Vanny rich on rear cylinder only?

Field6565 · 05-23-2015, 08:42 PM

My 16hp vanny seems to running rich on the rear cylinder. I've pulled my plugs several times and the front cylinder looks correct but the rear cylinder is always rich. Does the valve lash need set? It's not fouling plugs but definitely has a dark charcoal look to it. What to check? Thanks

1989Marathon · 05-23-2015, 08:43 PM

Single barrel or 2-barrel carb?

Field6565 · 05-23-2015, 09:04 PM

Quote:

Originally Posted by 1989Marathon

Single barrel or 2-barrel carb?

Don.....single barrel

1989Marathon · 05-23-2015, 09:12 PM

Could be a few things.
Bad intake valve seal, weak coil, valve lash, bad rings, to name a few.
BTW, I like vanny plugs a little on the dark side.

1989Marathon · 05-23-2015, 09:13 PM

Quote:

Originally Posted by Field6565

Don.....single barrel

Sorry, couldn't remember. I deal with too many Vanguards, if that is possible.

Field6565 · 05-23-2015, 09:17 PM

Quote:

Originally Posted by 1989Marathon

BTW, I like vanny plugs a little on the dark side.

I use my cart in a campground only, so high speed is few and far between. Could this have an effect on it? I'm running a slightly hotter plug than stock.

1989Marathon · 05-23-2015, 09:19 PM

Both cylinders should burn the same.
Why are you running a hotter plug?
What plugs are you using?

Field6565 · 05-23-2015, 09:27 PM

Quote:

Originally Posted by 1989Marathon

Both cylinders should burn the same.
Why are you running a hotter plug?
What plugs are you using?

I've had Champion rc12yc, Autolite 3924, and now NGK bcpr5es. Same thing.....rich on the rear cylinder.

1989Marathon · 05-23-2015, 09:32 PM

Maybe it's not rich on the rear cylinder. Maybe it's lean on the front. Check for an intake leak on the front head. Vanny plugs generally run a bit dark.
BTW, 3924 is the plug to use.
If you rebuilt the motor, intake leaks are common unless you float the heads in.

Field6565 · 05-23-2015, 10:13 PM

I never thought about the front cylinder running lean. Could a leaking exhaust gasket be the culprit?

05-23-2015, 08:42 PM	#1
Field6565 Gone Wild Join Date: Oct 2010 Location: Pittsburgh Pa Posts: 1,551	Vanny rich on rear cylinder only? My 16hp vanny seems to running rich on the rear cylinder. I've pulled my plugs several times and the front cylinder looks correct but the rear cylinder is always rich. Does the valve lash need set? It's not fouling plugs but definitely has a dark charcoal look to it. What to check? Thanks

05-23-2015, 08:43 PM	#2
1989Marathon Gone Wild Join Date: Oct 2010 Posts: 6,730	Re: Vanny rich on rear cylinder only? Single barrel or 2-barrel carb?
1989Marathon Gone Wild Join Date: Oct 2010 Posts: 6,730

05-23-2015, 09:12 PM	#4
1989Marathon Gone Wild Join Date: Oct 2010 Posts: 6,730	Re: Vanny rich on rear cylinder only? Could be a few things. Bad intake valve seal, weak coil, valve lash, bad rings, to name a few. BTW, I like vanny plugs a little on the dark side.
1989Marathon Gone Wild Join Date: Oct 2010 Posts: 6,730

05-23-2015, 09:19 PM	#7
1989Marathon Gone Wild Join Date: Oct 2010 Posts: 6,730	Re: Vanny rich on rear cylinder only? Both cylinders should burn the same. Why are you running a hotter plug? What plugs are you using?
1989Marathon Gone Wild Join Date: Oct 2010 Posts: 6,730

05-23-2015, 09:32 PM	#9
1989Marathon Gone Wild Join Date: Oct 2010 Posts: 6,730	Re: Vanny rich on rear cylinder only? Maybe it's not rich on the rear cylinder. Maybe it's lean on the front. Check for an intake leak on the front head. Vanny plugs generally run a bit dark. BTW, 3924 is the plug to use. If you rebuilt the motor, intake leaks are common unless you float the heads in.
1989Marathon Gone Wild Join Date: Oct 2010 Posts: 6,730

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05-23-2015, 10:13 PM	#10
Field6565 Gone Wild Join Date: Oct 2010 Location: Pittsburgh Pa Posts: 1,551	Re: Vanny rich on rear cylinder only? I never thought about the front cylinder running lean. Could a leaking exhaust gasket be the culprit?

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