Help sorting a 122

[kopeck]

Hello, been a long while since I've posted something, haven't had much time to play with Cubs recently...

I have had this 122 for about 10 years. I bought it with two problems, a clutch that sticks and and engine that misses.

I'm really only interested in the engine right now. It just randomly misses, seems to do it at all RPMs though it's more noticeable at higher RPMs. It also doesn't like throttle up smoothly though it does it with out hesitation it's also pops pretty badly throttling down (which is a single cylinder thing but this one seems worse than other K series I've worked on). It does seem to get a bit worse when it's hot.

The carb is new (the old one worked but it had a break that I patched up with JB weld and I never really liked).

New points, condenser, plug and wire today, cleaned all the ground points and it's improved but still just wont run "right".

The only thing left in the ignition is the coil. It's test ok on my meter but I know coils are funky thing. The only other thing I can think of is valve lash but I've found that tight valves often make for hard starting engines which this is not.

Ideas?

Thanks,

K

[Billy-O]

Usually I would say condenser a likely culprit on the misses ......but I see you mention having replaced it already. So...... Reading down your post, the popping on de-throttling has me wondering if you are running too lean? The popping being bit worse when hot is the other clue leaning me to say you are lean!

Among other things... Make sure you have good air flow behind the tins. Good head gasket. Valves working OK? Lash?

[ironman]

????? sticky valve ?????

[kopeck]

I'm sort of leaning towards something with the valves. I do have a head gasket on hand so I can pull the head and take a peak in there too.

Not sure if I should just order a coil just to eliminate that possibility. I do hate throwing money at a problem.

As far as the lean thing, yeah that's how it feels. The K series I've worked on before will throttle up/down poorly until you get the high speed mixture right. This one is some what similar except I can't find the right mixture. I've pulled the carb apart twice to clean it...

K

[Red Dave]

Those engines have a reputation for sticky valves. What you describe sounds a lot like a valve problem I had.

I picked up a 125 many years ago that would run for awhile, then start to miss, pop and then stall. Let it cool a bit and it would run fine again until the exhaust valve started sticking again.

I put about a half cup of Marvel Mystery oil in the crankcase and about the same amount in the gas tank. It would stay running with the MMO in it.

I limped along with it for more than a year until I had time to rebuild that engine, and of course replace the exhaust valve.

[ironman]

If you have access to a leak down tester you might give that a try before you pull the head.
I would test it cold, get a reading, then run it till it's hot and test again,
See if there's a big difference between the readings.

[kopeck]

I hate it when I google something, find a thread but it never has the solution so this time I'm going to not so that... :-)

Looks like it was the coil. I don't have a ton a free time so I figured that's something easy to try though I usually don't like to just try stuff for the fun of it. I ended up getting one of the Bosch coils as well, it cost the same amount(or even a little less) than an OE or one from NAPA and I was ordering some parts from RockAuto anyway.

The kids just put a few hours on it riding around (my kids love tractors) and they said the only time it ran unevenly was going down hill which is what it is.

Now for the clutch...

K

[kopeck]

So I lied.

I forgot that I added some MM oil to the tank. Kids ran it out of gas, I refilled (w/o MM) and with in a few minutes it started in again.

So that pretty much makes it a sticky valve. Oh well, I think I'll get the clutch parts and do it all at once.

The blue coil sure does make it look cool at any rate.

K