48 John Deere B starting issue

[Markpa13]

I just got done completely restoring a 48 B, and can't get it to start. I'm completely baffled. The entire engine has been rebuilt, rebuilt mag, and a new carb. I'm getting gas to the motor, have a nice blue spark at TDC on 3116 plugs, and 110 psi compression. It doesn't even attempt to start. Switched the plug wires around, still no luck. Twice it's ignited the raw fuel in the exhaust stack (that will wake you up). So it leads me to believe it is a timing issue. However, I've gone over the timing at least 10 times. With #1 TDC, the governor shaft is horizontal and all timing marks align perfectly. The only thing I can think of is the lag timing on the back of the magneto. It is a Wico C with timing marks at 35 degrees. Would anyone know if this is the correct lag timing or have any advice?

 

[teddy52food]

Mag should snap at TDC, lag has nothing to do with starting. Does the spark jump at least 1/4 inch? If so, try pulling it. I redid 2 B's (both hand start) that wouldn't go without a pull the first time. Adjusted the carb for best running & they both start easy now.

 

[Paul from MI]

Verify your cam timing, check the marks on the gears if the cam/crank relationship could have changed during your overhaul. Just a thought.

 

[Mark-Ia]

If you have raw fuel in the exhaust stack, I'd guess the plugs are fouled. Install new ones and don't choke the carb too much.

 

[Mike M]

Are you for sure your on # 1 TDC of compression stroke ? and have the plug wires to the correct cylinders ?

I'm betting everyone on here has had them reversed at least one time in there lives. That makes a heck of a bang out the exhaust !

 

[Markpa13]

Thanks for the advice. I may try to pull it tonight. I think that is the only thing that I haven't tried. Do you think priming the cylinders with gas would help? Seems like I'm already getting enough fuel though, always a puddle on the floor below the petcocks after cranking a while.

 

[rick deere]

have you pulled it , pull it if its getting spark and gas it will do something???????

 

[John T]

Mark,

1) Okay the initial static start timing (when impulse SNAPS) needs to be on TDC (Left Hand Impulse flywheel timing mark at the 3 o clock hash mark) and it sounds like you have that. I assume you're aware that's when the LEFT piston is at TDC right, Flywheels LHI @ 3 o clock?????????

2) If she's snapping/impulsing right at TDC (LHI @ 3 o clock, left piston at TDC) the spark plug wire that leads to the LEFT Cylinder needs to be the one that fires that time!!!! Its easy to get that 180 out and if so she may pop n bang maybe backfire something awful but will never start. If that's the case try swapping plug wires as that will make her run (if all else is okay)

3) "only thing I can think of is the lag timing on the back of the magneto."

You may or may not have the Lag Angle set correctly, but regardless, if the mag is timed/rotated so it impulses at TDC and fires the correct plug at that time, she can start.

4) "It is a Wico C with timing marks at 35 degrees. Would anyone know if this is the correct lag timing or have any advice?"

YES, for one, you adjust the rear lag angle adjustment to match the drive cup you have. If you have a 35 degree drive cup, the lag angle needs to be adjusted (loosen 4 screws on rear and rotate) to 35 degrees. That would be 4 1/2 hash marks to the left of top to give you 22 1/2 + 12 1/2 = 35 degrees.

5) Many of the older Wico C's used a 35 degree drive cup as they were designed for low octane all fuel use. However, for gasoline only, 25 degrees is plenty of advance. Often many of the later Wico X mags used a 25 degree drive cup.

6) Adjusting the Lag Angle ONLY affects start timing, Rotating/Turning Mag in governor affects BOTHN start and run timing.

INSURE THE PLUG WIRES ARE CORRECT AS A SWAP MAY FIX IT (if the mag is 180 out)
Clean and dry the plugs as they may be fouling
She may be flooding
Try carb adjustments
Don't overchoke and flood

John T

 

[John T]

"I'm betting everyone on here has had them reversed at least one time in there lives. That makes a heck of a bang out the exhaust "

Once at a tractor show my *&^%$# buddies swapped my wires then hid and laughed as I tried to start it as she popped n banged n backfired something terrible grrrrrrrrrrrrrrr

I agree 100% to BOTH lol

John T

 

[ET]

When you put the cam in did you use the right marks to time it to the crank? They are on the inside of the gears and the one on the crankshaft is hard to see because it's right up against the crank throw.

 

[Wemedeeres]

John T can I come follow you around your shop for a month or so? LOL I'm printing off your explanation so I'll have it in case I ever run into this problem. There's a lot of knowledge here on this forum that needs to be soaked up and passed on!!!!!

 

[old popper]

You have been given a lot of good advice, the only thing I can add, is those late B's don't start well unless the throttle is barely open. Any more and they won't go. We have 2 '50s and a '52, and they are all like that. My $.02 worth.

 

[Kent Petersen]

every shop i ever worked in you would were told if you ever pull a tractor to start the first time you would be fired on the spot that was the way i ran my shop for 50 years. that tractor will start very easy if you have it timed right. the correct mag is a model x wico and the lag is 25 degrees for gas tractors

 

[John T]

Thanks for the kind words. Some years back I gave hour long Seminars on Wico C and X Mags at Gathering of the Green and Two Cylinder Expos, I cant put here in a few sentences all that's involved but posted enough to get him started MAYBE lol. When I did that I learned a lot from the late Duane Larson and Glen in Texas who had a mag shop and I've forgot a lot since grrrrrrrrrr

The past years I no longer give seminars and am slowing down in the business and getting rusty but still enjoy it and helping when I can.

John T

 

[gtx1967jewison]

I would never pull start a fresh engine. Dangerous, easy way to damage parts, & unnecessary entirely. Fix the problem & it will start. Also I do agree with the barely open throttle. Put the carb about 1/4-1/3 open.

 

[Lee B]

I'm going to second Kent's opinion of tow em to start em mechanics - DON'T. 25 to 35 lag angle will work aces either way - NOT the issue when they don't start like this one.

Your engine is exhibiting all the signs of classic cam timing being way off. It won't start to begin with so take the time and use the flywheel marks to verify that your left side exhaust valve is just beginning to open when that mark aligns with the timing mark on the transmission gear case. Pull the valve cover and just check this first. It will be way off. Somehow, someway the cam is not right, that's the only problem it could have since you've done everything else just about perfect. If your drive slot is horizontal and your mag is impulsing loudly at 3 o'clock with the impulse mark on the flywheel - it's the cam. Or your flywheel is on the wrong spline, check this thru the spark plug hole, impulse mark is TDC. So easy this should be first.

 

[teddy52food]

How is it dangerous? It is a good way to get the oil pressure up before firing.

 

[dan_41jdh]

"I'm betting everyone on here has had them reversed at least one time in there lives. That makes a heck of a bang out the exhaust "

John, looks like Mike M has a pretty safe bet there. I've certainly done it...

With those mags firing every 180 degrees of crankshaft rotation and if the plug wires are reversed, the spark will occur at every BOTTOM dead center instead of the desired TOP dead center (at cranking speed, of course).

And at bottom dead center, one of the valves will be (partially) open - If the piston is at the bottom of the intake stroke, the intake valve will be closing, but it will still be open. And if the piston is at the bottom of the power stroke, the exhaust valve will start to open a bit before that.

So, when the mag fires: you'll get either a nasty pop back through the carburetor (with air cleaner oil puking out your intake) or a get a loud explosion out the exhaust.

Either of which will cause your "buddies" to roll on the ground with fits of laughter....

 

[John T]

Yep and with friends like that, who needs enemies lol. That was right after I restored the tractor and all was new n bright n shiny and about as perfect as possible and I was always bragging how it started on the first or second flywheel roll BUT NOT THAT TIME GRRRRRRRRRRR

John T

 

[RandyB(MI)]

I don't think you have half the problem you think you have. A lot of times a "new" / "rebuilt" carb will have a settle in time for the float/needle valve and thus will flood the engine first time you attempt to start therefore fouling even a new set of plugs. If the insulator is wet the electricity will flow down it to ground instead of jumping a gap. Open compression cocks and take plugs out and roll until dry. (also a better way to get oil pressure to a new engine than "pull starting". Spray down plugs with brake clean/MAFF sensor cleaner and compressed air. I think you have everything else correct by now. Wouldn't have 110 # compression if cam was off. Set it at idle and it should start. Let us know what happens. For some reason some on here forget to do that. We never stop learning from others.

 

[gtx1967jewison]

Exactly. I agree.

 

[Markpa13]

Well, after trying everything with no luck, I circled back to the magneto. I noticed the points gap was quite large. When I set it to 0.015, I lost all spark. This was supposed to be a rebuilt one I got off eBay a while back. Guess you get what you pay for. I purchased a mag from an actual shop, bolted it on and she fired right up. Thanks again for all the advice. I think I'm going to print off this forum and keep it in the garage, lots of great info!

 

[soldiertom]

On my 45 B, I found an odd development today that may help some folks sometime down the road. The Flywheel was replaced during a starter install, but it was 2 splines off where it should've been and that put everything 45 degrees off. When you don't know the origins, don't take ANYTHING for granted. Double-Check the basics up front.
Walk in peace
Tom