[ricohman]

I decided to change the points on my 446 tonight so I drove it into the garage and pulled the old points and condensor. The old points were worn so bad the contacts are gone. I don't understand how it ran.
But now it doesn't, run that is. I am a mechanic but not a small engine mechanic. I've changed many points in my day and I did this by the manual.
But I have no spark.
No distributor or timing to fool with so do I have these points out of phase?
Should I turn the engine 180 and then set them?
I'm not sure what the timing lobe on the cam even looks like. Do both plugs fire at once?

 

[ricohman]

Hmmm.
I have good readings at the coil so I turned the big lights down and sure enough, I have spark. Not bright like my BMW R1150GSA but its there. I don't know how intense the spark is on these Onans.
But I have noticed the electric fuel pump is pushing fuel passed the seat and the engine is very flooded. Tomorrow I will inject a bit of oil into each cylinder and see if I can start this thing up. Then I will have to get the factory pump (that has been bypassed) working. Who knows what the electic is rated at. But the tractor ran fine.
The P/O installed an electric as the tractor would quit when working. I've had no trouble since I opened the original points.

 

[jayvee43]

It's a 12 volt coil ignition, so My guess is the spark has to be the same as any other automotive ignigion. I too am a mechanic, i know what you mean.

The points open at every 180 revolution, so timing is not an issue, make sure it is set at .020 thousanth of an inch, and you have it grounded good back to the (-) negative side of the ignition coil.
Check you have a good source (+) positive at the coil pos side and open and colapse the point using a little screw-driver to simulate the motor moving the points open/closed/open etc. see how powerful your spark is. you should hear it crisp, and see it blueish in color.
If I missed anything else, someone please chimme in.
Jay

 

[ricohman]

I did this last night so I don't know what to expect. Points are .021 plugs are new last week and I drove it in there. But its been cold and the extra fuel isn't causing any problems outside. And since it starts cold without the choke I have lots of fuel!
I am thinking the pump is the real problem and the walls are washed with gas so there is little compression left. I will squirt in a bit of oil and I bet it will fire up. Then I will sort the fuel delivery out. No use creating additional things to complicate this further.

 

[CADplans]

I did this last night so I don't know what to expect. Points are .021 plugs are new last week and I drove it in there. But its been cold and the extra fuel isn't causing any problems outside. And since it starts cold without the choke I have lots of fuel!
I am thinking the pump is the real problem and the walls are washed with gas so there is little compression left. I will squirt in a bit of oil and I bet it will fire up. Then I will sort the fuel delivery out. No use creating additional things to complicate this further.

But, is the ignition fixed!!?? :dunno:

 

[Alan_Heist]

Not sure if the Onan has a procedure for static timing or not.

Kohler Singles have a timing mark on the flywheel and can be static timed if the standard 0.020 is not getting the engine fired, I had to use this method on my JD 112 and it runs like a top now.

HTH:fing32:

 

[refracman]

Sometimes the points have film on the them that causes the problem. A car has more voltage/amps than a small engine and can overcome this.
Take some emery paper and give them a pass, then take a some paper( i use a envelope) and with the points closed give them a couple of passes with the paper. You'll see the residue on the paper. They should make good contact then.

 

[ricohman]

Couple squirts of oil into the cylinders and it fired right up. So the ignition is ok.
But when I turned the main mix screw in all the way the engine still runs, and runs rich. Fuel is dribbling into the carb. I think that pump must have at least 15psi. Anyone install an electric? What psi do you run?
So I disconnected the fuel pump line and turn on the ignition. Fuel shoots halfway across the garage and my thumb cannot stop this flow. This automotive pump is way to much for this engine so its coming off.
I have installed a new vacuum line to the factory pump and I am going to run the fuel line without the electric pump. My other 446 runs fine with the factory vacuum pump.
But I need to drive into town for a barbed connector so we shall see.
I noticed that the intake manifold must be removed in order to remove the carb.

 

[jayvee43]

Couple squirts of oil into the cylinders and it fired right up. So the ignition is ok.
But when I turned the main mix screw in all the way the engine still runs, and runs rich. Fuel is dribbling into the carb. I think that pump must have at least 15psi. Anyone install an electric? What psi do you run?
So I disconnected the fuel pump line and turn on the ignition. Fuel shoots halfway across the garage and my thumb cannot stop this flow. This automotive pump is way to much for this engine so its coming off.
I have installed a new vacuum line to the factory pump and I am going to run the fuel line without the electric pump. My other 446 runs fine with the factory vacuum pump.
But I need to drive into town for a barbed connector so we shall see.
I noticed that the intake manifold must be removed in order to remove the carb.

Good Job. :trink39:
Now, fix this fuel pump to original. you should have about 3 to 6 psi of pressure on the inlet needle, no more that a gravity feed fuel line would have for pressure, your thumb would defenitely stop the flow.

keep us posted.

 

[ricohman]

The line from the crankcase has good vacuum. So I removed the pump from the carb and this is what I got. I have had a look at various pics on-line of the different pumps. It seems I am missing a spring and a little cap. Anything else?

This tractor came with a pallet of spare parts so I dug through a few boxes and found this. I have a few springs caps and gaskets to choose from. Some are different colors and one seems smaller than the others. These bags are sealed. Should the larger black cap be used?
My valve has only one black flap on one side. The new one in the bag has a metal one on both sides. Has the one in my pump been tampered with? The log for the tractor reads "pump disabled".
Will this one fit my pump?

 

[jayvee43]

I think youre on the right track, it works like a mikuni pump off of a snowmobile, there needs to be 2 flaps on both sides to the block, open to draw negative pressure/fuel in, and close to pressurize, then reopens etc...

If this was to fail, i were you, I'd put the old pump block on the side of the carburator, and install a vaccum "MIKUNI" puump in the place of the electric pump. You say you have a good impulse line, there is no reason it would not work.

 

[ricohman]

I've put the pump together with new parts and it seems to be working however the tractor will only idle. I removed the top of the carb and there is great flow from the pump. I may have to check the float level.
Seems to be about a 1/2 inch of fuel in the bowl.

 

[jayvee43]

I've put the pump together with new parts and it seems to be working however the tractor will only idle. I removed the top of the carb and there is great flow from the pump. I may have to check the float level.
Seems to be about a 1/2 inch of fuel in the bowl.

That's good news, so far you got your spark fixed, your fuel flow fixed, and now youre on your way to a carburator cleaning job. your intermediate/high speed jet must be getting restricted a little.
For the record, Is there a accelerator pump on the throttle body of tis type carburator? you may want to check into that.

 

[ricohman]

No accel pump on this carb. Very simple little card though.
Since I'm not a small engine, guy I assume the throttle plate is being closed by the govenor and opens up under load?

 

[bhildret]

Throttle opening is nominally controlled by the governor, but the throttle cable should have enough pressure on the gov to pull it up from idle to 3600 RPM or anywhere in between. Then the governor modulates the throttle to hold that speed.

Look up an Onan service manual .. many posted around the web, for throttle cable setting procedure.

Brian

 

[ricohman]

I took the main and idle needles out and blew some air through the holes. Blew some air through the needle and seat and put it back together.
It seems to run pretty good at all speeds. I will do some reading and set the carb up properly now.
But the weird thing is this. The company that owned this tractor had all the parts to fix it, but they choose instead to run an electric pump to big for this application. And I know they had real tractor mechanics look at it. Weird.
It idles a lot quiter now and no more exhaust soot.
I wonder if I should pull the heads and clean up in there. I am certain with running it this rich there has to be some deposits inside the combustion chambers. I have two or three sets of gaskets for the motor.

 

[ricohman]

bhildret, those parts sailed right into my mailbox last week. Thanks again!
But now that I'm in the garage my wife isn't to happy with you.:fing32:

 

[jayvee43]

I took the main and idle needles out and blew some air through the holes. Blew some air through the needle and seat and put it back together.
It seems to run pretty good at all speeds. I will do some reading and set the carb up properly now.
But the weird thing is this. The company that owned this tractor had all the parts to fix it, but they choose instead to run an electric pump to big for this application. And I know they had real tractor mechanics look at it. Weird.
It idles a lot quiter now and no more exhaust soot.
I wonder if I should pull the heads and clean up in there. I am certain with running it this rich there has to be some deposits inside the combustion chambers. I have two or three sets of gaskets for the motor.

Good job. :fing32::trink39::trink40:

If it's running to your liking right now, I would leave it alone. all you need now is a broken head bolt and you are grounded again.

You said that the motor flooded easily, did you do an oil sample smell job, if it looks dilluted, or burned, I'd change the oil again. It is easy to loose friction properties with gas mixed oil.

Other than that, Enjoy and get as much seat time as you can. D'you have any snow your way yet?

 

[ricohman]

Oil looks ok. I just changed it a few hours ago. No snow here but that's ok with me as we don't have -40 either!
I have read about head bolts breaking but I have also read about rods snapping. I have to think about this.

 

[jayvee43]

Oil looks ok. I just changed it a few hours ago. No snow here but that's ok with me as we don't have -40 either!
I have read about head bolts breaking but I have also read about rods snapping. I have to think about this.

Yeah, the conn rods snap on an operator that doesn't listen to his engine. you said this thing is idling smooth now. does it knock?

No knock, no build up.
Also anothe indicator you have exess carbon build up would be "hard to crank "turn over" at cold start up. And, Continued detonation after you shut off the key. Like the old Chrystler cars in the 80's. The engines would start turning backwards FOR a few seconds.

It's your choice. But I always say: IF IT AINT BROKE... :dunno:

:trink39: