IH Cub 129 K301a Timing

[Methos]

Originally Posted by jsoluna

I've over-checked myself at least 6 or 7 times, but I'll try again tomorrow morning. Has anyone else ever checked the resulting gap after static timing method and come up with a gap that large?

It takes acouple of times the first time you do it. I've never checked the gap after I VOM set the timming. I didn't see the point as long as it runs good.

My old 122 that Allen has is set perfect and has a awesome low idle that makes the stack cap tap away when it runs. I owe it to Matt's guide. It took me a while and I thought I was losing it when I was doing it but it turned out great.

[jsoluna]

Ok, I just had a thought, and there is one thing that confuses me about points ignition:

It should only spark before TDC on the compression stroke, right?

Is it possible I had the "S" lined up and the points set correctly but that I had it on the wrong cycle?

[Methos]

Originally Posted by jsoluna

Ok, I just had a thought, and there is one thing that confuses me about points ignition:

It should only spark before TDC on the compression stroke, right?

Is it possible I had the "S" lined up and the points set correctly but that I had it on the wrong cycle?

Unless your key on your fly wheel is sheered then it would make a diffrence. If the S is in the sight hole and the points are breaking open it's set right. Maybe after sleeping on it you'll have better luck tomorrow.

[jsoluna]

Yeah, that's my plan.
Thanks for the words of wisdom guys, I'll hop on it first thing in the morning after some coffee. The daughter stayed overnight at grandma's too, so I'll have some peace and quiet out there to focus on it. I'm thinking of pulling the spark plug and verifying cylinder TDC too.

The S mark is supposed to be 20 degrees before TDC, is that correct?

[Methos]

Originally Posted by jsoluna

The S mark is supposed to be 20 degrees before TDC, is that correct?

Yes

[jsoluna]

So....here's the update:

Double checked timing after setting it to the "S" mark, triple checked it, and definitely had it "correct", but the engine still wouldn't run at that setting for some reason.

I ended up getting real frustrated, actually, because after that I set point gap to the last known good setting, which was .015, and it still wouldn't run! Started thinking there was a larger problem going on, got upset and left to cool off my brain....

Came back, set it to .010 and BAM. It ran great. I think it could stand to be just a tad less advanced, with the carbon buildup in the combustion chamber I think the compression ratio has changed. So, next thing on the list is to do a head gasket and clean the carbon out, then re-time it.

I'm still not entirely convinced that there's something wrong with the tractor, but at least I got it running, and running well. I need to buy a timing light for my shop anyway, so this would be as good excuse as any.

Thanks for the help guys - I'm going to start a new post on the cooling system mods I made the other day too, and I'll return to this one when I go back and re-time after the head gasket job.

Thanks for the advice on the "magneto" ignition system ...still embarssed bout that....

[jsoluna]

So, for anyone who followed or will be interested otherwise in the thread, here's n update - several weeks of tinkering later:

Ok, to start off, I did verify that my method of timing was correct. I had it messed up the first time somehow, but every sequential trial has been spot on.

I read in the manual that an acceptable gap range when timing my 12hp Kohler is from about .015 - .019. When I timed is dead on with the "S" mark, I end up with about a .015. Problem is, at .015, my particular engine does not want to start up. It will fire once every compressions stroke, but will not get itself running without much labor.

So after I did get it to run, having it timed correctly, I noticed spark knock, mainly under load, and unburnt fuel smoke under load as well.

I decided to do my head gasket and clean the chamber. Whew! It was gross, and head was warped. Resurfaced it myself to within spec and put her back together. Not much difference, really.

So, after racking my brains, I think I figured out why my specific engine doesn't like this timing, why this thing has been confusing for me.

I think it's just that the engine is wore out, not too bad, but I think it's tad low on compression. After seeing the piston to cylinder wall clearance, and noticing the slight amount of oil in the combustion chamber, I'm pretty sure the 40 year old Kohler is just wore out a bit. It's still solid, but a bit wore out. Don't have a compression gauge (still slowly building up my toolset for the shop), but it makes sense now. That's why my timing needs to be retarded a bit to help start the engine and get it to have sufficient power without spark knock.

My engine likes its points gap to be about .008. This puts it around 10deg before TDC as opposed to 20deg TDC, allowing the engine to build up just enough more compression to get itself rotating under its own power. Around .009 and .010 it will start fine but have a misfire at WOT. At gaps nearing the 20deg before TDC mark, it has a real hard time starting unless its warmed up, and will knock slightly under load.

So, after many hours of thought, that's my conclusion, and my contribution to the OCC community. I may be wrong, and I'm open to suggestions here, but I postulate that while the Static Timing Method may be the "correct" means of timing the K Series, always go with your gut and use your mechanical intuition. As with anything mechanical, with all the years and hours of use, things can change. It's certainly the case with my K301.

Oh, and for reading that long novel, here's some new pics,including some mild cooling modifications, rattle can paint removal to expose original Federal Yellow, etc etc....

Finally getting to do some cosmetic work, and grabbed some used Ag tires for it tonight!

[Matt G.]

I've timed engines ranging from rebuilt to completely worn out with that method with good results. I think you may have a different problem. You've got a bit of carbon in there, but overall the piston doesn't look too bad. You say you think it might be low on compression; if the valves aren't sealing or the valve lash is too tight, it'll start hard and do what you are describing, and probably be down on power, too. I would have ground the valves and reset the valve lash while you had the head off.

[jsoluna]

Yeah the piston doesn't look too bad - the typical wear spot next to the exhaust valve wasn't present - but it did have a lot of play in the bore, and I know I'm getting some blowby as well.

Is it the whole problem? That was my thought, but like I said I could certainly be wrong. Valve lash was the very last thing the previous owner did to it before I acquired it . It did cross my mind that valves improperly set or not seating properly would cause that. Ill check that and keep you all updated.

At least for now it starts and runs great with no abnormal noises and has good power.

[hydrocub]

What are the black plastic "doo hickies" mounted above the check valves
and screwed into the fender pan ?