Archive through February 28, 2018

[cyarrison]

Ethan, Ill have to do some reading and try to see if the timing is off.
Also, the engine will backfire (occasionally) with both the carb and with starting fluid. Other than that the starter just spins everything up but the engine doesnt fire. Any chance its the coil?

 

[ekincaid]

If the coils New,there’s always the chance of a defect.What I’d do is see if you could use/find a known good coil and test that coil on the tractor,if the coil is the original to the tractor than test the voltage out of the coil to the spark plug,now here’s the rub I don’t know myself what the proper reading out of the coil should be.Maybe someone else will chime in on that or consult the service manual section here on the forum

 

[ekincaid]

Christopher-I also have the advantages of having someone in mylife who’s been working on these old Kohlers Briggs Onan engines longer than I’ve been alive right across the street from me LOL

 

[sblunier]

How fast is it turning over? Compression? Valve stuck open?

 

[fcurrier]

 

[cyarrison]

Steve, it turns over as soon as I turn the key. If i hold the key in the start position it will eventually backfire. Exactly how would i test for compression?

Frank, Im getting 4 ohms across the positive and negative side of the coil. The other checks seem to be satisfactory as well.

 

[dschwandt]

Christian, Have you had this engine apart, as in removing crank, cam etc??

take the plug out and spin the engine over. you should detect air coming out of the plug hole on each compression stroke.

Have you static timed the engine??
I'd bet there in lies the issue.
Static time the engine, it will fire on the first crank if done right, providing there is spark.

 

[dropte]

If you've got spark, and fuel the only other things it could be are timing and compression.

I like to time it with my multimeter in continuity mode beeping at me until the points open. .020 is a rough starting point, but not always the right gap.

Dave S's suggestion is quick and dirty way to check for compression. You could also pull the valve cover off and make sure the valves are moving up and down and not hanging up or anything.

 

[danderson]

Chistopher- Look here for a good timing write up.
http://www.mgonitzke.net/cubcadet/tools/static_timing.pdf

 

[eford]

Sometimes I wish people lived closer! Brother asked about fixing an old Even rude. He called me, lives in Minneapolis, had guy on another phone who was in Alberta, being a relay of sorts. Does have an "O" from what I gather at the cabin there with a pull start. I said ask me questions about that, nope. No problems with it!!

Chris Y. I'd check the mechanical aspect of timing in general. I thought you said the engine was rebuilt, it might have been put together incorrectly. I had this same thing happen last year on a push mower, flywheel key sheared throwing timing off. Just backfired. Guy told me to keep it, he didn't want to pay to fix it. Runs great for me!

 

[eford]

I know! For the anniversary, post some pics of strippers! Your favorite method for removing paint and grease when working on these little fellars

 

[cyarrison]

Earl, Im not sure that the engine was rebuilt. I had bought the 127 off a guy that had gotten it from another guy whom didnt finish the restoration. With that said, im not sure if the engine was rebuilt of not.
Doug, Thanks for the link to that write up. I went ahead and started to do the static timing on it. When turning the flywheel by hand and looking into the peep hole to view the "S" what i find is that the "S" is dead center of the hole as the points begin to open but what is interesting to me is that the points stay open to roughly .023 gap and the "S" comes back around again prior to the points ever coming back in contact.

In other words, the Points only come in contact 1 time for every 2 rotations of the fly wheel. Does this seem right?

 

[dropte]

Points should be closed the entire time except when the camshaft pushes up the plunger to open them. That should happen once every other rotation of the flywheel, since the cam turns at half the speed of the crankshaft.

 

[rrschmitt]

Chris Y,

Yes, that is correct on a 4-stroke engine (Intake (Dwn) , Compression (Up), Power (Dwn), Exhaust (Up). (Up & Down = direction of travel for the piston). The points are opened and closed by the camshaft. The crankshaft makes two complete revolutions while the camshaft rotates only one revolution. The points should open about 20-degrees before Top Dead Center (TDC) which is the timing mark "S" centered in the viewing hole. When the points open the spark plug should fire.

When you take the spark plug out of the head, ground it to the frame and crank the starter, do you see a bright blue, regularly repeating spark? If you do then the ignition may be fine.

Next I would look at compression. Have you checked the gap on the valves to make sure they are fully closing? You can check this by removing the Carb and then the valve cover assembly to gain access. Make sure the inner pan of the valve cover assembly has the little drain hole at the bottom. Get a feeler gage and check the gaps to make sure they are per the specs in the manual. Also rotate the engine by hand and observe the valves to make sure they go up and down smoothly and don't hang up. If the valves are closing properly, then you are not getting adequate compression to fire the engine other than the occasional backfire.

 

[danderson]

Christopher- The points should open once per two revolutions. That is when the plug sparks. If the points are staying open then something is amiss. They should close very soon after they open. Make sure the spring on the points isn't broken. Maybe pull the points, put your finger on the plunger that opens the pointS, and make sure it's moving in and out properly while you turn the engine over BY HAND, KEY OFF.

 

[cyarrison]

Ron, thanks for the detailed reply. I'm getting a nice blue spark with the plug pulled and grounded. I think I'll pull the carb as you suggested and get to the valves and check their gap. I'll keep you guys posted.

 

[cyarrison]

Also, with the spark plug removed and cranking the motor I feel air coming out of the spark plug hole.

 

[bigsteve]

Try a different spark plug I have seen new plugs bad.

 

[kide]

Christopher.... completely as you can, verify a function before moving on to the next. You stated the points were staying open. As Doug Anderson said, they shouldn't hang open..... Also note that this is battery ignition with the points actuated by a cam, not the flywheel, so if the flywheel has sheared the key and turned on the crank, you can still get a spark and you might have it lined up with the timing mark, but it'll be at the wrong time. A quick thing to do is verify the TDC mark on the flywheel is showing in the window at actual TDC, by using a bent piece of wire in the plug hole to touch the top of the piston and rocking the flywheel back and forth - you can get close enough to set rough timing without pulling the head to check.

Kraig - do you have offline archives back to '99? I used to have a copy of my first post - can't find it anymore..

 

[mgwin]

Christopher,

Looks like everyone has got you covered on the electrical part.

This will probably not solve your problem, but make sure you have a coil with an internal resistor.
A friend of mine burnt up part of his wiring harness with the wrong coil.

Just a thought.
You said you are getting fuel.
If you haven't already;

Take the bowl off of the carb. Hold a cup under it and cut the gas on.
See how much gas comes out. There should be a good flow.
Then raise the float and see if the gas stops.
Do this several times to see if the needle valve ever sticks.

Just a thought.

At least we will feel better if you have done this!