Briggs 16 Hp Motor

jgbanshee · Sep 20, 2004

I have a Briggs and Stratton I/C 16Hp opposed twin motor. Model 402707. I can only get it to start by placing my hand directly on top of the carb. and turning the key. Once it starts, it runs good with no knocks or smoke. Can someone tell me what the problem is. Why I cannot start it without taking the airfilter off and covering the carb.? The choke doesn't even help.

kubmech · Sep 20, 2004

The choke does not completely cover the carb inlet even when it's fully closed, there is an air passage through it. If you have verified that the choke is closing fully and it takes full blockage to start the engine, then there is a possibility that you have a problem with the low speed jet. Those engines really want/need to run rich. Always have and most likely always will. That carb is a tad bit finicky as well, it has a diaphram fuel pump built in to the carb. You may be looking at a rebuild.....................................

jgbanshee · Sep 20, 2004

Choke does close all the way. There is a half circle in the steel where air passes. It does need fully coverage to start motor. Which is the low speed jet?

bontai_Joe · Sep 21, 2004

You might also have a leaking gasket where the carb mounts to the engine allowing extra air in that is bypassing the choke, esentially canceling out what the choke is doing.

kubmech · Sep 23, 2004

That's right Joe. You also jogged my memory. Some of those engines had a two piece intake manifold that would occasionally devolop air leaks.
The low speed jet is actually in and part of the carb. That carb has an adjuster in the front of the carb. Maybe you can get away with this trick: Carefully turn the adjustment screw all the way in counting how many turns. Then remove it. Watch for the o-ring. Once removed, spray carb clean through the open hole,(put the plastic tube on the can and stick it right in there). Put the mixture screw back in all the way then back off the amount of turns you initially counted and try it.

jgbanshee · Sep 27, 2004

Over the weekend I checked to make sure that everything was tight. I even replaced the carb with another that I rebuilt and know works great. Still when I came out the next morning the motor won't start. I would remove the air filter and choke it by hand. Starts right up. After that I can start it by using the choke on the dash, this only works when it doesn't sit for a long time. I even cut some grass with it until I broke the drive belt. Parked it and it wouldn't start later that day.

Cook123 · Sep 27, 2004

have compression checked. sounds like it may only start good once it is warmed up.

jgbanshee · Oct 8, 2004

Checked the compression in both sides. Both cylinders are around 110 lbs. This is good. When i took the spark plugs out, they were black NOT wet. What does this tell me?

Molerj · Oct 9, 2004

Black spark plugs tells you that the engine is running rich. Possibly the choke isn't opening all the way or air filter is dirty. Also make sure you are using fresh fuel.