grounding.

[TT-(Moderator) 1,128]

I'm pretty sure that the diodes are needed to keep one coil from (somehow) making the other coil fire when it isn't supposed to.

I vaguely recall someone trying to install a "plain" (no diodes) wire between the two coils and the engine ran erratically/misfired.

The next time I have one apart at work, I'll have to experiment. :handgestures-thumbup:

[Rooster 191]

Without the diodes if both coils are connected together they won't fire at all. Not sure how it works, but I know what will happen. TT's diagnostic method is the best way without meters, and even with a meter is the easiest.

[Rooster 191]

Since I don't know how to edit from tapatalk.... Lol.

I should've said, hooking both together usually kills one or the other. And now that TT has mentioned that, usually the right cylinder is the one that dies..

[Save Old Iron 1,563]

I'm pretty sure that the diodes are needed to keep one coil from (somehow) making the other coil fire when it isn't supposed to.

Hmmmmmmm

it is possible if there is a "back EMF" induced into the windings of the mag coil. Any time you have a collapsing magnetic field, iron core and a wire leading out of the primary winding of the core, you can get a significant voltage developed after the secondary fires. This may travel into the primary winding of the other mag coil and possibly fire it. This is the same phenomena a condenser sees when a coil based ignition system fires - a back voltage induced by the secondary winding firing back into the primary winding.

Guess I'll have to break out the scope and check what happens on the kill wire of a Kohler twin mag setup. I don't have access to a Vanguard.

Interesting opportunity for learning.

[Save Old Iron 1,563]

usually the right cylinder is the one that dies..

any idea why? closer to a more intense source of heat or less airflow ?

[Rooster 191]

Usually if the diodes fail, the right cylinder is the one that won't run because the diodes are shorted out. Why the right? I have no idea.

Here is something interesting though. On intek twins, we have always been able to wire a kill switch by replacing the diode harness with two wires hooked to a switch. When the switch is closed and both kill wires hooked together the Intek will die. Nothing hooked to ground anywhere. On a Vanny this usually doesn't work. The Vanny will either run on one cylinder or like TT said it will mid- fire and run erratically.

Now don't ask me why, lol. Most of my experience with V-twins is from race mowers. I found this out when a buddy of mine who is NOT a wire head could not get his intek to run I went and looked at it and told him he could not use straight wire, he needed the diode harness. The next day when I showed up he had each cool wired individually to both sides of his kill switch. It was one of those " nobody told him that won't work moments". We have wired Inteks that way every since then. When he started racing vannys we discovered that it will not work on vannys. ???

[Save Old Iron 1,563]

Possibly on the Inteks, if one coil's electrical "backwash" fires the other coil, the opposite coil may be triggered during the exhaust stroke - like a wasted spark setup.

I'm not sure about the firing cycles of the V Briggs. The dual coils without diodes may allow one coil to fire on time and the 2nd coil to ignite the 2nd cyclinder prematurely on the intake or compression strokes.

On horizontals, dual coils fire at the same time and one cyclinder recieves spark on the exhaust cycle - so no problem with both coils triggering.

[Rooster 191]

Both coils fire every rev.

The Diodes simply isolate the coils so that they do not ground each other out.

[Save Old Iron 1,563]

Both coils fire every rev.

Thanks Rooster.

Understood. That would have to be the case considering the mags are fired off the flywheel. Never having owned a V twin Briggs, my question would be if the right cylinder is at beginning of its power stroke, what is cylinder B doing at the same moment.

Any idea if the diode(s) fail, do they fail by shorting out or opening up?

I assume if a diode opens up (electrically like someone cut the wire off the diode), the cylinder will stay alive when the ignition switch is turned off. A diode shorting out (becoming like a piece of wire) would cause the interference between the coils.

Interesting.