Won't start revisited

Tue May 14, 2013 1:35 pm

In reference to the post below "Hard starting". I have a 49 cub that I have been trying to get to start for three years. I have done all the suggested things to no avail. I bought a rebuilt mag from a member of this board. I have good spark and fuel flow.
The compression is not great but I think it should run.
In the post below Eugene said "compression tests will tell you a lot about engine condition". Will you "Eugene" or anyone explain just what a compression test will tell me. It's not that I have spent a great amount of time on this but I have done quit a bit of work and am no closer to getting to running than I was when I started.
I think I know but hearing from someone else will boast my confidence


Re: Won't start revisited

Tue May 14, 2013 2:06 pm

Consider an engine as a large vacuum pump. Takes several things for an engine to run: compression, ignition at the right time, correct air fuel mixture. You need suction (compression related) to pull the air fuel mixture into combustion chamber. Missing any one of the listed items, or any listed function faulty, and engine does not run.

Compression test dry will tell you if you compression on all 4 cylinders. No compression on one or more cylinders usually indicates stuck valve(s). Disruption of suction (lack of compression at any point) effects the engines ability to draw the air fuel mixture into the cylinders.

Wet compression test will indicate if the major fault is either rings or valves not sealing properly.

Re: Won't start revisited

Tue May 14, 2013 2:07 pm

Avery, the compression test will tell you if the pressure in the cylinder ( at TDC) is enough to make the tractor run. If you have not, run a "dry" test, then a wet test ( with several tsp. oil in cylinder ). Dry will tell if you have enough compression, wet test will tell if rings or valves are leaking. Since you have fire (blue?) and fuel I would suspect timing since you had the magneto off . Others will be along to make this clearer than I have. You probably closer than you think, hang in there! If timing is spot on and the compression is low you may be able to pull start it (in3rd gear only).

Re: Won't start revisited

Tue May 14, 2013 2:08 pm

Too slow for Eugene!

Re: Won't start revisited

Tue May 14, 2013 2:43 pm

"It is impossible for a man to learn what he thinks he already knows." -Epictetus

I'm wondering if I my be trapped in this mentality, because nothing that I read here is new to me. I have done all things suggested to no avail.
An act of futility, " to do the same thing over and over and expect different results".

I think it to be something simple and I will stumble on the problem sooner or later.


Re: Won't start revisited

Tue May 14, 2013 3:33 pm

Avery, Take a vacation and head out to a CubFest with your Cub May 31 and June 1. You can go to Hog Waller in Randolph Va or Barnyard Bash near Cincinnati. There is another this week end near California Missouri. Somebody at one of these fests will help you out. If it is capable of running then it will be when any of these guys get done with it. You will meet some great guys and have a great time to boot.

Re: Won't start revisited

Tue May 14, 2013 4:20 pm

If the magneto has been sitting, the points can "glaze" over and cause a no fire condition. If you have fire, it should be a blue white spark. If that is good, then you need to confirm it sparks at the right time, so engine timing to be confirmed. If all that seems well, then the problem is in carburetion. Any questions about mag, I will be happy to try and help with.

Re: Won't start revisited

Tue May 14, 2013 5:13 pm

Yeah to what Barn Yard says. Enough knowledgeable people are at a Cubfest to get you going. I see from your Zip that you are north of Atlanta. Plenty of talent in that part of the World.

Re: Won't start revisited

Tue May 14, 2013 5:55 pm

Avery do you ever get any kind of engine fire? A pop, bang, poof or even some smoke. Like has been said, and you already know, these are simple machines. You need fuel and spark, and at the right time, hence compression and timing. As you stated it probably is some thing simple that is being over looked. One of the simple things that comes to mind is the firing order. Are the plug wires in the right order to the rotation of the mag? I know that's some thing I've overlooked in the past.

You said so far there is nothing suggested that you haven't tried, does that include pulling? If you have fuel, the spark is good, and timed correctly you can have an engine with practicably no compression and pulling will get it running.

A couple years ago I had one of those green tractors with, if I remember right, about 30# on one cylinder and almost 40# on the other. It was a hand start tractor and when turning it over I could just barely tell when it was coming up on TDC. I turned the flywheel until I was completely tired out without as much as a poof, but when we pulled it with another tractor it was running in less then 20 ft.

Re: Won't start revisited

Wed May 15, 2013 10:49 am


It is probably something simple. A lot of what you describe is similar to what I had experienced with Granny after letting her sit for almost 3 years since we had her running good and strong in '09 at CubFest Northeast NB. I beat myself up over it for a long time, did everything I could think of -- and eventually ended up with her out of time, valves stuck and of course zero compression. Redid it all from retiming the mag/governor, firing order - verified by the valve order, got valves all free - the whole 9 yards. Still nada. Not even a pop at times. Every now and then I would get a couple pops but that was all.

Bit the bullet, hooked Granny up to the 2000 DGC and took her for a ride. Took about a dozen attempts but I got her to finally fire. Rough as could be but she fired. Another half dozen tries and she finally caught and after a few minutes evened out and started running better.

Not sure what the answer is aside from the Tractor Gemlins were active again ... :big give up:

So I guess the point is -- go through it again, carefully and if it still don't fire - PULL Start it :!: If that don't work ... put it on a trailer and take it to your closest CubFest -- between you and the rest of em, she will run :D

Re: Won't start revisited

Thu May 16, 2013 7:38 am

Just be careful when pull starting. Don't attach your tow strap to the front of the tractor. Attach to the drawbar and run the strap under the cub.
Use third gear and don't pull it faster than the tractor is meant to go.
Most of all, BE CAREFUL! and a way to communicate with the vehicle drivers.

Re: Won't start revisited

Thu May 16, 2013 2:33 pm

Here is what Id try if you didnt first if you no your getting spark short shot of starter fluid if its a fuel issue it will do something,Second if that doesnt work pull the dist out do a half turn put it in and try...Ive had two tractors beat me up being out of time....

Re: Won't start revisited

Thu May 16, 2013 6:18 pm

Thanks Everyone:

I am going to be busy for a few days. When I get time I will do compression test and post the results. I am almost convinced that
the compression is the culprit. I have honed the cylinder walls, new head gasket, lapped the valves, and done all the things
Maybe be a couple of weeks, I have grandsons graduating from high school. One in Birmingham and another in Lawrennceville, Ga.

P.S. I removed plugs and placed them on the head with wires attached. Turned over with hand crank and the plugs fired at the right
time and in the right order.

Re: Won't start revisited

Thu May 16, 2013 9:13 pm

I may just need a little oil squirted into the cylinders to get a good compression seal and start.