K301A no start!

[TAZhungry]

I am restoring a Cub Cadet 125 with a Kohler K301A 12hp engine and I have a few issues. The original carburetor leaked gas back out the throat and continually flooded so I purchased a replacement, the new carb still floods with choke closed. Even had gas coming out of the exhaust port at one time (muffler not on). The other issue is chasing the timing. The mark on the bearing plate appears to be missing so I'm not 100% sure where in the hole the mark should be at, I'm also assuming that the - above the S is the actual mark on the flywheel. I've gotten the engine to backfire out the carb a few times but no start. I've fiddled with setting the points while the - and S were in various positions in the peep hole and so far the strongest pop seems to be where the - is in the middle from top to bottom in the peep hole but still no start, closing the choke seems to make the engine try harder to start but then it floods and starts making a hollow pop sound. Is this all a fuel/spark issue or possibly an internal problem. I did clean the valves and the valve seats, possibly a compression issue? I'm about to pull the engine and tear it down again but really don't want to be wasting my time if it is fuel/timing. also not interested in tearing the engine down just to find a mechanical issue that I cant fix . Any ideas where I should look first when I go back at it tomorrow? I apologize for the long explanation. I did look for other post about similar issues but failed to find any that would help. Thank you for your time, and I appreciate any help I can get!

[jbrewer]

You have a lot going on here now.



If you still have fuel flowing out of the carb, then there's no reason to play with timing until you get that taken care of. I'd say it's unusual but not impossible that you have two carbs with stuck floats, but that seems like what you're describing. I'd fix that first. With some care, you can remove the bowl without ruining the gasket and make sure that the "needle" is free and will fall out of the carb body on it's own if you remove the float pin.

Usually if the carb is flooding, this process will fix it.

The timing marks are not easy to see, but I've never found a cub where I can't eventually locate them. The process for setting timing in the manual is straightforward and works well.



Even without ANY carb, the engine will fire and run for a short time if you squirt a bit of gas in the intake (I use a ketchup squeeze dispenser). These engines are crude and reliable.



You've got a lot of things taken apart and changed now, which makes this a bit more tricky, but do the basics...make sure the coil has power. Make sure the points are making contact using a multimeter. Make sure the plug is making spark. Set the timing per the manual. Fix the carb float/needle/seat. Crank the engine with the plug out and observe if you have compression.


It'll run

[finsruskw]

1st off...
Did you have the engine apart, flywheel off, crank and cam removed, etc?
"restoring" means many things to many people.

[TAZhungry]

when I took the engine out I took off the flywheel and the front bearing plate to check all the innards from a different perspective that just the bottom of the crank. Checking to make sure nothing was broken or cracked. Ill pull the carb and see if I can sort out the float but I don't think this is the issue with the starting as I can close off the fuel from the tank at the sediment bowl and just spray ether into the carb and I get pops and sputters but no start. It really acts like it wants to start but just wont catch which is what got me thinking about the timing. fuel spark compression timing, one of those is not working correctly or a combination. I don't have a compression tester but I do know that on the intake stroke there is a strong vacuum created at the carb, which I assume that if the exhaust wasn't sealing it wouldn't have the vacuum. I do wonder about the intake valve though. Could be pulling the fuel in on the intake and spitting it back out on the next stroke. Could this cause the same symptoms? I've never done a valve job and don't have the right tools at the moment but if anyone thinks this is worth pursuing I will pull the engine and break it down again...Ive never actually rebuilt an engine, it seems like this might be the way I need to go though.

[ol'George]

If You didn't, check the valve clearance, they could need adjustment.
Also on the carb leaking:
Debris' under the needle valve/seat can come from many places. do make sure
your fuel filter is clean and not allowing "chit" from finding its way under the needle/seat.
And many times I have found a small piece of fuel hose that broke off while attaching it to the hose barb on the carb, especially if the hose is old.
But I have seen crud in new hose off the roll in the retail store.
Assume nothing,
a human hair is thick enough to keep a needle from seating and will cause seepage.
And by all means keep your OEM carb,
as this newer off shore parts on the 'net are a crap shoot.
the OEM card almost always can be cleaned and will perform better, if the new one does not work as expected.

[athomas]

There is no timing mark on the brg plate that i am aware of, there is an S, a line and a T on the flywheel which hopefully you cleaned off when the flywheel was out ! when rotating the engine the proper direction the S will appear in the little window/hole and on the compression stroke you want the points to break as the S appears in the window, have a meter hooked up to read loss of continuity when this happens ( hope I'm saying it correctly ) easier to do than describe ! also as stated make sure valves are adjusted properly. As far as the carb, rebuild the original, although I've battled a leak on my 109 several times and just keep the fuel shut off when not in use !

[TAZhungry]

I have pulled the engine out of the 125 again, I figured it would be better to just do a full rebuild on it; new piston, rings, the whole works than running down each little problem. I pulled the pto in prep to possibly do a rebuild, however the set screw on the bearing retainer broke....I'm really hoping I can get a bearing puller to pull it off because there is no way that I can see to drill it out (no straight shot at it) unless I drill through the pto basket. If I cant get it off then I guess Ill have to find a replacement engine and rebuild that.

just noticed the 1/4 turn on the retainer requirement to get the bearing off, unsure if I can get it to turn with the broken set screw.....

Found a 123 at a decent price, same engine and multiple spare parts!

[TAZhungry]

New update, had to drill a hole in the pto basket but I got the pto bearing off as well as the basket. The valves were definitly out of round and no where near sealing because of it. I forgot to get a valve spring compressor at Harbor Freight so I dont have the valves out, but the piston and crank is out. Definatly needs a rebuild. Picking up a 123 on Monday for a parts tractor and possible future restoration. Now I just need to buy a rebuild kit, I need to mic out the cylinder to make sure I order the right size.

[TAZhungry]

Valves are toast but the rest seems in decent shape. I used a caliper on the piston and it came out to 3.334, .33 under, if I measured right so I believe a rebuild is necessary. Plenty of material to go .010 over in the cylinder. With new valves and seats it should run like a brand new engine.
I would upload pictures but I don’t have them stored online.

[ol'George]

FWIW:
A caliper is good for measuring approximate sizes.
A mike is accurate, and measure at the bottom of the skirt, right angle to the wrist pin as most pistons are cam ground.
There are exceptions on some engines, so the service manual is ones best friend.

As you now know the piston is a few tho' smaller that the bore for clearance.
a dial bore gauge will tell you the cylinder taper, out of around and actual diameter.
lacking that, a telescoping gauge is accurate in skilled hands.

I'm assuming you are not going to do your own machining?
If so your machinist will do the measuring for you.

FWIW: valves can be ground and seats cut or ground.
Also, the valves can be easily removed with 2 screwdrivers under the keepers if one doesn't have a spring compressor on these little engines.
The crankshaft needs measured with a mike to check out of round and taper.

if the bore is well worn, most times the crank journal is tapered and out of round causing a "noisy engine" ----like a wood pecker on a tin roof.
have fun